CA1039077A - Nitrogenous fertilizers - Google Patents
Nitrogenous fertilizersInfo
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- CA1039077A CA1039077A CA179,757A CA179757A CA1039077A CA 1039077 A CA1039077 A CA 1039077A CA 179757 A CA179757 A CA 179757A CA 1039077 A CA1039077 A CA 1039077A
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Abstract
ABSTRACT OF THE DISCLOSURE
A process for the preparation of a nitrogenous fertilizer, which process comprises treating a coal of low rank with a suit-able hydrotropic solvent to dissolve at least a substantial amount of the humus content of the coal, subjecting the thus formed solu-tion to oxidising conditions, adding a nitrogen-donating compound to the oxidised solution so as to form a gel, and drying the gel.
A process for the preparation of a nitrogenous fertilizer, which process comprises treating a coal of low rank with a suit-able hydrotropic solvent to dissolve at least a substantial amount of the humus content of the coal, subjecting the thus formed solu-tion to oxidising conditions, adding a nitrogen-donating compound to the oxidised solution so as to form a gel, and drying the gel.
Description
1t~3~ 7 This invention relates to nitrogenous fertilizers and in particular to processes for preparing the same.
Research has indicated that the properties of coal humus are similar.to those of soil humus in that both consist of dark brown complex'organic colloidal compounds which are soluble in an alkali medium but not in water. In addition, both have a high base exchange capacity and contain acidic oxygen-containing func-tional groups. In view of these similarities and because coals of low rank, for example brown coal (lignite), contain a higher pro-portion of humus than other coals, it was considered that if coalsof 1GW rank could be subjected to a suitable treatment to extract the humus content, it might well be possible to produce a nitro-genous fertilizer having all or most of the desirable properties of known fertilizers and at appreciably less cost.
With this consideration in mind, it has now been dis-~overed that by treating a coal of low rank with a suitable hydro-tropic solvent to dissolve at least a substantial amount of the humus content of the coal, subjecting the thus formed solution to;oxidising conditions, adding ammonia or a like nitrogen-donat-ing compound to the oxidised solution so as to form a gel, anddrying the gel, such a fertilizer may be obtained.
Thus, the present invention provides a process for the pre-paration of a nitrogenous fertilizer, which process comprises treat-. , ing a coal of low rank with a suitable hydrotropic solvent which is an aqueous solution of a nitrogen-conferring material which acts as a weak base to dissolve at least a substantial amount of .. . .
the humus content of the coal, which content is otherwise sparing-ly soluble in water, subjecting the thus formed solution to-oxidi-sing conditions, adding a nitrogen-donating compound to the oxi-dised solution so as to form a gel, and drying the gel.
; ' -1-f~
0~7 The expression "hydrotropic solvent" as used throughout the specification, including the claims, refers to an aqueous soluti~n containing a nitrogen-conferring material - the hydro-tropic mate~rial - which acts as a weak base to facilitate solubi-lization of the humus content of a coal of low rank, which con-tent is otherwise sparingly soluble in water. The aqueous solu-tion may ~e formed in situ, the hydrotropic material dissolving in water present in the coal. In fact, in coals of very low rank with a hlgh water content, in situ formation i~ decidedly preferr-ed; this may involve milling of the hydrotropic material and the coal.
The actual amount of coal employed in the process will be dependent upon the type of coal, since the proportion of humus present varies from coal to coal. This amount can be readily de-termined by simple experiment. A pre~erred range, however, is 60%
to 80% by weight, based on the overall weight of reactants.
By this process it is possible to provide a fertilizer ex-hibiting the following properties: -1) It permits a slow release of combined nitrogen, thus avoidin~ the high initial yield and following rapid fall-off in efficiency, characteristic of chemical fertilizers such as ammonium sulphate.
Research has indicated that the properties of coal humus are similar.to those of soil humus in that both consist of dark brown complex'organic colloidal compounds which are soluble in an alkali medium but not in water. In addition, both have a high base exchange capacity and contain acidic oxygen-containing func-tional groups. In view of these similarities and because coals of low rank, for example brown coal (lignite), contain a higher pro-portion of humus than other coals, it was considered that if coalsof 1GW rank could be subjected to a suitable treatment to extract the humus content, it might well be possible to produce a nitro-genous fertilizer having all or most of the desirable properties of known fertilizers and at appreciably less cost.
With this consideration in mind, it has now been dis-~overed that by treating a coal of low rank with a suitable hydro-tropic solvent to dissolve at least a substantial amount of the humus content of the coal, subjecting the thus formed solution to;oxidising conditions, adding ammonia or a like nitrogen-donat-ing compound to the oxidised solution so as to form a gel, anddrying the gel, such a fertilizer may be obtained.
Thus, the present invention provides a process for the pre-paration of a nitrogenous fertilizer, which process comprises treat-. , ing a coal of low rank with a suitable hydrotropic solvent which is an aqueous solution of a nitrogen-conferring material which acts as a weak base to dissolve at least a substantial amount of .. . .
the humus content of the coal, which content is otherwise sparing-ly soluble in water, subjecting the thus formed solution to-oxidi-sing conditions, adding a nitrogen-donating compound to the oxi-dised solution so as to form a gel, and drying the gel.
; ' -1-f~
0~7 The expression "hydrotropic solvent" as used throughout the specification, including the claims, refers to an aqueous soluti~n containing a nitrogen-conferring material - the hydro-tropic mate~rial - which acts as a weak base to facilitate solubi-lization of the humus content of a coal of low rank, which con-tent is otherwise sparingly soluble in water. The aqueous solu-tion may ~e formed in situ, the hydrotropic material dissolving in water present in the coal. In fact, in coals of very low rank with a hlgh water content, in situ formation i~ decidedly preferr-ed; this may involve milling of the hydrotropic material and the coal.
The actual amount of coal employed in the process will be dependent upon the type of coal, since the proportion of humus present varies from coal to coal. This amount can be readily de-termined by simple experiment. A pre~erred range, however, is 60%
to 80% by weight, based on the overall weight of reactants.
By this process it is possible to provide a fertilizer ex-hibiting the following properties: -1) It permits a slow release of combined nitrogen, thus avoidin~ the high initial yield and following rapid fall-off in efficiency, characteristic of chemical fertilizers such as ammonium sulphate.
2) It permits a retention of essential plant nutrients, such as phosphorus and iron, in an easily available form.
3) It improves the water retention and heat absorbing capacity of the soil.
4) It constitutes a buffer which prevents rapid changes in the acidity or alkalinity of soils.
Though any coal of low rank may be used, brown coal is , .. .. . . .. . . .
- ': , ~3~C~77 preferred, usually in amounts of from 60% to 80% by weight, based on the overall weight of reactants. Certain peats or peat coals may also be put to good use.
Simple experiment will determine the types of hydrotropic materials suitable for the present invention. Of the materials capable of conferring nitrogen to the fertilizer, urea is especi-ally suitable, preferably in amounts of from 18 to 22% by weight, based on the overall weight of reactants. Other suitable hydro-tropic materials include urea nitrate, urea peroxide, sugar, biu-ret and thiourea.
Oxidation may be carried out by means of conventional oxi-dants. For example, nitric acid, preferably concentrated commer-cial nitric acid, or hydrogen peroxide may be employed The amounts of nitric acid preferably range from 1.7 to 3% by weight and the amounts of hydrogen peroxide from 0.5 to 2.0 by weight.
~ Sodium hydroxide or potassium hydroxide are desirably introduced ; into the solution following or before addition of the oxidant, usually in amounts ranging from 0.4 to 1% by weight.
Ammonia is the preferred nitrogen-donating compound. 880 ammonia, namely concentrated (about 36%) ammonium hydroxide solu-tion having a density of 0.880 in amounts of from 5 to 7~ by weight are more preferred.
Oxidation establishes functional groups such as phenolic, ; carbonyl and carboxylic groups, which are capable of readily com-bining with the nitrogen-donating compound, preferably ammonia, to form a gel. On drying to a granular consistency, the gel is found to be slowly peptised in water. Analysis of the product reveals a nitrogen content of the order of 23 to 25%.
The invention will now be further illustrated by reference to the following examples.
:' ;; .
:: .. . :, . - ~
1~3~C)q7 EXAMPEE I
.
301b. of brown coal from the Morwell-Yallourn area of Victoria, Australia, was dissolved in a concentrated aqueous solu-tion of urea containing 91b. of urea. 12 02. of concentrated com-mercial nitric acid was then added to the solution followed by 30z. of sodium hydroxide. 31b. of ammonia (s.g. 0.88~ was then introduced into the solution and the resulting gel filtered off and dried to a granular consistency.
EXAMPLE II
lOlb. of brown coal from the Morwell-Yallourn area of Victoria, Australia, was dissolved in an aqueous solution of urea containing 31b. of urea. 102. of sodium hydroxide was then added to the solution followed by 1-40æ. of H202 (100) Vol. llb. of ammonia was then pumped into the solution and the resulting gel dried to a granular consistency.
The products of Examples I and II were shown to exhibit all the abovementioned four properties, as well as being chemic-ally ~table in the dry state, thereby permitting normal packag-ing for transport purposes.
Apart from providing a process of preparing such fertilizers, ' the present invention also provides a fertilizer whenever prepar-ed by such a process.
' "'.
` `' C
~ ~3~(~q7 SUPPLEMENTARY DISCLOSURE
Additional aspects of the invention described and claimed in the principal disclosure are hereinafter described.
In general, low rank coals such as lignite are known to enhance the desired formation of crumb structures of soil parti-cles and to impart porosity, aeration and water-absorption. How-ever, these coals may be so acidic that they can hardly be applied as they are without having detrimental effects upon plant life. Treatment of the coals is therefore necessary to render them satisfactory for purposes of addition to soil. - -One classical method for obtaining humates or humic acid involves treating coal with an aqueous sodium hydroxide extrac-tant. Humates are dissolved in the extracting solution and sepa- ;~
rated from insoluble tailings. The extractant may then be acidi- ~ -fied and humic acid precipitated. U.S. patent Specification No.
1~ 2,992,093 to E. M. Burdick discloses on~such treatment.
The aqueous caustic extraction system, though ef~fective, ; has been found to be objectionable because of the low concentra-tions of humic acid which are dissolved in the aqueous caustic extraction liquor. The maximum amount of humic acid which can be dissolved in the extraction liquor is about 8% by weight, and --this occurs only in strongly caustic solutions. In practice, be-cause of the low concentration of humic acid salts in the ex-tracting solution, large quantities of sodium hydroxide and water are necessary to recover humic acid in commercial operations.
In an effort to obtain more efficient recovery of the humic acid, other extraction systems have been attempted, such as flotation processes using a non-polar medium such as carbon tet-rachloride, and organic solvent extraction systems using ac~tone and water extracting mediums. While these processes are .
. ~. .
lQ3~77 effective, they are expensive to operate and require complicated purification techniques.
Humic acid itself contains carbon, hydrogen and oxyten atoms only, and finds use as a soil conditioner but not as a fer-tilizer because of the absence of any essential plant nutrients such as nitrogen, potassium or phosphorus. In preparing the humates, however, if ammonium hydroxide or potassium hydroxide are used as the extractant in place of sodium hydroxide, nitrogen or potassium becomes available for supply to plants. Here again, though, ammonium or potassium hydroxide are not particularly good extractants, being no better than sodium hydroxide in quantity of humus dissolved, which in turn means that little nitrogen or po-tassium is available for plant supply. Moreover, at least in the case of nitrogen, this is present predominantly in a form which is released at a fairly rapid rate. The nitrogen bearing compo-nents of the composition are rather easily dissolved in water.
Ammonium humates are thus not suitable where the aim is to pro-vide a fertilizer which will permit the slow release of nitrogen.
Coals have also been subjected to treatment with nitric acid, this giving rise to a compound commonly referred to as nitro humic acid. As with the aqueous caustic extractant, nitric acid is not a particularly effective extractant unless high con-centrations of nitric acid and high extraction temperatures are employed, and even then the maximum amount of humic acid ex-tracted is not very high. Nitro humlc acid contains little ni-trogen - generally little more than about 2% by weight, based on the overall weiyht of the acid- and the bulk of whatever nitrogen is available in water-soluble and in quick-release form.
In an endeavour to improve the fertilizer characteristics of nitro humic acid, the acid has been treated with such compounds . ~ ;
1~)3~ 77 as gaseous ammonia or urea. There is, however, no chemical reac-tion between the acid and the additive, and the resultant product is merely a physical admixture of the two components. The addi- ~- -tive serves to boost the overall nitrogen content, but yet again most of the nitrogen is in a water-soluble form available for quick release. In the case of the addition of ur~a, this addi-tive suffers the same failures as soluble nitrates, that is to ~l' say, it is too easily washed out of soil.
In contrast to the above extraction techniques - alkaline, organic and acidic - and their attendant disadvantages, it has now been found that coals of low rank may be extracted with an aque-ous urea solution, which is substantially neutral, with surpri-singly good results.
More particularly, one aspect of the present invention provides a process for the preparation of a nitrogenous composi- --tion suitable for use as a fertilizer, which process comprises treating a coal of low rank with a suitable hydrotropic solvent which is an aqueous solution of a nitrogen-conferring material which acts as a weak base to facilitate dissolution of the humus ~0 content of the coal; subjecting at least a portion of the thus-formed composition to oxidizing conditions; adding to at least a portion of the composition, either before or after the step of ` subjecting to oxidizing conditions, a member selected from the group of a nitrogen-donating compound, an alkali, and a mixture of the two; and removing water from the oxidized composition to form the nitrogenous composition.
- Another aspect of the invention provides a process for the preparation of a nitrogenous compound suitable for use as a ` fertilizer and a soil conditioner comprising the steps of:
30 treatlng a coal of low rank with an aqueous urea solution at ; - 7 -., 1(~3~7~
about room temperature, at least a part of the aqueous urea solu-tion being formed in situ by virtue of the initial moisture con-tent of the coal; subjecting the composltion thus formed to oxi-dizing conditions; introducing an alkali into the composition;
and removing the water from the oxidized composition to form the nitrogenous compound.
It is of importance to note that in the dissolution of the humus content of the coal in the aqueous urea solution there is no reaction of the urea and humus to form a soluble salt. The aqueous urea solution acts in the capacity of an extractant rather than reactant and in so doing renders the humus more amen-able to oxidation. Furthermore, the extract is acidic, the de-gree of acidity depending upon the initial pH of the coal to be treated.
As the rank of coal goes down so does the water content go up, and with coals of low rank the water content is generally within the range of 50% to 80% by weight, based on the total weight of coal. Thus, aqueous urea solution may be ormed in situ by the mixing of the low rank coal with dry urea. In some instances, where the water content of the low rank coal is low, say of the order of 50 to 55% by weight, it may be desirable to add ~ater to the coal and urea to boost the water content to about 60% by weight and so effect maximum dissolution.
The insoluble fraction of the coal is not generally sepa-rated from the soluble fraction, though it may be. Where there is no separation~ the insoluble fraction is carried through to ;~
the end product and, as far as can be established, has no adverse effects on that product.
The actual amount of coal employed in the process will be ~ 30 dependent upon the type of coal, since the proportion of humus ; .
;' lQ3~0~77 present varies from coal to coal. This amount can be readily de-termined by simple experiment. A preferred range, however, is 60% to 80~ by weight, based on the overall weight of reactants.
By this process it is possible to provide a fertilizer exhibiting the following properties~
(1) It permits a slow release of combined nitrogen, thus avoid-ing the high initial yield and following rapid fall-off in efficiency, characteristic of chemical fertilizers such as ammonium sulphate and prior humus extracts.
(2) It permits a retention of essential plant nutrients, such as phosphorus and iron, in an easily available form.
(3) It improves the water retention and heat absorbing capacity of the soil.
(4) It constitutes a buffer which prevents rapid changes in the acidity or alkalinity of soils.
Though any coal of low rank may be used, brown coal is preferred, usually in amounts of from 60~ to 80% by weight, based on the overall weight of reactants. The amount of coal may, of course, vary considerably, even outside of this range, and will depend on the amounts of the other reactants used. These latter amounts are set out hereinafter. Certain peats or peat coals may also be put to good use.
The coal should be in particulate form to facilitate dis-solution in the aqueous urea solution, and as might be expected the smaller the average particle size the less the time required for effecting dissolution.
The treat is preferably carried out at room temperature for the simple reason that elevated temperatures are only margin-ally better in terms of overall efficiency.
The urea is preferably present in an amount greater than ~' _ g _ ... . , ~ , ~
~3!~77 about 15% by weight based on the overal weight of the coal, added water (if any) and urea. Extraction is to a degree proportion-ately related to the amount of urea and the relative amounts of urea and water present, and in some instances amounts of urea less than 15~ by weight may give rise to an inferior end product because of incomplete dissolution. Preferably, the amount of urea is less than about 30% by weight since higher amounts in-crease cost without enhancing extraction efficiency and may re-sult in the presence o~ some unreacted urea in the final product.
It is found that urea is most preferably present in amounts of from about 18 to 22% by weight. This range appears to give opti- -mum extraction, bearing in mind cost and efficiency factors.
Oxidation may be carried out by means of conventional oxidants, although generally speaking solid and liquid oxidants are preferred to gaseous oxidants because of ease of handling.
By way of example, there is mentioned urea peroxide, sodium pero- ;~
xide, nitric acid and hydrogen peroxide. Needless to say, the oxidant should not be one having one or more elements which are toxic to basic plant life. Nitric acid, particularly concentra-ted commercial nitric acid, and hydrogen peroxide are most pre-ferred.
The amounts of nitric acid preferably range from about 1.5 to 5% by weight, based on the overall weight of reactants.
Oxidation will proceed with amounts below about 1.5% by weight, ~, but it may with some coals be incomplete so that not all of the humus content is utilized in the process. There is little advan-tage in using more than about 5% by weight of nitric acid when increased efficiency is balanced against increased material costs. A range of 1.7 to 3% by weight is generally quite satis-factory.
i :
~ -- 10 --: ,.. , , , ; ~
9~77 : ~
The amounts of hydrogen peroxide preferably range from about 0.5 to 3.0~ by weight, based on the overall weight of reac-tants, the upper and lower limits being determined by the same factors as mentioned above in relation to nitric acid. Generally, up to 2% by weight will suffice.
Oxidation establishes functional groups such as phenolic, carbonyl and carboxylic groups on the humic acid molecules, which are capable of readily combining simultaneously with the NH
groups which are a product of the oxidation of the urea, and the ammonia, if present, to form a gel. On drying to an effectively dry granular consistency suitable for packaging and shipping, the gel is found to be slowly peptised in water.
The alkali is preferably selected from the group consist-ing of sodium hydroxide, potassium hydroxide and ammonia, and is introduced after the dissolving step and either before or after the step of subjecting the solution to oxidizing conditions. The amount of alkali will be largely dictated by the amount of oxi-dant, but usually the alkali is added in an amount ranging from 0.4 to 1~ by weight when either sodium hydroxide or potassium hydroxide, and from 5 to 7% by weight when ammonia. With ammonia there is the additional benefit of a compound which is able to confer further nltrogen to the end product. In some instances, -s ammonia and either of the alkali metal hydroxides may be added.
The amount of total nitrogen and fixed nitrogen in the end product is a function of the nature of the coal used as the starting material and the amount of functional groups provided by that coal. Where ammonia is used, however, the final product will usually contain from about 15 to 25~ by weight of nitrogen of which about 4 to 6% is essentially water-insoluble and avail-able for slow release. Where ammonia is not used, the final ..... ~. . ~
- .
1~3~ 7 product may still contain upwards of about 10% by weight of ni-trogen, 4 to 6% being essentially water-insoluble and available for slow release. When the oxidant is nitric acid, the alkali preferably is added after the oxidant, whereas the reverse is the case where hydrogen peroxide is employed as the oxidant.
~ he invention will now be further illustrated by refer-ence to the following examples.
EXAMPLE I
a 30-lb sample of brown coal from the Morwell-Yallourn area of Victoria, Australiaf in finely-divided form, was mixed with 9 lb of dry urea powder in a mill. No additional water was necessary. Following dissolution, 12 oz of concentrated commer-cial nitric acid ~7as added to the mixture followed by 3 oz of sodium hydroxide dissolved in a small amount of water. 3 lb of aqueous ammonia solution (s.g. 0.880) was then introduced into the mixture and the resulting gel dried to a granular consis-tency. There was no separation of the soluble and insoluble fractions following dissolution. The gel and dried product analysed as follows:
Ge Z 52.7% moisture 47.3% total solids 11.85% total nitrogen 9.0 pH
Dried Prod~ct (subjected to washing) 4.1% fixed nitrogen (residue) 13.26% soluble nitrogen (filtrate) A second 30-lb sample from the same area was treated in the same manner and ~he gel and dried product analysed as follows:
, . .
' - - ?
Q~
~eI 50.5% moisture 49.5% total solids 15.38% total nitrogen 9.21 pH
DYied Product 4.46% fixed nitrogen -12.51% soluble nitrogen EXAMPLE II .
Example I was repeated, except that no aqueous ammonia solution was introduced at the end. The gel and dried product analysed as follows:
; Ge ~ 49 .1% moisture ~ ;
50.9~ total solids 10.91% total nitrogen ~;
6.92 pH
Dried Product 4. % fixed nitrogen 11.09% soluble nitrogen EXAMPLE III
10 lb of brown coal from the Morwell-Yallourn area of Victoria, Australia, in finely-divided particulate form, was mixed with 3 lb of dry urea powder in a mill. No additional water was necessary. Following dissolution, l oz o sodium hy-droxide dissolved in a small amount of water was added to the mixture followed by 4 oz of H2O2 (100) Vol. 1 lb of aqueous i ammonia solution (s.g. 0~880) was then introduced into the mix-ture and the resulting gel dried to a granular consistency.
~, There was no separation of the soluble and insoluble fractions '~ following dissolution. The gel and the dried product analysed as follows:
~, :, ~
~Lf~Y77 ~
Ge ~ 4g . 8% moi~ture 50.2% total solids 11.38% total nitrogen 9.01 pH
Dried Product 3.95% fixed nitrogen 12.05% soluble nitrogen EXAMPLE IV
Example III was repeated, except that no ammonia was in-troduced at the end. Analyses of the resulting gel and dried product were similar to those above. -The products of Examples I to IV were shown to exhibit all the above-mentioned four properties, as well as being chemi- - ;
cally ~table in the dry state, thereby permitting normal packag-ing for transport purposes.
:,~
... , ., ,, . .... . . . . ~. :
Though any coal of low rank may be used, brown coal is , .. .. . . .. . . .
- ': , ~3~C~77 preferred, usually in amounts of from 60% to 80% by weight, based on the overall weight of reactants. Certain peats or peat coals may also be put to good use.
Simple experiment will determine the types of hydrotropic materials suitable for the present invention. Of the materials capable of conferring nitrogen to the fertilizer, urea is especi-ally suitable, preferably in amounts of from 18 to 22% by weight, based on the overall weight of reactants. Other suitable hydro-tropic materials include urea nitrate, urea peroxide, sugar, biu-ret and thiourea.
Oxidation may be carried out by means of conventional oxi-dants. For example, nitric acid, preferably concentrated commer-cial nitric acid, or hydrogen peroxide may be employed The amounts of nitric acid preferably range from 1.7 to 3% by weight and the amounts of hydrogen peroxide from 0.5 to 2.0 by weight.
~ Sodium hydroxide or potassium hydroxide are desirably introduced ; into the solution following or before addition of the oxidant, usually in amounts ranging from 0.4 to 1% by weight.
Ammonia is the preferred nitrogen-donating compound. 880 ammonia, namely concentrated (about 36%) ammonium hydroxide solu-tion having a density of 0.880 in amounts of from 5 to 7~ by weight are more preferred.
Oxidation establishes functional groups such as phenolic, ; carbonyl and carboxylic groups, which are capable of readily com-bining with the nitrogen-donating compound, preferably ammonia, to form a gel. On drying to a granular consistency, the gel is found to be slowly peptised in water. Analysis of the product reveals a nitrogen content of the order of 23 to 25%.
The invention will now be further illustrated by reference to the following examples.
:' ;; .
:: .. . :, . - ~
1~3~C)q7 EXAMPEE I
.
301b. of brown coal from the Morwell-Yallourn area of Victoria, Australia, was dissolved in a concentrated aqueous solu-tion of urea containing 91b. of urea. 12 02. of concentrated com-mercial nitric acid was then added to the solution followed by 30z. of sodium hydroxide. 31b. of ammonia (s.g. 0.88~ was then introduced into the solution and the resulting gel filtered off and dried to a granular consistency.
EXAMPLE II
lOlb. of brown coal from the Morwell-Yallourn area of Victoria, Australia, was dissolved in an aqueous solution of urea containing 31b. of urea. 102. of sodium hydroxide was then added to the solution followed by 1-40æ. of H202 (100) Vol. llb. of ammonia was then pumped into the solution and the resulting gel dried to a granular consistency.
The products of Examples I and II were shown to exhibit all the abovementioned four properties, as well as being chemic-ally ~table in the dry state, thereby permitting normal packag-ing for transport purposes.
Apart from providing a process of preparing such fertilizers, ' the present invention also provides a fertilizer whenever prepar-ed by such a process.
' "'.
` `' C
~ ~3~(~q7 SUPPLEMENTARY DISCLOSURE
Additional aspects of the invention described and claimed in the principal disclosure are hereinafter described.
In general, low rank coals such as lignite are known to enhance the desired formation of crumb structures of soil parti-cles and to impart porosity, aeration and water-absorption. How-ever, these coals may be so acidic that they can hardly be applied as they are without having detrimental effects upon plant life. Treatment of the coals is therefore necessary to render them satisfactory for purposes of addition to soil. - -One classical method for obtaining humates or humic acid involves treating coal with an aqueous sodium hydroxide extrac-tant. Humates are dissolved in the extracting solution and sepa- ;~
rated from insoluble tailings. The extractant may then be acidi- ~ -fied and humic acid precipitated. U.S. patent Specification No.
1~ 2,992,093 to E. M. Burdick discloses on~such treatment.
The aqueous caustic extraction system, though ef~fective, ; has been found to be objectionable because of the low concentra-tions of humic acid which are dissolved in the aqueous caustic extraction liquor. The maximum amount of humic acid which can be dissolved in the extraction liquor is about 8% by weight, and --this occurs only in strongly caustic solutions. In practice, be-cause of the low concentration of humic acid salts in the ex-tracting solution, large quantities of sodium hydroxide and water are necessary to recover humic acid in commercial operations.
In an effort to obtain more efficient recovery of the humic acid, other extraction systems have been attempted, such as flotation processes using a non-polar medium such as carbon tet-rachloride, and organic solvent extraction systems using ac~tone and water extracting mediums. While these processes are .
. ~. .
lQ3~77 effective, they are expensive to operate and require complicated purification techniques.
Humic acid itself contains carbon, hydrogen and oxyten atoms only, and finds use as a soil conditioner but not as a fer-tilizer because of the absence of any essential plant nutrients such as nitrogen, potassium or phosphorus. In preparing the humates, however, if ammonium hydroxide or potassium hydroxide are used as the extractant in place of sodium hydroxide, nitrogen or potassium becomes available for supply to plants. Here again, though, ammonium or potassium hydroxide are not particularly good extractants, being no better than sodium hydroxide in quantity of humus dissolved, which in turn means that little nitrogen or po-tassium is available for plant supply. Moreover, at least in the case of nitrogen, this is present predominantly in a form which is released at a fairly rapid rate. The nitrogen bearing compo-nents of the composition are rather easily dissolved in water.
Ammonium humates are thus not suitable where the aim is to pro-vide a fertilizer which will permit the slow release of nitrogen.
Coals have also been subjected to treatment with nitric acid, this giving rise to a compound commonly referred to as nitro humic acid. As with the aqueous caustic extractant, nitric acid is not a particularly effective extractant unless high con-centrations of nitric acid and high extraction temperatures are employed, and even then the maximum amount of humic acid ex-tracted is not very high. Nitro humlc acid contains little ni-trogen - generally little more than about 2% by weight, based on the overall weiyht of the acid- and the bulk of whatever nitrogen is available in water-soluble and in quick-release form.
In an endeavour to improve the fertilizer characteristics of nitro humic acid, the acid has been treated with such compounds . ~ ;
1~)3~ 77 as gaseous ammonia or urea. There is, however, no chemical reac-tion between the acid and the additive, and the resultant product is merely a physical admixture of the two components. The addi- ~- -tive serves to boost the overall nitrogen content, but yet again most of the nitrogen is in a water-soluble form available for quick release. In the case of the addition of ur~a, this addi-tive suffers the same failures as soluble nitrates, that is to ~l' say, it is too easily washed out of soil.
In contrast to the above extraction techniques - alkaline, organic and acidic - and their attendant disadvantages, it has now been found that coals of low rank may be extracted with an aque-ous urea solution, which is substantially neutral, with surpri-singly good results.
More particularly, one aspect of the present invention provides a process for the preparation of a nitrogenous composi- --tion suitable for use as a fertilizer, which process comprises treating a coal of low rank with a suitable hydrotropic solvent which is an aqueous solution of a nitrogen-conferring material which acts as a weak base to facilitate dissolution of the humus ~0 content of the coal; subjecting at least a portion of the thus-formed composition to oxidizing conditions; adding to at least a portion of the composition, either before or after the step of ` subjecting to oxidizing conditions, a member selected from the group of a nitrogen-donating compound, an alkali, and a mixture of the two; and removing water from the oxidized composition to form the nitrogenous composition.
- Another aspect of the invention provides a process for the preparation of a nitrogenous compound suitable for use as a ` fertilizer and a soil conditioner comprising the steps of:
30 treatlng a coal of low rank with an aqueous urea solution at ; - 7 -., 1(~3~7~
about room temperature, at least a part of the aqueous urea solu-tion being formed in situ by virtue of the initial moisture con-tent of the coal; subjecting the composltion thus formed to oxi-dizing conditions; introducing an alkali into the composition;
and removing the water from the oxidized composition to form the nitrogenous compound.
It is of importance to note that in the dissolution of the humus content of the coal in the aqueous urea solution there is no reaction of the urea and humus to form a soluble salt. The aqueous urea solution acts in the capacity of an extractant rather than reactant and in so doing renders the humus more amen-able to oxidation. Furthermore, the extract is acidic, the de-gree of acidity depending upon the initial pH of the coal to be treated.
As the rank of coal goes down so does the water content go up, and with coals of low rank the water content is generally within the range of 50% to 80% by weight, based on the total weight of coal. Thus, aqueous urea solution may be ormed in situ by the mixing of the low rank coal with dry urea. In some instances, where the water content of the low rank coal is low, say of the order of 50 to 55% by weight, it may be desirable to add ~ater to the coal and urea to boost the water content to about 60% by weight and so effect maximum dissolution.
The insoluble fraction of the coal is not generally sepa-rated from the soluble fraction, though it may be. Where there is no separation~ the insoluble fraction is carried through to ;~
the end product and, as far as can be established, has no adverse effects on that product.
The actual amount of coal employed in the process will be ~ 30 dependent upon the type of coal, since the proportion of humus ; .
;' lQ3~0~77 present varies from coal to coal. This amount can be readily de-termined by simple experiment. A preferred range, however, is 60% to 80~ by weight, based on the overall weight of reactants.
By this process it is possible to provide a fertilizer exhibiting the following properties~
(1) It permits a slow release of combined nitrogen, thus avoid-ing the high initial yield and following rapid fall-off in efficiency, characteristic of chemical fertilizers such as ammonium sulphate and prior humus extracts.
(2) It permits a retention of essential plant nutrients, such as phosphorus and iron, in an easily available form.
(3) It improves the water retention and heat absorbing capacity of the soil.
(4) It constitutes a buffer which prevents rapid changes in the acidity or alkalinity of soils.
Though any coal of low rank may be used, brown coal is preferred, usually in amounts of from 60~ to 80% by weight, based on the overall weight of reactants. The amount of coal may, of course, vary considerably, even outside of this range, and will depend on the amounts of the other reactants used. These latter amounts are set out hereinafter. Certain peats or peat coals may also be put to good use.
The coal should be in particulate form to facilitate dis-solution in the aqueous urea solution, and as might be expected the smaller the average particle size the less the time required for effecting dissolution.
The treat is preferably carried out at room temperature for the simple reason that elevated temperatures are only margin-ally better in terms of overall efficiency.
The urea is preferably present in an amount greater than ~' _ g _ ... . , ~ , ~
~3!~77 about 15% by weight based on the overal weight of the coal, added water (if any) and urea. Extraction is to a degree proportion-ately related to the amount of urea and the relative amounts of urea and water present, and in some instances amounts of urea less than 15~ by weight may give rise to an inferior end product because of incomplete dissolution. Preferably, the amount of urea is less than about 30% by weight since higher amounts in-crease cost without enhancing extraction efficiency and may re-sult in the presence o~ some unreacted urea in the final product.
It is found that urea is most preferably present in amounts of from about 18 to 22% by weight. This range appears to give opti- -mum extraction, bearing in mind cost and efficiency factors.
Oxidation may be carried out by means of conventional oxidants, although generally speaking solid and liquid oxidants are preferred to gaseous oxidants because of ease of handling.
By way of example, there is mentioned urea peroxide, sodium pero- ;~
xide, nitric acid and hydrogen peroxide. Needless to say, the oxidant should not be one having one or more elements which are toxic to basic plant life. Nitric acid, particularly concentra-ted commercial nitric acid, and hydrogen peroxide are most pre-ferred.
The amounts of nitric acid preferably range from about 1.5 to 5% by weight, based on the overall weight of reactants.
Oxidation will proceed with amounts below about 1.5% by weight, ~, but it may with some coals be incomplete so that not all of the humus content is utilized in the process. There is little advan-tage in using more than about 5% by weight of nitric acid when increased efficiency is balanced against increased material costs. A range of 1.7 to 3% by weight is generally quite satis-factory.
i :
~ -- 10 --: ,.. , , , ; ~
9~77 : ~
The amounts of hydrogen peroxide preferably range from about 0.5 to 3.0~ by weight, based on the overall weight of reac-tants, the upper and lower limits being determined by the same factors as mentioned above in relation to nitric acid. Generally, up to 2% by weight will suffice.
Oxidation establishes functional groups such as phenolic, carbonyl and carboxylic groups on the humic acid molecules, which are capable of readily combining simultaneously with the NH
groups which are a product of the oxidation of the urea, and the ammonia, if present, to form a gel. On drying to an effectively dry granular consistency suitable for packaging and shipping, the gel is found to be slowly peptised in water.
The alkali is preferably selected from the group consist-ing of sodium hydroxide, potassium hydroxide and ammonia, and is introduced after the dissolving step and either before or after the step of subjecting the solution to oxidizing conditions. The amount of alkali will be largely dictated by the amount of oxi-dant, but usually the alkali is added in an amount ranging from 0.4 to 1~ by weight when either sodium hydroxide or potassium hydroxide, and from 5 to 7% by weight when ammonia. With ammonia there is the additional benefit of a compound which is able to confer further nltrogen to the end product. In some instances, -s ammonia and either of the alkali metal hydroxides may be added.
The amount of total nitrogen and fixed nitrogen in the end product is a function of the nature of the coal used as the starting material and the amount of functional groups provided by that coal. Where ammonia is used, however, the final product will usually contain from about 15 to 25~ by weight of nitrogen of which about 4 to 6% is essentially water-insoluble and avail-able for slow release. Where ammonia is not used, the final ..... ~. . ~
- .
1~3~ 7 product may still contain upwards of about 10% by weight of ni-trogen, 4 to 6% being essentially water-insoluble and available for slow release. When the oxidant is nitric acid, the alkali preferably is added after the oxidant, whereas the reverse is the case where hydrogen peroxide is employed as the oxidant.
~ he invention will now be further illustrated by refer-ence to the following examples.
EXAMPLE I
a 30-lb sample of brown coal from the Morwell-Yallourn area of Victoria, Australiaf in finely-divided form, was mixed with 9 lb of dry urea powder in a mill. No additional water was necessary. Following dissolution, 12 oz of concentrated commer-cial nitric acid ~7as added to the mixture followed by 3 oz of sodium hydroxide dissolved in a small amount of water. 3 lb of aqueous ammonia solution (s.g. 0.880) was then introduced into the mixture and the resulting gel dried to a granular consis-tency. There was no separation of the soluble and insoluble fractions following dissolution. The gel and dried product analysed as follows:
Ge Z 52.7% moisture 47.3% total solids 11.85% total nitrogen 9.0 pH
Dried Prod~ct (subjected to washing) 4.1% fixed nitrogen (residue) 13.26% soluble nitrogen (filtrate) A second 30-lb sample from the same area was treated in the same manner and ~he gel and dried product analysed as follows:
, . .
' - - ?
Q~
~eI 50.5% moisture 49.5% total solids 15.38% total nitrogen 9.21 pH
DYied Product 4.46% fixed nitrogen -12.51% soluble nitrogen EXAMPLE II .
Example I was repeated, except that no aqueous ammonia solution was introduced at the end. The gel and dried product analysed as follows:
; Ge ~ 49 .1% moisture ~ ;
50.9~ total solids 10.91% total nitrogen ~;
6.92 pH
Dried Product 4. % fixed nitrogen 11.09% soluble nitrogen EXAMPLE III
10 lb of brown coal from the Morwell-Yallourn area of Victoria, Australia, in finely-divided particulate form, was mixed with 3 lb of dry urea powder in a mill. No additional water was necessary. Following dissolution, l oz o sodium hy-droxide dissolved in a small amount of water was added to the mixture followed by 4 oz of H2O2 (100) Vol. 1 lb of aqueous i ammonia solution (s.g. 0~880) was then introduced into the mix-ture and the resulting gel dried to a granular consistency.
~, There was no separation of the soluble and insoluble fractions '~ following dissolution. The gel and the dried product analysed as follows:
~, :, ~
~Lf~Y77 ~
Ge ~ 4g . 8% moi~ture 50.2% total solids 11.38% total nitrogen 9.01 pH
Dried Product 3.95% fixed nitrogen 12.05% soluble nitrogen EXAMPLE IV
Example III was repeated, except that no ammonia was in-troduced at the end. Analyses of the resulting gel and dried product were similar to those above. -The products of Examples I to IV were shown to exhibit all the above-mentioned four properties, as well as being chemi- - ;
cally ~table in the dry state, thereby permitting normal packag-ing for transport purposes.
:,~
... , ., ,, . .... . . . . ~. :
Claims (29)
1. A process for the preparation of a nitrogenous fertilizer, which process comprises treating a coal of low rank with a suit-able hydrotropic solvent which is an aqueous solution of a nito-gen-conferring material which acts as a weak base to dissolve at least a substantial amount of the humus content of the coal, which content is otherwise sparingly soluble in water, subjecting the thus formed solution to oxidising conditions, adding a nitrogen-donating compound to the oxidised solution so as to form a gel, and drying the gel.
2. A process according to claim 1, wherein the hydrotropic solvent is formed in situ.
3. A process according to claim 1, wherein the coal is pre-sent in an amount of from 60% to 80% by weight, based on the over-all weight of reactants.
4. A process according to claim 1, wherein the coal is brown coal.
5. A process according to claim 1, wherein the nitrogen-con-ferring material is selected from the group consisting of urea, urea nitrate, urea peroxide, biuret and thiourea.
6. A process according to claim 1, wherein the hydrotropic solvent is urea, present in an amount of from 18 to 22% by weight, based on the overall weight of reactants.
7. A process according to claim 1, wherein the solution is oxidised by means of nitric acid or hydrogen peroxide.
8. A process according to claim 7, wherein nitric acid is employed in an amount of from 1.7 to 3% by weight, based on the overall weight of reactants.
9. A process according to claim 7, wherein hydrogen peroxide is employed in an amount of from 0.5 to 2.0 by weight, based on the overall weight of reactants.
10. A process according to claim 1, wherein an alkali is intro-duced into the solution either before or after the solution is subjected to oxidising conditions.
11. A process according to claim 10, wherein the alkali is sodium or potassium hydroxide, present in an amount of from 0.4 to 1% by weight, based on the overall weight of reactants.
12. A process according to claim 1, wherein the nitrogen-donat-ing compound is ammonia.
13. A process according to claim 12, wherein the ammonia is 880 ammonia, present in an amount of from 5 to 7% by weight, based on the overall weight of reactants.
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
14. A process for the preparation of a nitrogenous composi-tion suitable for use as a fertilizer, which process comprises treating a coal of low rank with a suitable hydrotropic solvent which is an aqueous solution of a nitrogen-conferring material which acts as a weak base to facilitate dissolution of the humus content of the coal; subjecting at least a portion of the thus formed composition to oxidising conditions; adding to at least a portion of the composition, either before or after the step of subjecting to oxidising conditions, a member selected from the group of a nitrogen donating compound, an alkali, and a mixture of the two; and removing water from the oxidised composition to form the nitrogenous composition.
15. A process according to claim 14 for the preparation of a nitrogenous composition suitable for use as a fertilizer and a soil conditioner and having a substantial nitrogen content of which a significant amount is in insoluble, slow-release form, wherein said hydrotropic solvent is an aqueous urea solution and said member added to at least a portion of the composition is an alkali.
16. A process according to claim 15, wherein the urea is present in an amount of from 18 to 22% by weight, based on the weight of the coal, water and urea.
17. A process according to claim 15, wherein at least a portion of the composition is oxidised by means of an oxidising agent selected from the group consisting of nitric acid and hydro-gen peroxide.
18. A process for the preparation of a nitrogenous composi-tion suitable for use as a fertilizer and a soil conditioner com-prising the steps of:-treating a coal of low rank with an aqueous urea solu-tion at about room temperature, at least a part of the aqueous urea solution being formed in situ by virtue of the initial mois-ture content of the coal;
subjecting the composition thus formed to oxidising conditions;
introducing an alkali into the composition; and removing water from the oxidised composition to form the nitrogenous composition.
subjecting the composition thus formed to oxidising conditions;
introducing an alkali into the composition; and removing water from the oxidised composition to form the nitrogenous composition.
19. A process according to claim 18, wherein the urea is present in an amount of from 18 to 22% by weight, based on the weight of the coal, water and urea.
20. A process according to claim 18, wherein the composition is oxidised by means of an oxidising agent selected from the group consisting of nitric acid and hydrogen peroxide.
21. A process according to claim 15 or 18, wherein the alkali is selected from the group consisting of sodium hydroxide, potassium hydroxide and ammonia.
22. A process according to claim 17 or 20, wherein the oxidising agent is nitric acid and the alkali is added after the oxidising agent.
23. A process according to claim 17 or 20, wherein the oxidising agent is hydrogen peroxide and the alkali is added before the oxidising agent.
24. A nitrogenous composition suitable for use as a ferti-lizer and a soil conditioner and being prepared by the process of claim 14, the composition containing from about 19% to 25% by weight of nitrogen of which about 4% to 6% by weight is in insoluble and slow-release form.
25. A process for preparation of a nitrogenous composition suitable for use as a soil conditioner and slow release fertilizer containing about 4% or more of essentially water insoluble nitro-gen compounds comprising the steps of: -contacting a coal of low rank containing about 50% or more water with urea whereby an aqueous composition containing urea and humus is formed;
subjecting the composition to oxidising conditions;
introducing alkali into the composition; and removing water from the composition to form an effec-tively dry nitrogenous fertilizer composition.
subjecting the composition to oxidising conditions;
introducing alkali into the composition; and removing water from the composition to form an effec-tively dry nitrogenous fertilizer composition.
26. A process according to claim 25, further comprising the step of adding water to the coal and urea, when the coal contains no more than about 55% water, to bring the total water to at least about 60%.
27. A process according to claim 14, wherein the composition is oxidised by means of from about 1.5 to about 5% by weight of nitric acid based on the weight of the reactants.
28. A process according to claim 14, wherein the composition is oxidised by means of from about 0.5 to about 3% by weight of hydrogen peroxide based on the weight of the reactants.
29. A process for the preparation of a nitrogenous composi-tion suitable for use as a fertilizer and soil conditioner com-prising the steps of:-treating a coal of low rank with an aqueous urea solu-tion, to dissolve at least a substantial amount of the humus content of the coal, the amount of urea present being from 18 to 22% by weight based on the weight of coal, water and urea;
subjecting the solution thus formed to oxidation with an oxidising agent selected from the group consisting of nitric acid, in an amount of from 1.5 to 5.0% by weight, based on the overall weight of reactants, and hydrogen peroxide, in an amount of from 1.7 to 3% by weight based on the overall weight of the reactants;
introducing into the solution an alkali selected from the group consisting of sodium hydroxide, and potassium hydroxide in an amount ranging from 0.4% to 1% by weight, based on the total weight of reactants, and ammonium hydroxide, in an amount from 5 to 7% by weight, based on the total weight of reactants;
and removing water from the oxidised solution to form a nitrogenous composition containing from about 10 to 25% by weight of nitrogen of which at least about 4% to 5% by weight is in insoluble and slow-release form.
subjecting the solution thus formed to oxidation with an oxidising agent selected from the group consisting of nitric acid, in an amount of from 1.5 to 5.0% by weight, based on the overall weight of reactants, and hydrogen peroxide, in an amount of from 1.7 to 3% by weight based on the overall weight of the reactants;
introducing into the solution an alkali selected from the group consisting of sodium hydroxide, and potassium hydroxide in an amount ranging from 0.4% to 1% by weight, based on the total weight of reactants, and ammonium hydroxide, in an amount from 5 to 7% by weight, based on the total weight of reactants;
and removing water from the oxidised solution to form a nitrogenous composition containing from about 10 to 25% by weight of nitrogen of which at least about 4% to 5% by weight is in insoluble and slow-release form.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA179,757A CA1039077A (en) | 1973-08-28 | 1973-08-28 | Nitrogenous fertilizers |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA179,757A CA1039077A (en) | 1973-08-28 | 1973-08-28 | Nitrogenous fertilizers |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1039077A true CA1039077A (en) | 1978-09-26 |
Family
ID=4097674
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA179,757A Expired CA1039077A (en) | 1973-08-28 | 1973-08-28 | Nitrogenous fertilizers |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1039077A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4846870A (en) * | 1988-05-09 | 1989-07-11 | Soilizer Corporation | Fertilizer and/or soil amendment |
| US4919702A (en) * | 1988-05-09 | 1990-04-24 | Soilizer Corporation | Fertilizer and/or soil amendment |
| US5451240A (en) * | 1991-11-19 | 1995-09-19 | Trowbridge; Robert | Compositions for stimulating plant growth; their preparation and usage |
-
1973
- 1973-08-28 CA CA179,757A patent/CA1039077A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4846870A (en) * | 1988-05-09 | 1989-07-11 | Soilizer Corporation | Fertilizer and/or soil amendment |
| US4919702A (en) * | 1988-05-09 | 1990-04-24 | Soilizer Corporation | Fertilizer and/or soil amendment |
| US5451240A (en) * | 1991-11-19 | 1995-09-19 | Trowbridge; Robert | Compositions for stimulating plant growth; their preparation and usage |
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