An adsorbent that can be used to remove environmental contaminants such as organics, cations and anions in a single process step is prepared from humic acid. The adsorbent can be a soluble humic acid in liquid form (e.g., in aqueous solution) or the humic acid can be insolubilized and/or immobilized on a solid support. The adsorbent can also be used to recover agriculturally desirable metals in chelated form from contaminated water. The liquid form of the adsorbent can be used to wash solids to remove contaminants.

FIELD OF THE INVENTION 
The present invention is directed to an adsorbent based on humic acid which 
can be used to remove metals, radionuclides, and/or organic materials 
generally present as an environmental contaminants at a variety of sites. 
BACKGROUND OF THE INVENTION 
Heavy metal and organic contamination of soils, building and equipment 
systems is a major environmental concern at both industrial and government 
sites. The contamination is primarily due to improperly disposed 
industrial wastes. The presence of toxic heavy metal ions, volatile 
organic compounds and pesticides in the environment is of great concern 
and could affect worker safety as well as the safety of drinking water and 
air for the general public. 
Federal and state pollution control standards for heavy metal content of 
mineral-producing discharges and for other types of waste disposal have 
become more and more stringent. In addition, acid mine runoff contaminated 
with dissolved metals from abandoned mines contributes to environmental 
degradation. Other sources of contamination include discharge from federal 
facilities, e.g., military weapons complexes, which are a source of 
metals, organics, and radionuclides. Additional sources of contamination 
include oil and gas exploration and production operations. Where dissolved 
metals must be removed from such a waste stream prior to discharge, 
precipitation is the most common method, generally precipitating the 
metals by adding calcium oxide. Although calcium oxide addition is 
relatively simple and cheap, this method results in a great volume of 
sludge which is costly and hazardous to dispose of. Moreover, because of 
incomplete reaction, the effluent is often not completely removed from the 
water, and the metal values are not recovered and are thereby wasted. 
Also, the precipitation layer in settling ponds undergoes an inversion at 
temperatures around 4.degree. C. 
Many waters are contaminated with mixed wastes, which conventionally are 
treated with activated carbon followed by elution through ion exchange 
resin columns. Because these two methods operate on different principles, 
both technologies are applied sequentially, rather than simultaneously. 
This conventional technology is very expensive and cumbersome to use. 
In Bureau of Mines Report of Investigations, 9200, Pahlman et al. describe 
the use of lignochemicals and humic acids to remove heavy metals from 
process waste streams. The sodium salt of lignin and the humic acids of 
peat, lignite, and subbituminous coal were found to be excellent at 
removing the more toxic heavy metals ions, including Cd.sup.+2, Pb.sup.+2 
and Hg.sup.+2, while calcium oxide addition was found to be poor to fair 
for their removal. However, the coagulability of the heavy metal 
sequestrates of the lignin sodium salt at pH 7 makes removal less 
efficient and causes difficulty in filtration. 
Pahlman et al. found that a mixture of three humic acids has a particular 
affinity for Cd.sup.+2, Hg.sup.+2 and Pb+2, and can be used to effect 
almost total removal of these ions from waste streams. The humic acids 
used were prepared by caustic treatment of a North Dakota lignite, a 
Montana subbituminous coal, and a Minnesota peat. 
Alexander, in U.S. Pat. No. 5,034,045, describes a method for improving 
agricultural crop yields using a mixture of a water-soluble alkali metal 
salt of humic acid and plant nutrient components such as nitrogen, 
potassium, and/or phosphorus. In this case, the oxidized sites of humic 
acid are filled with non- volatile alkali metal ions that maintain the 
water solubility of the humate salt used. 
Moran, in U.S. Pat. No. 4,459,149, discloses a process for treating humus 
materials comprising freeing humic acid from the combined state in which 
it frequently exists in humus materials, dispersing it as a fine, 
insoluble solid in acid process water, separating it from the impurities 
with which it is associated, and recovering it as a high solids filter 
cake. The humic acid can be solubilized by mixing with solubilizing agent 
such as alkaline salts and the like. Insoluble humates are obtained by 
adding a metal compound to a humate solution. 
Muir, in U.S. Pat. No. 4,952,229, discloses a soil and foliar supplement 
for plants comprising a quantity of specific microbes and an organic acid 
such as humic acid, fulvic acid and ulvic acid, along with optional trace 
minerals and chelated micronutrients. 
Although activated carbon is very effective in removing organic compounds, 
it is associated with high capital and operating costs, especially when 
regeneration is effected by the most effective process, thermal 
reactivation. Also, this technique is very sensitive to the presence of 
suspended solids, oil and grease, requiring pretreatment for effective 
performance. 
Although conventional means for decontaminating surface and groundwater 
include a broad spectrum of treatment options such as precipitation, 
ion-exchange, microbial digestion, membrane separation, activated carbon 
absorption, etc., the state of the art technologies can in one pass 
remediate only one class of contaminants, i.e., either volatile organic 
compounds using activated carbon or heavy metals using ion exchange. This 
requires the use of at least two different stepwise processes to remediate 
a site. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to overcome the aforesaid 
deficiencies in the prior art. 
It is an object of the present invention to provide an adsorbent which 
adsorbs anions, cations, and volatile organic compounds from contaminated 
objects and sites, such as from water, equipment, buildings, soil, ground 
water, oil and gas exploration and production sites, and similar sites. 
It is another object of the present invention to provide a method to remove 
organic compounds metal ions, and anions when present, either singly or in 
combination, from waste, process, or runoff streams. 
Another object of the present invention is to recover agriculturally 
valuable metals from contaminated waters and to market the metals as 
chelated micronutrients. 
Still another object of the present invention is to recover commercially 
valuable metals from contaminated waters. 
According to the present invention, a sorbent is provided that can be used 
to treat organic compounds, or both organics and metal ions in a single 
process step or in a series of steps. As compared to conventional methods 
of reclamation, which include separate steps using, e.g., both carbon 
adsorption and ion exchange resins, the process of the present invention 
is less expensive and easier for treating all types of process streams. 
The adsorbent of the present invention is based upon humic acid. The humic 
acid may be used either in a water soluble or water insoluble form, 
depending upon the contaminants to be removed, the concentration of the 
contaminants, and the use to which the adsorbent/contaminants complex is 
to be put. If the water stream to be cleaned contains metal ions useful 
for agricultural purposes, such as iron, zinc, copper, boron, manganese, 
magnesium, molybdenum and other agriculturally useful metals in high 
enough concentration to be economically recoverable, then the method of 
recovery comprises mixing water soluble humic acid with the water to be 
cleaned. The water soluble humic acid will chelate the metals to be 
recovered and form an insoluble humate. The insoluble humate is recovered 
from the water by sedimentation followed by filtration or other separation 
means and is useful as a source of chelated micronutrients for 
agriculture. If the agriculturally viable metal content of the 
contaminated water is too low for economic recovery, or if the metals are 
not useful for agriculture such as lead, chromium, mercury or the like, 
then a water insoluble form of humic acid can be used. Once the humic acid 
has been cross-linked and its solubility decreased, the metal ions are 
retained on the insolubilized humic acid. The cross-linked humic acid can 
be further insolubilized by immobilization on a carrier such as a gel. 
To prepare the absorbent according to the present invention, humic acid is 
purified by acid precipitation followed by dissolution in distilled water 
at a pH of approximately 7. This dissolution and precipitation is 
repeated, after which the precipitated humic acid is washed with a 
suitable buffer and filtered through an appropriate filtration device. 
Alternatively, the precipitated humic acid is washed by centrifugation and 
resuspension of solid humic acid. After washing, the material is dried 
overnight at temperatures from about 60-70.degree. C. The dried material 
is then water-insolubilized, although it is still capable of adsorbing 
metals or organics. The water insoluble adsorbent can be rendered soluble 
by contact with monovalent metal ions. 
In order to make humic acid insoluble at higher pH, the humic acid is 
cross-linked with conventional cross-linking agents such as aldehyde 
cross-linking agents, e.g., glutaraldehyde, or with at least one 
oxidoreductase enzyme. 
The solubility of cross-linked humic acid can be lowered further and its 
handling properties improved by immobilization in a solid support such as 
a matrix or gel.

DETAILED DESCRIPTION OF THE INVENTION 
Several humic acid products are available from ARCTECH, Inc. under the 
trade name HUMASORB. Of these, HUMASORB-L.TM. is a liquid, whereas 
HUMASORB-S.TM. and HUMASORB-CS.TM. are solids. Humasorb-S.TM. dissolves in 
water at elevated pH under certain conditions, such as in the presence of 
monovalent species. HUMASORB-CS.TM. is a cross-linked derivative of 
HUMASORB-L.TM./HUMASORB-S.TM. designed to lower solubility of the humic 
acid at higher pH, while retaining the properties of contaminant removal. 
The humic acid adsorbent of the present invention is useful in minimizing 
and reducing the volume of metal-, inorganic ion- and organic-contaminated 
water, wastewater, and soil. The insolubilized purified humic acids are 
particularly useful in treating all types of water because in one step 
they adsorb cations as well as organic molecules, with no requirement for 
sludge dewatering. Of particular importance is that the insolubilized 
purified humic acid can be used to reduce metals present as anions to the 
cationic state for removal by chelation or ion exchange, e.g., Cr(VI) to 
Cr(III). Only one secondary waste stream is generated. That secondary 
waste stream, which is primarily composed of combustible organic 
materials, can be further reduced by thermal destruction technologies to 
achieve a volume reduction of 100 to less than 1. 
Humic acid is a natural material with many properties which can be 
exploited for several cost effective applications. Humic substances are 
complex mixtures of naturally occurring organic materials. These 
substances are formed from the decay of plant and animal residues in the 
environment. Humic acid constitutes a significant portion of the acid 
radicals found in humic substances. 
Humic acid is dark brown to black in color and is considered to be a 
complex aromatic macromolecule with various linkages between the aromatic 
groups. The different compounds involved in linkages include amino acids, 
amino sugars, peptides, aliphatic acids and other aliphatic compounds. The 
carboxylic, phenolic, aliphatic and enolic-hydroxyl and carbonyl are the 
various functional groups in humic acid. Humic acid is an association of 
molecules forming aggregates of elongated bundles of fibers at low pHs and 
open flexible structures perforated by voids at high pHs. The voids can 
trap and adsorb both organic and inorganic particles if the charges are 
complementary. 
Humic acid has a large cation exchange capacity and holds both monovalent 
and multivalent elements very strongly. The molecular weight of humic acid 
ranges from about 800 daltons to about 500,000 daltons, with the weight 
average molecular weight being from about 5000 daltons to about 50,000 
daltons. The cation exchange capacity of humic acid varies from about 200 
to about 500 meq CaCO.sub.3 per 100 grams at pH 7, depending upon the 
source of the humic acid. 
Humic acid is a polyelectrolyte, and is believed to form complexes with 
clay particles. When the cation exchange sites on the humic acid molecule 
are filled predominantly with hydrogen ions, the material, which is 
considered to be an acid, is insoluble in water. However, when the 
predominant cations at the exchange sites are other than hydrogen, the 
material is called a humate. Humates of the monovalent alkali metals or 
ammonia are soluble in water, but the humates of most multivalent metals 
are insoluble. 
The sorption of chemicals onto the surfaces of humic substances has been 
studied by a large number of environmental chemists. Sorption mechanisms 
are defined to include Vander Waals attractions, hydrophobic bonding, 
hydrogen bonding, charge transfer, ion exchange, and ligand exchange. 
A major source of humic acid is coal--the most abundant and predominant 
product of plant residue coalification. All ranks of coal contain humic 
acid but lignites represent the most easily available and concentrated 
form of humic acid. Humic acid concentration of lignite varies from 
30-90%, depending upon location. Peat, humates and sewage sludge also 
contain significant quantities of humic acid. 
actosol.RTM. is manufactured by ARCTECH, Inc. of Chantilly, Va. as a soil 
amendment product. actosol.RTM. is a family of products based upon humic 
acid extracted from low rank coals, such as leonardite. HUMASORB.TM., 
derived from actosol.RTM., has the ability to adsorb organic material, 
capture metal ions, and capture radionuclides and anions. Because of the 
distribution of its functional groups, humic acid has cation exchange 
sites needed for the chelation and removal and/or recovery of metals. The 
metal binding capacity of humic acid is a function of pH. In addition, 
humic acid readily removes organics from waste waters through a physical 
adsorption phenomenon in a fashion similar to that of activated carbon. 
Humic acid was isolated and purified from actosol.RTM. by acidification 
using concentrated hydrochloric acid to lower the pH below about 2. The 
precipitated solids were purified by repeated washing with distilled water 
and acidification. A pressure filter (60 psig) was used to separate the 
precipitated humic acid from the other humic substances dissolved in 
water. The amount of humic acid recovered ranged from about 11.79% to 
about 14.79% by weight of actosol.RTM.. 
Humic acid can be insolubilized by two different methods. In one method, 
multivalent metals are complexed or chelated to humic acid to insolubilize 
the humic acid. These can be metals such as iron, aluminum, copper, 
manganese, lead, cadmium, mercury, chromium or other multivalent metals. 
Although univalent metals such as potassium, sodium and the like usually 
produce soluble complexes or chelates, when the cation is the hydronium 
ion (H+), the humic acid is insoluble in water. 
The other method for producing insoluble humic acid is to polymerize or 
cross-link the humic acid. By cross-linking humic acid, a water-insoluble 
polymer is formed which lowers the solubility of the adsorbent as the pH 
is increased. The active groups of the humic acid are protected by 
calcium. The cross-linked humic acid has a low solubility in water after 
cross-linking at near neutral pH even in the presence of sodium ions. 
Any conventional cross-linking agent can be used to cross-link the humic 
acid to produce an insoluble product, e.g., HUMASORB-CS.TM.. Among the 
cross-linking agents that can be used to produce HUMASORB-CS.TM. are 
aldehydes and oxidoreductase enzymes. These products showed significantly 
lower solubility at higher pH, as shown in FIG. 1. For example, when 
glutaraldehyde or a mixture of glutaraldehyde and mineral acid (HCl, 
HNO.sub.3, H.sub.2 SO.sub.4, H.sub.3 PO.sub.4, etc.) is used, the 
resulting cross-linked humic acid has a low solubility in water at near 
neutral pH in the presence of sodium ions. 
Among the aldehydes that can be used for cross-linking humic acid are 
aliphatic or aromatic aldehydes having from 1 to 22 carbon atoms. The 
aldehydes may be substituted with any substituent that does not adversely 
affect the cross-linking capabilities of the aldehydes. The aldehydes may 
be saturated or unsaturated. The aldehyde may be an aromatic aldehyde, 
such as benzaldehyde, tolualdehyde (o-, m-, or p-) or salicylaldehyde. 
Any type of oxidoreductase enzyme can be used to cross-link the humic acid, 
including peroxidases and hydrogenases. 
The cross-linking is effected by reacting the humic acid with the aldehyde 
or oxidoreductase enzymes such as peroxidase enzymes at room temperature 
or slightly above room temperature for a period of two to five hours. 
Not only does HUMASORB-CS.TM. retain the metal sorption capacity of humic 
acid after cross-linking, the metal sorption capacity of humic acid is 
greatly increased by virtue of the cross-linking. 
In order to lower the solubility of cross-linked humic acid even further, 
the cross-linked humic acid can be immobilized within a solid support, 
such as a gel or other matrix. Both soluble humic acid and insoluble 
(i.e., cross-linked) humic acid can be immobilized. Any type of inert 
gel/matrix or other insoluble material can be used to form a solid support 
for the humic acid adsorbent. Among the types of entrapment media which 
can be used are alginates, cross-linked dextran gels, agar, gellan, 
chitosan and curdlan. Other types of supports can be used to immobilize 
the humic acid adsorbent, including supports used for microorganisms in 
fermentation processes which are well known to those skilled in the art. 
Among these immobilizing supports are polystyrene beads, acrolein beads, 
and the like. The support, of course, does not enter into the adsorption 
process, but merely suspends the adsorbent in the liquid to aid the 
adsorbent's contacting the contaminants to be adsorbed. 
The preferred matrix for immobilizing any form, solid or liquid, of humic 
acid is a gel, such as calcium/alginate matrix/gel. The immobilization 
process produces beads of immobilized humic acid adsorbent encapsulated in 
a calcium/alginate matrix/gel which has a significantly lower solubility 
than the un-immobilized humic acid. When the immobilized HUMASORB.TM. is 
contacted with the contaminated water, the contaminated water diffuses 
through the matrix to contact the HUMASORB.TM.. Although there may be some 
diffusion limitations, these are expected to be negligible. The 
immobilized product was found to be effective in removing Cr.sup.+3 from 
simulated waste streams in both batch and column studies. The solubility 
characteristics of the immobilized product are compared with other forms 
of humic acid adsorbent in FIG. 10. 
For treating water containing agriculturally desirable metals according to 
the present invention, soluble humic acid, such as HUMASORB-L.TM., is 
admixed with water. When the humic acid contacts the multivalent metals in 
solution, an ion exchange complexation reaction occurs, chelating the 
multivalent metals. The multivalent metal chelated complex is insoluble in 
water and coagulates, settling out as a floc. 
The soluble humic acid, such as HUMASORB-L.TM., can be used to 
decontaminate soils and various structural material and equipment. The 
decontamination is easily accomplished by rinsing the contaminated soil or 
equipment with HUMASORB-L.TM. and separating the spent HUMASORB-L.TM.. 
Similarly, contaminated structural materials can be washed with 
HUMASORB-L.TM. to remove the contaminants. The spent HUMASORB-L.TM. from 
these operations can be further precipitated and separated for final 
disposal. 
Soluble humic acid, such as HUMASORB-L.TM., can be used to recover 
desirable metals for use as fertilizers. A study was conducted to recover 
micronutrients and remove toxic metals such as cadmium using a two-step 
process based upon HUMASORB-L.TM.. This study was conducted using 
contaminated water from a Superfund Site, which was representative of 
acidic water with large quantities of heavy metals dissolved therein. As 
part of this study, micronutrients recovered from the contaminated water 
were used in a fertilizer composition marketed as actosol.RTM. by ARCTECH, 
Inc. 
EXAMPLE 1 
In the study to remove heavy metals such as cadmium from contaminated 
water, an actual field waste stream was treated. Using the adsorbent 
according to the present invention HUMASORB.TM., nearly 98% of the copper 
and iron in the contaminated water was captured for use as fertilizer 
micronutrients, and significant percentages of other micronutrients such 
as zinc, manganese, and magnesium were captured as well. Toxic heavy 
metals such as cadmium and arsenic were removed to levels below the 
detection limit of standard laboratory tests before the water was 
discharged. Table 1 shows a comparison of the metals present in the 
contaminated water before and after the treatment was conducted: 
TABLE 1 
______________________________________ 
Raw Water Treated Water 
Metals ppm ppm 
______________________________________ 
Aluminum 255 7.87-B 
Arsenic 0.513 0.151-U 
Cadmium 1.99 0.0715-B 
Copper 198 0.287-B 
Iron 982 0.602-B 
Magnesium 417 271 
Manganese 195 52.4 
Potassium 9.21-B 3990 
Zinc 555 48.1 
______________________________________ 
B: Below method detection limit 
U: Undetected 
As shown in Table 1, aluminum, arsenic, cadmium, copper and iron were 
either undetected or below the method detection limit. The increase in the 
concentration of potassium in the treated water is believed to be due to 
the exchanges of metals in the contaminated water with potassium present 
in HUMASORB-L.TM.. This treatability study demonstrated that adsorbent of 
the present invention is useful for treatment and resource recovery of 
acidic, heavy metal laden waters. 
The soluble humic acid product of the present invention can be used to tie 
up contaminants in the water, such as heavy metals. FIGS. 1 and 2 show the 
use of HUMASORB-L.TM. to remove barium, uranium, cadmium, copper and 
nickel from water. 
For treating waters that do not contain sufficient amounts of 
agriculturally desirable metals to make it economically feasible to 
attempt recovery of such metals, or if the water contains undesirable 
metals or organic contamination, or both, insoluble cross-linked humic 
acid is used and the contaminated water is passed through a column of the 
adsorbent of the present invention to remove the undesired contaminants. 
For treating waters containing agriculturally desirable metals, the 
HUMASORB-L.TM. is mixed with the metal containing water. When the humic 
acid contacts the metals in solution, an ion exchange/complexation 
reaction occurs. Insoluble humates are formed which are then recovered as 
chelated micronutrients by sedimentation followed by filtration. The 
amount of HUMASORB-L.TM. to use will vary depending on the concentration 
of desirable metals in the contaminated water, and must be determined by 
experimentation. The amount of HUMASORB-L.TM. to be used can readily be 
determined by one skilled in the art without undue experimentation. 
The adsorbent of the present invention treats organics, metal ions and 
anions in a single process step. When the adsorbent is used to treat 
waters containing agriculturally useful metals or micronutrients, the 
products of the treatment are marketable as a soil amendment product. When 
the adsorbent of the present invention is compared to carbon adsorption 
and ion exchange resins in terms of performance and cost savings, the 
adsorbent of the present invention is the method of choice. 
For treating waters that do not contain sufficient amounts of 
agriculturally desirable metals, or if the water contains undesirable 
metals or organic contamination, insoluble (i.e., cross-linked) humic acid 
(e.g., HUMASORB-CS.TM.) is used and the contaminated water is passed 
through a column of the insoluble adsorbent. 
The adsorbent of the present invention is useful in removing metal ions 
such as Fe.sup.3+, Al.sup.3+. Cr.sup.3+, Pb.sup.2+, Cu.sup.2+, Zn.sup.2+, 
Co.sup.2+, Hg.sup.+, Cd.sup.2+, Ni.sup.2+, and Mn.sup.2+, either singly or 
together. Because the adsorbent of the present invention also adsorbs 
organics and removes metals present as anions as well as cations, no 
separate treatment with activated carbon or with an anion exchange resin 
is required to remove all contaminants from the material treated. 
Precipitates formed between metal ions and the adsorbent of the present 
invention are compact and noncolloidal. The volume of their sludge is 
sharply reduced in comparison to that of finely dispersed calcium oxide 
precipitates, which have conventionally been used for treating waste 
streams. Therefore, it is easy to remove the precipitates formed by 
adsorbents of the present invention by simple filtration or settling. If 
it is desired to recover the metal values sequestered in the adsorbent, it 
is possible to elute these metal values from the precipitates with an 
appropriate acid. This is not possible with conventional calcium oxide 
precipitation of heavy metals. 
The humic acid based adsorbent of the present invention may be used in 
either soluble or insoluble form, either alone or in admixture with other 
forms of humic acid according to the present invention. Anions such as 
nitrate or nitrite or similar anions are weakly adsorbed due to the 
charged nature of the humic acid molecule and the multitude of active 
(charged) sites. Although adsorption according to the present invention is 
not governed by any one theory, it is believed that organic molecules are 
adsorbed because of the oleophilic nature of the humic acid molecule. In 
other words, it is believed that the organic molecules adsorbed partition 
onto the "organic like" surface of the humic acid molecule. 
EXAMPLE 2 
Water contaminated with benzene was treated with soluble humic acid 
(HUMASORB-L.TM.) in a 125 ml serum vial with a ratio of 4.16676 ml 
actosol.RTM. per ml of spiked water (i.e., approximately 1 gram of humic 
acid per mg of benzene). The benzene-contaminated water was contacted with 
HUMASORB-L.TM. was at room temperature for approximately two hours. After 
two hours, the benzene was completely removed from the water. The 
benzene-containing HUMASORB-L.TM. separated from the water by coagulation 
with alum followed by filtration. 
Metal sorption 
The effect of pH on the sorption of metals by HUMASORB-L.TM. was evaluated 
by adjusting the pH with sodium hydroxide (1.N) or concentrated 
hydrochloric acid (1.0N). In polypropylene centrifuge bottles, 
HUMASORB-L.TM. was contacted with spiked water solution containing known 
concentrations of metals. The spiked solutions were prepared by dissolving 
the metal salts in water. The centrifuge bottles were shaken at 300 rpm 
and 25.degree. C. for the desired contact time. After the desired contact 
time, 10% alum solution was added to the centrifuge bottles to coagulate 
humic acid. The bottles were then centrifuged at 2000 rpm for 30 minutes 
to separate the solid and liquid phases. The supernatant in the bottles 
was analyzed for the target metal. 
The desired contact time for all of these processes is the time needed to 
obtain equilibrium conditions. It has been determined that for metals, 
this time is approximately two to three hours, and for organics, the time 
to reach equilibrium is about 24 hours. 
The adsorption capacity of purified humic acid was evaluated by developing 
metal sorption isotherms. The spiked water solution was contacted with 
different amounts of humic acid in centrifuge bottles. The pH was not 
adjusted in these tests. The centrifuge bottles were shaken at 300 rpm and 
25.degree. C. for two hours. After the desired contact time, the bottles 
were centrifuged at 2000 rpm for 30 minutes to separate the solid and 
liquid phases. The ability of humic acid to reduce toxic metals such as Cr 
(VI), present as anions (Cr.sub.2 O.sub.7).sup.-2, to less toxic Cr(III) 
was also evaluated in a similar manner. 
EXAMPLE 3 
HUMASORB.TM. was immobilized further to reduce solubility and improve 
handling properties. The different forms of HUMASORB.TM. were immobilized 
in calcium-alginate matrix/gel. The adsorbents were immobilized both in 
the presence and absence of glutaraldehyde, a cross-linking agent. 
Immobilized HUMASORB.TM. was then evaluated for removal of chromium, a 
representative target contaminant from simulated waste streams. 
In this study, the initial chromium concentration was 200 ppm. The 
simulated waste stream was contacted with the adsorbent for two hours at 
25.degree. C. and 300 rpm. The adsorbent loading was 0.5 grams in 25 ml 
contaminated water. All of the adsorbents tested were immobilized in 
calcium-alginate matrix/gel. The results of this study and the pH are 
shown in Tables 2 and 3. 
TABLE 2 
______________________________________ 
Chromium Removal using Immobilized HUMASORB .TM. 
ADSORBENT.sup.++ PERCENT REMOVAL 
pH 
______________________________________ 
HUMASORB-L .TM. 81.06 5.07 
HUMASORB-L .TM. 82.37 5.22 
HUMASORB-L .TM./Glu** 
60.69 4.51 
HUMASORB-L .TM./Glu** 
66.24 4.54 
HUMASORB-S .TM. 30.20 2.89 
HUMASORB-S .TM. 12.24 2.87 
HUMASORB-S .TM./Glu** 
49.14 2.95 
HUMASORB-S .TM./Glu** 
37.49 2.95 
Calcium-alginate (control) 
49.20 3.95 
Calcium-alginate (control) 
41.63 3.99 
______________________________________ 
.sup.++ All adsorbents immobilized in calciumalginate matrix/gel. 
**Glutaraldehyde 
Reaction conditions: 
Initial chromium concentration: 200 ppm 
Contact time: 2 hrs at 25.degree. C. and 300 rpm 
Adsorbent loading: 0.5 grams in 25 ml contaminated water. 
TABLE 3 
______________________________________ 
Chromium Removal Using Immobilized HUMASORB .TM. Over Time 
TIME, HRS PERCENT REMOVAL 
______________________________________ 
2 89.01 
4 97.39 
8 97.61 
16 100 
______________________________________ 
Reaction Conditions: 
Initial chromium concentration: 200 ppm 
Contacted at 25.degree. C. and 300 rpm; pH: 5-5.5 
Adsorbent: HUMASORBL .TM. Glutaraldehyde (Immobilized in calciumalginate 
matrix/gel) 
Adsorbent loading: 0.5 grams in 25 ml contaminated water 
Several of the adsorbents were used in additional experiments conducted in 
succinate buffer to keep the pH relatively constant and to demonstrate 
that the differences in pH were not primarily responsible for increased 
chromium removal with immobilized HUMASORB.TM.. In addition, silica gel, a 
relatively inert material, was also immobilized, using calcium-alginate 
matrix/gel for comparison. In the first study, the results of which are 
shown in Table 4, the adsorbent loading was 0.5 grams of adsorbent in 25 
ml contaminated water. The contact time was two hours at 25.degree. C. and 
300 rpm. In the second study, the results of which are shown in Table 5, 
the adsorbent loading was 0.5 grams in 25 ml contaminated water, and the 
contact time was twelve hours at 25.degree. C. and 300 rpm. 
TABLE 4 
______________________________________ 
Chromium Removal Using Immobilized HUMASORB .TM. 
(In succinate buffer) 
Initial 
Final Chromium Percent 
Adsorbent pH pH Concentration, ppm 
Removal 
______________________________________ 
Control (chromium 
5.0 4.87 196.58 -- 
solution) 
Calcium alginate beads 
5.0 4.96 183.04 6.89 
Silica gel/Ca-alginate 
5.0 5.03 178.11 9.40 
HUMASORB-S .TM./ 
5.0 4.72 164.32 16.41 
Ca-alginate 
HUMASORB-L .TM./ 
5.0 5.30 157.47 19.90 
Glu/Ca-alginate 
______________________________________ 
Reaction Conditions: 
Adsorbent loading: 0.5 grams in 25 ml contaminated water 
Contact time: Two hours at 25.degree. C. and 300 ppm (In succinate buffer 
TABLE 5 
______________________________________ 
Chromium Removal Using Immobilized HUMASORB .TM. 
(Longer Contact Time) (In succinate buffer) 
Initial 
Final Chromium Percent 
Adsorbent pH pH Concentration, ppm 
Removal 
______________________________________ 
Control (chromium 
5.26 5.31 197.25 -- 
solution) 
Calcium alginate beads 
5.16 5.06 158.0 19.90 
Silica gel/Ca-alginate 
5.15 5.08 174.9 11.33 
HUMASORB-L .TM./ 
5.23 5.84 115.6 41.39 
Glu/Ca-alginate 
______________________________________ 
Reaction Conditions: 
Adsorbent loading: 0.5 grams in 25 ml contaminated water 
Contact time: 12 hours at 25.degree. C. and 300 rpm (In succinate buffer) 
The results of these experiments shown in Tables 4 and 5 clearly indicate 
that immobilized HUMASORB.TM. is more effective than the calcium-alginate 
beads (control), and silica gel immobilized using calcium-alginate beads. 
The lower removal of chromium in succinate buffer is believed to be due to 
sodium in the succinate buffer competing for sites in the adsorbent. 
Organic Adsorption 
Isotherms for adsorption of chlorinated and petroleum hydrocarbons were 
developed using HUMASORB-S.TM.. Initial experiments were conducted using 
HUMASORB-L.TM.. The chlorinated hydrocarbons used were trichloroethylene 
(TCE) and tetrachloroethylene (PCE); benzene was the representative 
petroleum hydrocarbon used in this study. 
Isotherms were developed by contacting spiked water samples with different 
amounts of humic acid in a 20 ml serum vial. HUMASORB.TM. was ground to 
less than 325 mesh when used in solid form in the experiments. The spiked 
water solution and the HUMASORB.TM. were contacted in crimp-sealed vials 
at 350 rpm and 251 for the desired time. The vials were centrifuged at 
2000 rpm for 30 minutes after the contact time to separate the liquid and 
solid phases. The liquid phase was analyzed by using purge and trap GC- 
MS. The experimental procedure was similar for all forms of HUMASORB.TM., 
liquid or solid. 
Metal Sorption 
The effect of pH on uranium removal using HUMASORB-L.TM. humic acid is 
shown in FIG. 1. Clearly, the results indicate that HUMASORB-L.TM. is very 
effective in removing uranium from water under acidic conditions. Uranium 
is soluble in water under acidic conditions, and increasing the pH to 4 
using NaOH results in only 6% removal of uranium. Uranium is completely 
removed from the solution at pHs greater than 6. 
However, at pH 4, the addition of HUMASORB-L.TM. removed all of the uranium 
from solution and the uranium was recovered as a solid bound to humic 
acid. The recovery of uranium decreased at higher pH in the presence of 
humic acid. The observed decrease in uranium recovery at higher pH in the 
presence of humic acid is expected, as humic acid dissolves in water at 
higher pH levels. The comparison of uranium recovery both in the absence 
and presence of HUMASORB-L.TM. indicates that uranium is bound to humic 
acid over the pH range of 2-12 and remains in solution under basic 
conditions in the presence of humic acid. The addition of a coagulant such 
as alum did not have a significant effect at higher pH. However, at near 
neutral pH(6-8), the addition of alum increased the amount of uranium 
recovery from water. The effect of pH on the removal of different metals 
using HUMASORB-L.TM. is shown in FIG. 2. 
The sorption of copper and nickel by purified humic acid (HUMASORB-S.TM.) 
was represented well by both the Freundlich and Langmuir models (FIGS. 3 
and 4). The Langmuir model for nickel, however, gave negative values for 
the constants. However, the sorption of cadmium did not follow either the 
Freundlich or the Langmuir model indicating a complex multilayer sorption. 
The metal sorption data were also analyzed using the method developed by 
Scathard in Ann. New York Acad. Sci. 51:660-672, 1949. The presence or 
more than one inflection point on a plot based on Scatchard analysis 
usually indicates the presence of more than one type of binding site. The 
Scatchard plot for the sorption of different metals by humic acid is shown 
in FIG. 5. The plot clearly indicates the presence of more than one type 
of binding site for copper and nickel sorption. The plot was, however, 
linear for cadmium, indicating that possibly only one type of binding site 
was active for cadmium sorption. 
Humic acid can act as a reducing agent and influence oxidation-reduction of 
metal species. An unchelatable toxic oxo-anion such as chromium present as 
dichromate (Cr.sub.2 O.sub.7).sup.-2 is reduced to relatively non-toxic 
Cr(III). The reduced chromium is then stabilized through chelation by 
humic acid. The reduction of different metal species such as mercury, 
vanadium, ion and plutonium by humic acid has been reported by a number of 
investigators (Alberts, J. J. et al., Science 184, 895, 1974; Szalay, A. 
et al., Geochim. Cosmochim Acta. 1, 31, 1967; Theis, T. L. et al., Trace 
Met. Met-Org. Interact. Nat. Waters. Symp.!, 273, 1976; Bondiette, E. A. 
Transuranium Nuclides Environ., proc. Symp. 273, 1976. 
The purified soluble humic acid (HUMASORB-S.TM.) used in the present study 
was able to reduce Cr(VI) completely as shown in FIG. 6. 
FIG. 13 shows the concentration of both Cr(VI) and Cr(III) during treating 
water containing Cr(VI) with HUMASORB-S.TM.. FIG. 13 clearly shows that 
the total chromium concentration decreases during the reaction, indicating 
that Cr(VI) is reduced and the resulting Cr(III) is removed immediately. 
The removal of Cr(III) is believed to be by a combination of ion-exchange 
and complexation. 
Freundlich and Langmuir adsorption models were used to represent the data 
obtained for adsorption of organic compounds. The data for TCE adsorption 
was not represented by either model (FIG. 7). The isotherms show two 
distinctive phases with adsorption capacity increasing only slightly with 
concentrations up to 210 ppm and increasing rapidly above 210 ppm. The 
shape of the isotherm indicates the possibility of multi-layer adsorption, 
with adsorption capacity increasing rapidly at higher concentration. 
The adsorption of PCE on HUMASORB-S.TM. was also represented well by both 
Freundlich and Langmuir models as shown in FIG. 8. However, the Langmuir 
model gave negative values for the constants. The Freundlich and Langmuir 
model parameters determined from the isotherms for some of the 
contaminants evaluated herein are shown in Table 6. 
TABLE 6 
______________________________________ 
Freundlich and Langmuir Model Parameters 
Contaminant 
Freundlich Langmuir 
______________________________________ 
Copper K = 0.4064 mg/gm 
K = 142.91 mg/gm 
n = 1.0218 b = 0.0029 l/mg 
Nickel K = 0.0300 mg/gm 
Negative Values 
n = 0.7500 
PCE K = 0.07691 mg/gm 
Negative Values 
n = 0.6697 
______________________________________ 
Benzene adsorption on HUMASORB-S.TM. was represented very well by both the 
models at the relatively higher equilibrium concentrations obtained 
herein. The removal of PCE from spiked water was higher compared to the 
removal of both TCE and benzene under the conditions used for the 
development of the adsorption isotherms. However, removal of both TCE and 
benzene increased significantly with the increase in the amount of 
HUMASORB-S.TM., as shown in FIG. 9. 
The adsorption of trichloroethylene (TCE) by humic acid was also evaluated 
using HUMASORB-L.TM. in the same manner and ratio as for benzene. TCE 
removal was only 55% at the end of two hours contact time, but removal 
increased to 61% with a contact time of 18 hours. The removal increased to 
94% at the end of two hours when insoluble, acidified, purified humic acid 
(HUMASORB-S.TM.) was used. 
Accordingly, either soluble humic acid or insolubilized humic acid 
adsorbent, alone or together, can be used to remove organic contaminants 
from water by treating the water with the appropriate form of humic acid 
adsorbent and letting the water remain in contact with the humic acid 
adsorbent for a time sufficient to remove the organic contaminant. The 
time required to approximate equilibrium conditions for organic 
contaminants can be up to 24 hours. 
Remediation of contaminated streams and groundwater has been traditionally 
approached with at least a two-step process including some combination of 
activated carbon and ion-exchange process. Removal of heavy metals from 
contaminated water has traditionally been accomplished by techniques such 
as adding a precipitating agent, ion-exchange or reverse osmosis. These 
techniques require considerable capital investment and, addition, may 
require pretreatment in some case to remove oil and suspended solids. 
The humic acid based adsorbent (HUMASORB.TM.) of the present invention, 
which is derived from naturally occurring materials, can alleviate many of 
the limitations of the conventional remediation efforts into a single step 
process. The humic acid based adsorbents of the present invention can be 
used for groundwater cleanup both in situ and in a pump and treat process. 
The parameters for the cleanup process depend upon the particular 
contaminants and their concentration in the stream treated, and can be 
readily discerned by one skilled in the art without undue experimentation. 
Contaminated groundwater is treated by using cross-linked humic acid 
(HUMASORB-CS.TM.) placed into a cartridge or a trench. In this case the 
humate removes both metal ions and organics from the water in one step. If 
the water to be cleaned contains no monovalent ions to be removed, then 
humic acid made insoluble by complexing with multivalent metal ions may be 
used. 
A cross-linked humic acid based adsorbent was used to treat a simulated 
waste stream containing both inorganic and organic contaminants in bath 
mode. The results shown in Table 7 clearly demonstrate that the 
cross-linked humic acid based adsorbent, HUMASORB-CS.TM.) is very 
effective for remediation of water containing different types of 
contaminants. 
TABLE 7 
______________________________________ 
HUMASORB .TM. IS EFFECTIVE FOR RADIONUCLIDE AND 
METAL REMOVAL FROM DIFFERENT MATRICES.sup.1 
MIXED WASTE STREAM CONTAINING MULTIPLE METALS 
AND CHLORINATED ORGANICS 
SIMULATED WASTE STREAM FROM 
WASTE.sup.2 A SUPERFUND SITE.sup.3 
Concentration, ppm 
Concentration, ppm 
CON- Removal Removal 
TAMINANT Initial 
Final % Input 
Output 
% 
______________________________________ 
Chromium (III) 
88 &lt;0.5 &gt;99 -- -- -- 
Copper 98 &lt;0.5 &gt;99 -- -- -- 
Lead 18 &lt;0.5 &gt;97 -- -- -- 
Trichloroethylene 
140 1 99.29 -- -- -- 
(TCE) 
Perchloroethylene 
26 N.D. &gt;99 -- -- -- 
(PCE) 
______________________________________ 
.sup.1 Source of Data: ARCTECH, Inc. 14100 Park Meadow Drive, Chantilly, 
Virginia. 
.sup.2 Simulated waste stream with three metal and two chlorinated organi 
contaminants present. 
.sup.3 Treatability study using actual waste stream with multiple metals 
present. 
(N.D. Not Detected) 
Alternatively, if it is not possible or desirable to elute the heavy metals 
and regenerate the adsorbent, the dried metal sequestrates can be 
combusted for process heat. The heavy metals are then concentrated in the 
combustion ash for recovery or disposal. 
The process of the present invention provides a cost effective, one step 
process for treating mixed wastes containing organic compounds, metals and 
radionuclides. This one step process accomplishes the regulatory 
requirements for the treatment of EPA-classified priority pollutants 
resulting in a several fold reduction in the volume of the contaminated 
materials. The byproduct of the process is dry and is easily disposable. 
Alternatively, metals chelated by the process can be recovered by eluting 
under acid conditions. Alternatively, the metals can be made into a 
marketable, chelated, micronutrient agricultural product. 
The foregoing description of the specific embodiments will so fully reveal 
the general nature of the invention that others can, by applying current 
knowledge, readily modify and/or adapt for various application such 
specific embodiments without departing from the generic concept, and 
therefore such adaptations and modifications are intended to be 
comprehended within the meaning and range of equivalents of the disclosed 
embodiments. It is to be understood that the phraseology or terminology 
herein is for the purpose of description and not of limitation. 
All references cited in this specification are hereby incorporated by 
reference.