|Title of Invention||
"A METHOD FOR THE PREPARATION OF MODIFIED BIOADSORBENT PARTICLES FOR THE REMOVAL OF TOXIC METALS AND OTHER COMPOUNDS FROM WATER"
|Abstract||A method of preparation of modified bioadsorbent materials for the removal of toxic metal ions and other compounds from water A method of preparation of modified bioadsorbent materials for the removal of toxic metal ions and other compounds from water by agitating biomass powder in aqueous solution of surface modification reagents containing amino/imine group and immobilizing the modified bioadsorbent on biopolymer matrix by co-agulation.|
|Full Text||The present invention relates to a method for the preparation of modified bioadsorbent particles for the removal of toxic metals and other compounds from water.
Reference may be made to a few potent commercialized biosorbents like AlgaSORB, AMT - BIOCLAIM and Bio - Fix wherein biosorbent materials such as Chlorella vulgaris, Bacillus and biomass from a variety of sources including Spirulina, Yeast, algae and plants (Lemna sp and Sphagnum sp) are employed as granulated material which are able to remove metallic ions from dilute solutions (1 - 100 mg/L) and reduces the concentration to levels lower than the internationally permitted dose. The drawbacks are the high cost of the immobilization matrix and the loss of efficiency on prolonged use.
Background and The Prior Art
The conventional methods of waste water remediation - reverse osmosis, solvent extraction, lime coagulation, precipitation and ion exchange are highly expensive and produce large quantity of toxic and waste sludge (Peters, R. W., Young, K and Bhattacharya, D.I985. Evaluation of recent treatment techniques for removal of heavy metals from industrial waste waters. AICHE Symposium Series. 81. Pp 1605 - 1703.). Plant biomass has emerged as an option for developing economically feasible and environment friendly water treatment process. Various types of biological materials are known for biosorption of metal contaminants (Volesky, B & Kuyucak, N., U. S. Patent, 4,769,233. 1988 ; Volesky, B & Tsezos, M., U. S. Patent 4,320,093.1981 ; Kogtev, L. S., Velichko, B. A., Volokhova, M. B., Melikhova, M. D., Ambramova, G. V., Shutova, L. A.,
Kulakov, V. M., Lisin, S. K., Shubko, V. M. and Trukhlyaev, P. S. Patent No. SU 1824758. 1996 ; Garnham, G. W. and Green, M. J. Patent No. GB 2294258. 1996 ; Kudrjawisku, F. and Ringpfeil, M. Patent No. DE - 4416914.1995).
The metal binding capacity of the biomass is due to complexation/ adsorption/ ion exchange/ precipitation of the metal species on the cell wall structural functional groups . The metal binding capacity is enhanced by various chemical treatments such as acid hydrolysis, alkali extraction (Brierly, J. A. Brierly, C. L., Decker, R. F. and Goyak, G. M., U. S. Patent 4,690,984., 1987), cross linking with organic solvents (Zhao, M and J. R. Duncan. 1997. Use of formaldehyde cross-linked Saccharomyces cerevisiae in column bioreactors for removal of metals from aqueous solutions. Biotechnology Letters. 19. (10). Pp 953 - 955.) and masking or removing specific binding groups or exposing more binding sites (Ashkenazy, R., Gottlieb, L and Yannai, S. 1997. Characterization of acetone washed Yeast biomass functional groups involved in Lead biosorption. Biotechnology and Bioengineering. 55. (1). Pp. 1 -10). The drawbacks are:
1. Most of these treatment methods concerned with enhancement of cationic metal ion
removal and not for the anionic metals species.
2. Rigidity of the biomass is adversely affected by certain pre treatment methods.
The powdered biomass, though effective in biosorption, is characterized by poor mechanical strength, necessitates high hydrostatic pressure to achieve suitable flow rates. High flow rates causes excess pressure drop may in turn cause disintegration of the native biomass. To overcome the above mentioned difficulties immobilized biosorbents are used
( Patent No. WO 9007468. 1990 ; Siedel, D. C. and Jeffers, T. H. U. S. Patent 429,236. 1991 ; Paknikar, K. M.., Pethkar, A. V., Vernekar. J. V. 1995, Indian patent pending) in industrial biosorption process such as B. V. SORBEX Inc. Canada (Kuyucak & Volesky, 1988. New biosorbents for non-waste technology. Proc. Non-waste Technol. Conf, Helsinki, Finland.) and Bio - Recovery Systems Inc. Las Cruces. These involved the use of granular biosorbent - AlgaSORB ™, developed using a fresh water alga, Chlorella vulgaris; AMT - BIOCLAIM ™ consisting of Bacillus biomass and Bio - Fix containing biomass from a variety of sources - Spirulina, Yeast, Algae and plants like Lemna and Sphagnum. The drawbacks in the present immobilized biosorbent are:
1. The biosorbent granules exhibit poor mechanical strength and low chemical
2. The immobilization methods make use of costly synthetic polymeric matrices/ gels
that are economically non-viable for treatment of large volumes of contaminated
3. Though the cost of immobilization can be compensated by repeated use in multiple
cycles, prolonged use can lead to loss of biomass efficiency.
The main object of the present invention is to provide a method for the preparation of a modified bioadsorbent particles for the removal of toxic metals and other compounds from water, the modification includes various types of biomass pre treatments and immobilization protocols. The remediation of toxic metals and other compounds from water comprises purification of domestic and industrial waste water, drinking water, well water and any other contaminated surface water. It comprises of a new method of cell wall
modification of the biosorbent and subsequent immobilization of the biosorbent in a cost
effective matrix for successful application in a continuous sorption system for the removal
of heavy metals and toxic compounds from water which obviates the draw backs as
Another object of the present invention is to improve the performance of microbial
biomass waste generated as byproduct of various fermentation industries, by chemical
treatment to increase the binding sites.
Still another object of the present invention is to granulate the biosorbent powder in a
naturally obtained biopolymer matrix and development of mechanically sturdy and
chemically resistant biosorbent particles for on site remediation.
Yet another object of the present invention is to effectively utilize the granulated
biosorbent in adsorption and elution cycles.
Yet another object of the present invention is to remove traces of toxic metals from the
drinking water supply.
Still another object of the present invention is to remove pigments and coloring substances
from the effluent and other types of contaminated surface water.
Accordingly the present invention provides a method of preparation of modified bioadsorbent materials for the removal of toxic metal ions and other compounds from water which comprises modifying cell wall of dead biomass adsorbent by treating with 0.1 - 10 % solution of surface modification reagents containing amino/imino groups, immobilizing the modified biosorbent on biopolymer matrix by coagulation.
In an embodiment of the present invention the dead biomass used may be fungi, yeast,
Bacillus from fermentation industries or suitable plant materials.
In another embodiment of the present invention the biomass may be grounded and
powdered to the particle size in the range of 100 - 500 um.
In another embodiment of the present invention the biomass surface modification reagents
may be polyethylenimine (PEI), cetyl trimethyl ammonium bromide (CTAB) and 3-(2-
Amino ethyl amino) propyl trimethoxy silane (APTS).
In another embodiment of the present invention the natural biopolymers used may be latex
exudate from laticiferous tree, chitosan polymers extracted from the Crustaceans,
Carrageenan and alginates of algal origin or keratin materials of animal origin.
In another embodiment of the present invention the immobilization of surface modified
biosorbent on biopolymer matrix such as fresh latex obtained from laticiferous tree is
In yet another embodiment of the present invention the coagulation may be carried out by a
mixture of 0.5 - 10 M CaCl2. 2H2O : 10 - 95 % C2H5OH / 0.5 - 10 M CaCl2. 2H2O : 10 -
95 % Acetone to form granular biosorbent and or / coagulated with acids to form
In still another embodiment of the present invention the metal laden biosorbent granules
can be eluted in dilute alkalies to regenerate the sorbent and suggested effective
regeneration and the repeated use for more than 60 cycles without the loss of adsorption
The preparation of modified biosorbent particles comprises of many process steps. Bacterial or fungal waste biomass generated as fermentation byproduct from distilleries and pharmaceutical industries can be selected as cheap adsorbent material. The biomass after drying and grinding is separated into particles of fine size ranging from 100 - 500 u.m. The biomass modification step comprises of treatment with 0.1 - 10 % aqueous solution of PEI, CTAB and APTS for 2-24 hours at temperature ranging from 4-50 °C. After the pre treatments, the biomass needs subsequent steps of washing, drying (temp range 50 - 80°C) and sieving to obtain the desirable particle size. To make the biomass sturdy it was immobilized in suitable polymeric matrices like polysulfone, poly acrylamide, calcium alginate, polyvinyl alcohol (PVA) and polyisoprene. The immobilization in polyisoprene polymer employs fresh latex exudate collected from rubber trees as the entrapment polymeric matrix. For this, latex biomass slurries were prepared with 1 - 20 %, w/v biomass composition. After stirring, the slurry could be coagulated in a mixture of 1 - 10 M Ca C12. 2H2O:10 - 95 % C2H5OH /1- 10 M Ca C12. 2H2O:10 - 95 % Acetone to generate biomass beads of 1-10 mm diameter or coagulated with acids such as acetic acid or formic acid to make sheets of 1-10 mm thickness. The chemically modified and immobilized biomass could be employed for bioremediation of toxic heavy metals such as Cr (VI), Cu 2+ and Ni2+. Such immobilized granules and sheets can also be packed in suitable reactor set up such as fixed/ stirred tank/fluidized taking into consideration, the pressure drop across the bed. The adsorbed metal ions could be eluted in acid or alkaline eluants and the biosorbent can be regenerated for repeated use for at least 60 cycles without the loss of adsorption capacity.
The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.
Modification of Biomass: 1 gm of biomass powder with particle size in the range 90-125 um is suspended in 100 ml of 1 % Polyethylenimine (v/v), 3 % 3 - (2 - Amino ethyl amino) propyl trimethoxy silane (v/v) and 5 % Cetyl trimethyl ammonium bromide (w/v). Moderate stirring (120 rpm) is given for 24 hours to accomplish sufficient contact and uniform mixing of the biomass and the reagent at 30 + 2 °C. After filtration, the biomass is washed hi de ionized distilled water, separated and dried at 60 °C in an oven for 6 hours. The dried biomass powder is again ground to particles of uniform size.
14 gm of the modified, powdered biomass powder is blended into 100 ml latex solution collected from the rubber tree, Hevea brasiliensis. This slurry is dropped into 100 ml coagulation solvent consisting of 1 : 1 mixture of 4 M CaCk. 2H20 : 50 % C2H5OH/Acetone to make bisorbent granules of 3 mm diameter. After 4 hours of coagulation at 30 ±_2°C, the granulated biosorbent beads are washed in de ionized distilled water to remove traces of the coagulant and are stored in distilled water at 4 °C.
Batch experiments are conducted for biosorption of Cr (VI) anions from aqueous solution using modified biomass. 0.2 gm of each of the untreated and chemically modified free biomass was contacted with 100 ml of Cr solution with a concentration of 500 mg/L. Samples were taken after attainment of equilibrium (8 hours) and the residual
concentration of Cr ions determined spectrophotometrically for comparing the biosorption profile of the modified and the native bio mass.
Table 1. Cr (VI) adsorption and uptake profile of pre treated and unmodified Rhizopus nigricans (Cr Cone. - 500 mg/L., pH = 2.0, Biomass dose = 0.2 %, Contact period = 8h )
The efficiency of the polyisoprene entrapped biomass was compared with those immobilized in synthetic polymers. Biomass beads/ gels corresponding to 0.4 g biomass was suspended in 100 ml Cr (VI) solution, with concentrations ranging from 100 - 400 mg/L. Beads/ gels were agitated on a gyratory shaker at 120 rpm, at 30 ± 2 °C for 8 hours and equilibrated. The polyisoprene immobilized biomass was found to be superior to all other types of entrapped biomass.
Table 2. Cr (VI) uptake ( mg Cr/g biosorbent) by Rhizopus nigricans immobilized in various polymeric Matrices ( Cr cone. Range = 100 - 400 mg/L, pH = 2.0, Biomass dose = 0.4 %, Contact period = 8 h)
Rhizopus nigricans biomass was also studied for the biosorption of Cu2+ ions from aqueous solution and the maximum uptake capacity was estimated to be 39.33 mg/g biomass, at pH 4.5 and at ambient temperature (30 + 2°C).
In the present invention, biomass modification studies were carried out to specifically enhance the binding of anionic metal species like Cr (VI), which exist in solution as oxo anion complex. Rhizopus cell wall consists of 24 - 40 % chitin, which is composed of acetyl glucosamine monomers. The amines become protonated at acidic pH (range 1-5) and favor the electrostatic binding of negatively charged chromate ions.
The present method of biomass modification makes use of reagents such as PEI, CTAB and APIS, which are abundant in imino/ amino groups. Treatment of biomass powder in aqueous solutions (0.1-10 %, w/v) of the above mentioned reagents enhance the binding capacity in comparison to unmodified biomass. This enhancement in metal uptake could be attributed to the feet that addition of amino/ imino groups to the biomass by pre treatment resulted in more binding sites per unit surface area of the biomass.
In the present invention, the powdered biomass is immobilized by entrapment on a natural biopolymer, which can comprise of entrapment method employing fresh latex exudate from any laticiferous tree wherein a uniform biomass slurry was prepared comprising 1-20 %, w/v biomass loading which was then coagulated in a suitable coagulant which may also include a mixture of 0.5 - 10 M Ca C\z. 2HaO : 10-95 % C2H5OH / 0.5 - 10 M CaCl2. 2H2O : 10 - 95 % Acetone to granular biosorbent and / or coagulated with acids to form biosorbent sheets, which could be employed for batch or continuous sorption for the removal of toxic heavy metals like Cr (VI), Cu2+, Ni2+, Zn2+, Cd 2+ and so on and coloring matter like dyes, melanoidin pigments and the like, which can also be packed in suitable reactor configurations such as packed bed/ Continuous Stirred Tank Reactor/ Fluidized bed for industrial/ large scale sorption systems wherein the adsorbed toxic metals or compounds could be eluted in limited quantity of eluents.
The metal laden biomass granules can be eluted in dilute alkalies and the sorbent can be reused. Therefore the overall process become economical when compared to the operations involving immobilized biosorbents prepared in synthetic resins and polymers.
The main advantages of the present invention are:
1. Enhancement of hexavalent chromate ion adsorption efficiency to almost double after
modification by 3 % APIS.
2. The modified Rhizopus biomass is capable of adsorbing Cr (VI) ions from solution
( 1 - 500 mg/L ). The Cr (VI) concentration could be reduced to 3. The bound Cr (VI) ions can be successfully eluted using 0.01 N NaOH, Na2COa and
4. Biomass suspended in fresh latex can be coagulated into biosorbent granules of
suitable size and thus provides a new polymeric matrix for cell / biomass
5 The polyisoprene entrapped biomass granules possess good mechanical strength, chemical resistance and are as good as polysulfone, and better than PVA, alginate and polyacrylamide biosorbent beads for Cr adsorption.
1. 1. A method of preparation of modified bioadsorbent materials for the removal of
toxic metal ions and other compounds from water which comprises modifying the cell
wall of dead biomass adsorbent by treating with 0.1 - 10 % solution of surface
modification reagents containing amino / imino groups, immobilizing the modified
biosorbent on biopolymer matrix by coagulation.
2. A method for the preparation of modified bioadsorbent particles as claimed in claim 1
wherein the powdered adsorbent of any biological origin can be agitated in aqueous
solutions (concentration range 0.1 - 10 %) of Polyethylenimine (PEI), Cetyl
trimethyl ammonium bromide (CTAB) and 3 - (2 - Amino ethyl amino) propyl tri
methoxy silane (APIS) for enhancing the biosorption of any anionic contaminants.
3. A method for the preparation of modified bioadsobent particles as claimed in claims 1
- 2 wherein the immobilization matrix selected is a natural biopolymer such as latex
exudate collected from the rubber tree chitosan polymers extracted from the
Crustaceans, Carrageenan and alginates of algal origin or keratin materials of animal
origin which can be coagulated into granules (1-10 mm diameter) and sheets (1-10
4. A method for the preparation of modified bioadsorbent particles as claimed in claims
1 - 3 wherein the modified biosorbent can be entrapped in any polymeric matrix
(synthetic and natural) and can be made into beads/ sheets that can be used in any
reactor set up for bioremediation.
5. A method for the preparation of a modified and immobilized bioadsorbent as claimed
in claims 1 -4, the biomass can be favorably modified by treatment with 0.1 - 10 %
PEI, CTAB and APTS and immobilization in achieved by coagulation of the polymer in an organic acid such as acetic acid, formic acid, alcohol such as propanol, butanol, ethanol and / or methyl alcohol or other organic solvents such as ketones which include acetone, diethyl ketone, ethyl methyl ketone for 1 - 8 hours.
6. A method for the preparation of modified bioadsorbent particles as claimed in claims
1-5 wherein the metals adsorbed on to the modified and immobilized biosorbent is
eluted in suitable eluents such as NaOH, Na2CO3 and NaHCO3 and the biosorbent can
be regenerated for reuse for at least 60 cycles.
7. A method for the preparation of modified bioadsorbent particles for the remediation
of toxic metals and other compounds from water, substantially as herein described
with reference to the examples accompanying this specification.
|Indian Patent Application Number||567/DEL/2000|
|PG Journal Number||01/2009|
|Date of Filing||09-Jun-2000|
|Name of Patentee||COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH|
|Applicant Address||RAFI MARG, NEW DELHI-110 001, INDIA.|
|PCT International Classification Number||C02F 3/00|
|PCT International Application Number||N/A|
|PCT International Filing date|