|Title of Invention||
"A PROCESS FOR THE PREPARATION OF BIOSOROBENT USEFUL FOR REMOVAL OF DYES AND HEAVY METALS"
|Abstract||The present invention relates to a process for the preparation of biosorbent from Eichornia crassipes useful for removal of dyes and heavy metals. The dry biomass employed in the present invention was useful to maximize the degree of decolourization and for removal of heavy metals and to introduce newer methods for treatment of waste waters. The process invoves the treatment of Eichornia crassipes plant parts powder with acid and aldehyde at a temperaqture ranging 40-55°C followed by filteration and washing and drying to obtain biosorbent.0|
|Full Text||The present invention particularly relates to a process for the preparation of biosorbentuseful for removal of dyes and heavy metals. The dry biomass employed in the present invention was useful to maximize the degree of decolourization and for removal of heavy metals and to introduce newer methods for treatment of waste waters. Eichhomia .crassipes (Mart) Solms popularly known as water hyacinth, is an aquatic parrenial tropical weed which is a menace to navigation, interferes in fishing and hydroelectric-power generation etc. Attempts to eradicate the weed or control its growth have been only partly successful, to utilize the weed as a biosorbent to remove the colour and heavy metals from aqueous solution is an advantage.
Industrial effluents from dye manufacturing industry, textiles, pulp and paper mills and Leather industry are highly coloured and difficult to remove. Colour removal or reduction is generally achieved by 3 main processes such as:
(1) Physical process (osmosis, adsorption),
(2) Chemical process (coagulation, flocculation, precipitation and ion
(3) Combined process (chemical treatment followed by biological or physical
process) (Pragya Tewari and N.P. Shukla et al, 1994, Ind. J. Env. Prot. Vol.
Colour removal by chemical methods involves addition of appropriate coagulating/flocculating agents like Fe, Al or Mg salts with simultaneous pH adjustment to obtain supernatant water and form a floe. The resulting sludge gets disposed off without much concern to ground water contamination. Textile waste is reported to be biodegradable but those from the cotton processes include biologically resistant effluents. (Pragya Tewari and N.P. Shukla et al, 1994, Ind. J. Env. Prot. Vol. 14, No:7). Thus, Adsorption, a sludge free operation is gaining lot of importance. Activated carbon though an attractive
sorbent for colour removal would be cost prohibitive atleast in developing countries. A variety of low cost materials like fly ash, rice husk ash, saw dust, clay and coal for treatment of dye effluent in place of costly activated carbon have been tried by many researchers. However their physical characters like surface area and apparent density were not same as that of activated carbon. For eg Srinivasan et.al .(I.J.Env. Hlth. Vol.30,(4) 1988 ) and Singh et.al (I.J. Env. Hlth vol.36 (1) 1994)have reported that the surface area of rice husk ash and fly ash was 378m2 /gm and 7000-9000 cm 2' gm. The apparent density of rice husk ash was 0.36gms/cc.
Activated carbon briquets from lignite and cellulose materials were reported to be essentially decolourising materials. We have selected E. crassipes leaf and whole plant biomass as a base material as it contains lot of cellulose and yields high carbon content. Internal structures like surface area (621 m2/g) and apparent density (0.13 gms/cc) give the material the important properties for colour removal, by increasing the carbon yield which provides a high generating activity and retentivity of the product. Not only is the surface of the biomass more directly exposed to the solution but being lighter material remains suspended for longer time on the surface of the solution than denser materials , as seen in our experiments.
Industrial waste water often contain considerable amounts of heavy metals that would endanger public health and the environment if discharged without adequate treatment. Heavy metals are elements such as Pb, Hg, Cr, Ni, Cd and Zn which have high atomic density and are usually associated with toxicity and diseases like cancers etc.. Major anthropogenic sources of heavy metals in the environment include metal extraction, metal fabrication and surface finishing, paints and pigments as well as the manufacture of batteries. In natural water and waste water, chromium exists in two oxidation states hexavalent chromium (Cr+6) and trivalent chromium (Cr
III). The toxicity, solubility and mobility of chromium in environments are dependent upon its oxidation states. Since Cr (VI) is much more toxic, soluble and mobile than Cr (III), the reduction of Cr VI to Cr (III) represents a prevalent treatment of Cr VI containing wastes. Industries are under heavy pressure to adopt suitable methods to reduce the level of heavy metals from waste waters to permissible limits. Presently all options available for Cr VI reduction in waste water are chemical method which usually involve pH adjustment and addition of reducing agents. The treatment methods are expensive due to the use of large amounts of chemicals and the generation of chemical sludges.
Lead is most widely used metal for conducting water, electrical batteries, automobiles and in the manufacture of H2S04. Many methods came into light for treatment of lead bearing industrial waste water. The important methods being neutralisation, precipitation, reverse osmosis, ion exchange, co-precipitation and ion flotation. The methods employed at present are not cost effective if the metal concentration is low and discharge volume are large. Addition to the above constraints the high volume of sludge produced during the treatment posses disposal problems. Introduction of large quantities of Niclel into the environment which causes potential hazards to animals and human health through food chain. (Council of Agri. Sci. & Tech. Report, 1976). The major source of environment contamination by nickel include smelting, mining operation, manufacture of alloys, alkaline storage batteries and unavoidable use of biofertilisers and biosites. Heavy metals cadmium, lead, nickel, aluminium and zinc in the waste water a big occupational health hazard if their concentration was found to be excessive.
Much has been reported on deriving Active Carbon from various organic materials such as jute waste, paper waste, coconut shells, tree barks, plant leaves and agri by-products are used as adsorbents in removal of heavy metals from industrial effluents by adsorption. However the advantage of using the hyacinth leaf and whole plant biomass after treatment is because it is eco-friendly product. The use of non-living biomass eliminates the necessity of nutrient solution for supporting
the growth and maintenance of live materials like whole plants or microbes, metal can be adsorbed and desorbed readily and there is no need for neutralising the effluents.
Hitherto, several attempts have been made to effect colour removal from textile and dyeing waste waters, but so far it has met with very little success, as there are few research papers in this field and fewer methods /options.
1. Textile and Dye Industries in Hongkong are using microbes for removing dyes
from effluents. Brightly coloured azo dyes are consumed by the microbe
Acetobacter liquefaciens S-1 bacteria. The bacterial colony grows on agar plate
containing 100 ppm methyl red. When the colony is removed the area where the
dye has been consumed is clearly visible.
2. The decolourization of Dyeing and Textile Industry waste waters was
reported to be generally carried out by employing the combined use of Fe
(II), lime and bone charcoal or any one component individually. (Shen, X,
Bousher, A. and Edyvean, RGJ 1995. Young Res. Chem. Eng. 1st I.
Chem.Engg .Res. Event. European Conference: 1-469-471).
3. Some reports have suggested the use of dried roots of water hyacinth (Low,
K.S., Lee, C.K. and Tan, K.K. 1995. Bisorption of basic dyes by water
hyacinth roots. Bio Resour. Technol. 52 (1) 79-83 (cf/ca))
4. and the living plant of water hyacinth (Xia Xiaosong and Cingshurong 1987.
Decolourization of dye waste water by water hyacinth. Huanjung Kexue
Xuebao. 7 (3) 353-360 (cf/ca) ). This process could remove partly the dye,
and the rest was left for seeping into the grounds.
Hitherto, several methods were adopted like ion exchange, adsorption, precipitation and reduction to bring down the heavy metal pollution to permissible limits by many scientists /managers etc. However dried water hyacinth plants and certain parts of the plants powdered and activated by acid have not been used for such studies
before. This process introduces a novel method for heavy metals removal from waste water effluents. The relevant references pertaining to metal uptake are listed below :
1. Uptake of metal ions by non-living biomass derived from sphagnum mass
peat mass and water hyacinth roots. Hao et al. J. Envi. Sci. Hlth. Part A.
(1993) A 28 (10) 2333-43.
2. Eichhornia crassipes as biosorbant for heavy metal ions. Schneider I.A.M.
et al, miner eng. (1995) 8 (9) 979-88.
3. Biosorption of copper by water hyacinth roots. Low K.S. et al. J. Envi. Sci.
Health. Part A. (1994) A 29 (1) 171 -88.
4. Biosorption of heavy metal ions from aqueous solution by non-living water
hyacinth roots for cadmium, lead and mercury. Wang et al. Diss. Astri.
Int., (1996) 13, 57(1)524.
Hitherto, several attempts have been made to effect colour removal from textile and dyeing waste waters but so far it has met with very little success. Also there are few research papers in this field.
Textile and Dye Industries in Hongkong are using microbes for removing dyes from effluents. Brightly coloured azo dyes are consumed by the microbe Acetobacter liquefaciens S-1 bacteria. The bacterial colony grows on agar plate containing 100ppm methyl red. When the colony is removed the area where the dye has been consumed is clearly visible.
The decolourization of Dyeing and Textile Industry waste waters is generally carried out by employing the combined use of Fe (II), lime and bone charcoal or any one component individually. (Shen, X, Bousher, A. and Edyvean, RGJ 1995. Colour removal from a waste effluent by combined use of Fe (II), Lime and Bone charcoal. Young Res. Chem. Eng. 1st I. Chem.E.Res.Event.
European Conference: 1-469-471). Most of the dye effluent is channelled off into the grounds adjacent to the factories or let out into streams or lakes for dilutions.
Some reports have suggested the use of dried roots of water hyacinth (Low, K.S., Lee, C.K. and Tan, K.K. 1995. Bisorption of basic dyes by water hyacinth roots. Bio resour. Technol. 52 (1) 79-83 (cf/ca) f and the whole plant. (Xia XiaoSong and Cingshurong 1987. Decolourization of dye waste water by water hyacinth. Huanjung Kexue Xuebao. 7 (3) 353-360 (cf/ca) ). This process could remove partly the dye, and the rest was left for seeping the grounds. These methods however were limited to lab studies only. No report of its commercial exploitation has been found.
The main object of the present invention is to provide a process for the preparation of biosorbent for removal of dyes and toxic heavy metals which obviates the drawbacks of the existing methods.
Accordingly, the present invention provides a process for preparation of biosorbent from Eichornia crassipes useful for removal of dyes and heavy metals which comprises mixing dried powder of Eichornia crassipes , acid and aldehyde in the ratio of 5:50:10;stirring the mixture at a temperature in the range of 40-55°C for a period ranging 10-60 minutes;filtering the reactant mixture to obtain the crude biosorbent ;washing the crude biosorbent with distilled water several times ;drying the washed biosorbent as obtained in step d) to a temperature ranging 30-70°C to obtain the biosorbent.
In an embodiment of the present invention the plant / plant parts used may be such as leaves, petioles, roots, / whole plant.
In another embodiment of the invention the acid used may be such as H2S04, HN03 Acetic acid of strength in the range of 0.1 to 0.8 N .
In yet another embodiment of the invention the aldehyde used may be such as formaldehyde, acetaldehyde, in the range of 30-50 %.
In a feature of the invention removal of treatment mixture may be carried out by filtration, decantation or centrifugation.
Drying the biosorbent may be effected at room temperature or oven at a temperature in the range of 30-50°C
In a feature of the invention removal of treatment mixture may be carried out by filtration, decantation or centriffugation.
Drying the biosorbent may be effected at room temperature or oven at a temperature in the range of 30-70°C
The biosorbent thus prepared has the following characteristics : Chemical characteristics of the biomass / biosorbent
Chemical analysis of water hyacinth dried leaves was also carried out to corelate whether the adsorption is taking place through ion exchange phenomenon which is as follows:.
pH- 4.12, Ash content 11.74 (Percent/ wt.)
Silica (as Sio2) 0.44
Aluminium (as AI2o3) 11.90
Calcium oxide (Cao) 10.91
Iron (as Fe2o3) 1.01
Elemental analysis of water hyacinth dried leaves was also carried out
Elemental analysis of Water Hyacinth dried leaf biomass
C H N S Obydiff.
Untreated Hyacinth leaves 38.81 2.51 3.58 0.05 55.05
Treated Hyacinth leaves 41.24 7.09 3.86 0.09 47.72
Surface area = 621m2/gm Bulk density = 0.13 gms/cc
From the above table the activated carbon from dry water hyacinth leaves exhibit high values of apparent surface area as expected for micro porous substrates. The ash content of the activated carbon prepared from water hyacinth leaves is low which is an advantageous from the point of view of their use in waste water engineering. The data also revealed that the adsorption could be electrostatic due to the influence of electrical attraction forces responsible for adsorbing solution between negatively changed carbon particles or ions, reducing the barriers of diffusion and thus increasing the adsorption efficiency.
High removal of colour and of heavy metals was observed in separate experiments. Metal biosorption studies were carried out in three types of processes. (1) Powder form (2)Packed Column (3) Biomass mixed with active carbon in the ratio of 3:1. Non-living biomass offers attractive biosorbant material in place of expensive active carbons.
Colour in the effluents effects penetration of sunlight resulting in interruption to photosynthesis of the aquatic microflora, thereby reducing self purification capacity of streams, ponds and rivers and increases toxicity of colour compounds and heavy metals. Hence this viable alternative which is economically feasible, is the purpose of this invention.
Biosorption tests were carried out by batch wise studies as well as column studies after acid activation of the base material i.e. water hyacinth dry biomass. The biomass was processed to obtain material which has porous structure with distributed carbon over a large surface area.
The following examples are given by way of illustration which should not construed the limit of the scope of the invention.
Example No. 1
Eichhornia crassipes Mart (Solms) popularly known as Water hyacinth was selected as biomass for adsorption studies. Leaves of E. crassipes were shade dried, ground and sieved to average particle size of 0.16 mm so that it has a larger surface area per unit mass. A mixture of 5 parts by weight of ground leaf material, 50 parts by volume of H2So4 solution of (0.2N strength) and 10 parts b,y volume of 39% Formaldehyde (HCHO) was stirred at 50 °C for 30 minutes, washed with distilled water several times and dried (Sing etal, 1993). This method (Carbon and Graphite Hand Book by Charless L. Mantell 1968) or process of releasing carbon from its compounds at sufficiently low temperature in the absence of Hydrocarbons or other strongly adsorbed substances yielded Active carbon directly. The carbonaceous material prepared from E. crassipes by acid activation was used for Biosorbant studies. The treatment process and experiments consisted of utilizing :
1. Biomass (dried) without acid activation.
2. Biomass(dried) activated with Sulphuric acid.
3. Combination of the biomass (dried) mixed with activated charcoal.
Example 2 :-
The adsorbent studies were made in packed bed column and operated at a minimum flow rate i.e. 2ml/min using down flow technique. The column was packed with base material 2g at the bottom of the column supported by glass wool to avoid
loss of sorbent with the liquid flow. The basic dye solutions of methylene blue and malachite green of 100 ppm and 150 ppm strength were passed through the column and collected at the bottom of the column in 100 ml fractions. The results revealed that the colour removal was 60-70% in the firstl hr and afterwards it was significantly colourless. The above experiments were conducted in triplicates with the same findings.
EXAMPLE 3 :•
The seccond set of experiments were conducted with the biomass activated by H2So4 (0.2N Strength). The investigations revealed the potential of non-living dried water hyacinth leaf biomass for removing the colour of the two basic dyes. Methylene blue and malachite green were almost 95% removed the first hour, subsequently the filtrate was colourless showing colour removal by 100%. These studies revealed the same results when repeated several times.
Example 4 :-
The third set of experiments recorded very significant colour removal by utilising the combined materials of the biomass and commercial activated charcoal at 1:3 ratio (activated carbon and biomass). The colour removal was very very significant in the first one hour also. In general decolorization process by carbonaceous material will be of 3 types physical, chemical and electrostatic. (Wang LK. R.P. Leonard and DW Goupil 1972. Report No. VT-3045 M-3). Results revealed that adsorption could be a physical phenomenon resulting from
molecular condensation in the micropores of activated carbon by so called inner Vanderwals forces or dispersion forces.
It is evident that the characterstics as described herein are highly desirable for the colour removal. This data also revealed that adsorption could be electrostatic due to the influence of electrical attraction forces responsible for adsorbing solution between negatively charged carbon particles or ions, reducing the barriers of diffusion and thus increasing the adsorption efficiency.
From the above set of experiments it is concluded that acid activated biomass as well as combining it with the commercial activated charcoal in the ratio of 3:1 were potent decoloursing agents for commercial exploitation by dye manufacturing industry, textile industry, paper and pulp mills etc. Industries are under heavy pressure to adopt suitable methods to reduce the level of specially pollutants heavy metals to permissible limits.
There are many physico-chemical methods such as adsorption, reduction, ion-exchange and precipitation for removal of heavy metals. Much interest is shown in removing heavy metals by active carbon adsorption , since active carbon suffers from the disadvantage of high manufacturing costs.
Low cost adsorbants like fly ash, low grade coal, peat, lignite, sawdust, rice husk etc. have received considerable interest. Hence in our approach the non-living leaf biomass of water hyacinth after acid activation at relatively low temperature to get low carbonaceous biosorbant was employed. This was found to be on par with other commercial low cost materials. This process has an advantage since waste materials were utilised in place of expensive sorbants.
Batch Studies :-
Batch sorption tests were carried out by shaking 250 ml of metal ion solution of 25, 50 and 100 ppm strength with 5 gm of prepared sorbant in each experiment at pH 2.0 as the adsorption takes place highly in acidic solutions. After 6 hours and 8 hours of contact time the sorbants were separated by filtering through a whatman filter paper no.42. The filtrate was digested with aquaregia (Hcl:H No :3:1) and analysed for metal contents Cu, Cr, Cd, Pb, Ni and Zn by Atomic absorption spectra photometer (model 5000) and ICPAES. Experiments were conducted in replicates for each metal separately. Studies revealed that 6 hours contact time is not sufficient to remove heavy metal contents. However, 8 hours studies shows that percent removal is 80 to 85%.
Experiments were conducted using down flow technique in columns of 2cm dia and 62 cms long. The column was packed with 1gm of sorbant bed volume 5.5cm at the bottom supported by the glass wool to avoid loss of sorbant with the liquid flow. The feed solutions of Pb and Cr 50mg/lit (pH2) separately and 1:1 mixture of Pb and Cr were passed through the column and were collected at the bottom of column. A blank column was run with no sorbant to determine the loss of metal ions by adsorption on glass wool packing. The filtrate was collected in 100 ml fractions. Each fraction was acid digested and analysed for Pb and Cr content.
The results showed that the metal removal was 92-97% efficiency. A control was run simultaneously by using deionized water. The initial amount of Pb and Cr in 100ml feed minus the amount found in filtrate gave the amount of metal ion retained by the sorbant.
The percentage removal of metal ions was calculated from initial concentration (Co) and final concentration (Ce) as follows :
% metal ion removal = Co - Ce x 100 / Co
Chemical analysis of water hyacinth leaves was also carried out to co-relate the adsorption which is taking place through ion exchange also.
Because Zeolites, Iron, Aluminium oxide, Carbon, Silica and Cao constitute the vast majority of adsorption media in use today as they have metal binding affinity.
Chromium being the only anion metal, the removal of Cr was possible on the Alumina surface because the strong tendency from the chemical bonding between Cr and AI203.
The sorption of Pb is reported to be more at higher pH values due to enhanced ion exchange phenomenon, at pH range between 2-11. Column studied showed exhaustive capacity in removing metal ions Pb and Cr . This could be due to continuous large concentration at the interface of the sorption zone as the sorbant passed through the column. In case of solution having "both the Pb and Cr ions when filtered through sorbant (pH2) showed adsorption of the individual metals without interfering each other. (Gajghate etal, 1991).
Advantages of the present invention :
1. The biosorbant prepared by the process remove heavy metals and dyes from
waste waters or effluents from varies industries by utilising the weed biomass in
place of other expensive adsorbents which are generally employed.
2. The use of nonliving biomass eliminates the necessity for the supply of nutrients
for supporting the growth and maintenance of the organisms used in bioremediation.
3. Metals cen be accumulated, and desorbed readily and recovery is possible.
4. There is no potential for degradation of organometalic compounds due to the
absence of metabolic activity of the dead biomass.
5. A lab scale fixed bed reactor was conveniently operated. Columns were
reusable several times before discarding.
We Claim :
1. A process for preparation of biosorbent from Eichornia crassipes useful for removal of dyes and heavy metals which comprises :
a) mixing dried powder of Eichornia crassipes , acid and aldehyde
such as herein described in the ratio of 5:50:10;
b) stirring the mixture as obtained in step a) at a temperature in the
range of 40-55°C for a period ranging 10-60 minutes;
c) filtering the reactant mixture as obtained in step b) to obtain the
d) washing the crude biosorbent with distilled water several times ;
e) drying the washed biosorbent as obtained in step d) to a
temperature ranging 30-70°C to obtain the biosorbent..
2. A process as claimed in claim 1, wherein plant parts used comprises of
leaves, roots, petioles and the whole plant including the leaves, petioles
3. A process as cnaimed in claims 1-2, wherein the acid used is selected
from group of acid comprising of Sulphuric acid and phosphoric acid.
4. A process as claimed in claims 1-3, wherein the aldehyde used is
selected from the group of aldehyde consisting af formaldehyde and
acetaldehyde in the range of 30-50%
5. A process as claimed in claims 1-4, wherein the mixture of acid and
aldehyde used for treatment is in the range of 3-6 parts of acid with 0.5
to 2.0 parts of aldehyde.
6.A process as claimed in claims 1-5, wherein the removal of treatment"
mixture is preferably carried out by decantation, filtration, centrifugation.
7. A process claimed in claims 1-6, wherein drying is effected at room
temperature or oven drying, at a temperature in the range of 30-50°C.
8. A process for the preparation of the biosorbent from Eichornia crassipes
useful for removal of dyes and toxic metals substantially as herein
described with reference to the examples.
|Indian Patent Application Number||1308/DEL/1998|
|PG Journal Number||12/2008|
|Date of Filing||15-May-1998|
|Name of Patentee||COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH|
|Applicant Address||RAFI MARG, NEW DELHI-110001,INDIA.|
|PCT International Classification Number||A61L 17/00|
|PCT International Application Number||N/A|
|PCT International Filing date|