Title of Invention

A MODIFIED ACTIVATED CARBON AND A PROCESS FOR PREPARATION THEREOF

Abstract

The present invention provides an iron impregnated activated carbon for removal of arsenic from contaminated or drinking water. Coconut shell based activated carbon is impregnated with iron metal by heating the mixture of activated carbon and iron salts in an oven at 100-120 C in an alkaline pH. The iron impregnated activated carbon removes Arsenic III, Arsenic V and organic Arsenic up to more than 99% and the leaching of iron is less than 0.3 ppm. Due to this negligible leaching of iron, the modified activated carbon can be reused for arsenic remediation.

Full Text

FIELD OF INVENTION This invention relates to a modified coconut shell based activated carbon and a process for preparation thereof. PRIOR ART One of the conventional systems known in the art, for removing contaminants from water, is to pass the contaminated water through a body of activated carbon. The activated carbon for this purpose, is generally prepared from coconut husk, coconut shell and rice husk. The activated carbon thus prepared is granulated and without any surface modification. The disadvantage of using above mentioned activated carbon is that it does not have much adsorption for arsenic in aqueous medium. Another disadvantage of using above mentioned activated carbon is that over a period of time the contaminants build up on the activated carbon, which have to be periodically removed. ' Yet another disadvantage of using above mentioned activated carbon is that it functions simply to strip the contaminants of water and the contaminants thus removed from the activated carbon are more hazardous as they are in concentrated form. Another activated carbon known in the art is copper impregnated coconut husk carbon which is also known to remove arsenic from water. The disadvantage of above mentioned copper impregnated activated carbon is that it does not remove arsenic from drinking water to the desired limit. OBJECTS OF THE INVENTION The main object of the present invention is to provide a modified coconut shell based activated carbon and a process for preparation thereof wherein the modification is through impregnation of activated carbon with iron. Another object of the present invention is to provide modified activated carbon and a process for the preparation thereof, where-in modified activated carbon thus prepared has the capacity to adsorb arsenic from water upto an extent greater than 99%. Yet another object of the present invention is to provide modified activated carbon and a process for the preparation thereof, where-in modified activated carbon thus prepared has the capacity to remove all forms of arsenic viz. Arsenic III, Arsenic V and organic Arsenic to the desired permissible limit of drinking water prescribed by Environment Protection Agency (EPA). Still another object of the present invention is to provide modified activated carbon and a process for the preparation thereof, which is inexpensive. Further object of the present invention is to provide modified activated carbon and a process for the preparation thereof, where-in there is no leaching of metal ions.DESCRIPTION OF THE INVENTION According to the present invention there is provided a process for the preparation of modified coconut shell based granular activated carbon comprising the steps of: (a) Mixing washed and dried coconut shell based granular type of activated carbon with concentrated solution of iron salts such as iron nitrate or iron chloride or any combination thereof (b) heating the mixture (c) Washing the mixture with analytical grade water and drying in an oven till constant weight is achieved. The present invention comprises in washing the coconut shell based granular type of activated carbon with water and drying in oven at temperature range of 100-120 C till constant weight is achieved. A concentrated solution of iron salt such as iron nitrate or iron chloride or any combination thereof, in 1 to 4 M preferably 2 to 3 M range is prepared, and 200 to 300 ml preferably 230 to 260 ml of such a solution is mixed with 50-100 gm preferably 60 to 90 gm of activated carbon obtained and maintaining the pH of the mixture between 9-12 by adding concentrated solution of sodium hydroxide. Thus the volume to weight ratio between solution and activated carbon is kept in the range 2:1 to 6:1 preferably in 2.5:1 to 4.3:1. The mixture is heated in an oven at a temperature range of 100-120* C for 20-28 hours. The mixture is washed with analytical grade water and drying in an oven till constant weight is achieved. The invention will now be illustrated with a working example which is intended to be a typical example to illustrate the working of the invention and is not intended to imply any limitation on the scope of the present invention. WORKING EXAMPLE 100 gm of coconut based granular activated carbon having surface area 1150m1~/g was washed with analytical grade Milli-Q water and dried in an oven at 105 C for approximately 24 hours, till constant weight is achieved. To this 240 ml of of Fe(NO3)3.9H2O was added. pH of the solution was maintained at 12 by adding 250 ml of IN NaOH solution. The resultant mixture was kept in an oven for 24 hours at 120°C. The treated carbon so obtained was washed thoroughly with analytical grade Milli-Q water till water became colourless. Then dried it in an oven at 120°C for approximately 24 hours, till constant weight was achieved. Modified activated carbon thus obtained was then evaluated for its performance for the removal of arsenic from contaminated water. EVALUATION The total percentage of the iron impregnated on carbon is about 4-5% by weight as confirmed by XRF (X-ray fluorescence) technique. The increase in the BET (Brunauer, Emmett and Teller) surface area of carbon is about 100-200m2/g as studied by Micromeritics ASAP 2010 surface analyser. The modified activated carbon obtained according to the above process was then subjected to the physical characterization and to the adsorption/remediation experiments. The values as shown for each characteristic are given below: Parameter Analytical Value 1. Surface area (BET) (m2/g) 1200 -1300 2. pH (in water) 7 - 8 3. pH (in arsenic solution) 8-9 4. Iron (%) 4 - 5 5. Arsenic (III) removal (%) > 99 6. Arsenic (V) removal (%) > 99 7. Organic Arsenic removal (%) > 99 8. Total arsenic removal in real water sample (%) > 99 9. Leaching of iron (ppm) Varying doses (ranging from 5-80g/L) of the modified activated carbon was added to 100ml, Ippm (parts per million) synthetic solution of Arsenic III, Arsenic V, organic Arsenic and real water samples (450 and 600ppb) in stoppered glass bottles. The mixture was shaken for twenty four hours in thermostatic shaker at a speed of lOOrpm (rotation per minute) at 30°C. The solutions were allowed to settle and then filtered. Arsenic concentrations before and after adsorption were determined using GBC-HG-3000 Atomic absorption spectrophotometer. Iron concentration was also measured in the filtered solutions using Grafite Furnace - atomic absorption spectrophotometer technique. Results of these studies are shown in table below: It is clear from the foregoing description and the analytical data as described above, the modified activated carbon as disclosed in the present invention is definitely suitable for arsenic removal. In addition it has negligible leaching of iron in the water making it reusable for arsenic remediation. It is to be understood that the process of the present invention is susceptible to modifications, changes and adaptations by those skilled in the art. Such modifications, changes, adaptations are intended to be within the scope of the present invention which is further set forth under the following claims: WE CLAIM 1. A process for the preparation of modified coconut shell based granular activated carbon comprising the steps of: (a) Mixing washed and dried coconut shell based granular type of activated carbon with concentrated solution of iron salts such as iron nitrate or iron chloride or any combination thereof (b) heating the mixture (c) Washing the mixture with analytical grade water and drying in an oven till constant weight is achieved. 2. A process as claimed in claim 1, wherein the cone. Solutions of iron nitrate or iron chloride or a mixture thereof are prepared in 1 to 4 M preferably 2 to 3 M range. 3. A process as claimed in claim 1, wherein iron salt solutions are mixed with activated carbon in volume to weight ratio varying from 2:1 to 6:1 preferably 2.5:1 to 4.3:1. 4. A process as claimed in claim 1, wherein the pH of the mixture of the activated carbon and iron salt is maintained between 9-12 by addition of concentrated sodium hydroxide. 5. A process as claimed in claim 1, wherein the heating of mixture of activated carbon and iron salt(s) is carried out at 100-120°C for 20-28 hours. 6. A process for the preparation of modified activated carbon modified substantially as described and illustrated herein.

Documents:

192-DEL-2002-Abstract-(06-11-2007).pdf

192-del-2002-abstract.pdf

192-DEL-2002-Claims-(06-11-2007).pdf

192-del-2002-claims.pdf

192-del-2002-corespondence-others.pdf

192-del-2002-corespondence-po.pdf

192-DEL-2002-Correspondence-Others-(06-11-2007).pdf

192-DEL-2002-Description (Complete)-(06-11-2007).pdf

192-del-2002-description (complete).pdf

192-del-2002-form-1.pdf

192-del-2002-form-18.pdf

192-DEL-2002-Form-2-(06-11-2007).pdf

192-del-2002-form-2.pdf

192-DEL-2002-Form-3-(06-11-2007).pdf

192-del-2002-form-3.pdf

192-del-2002-gpa.pdf