This invention relates to a process for the preparation of activated carbon from botanical sources.
The botanical sources for carrying out the process proposed herein are Calotropis Gigantea, a waste land weed of Indian Origin, and Borassus Flabellifera, the palmyra palm. Both Calotropis Gigantea and Borassus Flabellifera have not so far been conceived as potential sources of activated carbon and as a result find no mention in known scientific literature..
Both the above mentioned sources of carbon possess inherent hollow and porous morphology and this property of the starting material is of benefit in generating uniform microporous high specific surface area carbon materials. Also volatile matter, ash content, apart from carbon content, are other properties of interest in general for choosing a precursor for the production of activated carbon.
There are several activating agents that have been employed for the production of activated carbon materials with desired pore structure. The purpose of activation is to create and develop (volume and size) porosity in the carbon material and thereby increase the adsorptive capacity. All the available methods of activation can be classified into two types, namely, physical activation and chemical activation depending on whether a gaseous or solid activating agent is used. Each of these methods have their own merits and demerits.

In the method of physical activation the reaction involved is between carbon atom and the oxidizing gas. It is this reaction that give rise to the pore creation and development as some parts of the char structure react fester than the others. During this reaction if carbon atoms were to be removed from the interior of incipient pores formed as a result of devolatilization during carbonization, enlargement of opened micropores and the opening up of the closed micropores take place. If the burn off were to be from outside of the particle no new porosity results but it facilitates the reduction of particle size. Since physical activation uses gaseous activation agents and does not produce waste water this method is considered to be an environmentally benign technology. But all is not well with this process. It takes a long time and much energy for producing mkroporous activated carbon through physical activation methods. Also another inherent draw back of this method is that a large amount of internal carbon mass is eliminated to obtain well developed pore structure. And thus one has to satisfy himself with limited carbon yields if one were to take this route.
On the other hand, chemical activation is a single step process for the preparation of activated carbon wherein carbonization of an organic precursor in the presence of chemical agents takes place. In this method a solid activating agent employed acts as a dehydrating agent that influences pyrolytic decomposition inhibiting the formation of tar and thereby enhancing the yield of carbon. The temperatures used in chemical activation are lower than that used in the physical activation process. As a result, the development of a porous structure is better

in the case of a chemical activation method. However, in spite of the afore mentioned benefits the chemical method has its own inherent drawbacks, such as, the need for washing of the product to remove residual inorganic material which causes serious pollution problems.
The process proposed herein for the preparation of activated carbon is distinctly different from either physical or chemical activation processes known so far, which saves time and energy, needs no expensive and sophisticated equipment like the ball mill or temperature programmed tubular furnace but yields highly ordered well aligned microporous high specific surface area carbon.
Needless to say, the procedure employed is simple, inexpensive, and environmentally benign thus satisfying the prerequisite to the use of these materials much beyond laboratory scale.
The process proposed herein includes removal of volatile matter m a muffle furnace where in limited supply of air will be present facilitating the easy (in terms of time and avoiding the need for inert gas) removal of volatile matter, yielding coal from respective carbonaceous sources. This step helps in avoiding the use of ball milling which is employed in literature to get fine particles of carbonaceous raw material to which chemical activating agents are added by solution impregnation in general.

The coal so obtained is carbonized farther and subjected to activation in a single step by the use of chemical activating agents and nitrogen gas. Also, instead of solution impregnation which in general takes a longtime, physical impregnation is adopted in the process proposed herein which considerably saves time. In the process proposed herein the required amount of activating agent is added to a predetermined amount of the carbon material obtained as aforesaid; and physically ground for a few minutes and loaded on to an alumina boat. The boat is placed in a tubular furnace. Inert (N2 gas) atmosphere is maintained in the tubular farnace. The temperature of the furnace is maintained between at 800 °C for 2 hours. Also to make the proposed process more environmentally friendly use of acids like HF is avoided for the removal of traces of inorganic impurities. Instead concentrated HC1 is employed for the removal of the decomposed products of the inorganic activating agent. In addition to the removal of the remains of activation it was found that HCl treatment facilitates the reduction of ash content by removing the mineral matter mat is inherently present in the carbon.
The process proposed herein will now be described with reference to the following Examples which illustrate, but do not limite, the scope of this invention.

Example: Preparation of activated carbon from Calotopis Gigantea The stems of the plant Calotopis Gigantea were collected and dried in sunlight The dried stems were placed in a muffle furnace. The temperature of the furnace is raised up to 300 °C. The material is kept at that temperature for 30 minutes. Partial removal of volatile matter takes place. The coal obtained is ground using a mortar and pestle and sieved through 200 mesh to get fine particles of carbon material. The specific surface area of the material thus obtained is 97 m2/g. In order to increase the specific surface area of the carbon material by developing porosity it was mixed by weight with different amounts of activating agent. The ratio of carbon as synthesised to the activating agent is 1:1, 1:2, 1:3, 1:4 and 1:5 (wt,/wt%). Each of the above mixtures is placed in a tubular furnace and subjected to thermo chemical activation at 800 °C for & h in inert atmosphere (N2
1
atmosphere). After reducing the temperature of the furnace to room temperature the sample is removed from the furnace and then subjected to acid treatment with cone. HCI for I h with the wt./wt.% ratio of carbon and HCI being 1:5. HCI treatment in addition to facilitating demineralization (removal of Na, K, Mg, Fe inherently present in the lignocellulosie material) also removes the species formed (like K, Na from K2CO3 and Na2CC>3 which are used as activating agents) by the in situ reduction of activating agent during thermochemical activation of carbon. Acid treatment step is followed by filtration through sintered funnel and washing with excess water.

The activated carbon thus obtained is dried in air oven at 200 °C . Example: Preparation of activated carbon from Borassus Flabellifera:
Dried male flower spikes of the plant Borassus Flabellifera were collected and taken in a glass beaker and placed in a muffle furnace. The temperature of the furnace is raised up to 300 °C. The material is kept at that temperature for 30 minutes. Partial removal of volatile matter takes place. The coal obtained is ground using a mortar and pestle and sieved through 200 mesh to get fine particles of as synthesized carbon material (char). The specific surface area of the material thus obtained is 17 m2/g. In order to increase the specific surface area of the as synthesized material it was physically mixed with K^Oa (Carbon *. K^X>3 * 1.1 by weight). The mixture of carbon and activating agent is then taken in an alumina boat and placed in a tubular furnace and subjected to thermo chemical activation at 800 °C for 8 h in inert atmosphere (N2 atmosphere). After reducing the temperature of the ftumace to room temperature the sample is removed from the furnace and men subjected to acid treatment with cone. HC1 fori h with the wt/wt % ratio of carbon and HCl being 1:5. HC1 treatment facilitates the removal of the decomposition product (K2Q) as well as the reduction product (potassium metal) from the activating agent (K2C03).

List of activating agents that may be used in the process proposed herein.
1. Potassium carbonate (K2CO3)
2. Sodium carbonate (Na2C03)
3. Sodium oxalate (Na2C204)
4. Zinc carbonate (ZnC03)
5. Sodium acetate (CH3COONa)
6. Calcium carbonate (CaC03)
7. Calcium oxide (CaO)
8. Lithium carbonate (Li2C03)
9. Urea (NH2CONH2)
10. Sodium citrate (Na3C6H507 2H20)
11. Sodium chloride (NaCl)
12. Sodium potassium tartarate (KNaC^Oe. 4H20)
13. Sodium tartarate (^C^Oe)
14. Sodium bromide (NaBr)
15. Potassium bromide (KBr)
16. Calcium hydroxide (Ca(OH)2)
17. Alumina (AI2O3)

We Claim:
1 A process for the preparation of activated carbon from botanical sources comprising the steps of drying parts of a plant selected from Calotopis Gigantea or Borassus Flabellifera; placing the dried parts in a muffle furnace; raising the temperature of the said furnace up to 300 °C and keeping the heated material in the furnace at the said temperature for 30 minutes during which period partial removal of volatile matter takes place; the coal so obtained being ground and sieved through 200 mesh to get fine particles of carbon material; mixing the said carbon material with activating agent; placing the resulting mixture in a tubular furnace and subjecting the same to thermo chemical activation at 800 °C for 8 h in inert "N2 atmosphere; reducing the temperature of the furnace to room temperature, removing the heated mass from the furnace and subjecting the same to acid treatment with cone. HCl for 1 h with the wt/wt.% ratio of carbon and HCl being 1:5; filtering the resultant and washing with excess water; and drying the activated carbon thus obtained in an oven.
2. A process as claimed in Claim 1 wherein the parts of the plant Calotopis Gigantea which ore dried are the stems of the said plant

3. A process as claimed in Claim 1 wherein the parts of the plant Borassus Flabellifera which are dried are the male flower spikes of the said plant.
4. A process as claimed in any one of the preceding Claims wherein the ooal obtained, before sieving, is ground with a mortar and pestle.
5. A process as claimed in any one of the preceding Claims wherein the mixture of carbon material with activating agent is placed in an alumina boat and then placed in the tubular furnace.
6. A process as claimed in any one of the preceding Claims wherein the activated carbon in dried in an air oven, at 200 °C.
7.A process for the preparation of activated carbon from botanical sources substantially as herein described and illustrated with reference to the Examples.
8 Activated carbon when prepared by a process as claimed in any one
ofthe preceding Claims.