Question

Agricultural waste from which activated carbon can be manufactured include(s)

(A) Rice husk

(B) Groundnut shell

(C) Oil cake

(D) Mango stone

Choose the correct answer from the options given below:

• A. (A) and (B) only.
• B. (A), (B), (C) and (D).
• C. (C) and (D) only.
• D. (A), (B) and (D) only.

Hint:

Ask which of these four wastes is nutrient rich and used as feed or manure rather than being a hard, carbon rich shell or husk.

Answer 1

The Correct Option is D

Step 1: Activated carbon needs a raw material rich in fixed carbon that leaves a strong porous skeleton after carbonization and activation. Lignocellulosic wastes such as husks, shells and stones fit this need well.

Step 2: Rice husk is one of the most common raw materials for activated carbon. It is abundant, has a high carbon and silica content, and gives good pore structure after activation. So (A) qualifies.

Step 3: Groundnut shell is another documented precursor. Like other nut shells, it carbonizes into a hard porous char suitable for activation, so (B) qualifies.

Step 4: Mango stone, the hard seed shell, is also reported as a workable precursor for activated carbon, since it is a hard, carbon rich, lignocellulosic material similar to other fruit stones used for this purpose. So (D) qualifies.

Step 5: Oil cake is what remains after oil is pressed out of an oilseed. It is rich in protein, residual fat and other nutrients, which is exactly why it is valued as animal feed and organic manure. It does not have the carbon rich, hard, ligneous structure needed to make good activated carbon, so (C) does not qualify.

Step 6: Combining the qualifying wastes gives (A), (B) and (D) only, matching option 4.