Coconut coir activated carbon: An adsorbent for removal of textile acid azo dye from aqueous solution

The objective of the study is to prepare an adsorbent from an agricultural waste and assess its effectiveness in removing textile acid azo dye from aqueous solution. Activated carbon was prepared from coconut coir and characterized. Adsorption of two textile acid azo dyes, Acid Red 18 and Acid Orange 7, by the activated carbon was examined by batch adsorption test. Extent of dye adsorption depended on contact time, pH and carbon dose. Equilibrium adsorption was attained in 2 h and maximum adsorption occurred at pH 3. Equilibrium adsorption data of the acid azo dyes by coconut coir activated carbon and a coal-based commercial activated carbon conformed to the Langmuir and Freundlich adsorption isotherm models. According to Freundlich isotherm, adsorption capacity of the coconut coir activated carbon for the acid azo dyes is higher compared to that of the commercial activated carbon, whereas according to Langmuir adsorption isotherm, the coconut coir activated carbon has 76-81% of the adsorption capacity of the commercial activated carbon. Coconut coir activated carbon is a low-cost substitute for commercial activated carbon in the removal of acid azo dyes from aqueous solution and textile dye waste.