Activated carbon from textile sludge for the adsorption of reactive black 5 and methylene blue

Adsorption is known to be one of the best techniques for treatment of dye in water. Many types of research had been done in preparing low-cost activated carbon from industrial wastes and agricultural by-products. In this study, activated carbon derived from textile sludge (TS) was synthesized and its performance was tested for removal of reactive black 5 (RB5) and methylene blue (MB) which represent anionic and cationic dyes, respectively. The activated carbon was synthesized through a chemical activation process by sulfuric acid followed with carbonization which was run at 650 ºC in a furnace under nitrogen flow. Textile sludge-activated carbon (TSAC) was characterized by Fourier transform infrared, field emission scanning electron microscopy, energy dispersive x-ray and nitrogen adsorption isotherm analysis. The characterization results revealed that the activated carbon from textile sludge had been successfully synthesized. The Brunauer, Emmett and Teller (BET) surface area of TSAC increased from 90.65 m2/g (BET surface area for TS) to 221.52 m2/g. The adsorption capacity was found to be dependent on adsorption time, pH, adsorbent dosage and initial dye concentration. The adsorption data for both dyes were well fitted to Freundlich isotherm model which explains the heterogeneous nature of the TSAC surface. The adsorption obeys the pseudo-second order kinetic model, which indicates that the adsorption was classified as chemisorption as the rate limiting step. The positive value of enthalpy change confirmed the endothermic nature of the overall process. The negative values of standard Gibbs free energy indicated the feasibility and spontaneity of the adsorption processes while the positive value of entropy change suggested the affinity of TSAC for both dyes and increased randomness at the solid/solution interface during the adsorption process. The highest adsorption capacity for the adsorption of RB5 and MB dyes obtained were 11.978 mg/g and 13.272 mg/g, respectively