Isotherm studies of methylene blue adsorption onto potassium salts-modified textile sludge

Abstract

In the present work, the adsorption of methylene blue from aqueous solution by textile sludge activated with potassium salts and a composite-KI, KCl, K2SO4 and KOH+KCl-was investigated. The impregnation ratio for all activating agents was set at 1:1 and the impregnated textile sludge samples were activated at 500oC for 1h in a furnace. The specific surface area of the activated carbon (AC) was evaluated using BET analysis. The BET surface area varied from 78.8 to 321m2/g, where it decreased in the order of K2SO4-AC > KCl-AC > KI-AC > KOH+KCl-AC. Under room temperature condition and a shaking time of 72h, the batch adsorption results show that the minimum and maximum adsorption capacities were recorded as 39.1 and 85.0mg/g for textile sludge activated with KCl and KI, respectively. Langmuir isotherm model gave the best fit to adsorption equilibrium compared to Freundlich isotherm model indicating a monolayer adsorption at homogeneous sites on the adsorbent. The Langmuir mechanism yielded a maximum monolayer adsorption capacity of 90.9mg/g. Among the four prepared activated carbons, textile sludge activated with potassium iodide (KI-AC) gave the best performance on the adsorption of methylene blue.