Adsorptive property and regeneration of activated carbon for dissolved salicylic acid and humic acids in water

Abstract

In this work, optimal conditions for individual adsorption and simultaneous adsorption of salicylic acid and humic acids onto granular activated carbon were studied. Adsorption conditions were optimized for batch method such as initial pH of solution, initial concentration and contact time. Optimal conditions for desorption of salicylic acid and humic acids from granular activated carbon were studied. Desorption conditions were optimized for batch method such as eluent type and contact time. The optimal initial pH for individual adsorption of salicylic acid and humic acids were 1.0 and 4.0, respectively. The optimal initial concentrations of salicylic acid and humic acids were 400 and 100 ppm, respectively while the equilibrium time of salicylic acid and humic acids was reached within 4 hours. Adsorption behaviors of salicylic acid and humic acids followed Langmuir and Freundlich adsorption isotherm. The maximum adsorption capacity of the granular activated carbon for adsorption of salicylic acid and humic acids were 175.4 and 16.3 mg/g, respectively. The rate of adsorption could be predicted with the pseudo second order model. The optimal conditions for simultaneous adsorption of salicylic acid and humic acids were found as follows, initial pH 4.0, initial concentration of salicylic acid and humic acids were 400 and 100 mg/L, respectively. The maximum adsorption capacities for salicylic acid and humic acids were 101.1 and 12.2 mg/g, respectively and the equilibrium time was reached within 4 hours. Optimal conditions for desorption of salicylic acid and humic acids from granular activated carbon were found to be 5% NaOH in 10% ethanol/water as eluent and 1 hour desorption time. Elution of salicylic acid and humic acids from granular activated carbon were 81.6 and 62.3%, respectively. A number of reuse of sorbent after regeneration was possible and the adsorption efficiency decreased gradually.