Phenol removal from aqueous solution by adsorption onto solidified landfilled sewage sludge and its modified sludges

Abstract

This study addresses the removal of phenol from aqueous solutions using solidified landfilled sewage sludge and its modified sludges as adsorbents. After the sludge was characterized using instrumental techniques, adsorption studies were performed in a batch system, and the effects of various experimental parameters were evaluated upon phenol adsorption. The characterization results revealed that more irregular pores, higher surface roughness, and a greater content of oxygen-containing functional groups formed in adsorbents derived from ZnCl2 or ZnCl2 and H2SO4 activation. Batch experiments revealed that pH had the weakest effect on phenol adsorption, regardless of the adsorbent type. With increasing adsorbent dosage, the phenol adsorption capacity decreased, and the phenol adsorption rate gradually increased. The maximum adsorption capacity occurred within 120 min, and a first-order kinetic model best described the adsorption. The equilibrium data fitted both the Langmuir and Freundlich isotherm models well, whereas a much higher adsorption capacity and better adsorption strength were observed for phenol adsorption onto adsorbents derived from ZnCl2 or ZnCl2 and H2SO4 activation. The results demonstrated that the solidified landfilled sewage sludge previously modified by activator treatment had a heterogeneous surface and was an effective adsorbent for phenol removal from aqueous solution.