Removal of Heavy Metals from Wastewater Using Sewage Sludge Ash (SSA) as Adsorbent

Abstract

The traditional disposal routs are expensive and environmentally sensitive problem with environmental quality standard being stricter. Therefore, it is important to seek a new tochniqe to this problem. Sewage sludge is carbonaceous in nature and can be riched in organic material. So it can be converted into adsorbent material produced after incineration facilities, in addition sludge incineration can help to stabilize and reduce the volume of sewage sludge, adsorption has been shown to be an alternative method for removing trace metals from wastewater. Adsorption of Chromium and lead ions onto sewage sludge ash from aqueous solutions was studied to enable comparison with alternative commonly available absorbents. Batch experiments were conducted to determine the factors affecting adsorption and kinetics of the process. The adsorption capacity was highest at solution pH range 6–7. The adsorbent to solution ratio and the metal ion concentration in the solution affect the degree of metal ion removal. The equilibrium data were satisfactorily fitted to Langmuir and Freundlich isotherms. Highest metal uptake of 45 and 62 mg/g were observed for Cr and Pb, respectively. Pb showed higher affinity and adsorption rate compared to Cr under all the experimental conditions. Kinetic studies revealed that Pb and Cr uptake was up with 90% or more of the adsorption occurring at 60 min. of contact time. The kinetic data fits to pseudo second order model with correlation coefficients greater than 95%. Increase in the total adsorption capacity was observed when both Cr and Pb ions are present in the solution.

Keywords: Adsorption; Heavy metals; Sewage Sludge Ash; Lead; Chromium; Sewage Sludge