Recycling Building Wastes and Dewatered Alum Sludge in Permeable Reactive Barriers (PRBs) to treat the Heavy Metals of the Ground Water Contaminated by Landfill-Leachate

Abstract:            Permeable Reactive Barriers (PRBs) can effectively be applied to treat the groundwater contaminated by the landfill-leachate. The introduction of low-cost reactive materials would make PRBs more applicable in this context. This study focused on investigating the applicability of building wastes (BW) and dewatered alum sludge (DAS) as reactive materials in PRBs using batch sorption experiments. Building wastes and DAS are controversial solid wastes due to the lack of disposal sites. The objectives of this study were to identify the influences of contact time and adsorbent dosage on the adsorption of heavy metals onto different types of BW and DAS, and thereby to obtain the adsorption capacities. The building wastes were classified into four categories; flooring wastes (FW), brick and mortar wastes (BMW), roofing wastes (RW), and concrete wastes (CW). Both kinematic and adsorption isotherm experiments were conducted to optimize the contact time and adsorbent dosage, respectively. The reactive materials best suited to treat Fe, Cd, Zn, Mn, Cu, Pb and As were BMW (removal efficiency - 90.9 %), BMW (75.5 %), DAS (68.4 %), CW (78.2 %), DAS (39.7 %), DAS (69.4 %) and BMW (48.6 %), respectively. The corresponding adsorption capacities for the removal of Fe by BMW, Zn by DAS, Mn by CW and Cu by DAS were 530, 2.8, 3.0, 0.1 mg/g, respectively. The Langmuir isotherm equation fitted most of the above adsorption processes.