Equilibrium, kinetic and thermodynamic study of Pb2+ removal from aqueous solution by waste brick dust

Abstract

Many studies have been focused on the investigation of new remediation techniques using adsorption for the fixation of toxic ions to second-rate and low-cost materials. The attention is now focused on waste ceramics, especially the waste brick dust (BD). The adsorption, kinetic and thermodynamic properties of two types of BD (Libochovice and Hevlín – BDL and BDH) were tested for the adsorption of Pb2+ from model solution. Fractionated BD was characterized using X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses, specific surface area (SBET) and pH of point of zero charge (pHPZC). The tests of pozzolanic activity and the stability of Pb2+ in saturated sorbents were also performed. The studied BDs differ significantly in their clay content, SBET and porosity. We can assume that a combination of these parameters is the driving force of the adsorption processes. In general, BDs were confirmed as very good adsorbents for Pb2+ ions. The BDL with a larger SBET and a higher pozzolanic activity proved more than twice the adsorption capacity of BDH. The rate constants and standard Gibbs energy indicated a more favourable and thermodynamically stable adsorption on the BDL compared to the BDH. Physico-chemical parameters of the individual size fractions of the BDs were not found to be critically different.