Lead (II) removal from aqueous solution over Al-pillared bentonite as low-cost adsorbent and optimization

Abstract

This study focuses on the optimization of lead ion (Pb2+) removal from aqueous solution by modified Aceh natural bentonite using response surface methodology (RSM). The modification process involves sodium ion (Na+) from NaCl intercalation and pillarization with aluminum ion (Al+) from AlCl3. The composition of natural and modified bentonite was examined via X-ray fluorescence (XRF). The surface area of the samples was characterized by Brunauer Emmett and Teller surface area (BET) analysis. In addition, the experiments were conducted based on Box-Behnken Design (BBD). Furthermore, adsorption characteristics were investigated as a function of three independent factors comprising bentonite mass (1.0–2.0 g), agitation time (30–200 min), and initial lead concentration (100–500 mg/l). Analysis of variance (ANOVA) depicted the influence of these variables is very significant. Also, optimization equations were developed for the natural, intercalated, and pillared samples. Based on the RSM model, the optimized conditions were found at 1.93 g bentonite mass, 176.42 min agitation time, 367.44 mg/l of its initial adsorbate concentrations viz. 250.264 mg/l (NB), 253.902 mg/l (IB), and 260.768 mg/l at approximately 1.00 desirability. Therefore, Pb2+ adsorption capacity onto the pillared bentonite (PB) appears greater compared to the intercalated and natural materials. Al-pillared bentonite appears to be a promising candidate for the adsorbent of Pb2+ from an aqueous solution.