Removing Pb(II) by means of natural and acid-activated nanoporous clays

Abstract

Heavy metals such as Pb(II) are harmful to both the environment and human health as they are both toxic and stable. Bentonite clays contain Montmorillonite, which is a nano-porous and nano-structured mineral that can act to remove metals. In these experiments, natural bentonite S1 was activated using sulfuric acid solutions under various conditions with a range of Liquid to Solid ratios (L/S), Temperatures (T), Times (t) and Concentrations (C). The activated samples S2 (L/S = 16 mL/g, T = 95 °C, t = 4 h, C = 5 M) and S3 (L/S = 16 mL/g, T = 95 °C, t = 6 h, C = 0.5 M) showed the highest and the lowest amounts of Pb(II) removal, respectively. The characterisation of natural and acid-activated bentonites in terms of Pb(II) separation applications were examined using Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), X-Ray fluorescence (XRF), Brunauer-Emmett-Teller (BET) surface area measurements, and Fourier Transform Infrared Spectroscopy (FTIR). Metal removal experiments were conducted using a suspension of 0.3 g suspended in 25 mL Pb(NO3)2 solution under fixed solution concentrations of 2,000 mg/L. The suspensions were thoroughly mixed for 24 hours at 250 rpm. The results showed the removal capacities of samples followed the order of S2 > S3 > S1, and suggested that the prevailing Pb(II) removal processes were adsorption and ion exchange.