EDTA-functionalized clinoptilolite nanoparticles as an effective adsorbent for Pb(II) removal

Abstract

An efficient Pb(II) adsorbent was prepared by the modification of clinoptilolite nanoparticles (CpN) with ethylenediaminetetraacetic acid (EDTA). Samples were characterized by XRD, FT-IR, SEM, BET, TG-DTG, CHNS analyzer, and energy dispersive analysis X-ray spectroscopy (EDX). The experiments were designed by response surface methodology (RSM) based on central composite design (CCD) that suggested a quadratic model to predict the conditions and the interactions between the variables including adsorbent dosage, removal time, C_Pb, and its solution pH. Adequacy of the suggested quadratic model was judged by ANOVA. The maximum Pb(II) removal of 0.27 mmol_Pb(II)/g_ads was achieved in optimal run including adsorbent dosage 2 g L⁻¹, removal time 271 min, C_Pb 22.51 mmol L⁻¹, and Pb(II) solution pH 5.88. In binary metal cation systems including 1000 mg L⁻¹ with respect to both Pb(II) and interfering cations, good selectivity of CpN-EDTA adsorbent was observed towards Pb(II) among the tested cations except Fe(III). Adsorption isotherm of lead removal by the adsorbent was well modeled by Langmuir equation, indicating a monolayer sorption of Pb(II) onto the adsorbent. The pseudo-second-order rate equation, indicating chemical reaction rate limiting step for the process, well modeled the kinetic of the process. An exothermic and spontaneous process was confirmed by the negative ∆H and ∆G.