Nano-Clay and Iron Impregnated Clay Nanocomposite for Cu and Pb Ions Removal from Aqueous Solutions

Abstract

Several physicochemical techniques have been widely studied for heavy metals removal despite most of them are associated with challenges of higher cost, accessibility, and complex technical feasibility. In this study, nano-sorbent materials were developed from a naturally available clay matrices and its heavy metals (Cu 2+ and Pb 2+ ) removal capacity was tested at its pristine and iron impregnated form. Both top to down and borohydride reduction methods were used to produce the nano-sorbents. The nano-sorbents were characterized by XRD, XRF, SEM, FTIR, BET, and TGA/DGA. The sorption was studied in batch experiments. The surface area, pore-volume, and pore diameter of nano-clay were found 43.49 m 2 /g, 0.104 cm3/g, and 2.81 nm, respectively while iron impregnated nano-clay has shown a surface area (73.11 m 2 /g), pore-volume (0.153 m 3 /g), and pore diameter (3.83 nm). Both nanoparticles have shown a mesoporous nature. The highest Cu 2+ and Pb 2+ removal capacity of nano-clay was 99.2% (~11.9 mg/g) and 99.6% (~11.95 mg/g), respectively. Whereas, the iron impregnated nano-clay has achieved the highest Cu 2+ and Pb 2+ removal efficiency 99.8% (~11.97 mg/g) and 99.7% (11.96 mg/g), respectively. The highest Cu 2+ adsorption efficiency of iron impregnated nanoclay was achieved at pH 5.0, adsorbent dose 0.83 g/L, contact time 150 minutes, and Cu 2+ initial concentration 4 ppm while its highest Pb 2+ adsorption activity was achieved at pH 5.0, contact time (90 minutes), Pb 2+ initial concentration (6 ppm), and the adsorbent dose (0.67 g/L). Whereas, the Cu 2+ adsorption using nano-clay was highest at pH 5.0, contact time (180 minutes), adsorbent dose (1.0 g/L), and Cu 2+ initial concentration (2 ppm). While, pH 5.0, contact time (90 minutes), adsorbent dose (0.83 g/L), and Pb 2+ initial concentration (4 ppm) was found to the conditions of highest Pb 2+ removal. In all cases, the pseudo-second-order kinetics indicated the presence of chemisorption. Langmuir adsorption characteristics has been reflected on Pb 2+ and Cu 2+ removal activities of the nanoclay and iron impregnated nanoclay, respectively. Whereas, Freundlich isotherm model was better fitted for Cu 2+ adsorption activity of the nanoclay. The −ΔG (<−20 KJ/mol), + ΔH °, and + ΔS ° have shown a spontaneous and endothermic adsorption activity with a high level of adsorbents disorder. In general, the result of iron impregnated nano-clay has shown a promising result for the removal of Cu 2+ and Pb 2+ aqueous solution.