Nano chromium embedded in f-CNT supported CoBi-LDH nanocomposites for selective adsorption of Pb2+and hazardous organic dyes

Abstract

Transition metal–doped carbon-coated layered double hydroxides for the removal of lead (II) and hazardous organic dyes have attracted increasing attention for wastewater treatment in recent years. In this work, nanostructured CoBi-LDH/Cr@CNT composites were successfully synthesized by hydrothermal route. The CoBi-LDH/Cr@CNT was characterized by instrumental techniques such as XRD, FTIR, TEM, SEM, XPS and TGA/DTA. Adsorption of Pb2+ and organic dyes, i.e.,Rose Bengal (RB) and Congo red (CR) by CoBi-LDH/Cr@CNT was performed by batch experiment.The effect of several parameters including contact time, adsorbent dose, pH, temperature, and concentration was also investigated. Under optimum conditions, the adsorption capacity of CoBi-LDH/Cr@CNT for RB, CR and Pb2+ pollutants were (278.4 mg g−1), (164.6 mg g−1) and (503.2 mg g−1) and the removal efficiency achieved is 98.2%, 95.0% and 100% respectively. The selectivity of CoBi-LDH/Cr@CNT nanocomposite towards Pb2+ has been studied using ICP-AES.The isothermal results were analyzed using Freundlich and Langmuir models. Adsorption isotherm for Pb2+(R2 = 0.975), RB (R2 = 0.997) and CR (R2 = 0.992) agrees with the Langmuir model indicating monolayer adsorption. The sorption kinetics data well fitted pseudo-first-order model for Pb2+ (R2 = 0.975), RB (R2 = 0.996), and CR (R2 = 0.995).The results demonstrated that the synthesized CoBi-LDH/Cr@CNT nanocomposite can be used as an effective sorbent for the removal of pollutants from wastewater.