Synthesis of a novel Guar gum-bentonite composite for effective removal of Pb(II) species from wastewater: Studies on isotherms, kinetics,thermodynamic and adsorption mechanisms
Xiao Wang, Changsheng Tian, Fengshu Sun, Shuangshuang Wu, Qi Jiang, Kaiyi Ji, Ru Li
Abstract
In this study, a novel guar gum-bentonite composite was synthesized and its efficiency for removal of the Pb(II) species from wastewater was evaluated. The results from adsorption experiments showed that the material achieved maximum adsorption of the Pb(II) ions at pH value of 4 and contact time of 120 min. The composite material was characterized by TEM, SEM, EDX, XRD, FTIR, and TGA. Kinetic studies were carried out based upon pseudo-first-order and pseudo-second order models, as well as intraparticle diffusion model, in which pseudo-second-order model exhibited optimal fitting results, confirming that chemisorption plays the role as rate-determining step in the adsorption process. Besides, the intraparticle diffusion model demonstrates that adsorption of the Pb(II) ions on guar gum-bentonite composes of three steps. The test results were fitted with Langmuir, Temkin, Sips as well as Freundlich isotherm models. The best fitting was observed with the Freundlich isotherm model, which implies a multilayer adsorption of Pb(II) on this material. For Langmuir isotherm model, maximum adsorption capacity was found to be 200.23 mg·g-1. Thermodynamic studies have shown that this process is spontaneous, heat-absorbing as well as stochastic increasing chemisorption process. The material was regenerated using 0.15 M HCl and the regeneration could reach the fifth cycle. The composite was also successfully used for removing heavy metals from the battery manufacturing wastewater.