Efficient and selective removal of Pb(II) from aqueous solution by modification crofton weed: Experiment and density functional theory calculation

Abstract

A low-cost and selective adsorbent (referred to as CC-CCW@DM) is prepared by modifying crofton weed using 1,3-diaminoguanidine monohydrochloride to achieve Pb(II) removal. Fourier transform infrared spectroscopy analysis results indicate that 1,3-diaminoguanidine monohydrochloride is successfully grafted in the crofton weed after modification. The Pb(II) adsorption process is investigated by adsorption isotherm/kinetic models and adsorption thermodynamics. The adsorption kinetic data are well fitted by the pseudo-second-order model. The adsorption equilibrium data can be better described by the Hill and Redlich-Peterson isotherm models. The maximum Pb(II) adsorption is 234.60 mg/g at a pH of 5 based on the Hill isotherm model. An adsorption thermodynamic study shows that the Pb(II) adsorption process is spontaneous, with △G0 values ranging from −25.85 to −32.52 kJ/mol at 298–318 K. CC-CCW@DM has good selectivity for Pb(II) adsorption in wastewater. Recycling experiments show that Pb(II) removal is 93.14% after three cycles. In addition, the adsorption mechanism is systematically studied. The density functional theory calculation results show that there are three ways to combine Pb(II) with N on CC-CCW@DM. In summary, CC-CCW@DM is a selective and reusable adsorbent with a high adsorption capability.