High adsorption capacity of Pb2+ by iminodiacetic acid functionalized ramie via radiation grafting

Abstract

Wastewater containing heavy metal ions discharged from industries has caused serious pollution to water. As for how to use renewable resources as the substrate, green preparation of adsorbents through eco-friendly processes and effective disposal of metal ions has become urgent. In this work, the low-cost, environmentally-friendly and easily modified natural renewable biomass ramie was used as the substrate, and glycidyl methacrylate (GMA) containing epoxy functional group was grafted onto ramie via electron beam irradiation (grafting rate up to 332.3 %). A ramie-poly-GMA-IDA (RGD) adsorbent was prepared by ring-opening reaction and grafted with iminodiacetic acid (IDA). The adsorption process was affected by pH, the RGD could effectively uptake Pb2+ when the pH = 5.0, and the adsorption equilibrium can be quickly reached within 50 min. Moreover, RGD possessed excellent uptake properties, and the Pb2+ adsorption capacity maximized to 225.71 mg/g. The adsorption procedure obeys a pseudo-2nd-order kinetic and Langmuir equation. The possible mechanisms for Pb2+ adsorption are complexation, electrostatic interaction and ion exchange. This study presents that IDA-functionalized ramie can be used as an efficient biomass-based adsorbent for Pb2+ uptake. Thus, a green, closed-loop utilization of agricultural and forestry wastes is achieved, which helps reduce heavy metal ion pollution and resource consumption and protect the environment.