A low-cost recyclable protonated 3D network gel for efficient Pb2+ capturing from contaminated wastewater

Abstract

Background

As a dangerous heavy metal element, lead can pose a serious health hazard to living organisms even at very low concentrations. The aim of the present work was to study the Pb²⁺ adsorption by surface protonated sodium alginate gel adsorbents (SA/H⁺ gel beads).

Methods

First, surface protonated sodium alginate gel adsorbents (SA/H⁺ gel beads) were synthesized by a simple two-step method. Secondly, the adsorption properties of the gel material were optimized and determined by batch adsorption experiments.

Significant findings

The adsorption experiments showed that the limiting adsorption capacity of SA/H⁺ hydrogel beads for Pb²⁺ could reach 307.90 mg/g under the conditions of pH=5 and temperature of 298 K. The results of isotherm and kinetic studies showed the Langmuir isotherm and pseudo-second order kinetic model were the best fitted models (R² > 0.99), which indicated that the adsorption process was a spontaneous heat absorption process with chemisorption dominated by the monolayer adsorption. In addition, the SA/H⁺ gel beads showed satisfactory results for removal of Pb²⁺ from actual water samples, excellent regeneration and the removal rate of Pb²⁺ still remained after six “adsorption-desorption-adsorption” cycles close to 96%. Accordingly, the SA/H⁺ gel beads provides a new feasible solution for the adsorption and recovery of Pb²⁺ pollutants in wastewater.