Synergistic and simultaneous removal of heavy metal ions over waste bamboo shoot particles encapsulated carboxymethyl cellulose/gelatin composite hydrogel.

Abstract

Carboxymethyl cellulose (CMC) hydrogels are commonly used for heavy metal removal due to their abundant hydroxyl and carboxyl groups. However, pristine CMC hydrogels always suffer from low gel strength and limited adsorption properties in large-scale applications. In this study, to improve the gel strength and heavy metal ions removal capacity, fish gelatin and bamboo shoot particle (BSP) were introduced to CMC hydrogels, respectively. The formation of the composite hydrogel with enhanced gel strength was primarily driven by hydrogen bonding, which exhibited an increase strain resistance with a critical strain value up to 214.68 %. As expected, the composite hydrogel can effectively remove Cd²⁺, Hg²⁺, and Pb²⁺ from aqueous solutions simultaneously. The physical adsorption process of heavy metals by the composite hydrogel was well described by the pseudo-second-order kinetic model, while the Langmuir model indicated maximum adsorption capacities of 147.7 mg/g for Cd²⁺, 88.62 mg/g for Hg²⁺, and 163.89 mg/g for Pb²⁺. Notably, the composite hydrogel exhibited enhanced recyclability, maintaining its efficacy for up to at least five cycles. This study underscores the potential of using naturally occurring biodegradable materials for the removal of heavy metals, and paved ways for heavy metal removal at industrial levels.