Structural design of cellulose-hyperbranched double-network for enhanced intramolecular diffusion kinetics of heavy metal ion capture processes

Abstract

Extracting cellulose from agricultural residues and converting it into environmentally friendly adsorbents to solve the heavy metal contamination problem of groundwater and farmland is an effective strategy to achieve high-value utilization of agricultural residues. Herein, we propose a streamlined crosslinking strategy to fabricate a cellulose-based amphoteric hyperbranched adsorbent (MAHPA) in a controlled manner. The strategy involves synthesizing the amphoteric hyperbranched functional reagent first and then crosslinking it with microcrystalline cellulose (MCC). This approach simplifies the complexity of the multi-component cross-linking system, resulting in a conversion rate of reaction reagents exceeding 99 %. MAHPA, with a three-dimensional hyperbranched structure (degree of branching: 0.77), exhibits a high swelling rate (247.62 %) and high densities of carboxyl (7.05 mmol·g−1) and amino (8.27 mmol·g−1) groups. Moreover, the cellulose-hyperbranched double-network structure of MAHPA greatly enhances the intramolecular diffusion kinetics of heavy metal ions on MAHPA, enabling it to complete the removal of low concentrations of Cr(VI), As(V), Pb(II), and Cd(II) within 20 min. Interestingly, MAHPA demonstrates excellent synchronous capture performance for Cr(VI), As(V), Pb(II), and Cd(II) in groundwater at a velocity of 1.60 × 10−2 m·s−1. Meanwhile, applying MAHPA can realize the safe utilization of Cd-As contaminated soil. This work offers a general strategy for the structural design of cellulose-based hyperbranched adsorbent holding great promise as heavy metal contaminated groundwater and soil remediation field.