Selective Removal of Hexavalent Chromium by Novel Nitrogen and Sulfur Containing Cellulose Composite: Role of Counter Anions

Exploiting an adsorbent with superb selectivity is of utmost importance for the remediation of Cr (VI)-laden wastewater. In this work, a novel nitrogen and sulfur functionalized 3D macroporous cellulose material (MPS) was prepared by homogeneous cross-link cellulose and polyvinylimidazole, followed by ion exchange with MoS. MPS exhibited high removal efficiency at a broad pH range (1.0-8.0) and large adsorption capacity (379.78 mg/g) toward Cr (VI). Particularly, outstanding selectivity with an enormous partition coefficient (1.01 × 10 mL/g) was achieved on MPS. Replacing MoS with Cl and MoO led to a sharp decline in adsorption selectivity, demonstrating that MoS contributed substantially to the selectivity. Results of FTIR, XPS, and apparent kinetic analysis revealed that Cr (VI) was first pre-enriched on the MPS surface via electrostatic and dispersion forces, and then reacted with MoS to generate Cr (III), which deposited on MPS by forming Cr(OH) and chromium(III) sulfide. This study provides a new idea for designing adsorbents with a superior selectivity for removing Cr (VI) from sewage.