A Novel Magnetic and Amino Grafted Chitosan-Based Composite for Efficient Adsorption and Reduction of Cr(VI): Performance and Removal Mechanism

The discharge of industrial wastewater containing Cr(VI) can severely damage the surrounding environment and cause serious threats to human health. Exploring high-performance adsorbents to rapidly remove Cr(VI) could be a popular idea for solving this problem. Herein, a composite (Fe₃O₄@CS-APTMS) was fabricated by using Fe₃O₄ as the core coated with chitosan and then functionalized with APTMS for simultaneous Cr(VI) reduction and adsorption. Although the APTMS grafting and the cross-linking reaction covered the Fe₃O₄@CS-APTMS surface with more obvious folding and wrinkling and blocked the interior pores, the graft-rich amino functional groups could effectively enhance the acidic pH adaptability and the performance of Fe₃O₄@CS-APTMS to achieve an adsorption capacity of 269.54 mg g⁻¹ at 298 K and pH 2.0. The primary reaction mechanism involving electrostatic attraction, reduction, and chelation of Cr(VI) has been thoroughly investigated through FTIR, XPS, and DFT analyses. Moreover, the concentration of Cr(VI) (32 mg L⁻¹) in artificial electroplating wastewater substantially decreased to 0.09 mg L⁻¹ post-treatment, significantly below China’s discharge standard (0.2 mg L⁻¹). Furthermore, the composite demonstrated excellent resistance to disturbances and recyclability. Thus, the synthesized composite emerges as a promising alternative material for efficiently treating chromium-containing electroplating wastewater, underscoring the importance of amino-modified materials in Cr(VI) reduction and detoxification in aquatic environments.

Graphical Abstract