Preparation of Slag-Based Carbon Powder-Sodium Alginate Composite Membrane and Its Efficient Adsorption of Cr(VI) from Aqueous Solutions
A novel slag-based carbon powder-sodium alginate composite membrane was fabricated by incorporating purified slag-derived carbon powder into a sodium alginate matrix, followed by dual crosslinking with polyethyleneimine and glutaraldehyde. The membrane was designed to achieve waste-to-treat-waste objectives, enhance the resource value of industrial slag, and provide an efficient, regenerable adsorbent for Cr(VI) removal from water. Adsorption performance was systematically evaluated. Optimal adsorption occurred at pH 2, with elevated temperature and initial Cr(VI) concentration favoring uptake; equilibrium was reached at approximately 73 h. The adsorption kinetics followed a pseudo-second-order model, and isotherm data fitted the Langmuir model, yielding a theoretical maximum adsorption capacity of 471.970 mg·g−1. Thermodynamic analysis indicated a spontaneous, endothermic process. In simulated wastewater containing multiple metal ions, competitive effects moderately reduced adsorption capacity. After three adsorption-desorption cycles, the membrane retained good structural stability despite a decline in capacity. Characterization via SEM-EDS, FTIR, and XPS revealed a porous structure and the involvement of functional groups such as –COOH and –NH2, with partial reduction of Cr(VI) to Cr(III). The adsorption mechanism was attributed to synergistic electrostatic interaction, chemical coordination, and redox reactions.