Phosphorus-functionalized dolomite for cadmium immobilization in water systems and acidic soil remediation: Mechanistic insights and scale validation

This study is to prepare a phosphorus-modified dolomite passivation material (P-DO) through hydrothermal method and synthesis for the remediation of cadmium (Cd) in acidic soil. The surface morphology and elemental composition of dolomite and its modified materials were characterized by scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The adsorption process was simulated using adsorption models to elucidate the Cd immobilization mechanisms. Experimental results demonstrated optimal alignment with the Freundlich isotherm and pseudo-second-order kinetic model, achieving adsorption equilibrium within 8   h. Spectroscopic analysis revealed three primary binding mechanisms: coordination through oxygen-containing carbon groups, Mg-O complexation, and phosphate ligand exchange via P-OH groups. Soil remediation trials established an optimal P-DO dosage of 1%, the passivation efficiency of Cd in soil by P-DO was 54.9%. Furthermore, this treatment decreased DTPA-extractable Cd by 12.696   mg·kg - ¹ and reduced acid-soluble Cd fractions by 42.3%. In summary, the modification of dolomite enables synergistic solid waste valorization and immobilization of Cd, positioning it as a high-performance functional material for sustainable remediation technologies.