Synthesis, characterization and performance evaluation of Fe₃O₄/CSH@MCC as an adsorbent for heavy metals

To develop a high-performance material for heavy metal remediation, calcium silicate hydrate (CSH) was synthesized using calcium chloride and sodium metasilicate as precursors via a constant-temperature solid-phase method. A novel ternary adsorbent, Fe₃O₄/CSH@MCC, was successfully constructed by coating Fe₃O₄-loaded CSH with microcrystalline cellulose (MCC). The surface characteristics, structural, morphological, and thermal stability were characterized using SEM, FTIR, XRD, BET, TGA and XPS analyses. The adsorption behavior was further elucidated through kinetic, thermodynamic, and isotherm modeling. The results indicated that under optimal conditions (pH = 5), the maximum adsorption capacities for Ni²⁺, Cu²⁺, Pb²⁺, and Ag⁺ reached 792.52 mg/g, 683.45 mg/g, 750.08 mg/g, and 351.05 mg/g, respectively. Rapid adsorption equilibrium was achieved within 60 min, with corresponding removal efficiencies of 99.53%, 86.32%, 97.19%, and 48.10%. Thermodynamic and kinetic analyses demonstrated that the adsorption process follows the Langmuir isotherm model, indicating a monolayer adsorption mechanism. The pseudo-second-order kinetic model suggested that chemisorption is the dominant adsorption mechanism. These findings underscore the potential of the Fe₃O₄/CSH@MCC composite as an efficient material for wastewater treatment, offering a promising solution for the environmental remediation of heavy metal pollutants.