Fabrication of highly efficient magnesium silicate and its adsorption behavior towards Cr(VI)

Heavy metal ions pollution has caused worldwide attention due to its toxicity to people's health. Existing as chromate anions, Cr(VI) is difficult to remove from polluted water. Owing to their low cost, stability, environmentally benign nature, and excellent properties, silicate materials are widely used in catalysis and adsorption. In this work, magnesium silicates with sepiolite and talc phase were synthesized through facile hydrothermal route using diatomite as substrate and silicon source. The Cr removal capacity of wire-like Mg₄Si₆O₁₅(OH)₂-diatomite exhibited a Cr adsorption capacity of 1292 mg/g, which was much higher than the other reported inorganic adsorbents. The adsorption followed Freundlich and Temkin models well, indicating that Cr species adsorbed onto adsorbent was a favorable, exothermic multilayer chemisorption process. The first-principles density functional theory (DFT) calculation results revealed the interaction between adsorptive sites of adsorbents and Cr species, also demonstrated ion-exchange behavior between interlayer Mg ion and Cr(III). We believe these low-cost synthesized adsorbents have great potentials for practical applications in the treatment of heavy metal ions polluted wastewater.