Efficient Removal of Cd(II) Using SiO₂-Mg(OH)₂ Nanocomposites Derived from Sepiolite

The pollution of Cadmium (Cd) species in natural water has attracted more and more attention due to its high cumulative toxicity. In the search for improved removal of cadmium from contaminated water, we characterized uptake on a recently identified nanomaterial (SiO₂-Mg(OH)₂) obtained by subjecting sepiolite to acid-base modification. The structural characteristics of SiO₂-Mg(OH)₂ were analyzed by means of SEM-EDS, Fourier Transform Infra-Red Spectroscopy (FTIR) and Powder X-ray Diffraction (PXRD). Static adsorption experiments were carried out to evaluate the effect of contact time, temperature, amount of adsorbent, and pH-value on the adsorption of Cd(II) by SiO₂-Mg(OH)₂. The results show that the pore structure of SiO₂-Mg(OH)₂ is well developed, with specific surface area, pore size and pore volume increased by 60.09%, 16.76%, and 43.59%, respectively, compared to natural sepiolite. After modification, the sepiolite substrate adsorbs Cd(II) following pseudo-second-order kinetics and a Langmuir surface adsorption model, suggesting both chemical and physical adsorption. At 298 K, the maximum saturated adsorption capacity fitted by Sips model of SiO₂-Mg(OH)₂ regarding Cd(II) is 121.23 mg/g. The results show that SiO₂-Mg(OH)₂ nanocomposite has efficient adsorption performance, which is expected to be a remediation agent for heavy metal cadmium polluted wastewater.