Preparation of SiO2–ZrO2 xerogel and its application for the removal of organic dye

SiO2–ZrO2 xerogel was prepared via a sol–gel method followed by ambient pressure drying. The xerogel was characterized by X-ray diffraction, thermal analysis, fourier transform infrared spectroscopy, scanning electron microscopy, and nitrogen adsorption/desorption analysis. The results showed that the SiO2–ZrO2 xerogel was amorphous and possessed a three-dimensional network structure with a narrow distribution of pore size. Its specific surface area reached up to 525.6 m2/g after 600 °C heat treatment, with a pore volume of 1.16 cm3/g and an average pore size of 8.5 nm. In order to explore the potential application of the SiO2–ZrO2 xerogel for the removal of organic dyes, its adsorption capacity was studied by removal of Rhodamine B (RhB) from aqueous solution through batch experiments. The results showed that the adsorption process of RhB onto SiO2–ZrO2 xerogel was slightly promoted under acidic conditions and significantly inhibited under strong alkaline conditions. And adsorption equilibrium can be achieved in 30 min. The kinetic data of the adsorption were analyzed using pseudo-first-order and pseudo-second-order models. The results indicated that the pseudo-second-order model described the adsorption mechanism better. The sorption behavior was evaluated by Langmuir and Freundlich isotherm models. The results suggested that the Langmuir model could accurately describe the experimental data and the adsorption capacity qmax was 177.7 mg/g. Thermodynamic analysis revealed that the adsorption of RhB onto the SiO2–ZrO2 xerogel was both spontaneous and exothermic in nature. Thus, the as-prepared SiO2–ZrO2 xerogel might be used as an adsorbent for wastewater treatment, especially for the removal of dyes.