Kinetic and isotherm studies on adsorption of toxic pollutants using porous ZnO@SiO2 monolith.

Removal of toxic effluents (like dyes and pesticides) by cost-effective and user-friendly method is needed to provide sustaining the environment for civilization. Here, low-cost mesoporous silica monolith (SiO2) and silica supported metal-oxide (ZnO@SiO2) monolith were synthesized to reduce the solemn impact of toxic effluents. Batch experiments were performed to remove Alizarin (AZ), Paradol (PD), Acid blue-113 (AB) and Rhodamine-B (RD) from aqueous solution via synthesized monoliths. The influence of various parameters (like pH, contact time, temperature and adsorbate concentration) has been optimized. The maximum adsorption capacity of ZnO@SiO2 monolith is 625, 500, 714 and 555mg/g for AZ, RD, AB, and PD respectively. The adsorption for AZ, PD, AB, and RD is spontaneous and exothermic. The adsorption process can be well described by the pseudo-second-order kinetic model (high regression coefficients) and the Freundlich isotherm model (R2=0.97-0.99).