Pb²⁺ and Cd²⁺ recovery from water using residual tea waste and SiO₂@TW nanocomposites

This work reports the fabrication of SiO₂@TW nanocomposites and their application for Pb²⁺ and Cd²⁺ ions sequestration from simulated water. Residual tea waste has also been used for metal ions sequestration to compare the potential of SiO₂@TW nanocomposites. The SEM, TEM, BET, FTIR and EDX techniques were employed for the characterization of SiO₂@TW nanocomposites and residual tea waste. Particle sizes of SiO₂@TW nanocomposites was in the range of 6.8-12 nm. The experiments were carried out in batch mode to explore the effect of various operating parameters on the sequestration of Pb²⁺ and Cd²⁺ ions from water. The experimental data was subjected to various thermodynamic, kinetic and isothermic models. According to Langmuir model, the maximum adsorption efficiency of the SiO₂@TW nanocomposites was 153 mg/g for Pb²⁺ and 222 mg/g for Cd²⁺ but maximum adsorption efficiency of residual tea waste for Pb²⁺ was 125 mg/g and for Cd²⁺ was 142.9 mg/g. This study suggested that due to the presence of active sites SiO₂@TW nanocomposites has greater potential for metal sequestration than residual tea waste.