Comparison Study of Paraquat Herbicide Adsorption by Xerogels: Application of Experimental Design

Abstract

This study dealt with the Paraquat dichloride herbicide (PQT) adsorption on xerogels. The xerogels were synthesized with tetra methoxy orthosilicate (TMOS) and tetra ethoxy orthosilicate (TEOS) as a precursor. Whereas xerogels have free silanol groups on their surface and PQT has a positive charge as an ion, xerogels have shown a high affinity for the PQT adsorption in aqueous solution. Scanning Electron Microscopy, Fourier Transform‐IR, and BET analysis were characterized xerogels. The effect of four process factors such as PQT dosage, pH, a dose of adsorbent, and time was evaluated by the Box‐Behnken design. Between four parameters, pH was more effective. The second order equation (quadratic model) was also used for the analysis of the experimental data. Additionally, the optimum points for parameters were determined by desirability function in the Experimental Design. Removal Percentages of PQT at the optimum process parameters were found to be 98.05 and 92.83%, for TMOS and TEOS xerogels, respectively. In addition, the isotherm study showed that the Freundlich isotherm indicated better harmonic between experimental and theoretical results. Finally, in the kinetic study, Pseudo‐second order model had a better correlation than Pseudo‐first order model. © 2018 American Institute of Chemical Engineers Environ Prog, 38: S128–S138, 2019