removing paraquat herbicide from aqueous solutions on teos nano-porous xerogel using experimental design

the present study dealt with the removal of paraquat dichloride herbicide (pqt) on xerogel. the xerogel synthesis with a precursor of, tetra ethoxy orthosilane (teos) by sol-gels drying method. it has shown high affinity for the pqt adsorption in aqueous solution. sem and bet analysis characterize xerogel. a three level and four-factor box-behnken design was employed to determine the effects of process factors such as pqt concentration (20-100 mg l^-1), ph of the solution (7-11), adsorbent dosage (0.01-0.05 gr) and contact time (5-45 min) on pqt adsorption from aqueous media. the study revealed that the adsorption of paraquat was highly ph dependent. the second order mathematical model was also developed by regression analysis of the experimental data. in addition, the isotherm study showed that the freundlich isotherm indicated better fit compared to the langmuir isotherm.