Optimization of GAC supported TiO_2 photocatalytic process for competent carbofuran removal from an aqueous system

摘要

The present study employed central composite design (CCD) and response surface methodology (RSM) to evaluate the carbofuran removal by photo catalytic process. The carbofuran removal process was carried out in a batch reactor with granular activated carbon (GAC) supported TiO_2 (GAC-TiO_2) as the photo catalyst. The influence of operating parameters such as initial carbofuran concentration, TiO_2 concentration and pH was modelled using CCD and RSM with 11 experimental runs. In the experimental runs, the carbofuran concentration was carried from 1 to 250 mg L~(-1), TiO_2 concentration was ranged from 5 to 75 mg L~(-1) and pH was varied from 3-11. The experimental outcomes from CCD revealed an increased carbofuran removal with increase in pH. Complete removal of carbofuran was observed within 240 min in all the runs except in those with higher carbofuran concentration (i.e., 250 mg L~(-1)) and lower pH (i.e., 3). Furthermore, Polynomial equations were developed to predict the carbofuran removal under different operating conditions. The result indicated that the carbofuran concentraration and pH as well as the interaction term of TiO_2 concentration and pH had significant effect on the removal process. Good correlation between observed and predicted values indicated that the developed model can be used to predict the carbofuran removal under different operating conditions within the range that is analysed in this particular study. The optimum conditions for carbofuran removal were observed for a carbofuran concentration of 50 mg L~(-1), TiO_2 concentration of 5 mg L~(-1) and pH 7.9. These observations revealed that the carbofuran removal was probably due to the adsorption of carbofuran on the GAC surface and subsequent accelerated degradation of carbofuran on the GAC/GAC-TiO_2 surface. Therefore, the adsorbent medium and the adsorbent supported catalyst could be effectively used for efficient treatment of carbofuran contaminated water in a batch-mode photocatalysis system.