Solar photacatalytic treatment of some recalcitrant pollutants

The major objectives of this thesis were to investigate solar treatment as a treatment alternative of certain industrial wastewaters and to optimise reaction conditions according to Box-Wilson Experimental Design Method. Another objective was to investigate the effectiveness of Fe(III)/H2O2/Solar-UV and Fe(III)/TiO2/Solar-UV processes for the treatment of synthetic wastewater and selected industrial wastewaters which are containing high chemical oxygen demand (COD), biochemical oxygen demand (BOD), total organic carbon (TOC) and color. One of the Advanced Oxidation Process (AOP) techniques is the Fe(III)/H2O2/Solar-UV process. Fe(III)/H2O2/Solar-UV process employed strong oxidants of hydrogen peroxide (H2O2) to degrade organic carbon, especially under the promotion of solar irradiation and catalyst addition (Fe(III)). Titanium dioxide (TiO2) was used in palce of H2O2 as an oxidant in the Fe(III)/TiO2/Solar-UV process to compare efficiencies of two processes. A batch solar reactor was designed to carry out experimental studies. The solar reactor consists of sun light collectors, water preparation tank, circulation pump and a control panel. In the first part of the experimental studies, synthetic wastewater treatment was studied with the azo dye Remazol Brilliant Blue R-A at a concentration of 50mg/L. Before starting experimentation with solar reactor some preliminary works were done in the laboratory to determine ranges of chemical dosages. So, H2O2 concentrations were studied from 803.1 to 2677mg/L, TiO2 concentrations were studied from 50 to 250mg/L, Fe(III) concentrations were studied from 0 to 1.0mM and the flowrate of wastewater varied from 10 to 50L/h in all Fe(III)/H2O2/Solar-UV and Fe(III)/H2O2/Solar-UV processes. Experimental points and conditions were determined according to the Box-Wilson Experimental Design Method. In the second part of the experimental studies, textile and paper industry wastewater treatment was studied with the solar reactor according to the Box-Wilson Experimental Design Method at the same experimantal points and conditions and TOC and color removal efficiencies were compared. Samples were taken at the beginning of the experiments with solar reactor and after every hour during eight hours batch treatment and analysed for COD, BOD, TOC and color. Adsorbable organic halogens (AOX) also analysed during the paper industry wastewater experiments. Wavelenght scan was conducted for each of synthetic wastewater, textile industry watewater and paper industry wastewater to find out the wavelenght that color measurements would be done. After eight hours batch treatment of synthetic wastewater with Fe(III)/H2O2/Solar-UV process maximum color removal efficiency was 100% and maximum TOC removal efficiency was 85%. Maximum color and TOC removal efficiencies were 98% and 59%, respectively, with Fe(III)/TiO2/Solar-UV process. Maximum color and TOC removal efficiencies were 64% and 72%, respectively, with Fe(III)/H2O2/Solar-UV process and 97% and 100% with Fe(III)/TiO2/Solar-UV process after eight hours batch treatment of textile industry wastewater. Maximum color and TOC removal efficiencies were 89% and 89%, respectively, with Fe(III)/H2O2/Solar-UV process and 83% and 64% with Fe(III)/TiO2/Solar-UV process after eight hours batch treatment of paper industry wastewater. In summary, the desinged solar reactor is an effective tool for the treatment of industrial wastewaters. Another finding is Fe(III)/H2O2/Solar-UV and Fe(III)/TiO2/Solar-UV processes are effective alternative treatment processes for industrial wastewaters. Keywords: Solar treatment, Box-Wilson experimental design method, Advanced oxidation techniques.