Preparation Of Mesoporous TiO₂/activated Carbon And Its Catalytic Decomposition Performance

Activated carbons were prepared from walnut shell, and mesoporous TiO2 was loaded on activated carbon by sol-gel method with ultrasonic treatment, which were of great significance to ease the energy crisis and treat wastewater.In this study, activated carbons were prepared from walnut shell by chemical activation with KOH. The optimal manufacture condition of walnut shell-based activated carbon was determined through single factor test. Mesoporous TiO2 was loaded into walnut shell-based activated carbon by sol-gel method with ultrasonic treatment. The composite was characterized using Field Emission Scanning Electron Microscopy, Specific Surface Area and Pore Size Analyzer, Fourier Transform Infrared Spectroscopy. The catalytic decomposition activities of composites were evaluated by the catalytic decomposition of acid red 3R and formaldehyde. The experimental results showed that:(1) The optimum adsorption capacity of activated carbon was obtained when the activation was conducted at 800℃ for 60min with alkali/carbon ratio 3:1. The prepared activated carbon exhibited a high surface area of 1551.85m2/g, microporous specific surface area of 1491.22m2/g, and a high microporosity of 89.87%. Ultra-micropore and super-micropore were also observed. The surface of activated carbon contains phenolic hydroxyl, carboxyl, amino and other functional groups.(2) By sol-gel method with ultrasonic treatment, mesoporous Ti82 and mesoporous TiO2/activated carbon were prepared. Mesoporous TiO2/activated carbon has smaller particle size, because the amorphous structure of activated carbon hinder TiO2 crystalline grain growth. The surface area of mesoporous TiO2/activated carbon and mesoporous TiO2/activated carbon, were 603.61m2/g and 831.20m2/g respectively. Mesoporous TiO2 could make up for the reduction of the specific surface area of activated carbon.(3) When the initial concentration of acid red 3R was 40 mg/L and the solution was 250mL, the adsorbent amount was 0.15g, the temperature was 25 ℃, adsorption equilibrium was 120min, the removal rate of acid red 3R by mesoporous TiO2/activated carbon reached a maximum value of 92.37%, which was obviously better than that of TiO2/activated carbon.(4)When the initial concentration of formaldehyde was 30 mg/L and the solution was 100mL, the temperature was 25 ℃, the adsorbent amount was 0.5g, adsorption equilibrium was 210min, the removal rate of formaldehyde by mesoporous TiO2/activated carbon reached a maximum value of 92.06%.The adsorption dynamics behavior of acid red 3R and formaldehyde on mesoporous TiO2/activated carbon and TiO2/activated carbon could be described well with pseudo-second-order kinetics equation, indicating that chemical adsorption reaction mainly controlled the adsorption process.