I am now reading “Removal of color substances using photocatalytic oxidation for membrane filtration processes” for deeper understanding of what membrane is capable of. The study was aimed to determine the effectivity of UV/TiO2/H2O2 to remove color. So the technique can remove TOC at 38% and color 400 at 89%. The interesting fact was if the dosage of H2O2 is less than 0.016 M, then the system is accelerated, produce better TOC rejection and color removal, over-dosage (more than 0.016) declines the rejection enhancement. I only get this point, it appears that there is a break point dosage at which best removal can be achieved. However, there is no information yet the comparison between only TiO2/UV and TiO2/UV/H2O2 of the efficiency.
So the introduction gives a brief overview why photocatalytic is used for the research. The paper explains about the humic acid. Humic acid is condensed, and composed of high molecular weight aromatic organic acid and is usually present in water, especially in biological wastewater, represented by the presence of color. Safe and cost effective are the keywords to treat TOC and color. Traditional methods chemical, physical, and biological have been applied such as ASP (biological), chlorination (chemical), ozonation (chemical), coagulation (physical and chemical), adsorption (physical) and membrane filtration (physical). THe problem is these methods tend to transfer pollutant to another more solid residues which need further safer disposal. Ozonation and chlorination is effective but expensive and produce DBP (Arai et al., 1986).
This is why photocatalytic has been proposed. The process generates hydroxyl radicals (OH radicals) which attracts organics and initiate a series of oxidative reactions and lead to complete mineralization of organic to CO2 and H2O or biodegradable material.
TiO2 —> (under the presence of UV) TiO2 (e- + h+)
Ti(IV)-OH- + h+ —> Ti(IV) - OH radicals
Ti(IV)-OH2 + h+ —> Ti(IV) - OH radicals
Several experiments have been conducted for this photocatalysis to remove TOC, color and dye. But these information are still limited.
The author also used P25 Degussa TiO2 which I can use this information.
To be continued…
Tay, J.H., D. Chen and D.D. Sun. Removal of color substances using photocatalytic oxidation for membrane filtration processes. Wat. Sci. Tech. 43 (10)(2001), 319-325