Modification Of TiO₂/Ti Catalyst And Its Photoelectric Catalysis Degradation Of Humic Acid In Water

The humic acid is of large molecular weight and complicated structure, whose removal from water solution is always a difficulty in water treatment industry, especially in the tap water processing project. Photoelectrical catalysis degradation for eliminating the organic pollutants is a new technology in recent years, which is carried out under the normal temperature and atmospheric pressure, and will not cause secondary pollution. Due to its unique superiority, this technology has also become a cutting-edge research project in the field of international environment treatment, and is deeply concerned by researchers in the world. In this paper, the depth processing research on humic acid wastewater by this technique was investigated.In view of the characteristics of anodic oxidation process during the preparation of TiO₂/Ti catalyst, the generating rule of hydroxyl free radical of the TiO₂/Ti photoelectric catalysis was studied, the corresponding reaction system to measure the hydroxyl free radical·OH concentration was established. The cloudy ion exchange membrane was introduced into the TiO₂/Ti photoelectrical catalysis and oxidation system, spectrophotometric method through Fe(phen)32+ was used to measure the accumulation concentration of hydroxyl free radical·OH, and the condition of influencing the system to produce the hydroxyl free radical·OH was optimized. The result indicates that employing Fe(phen)32+ in spectrophotometric method to measure hydroxyl free radical·OH's accumulation concentration is feasible through the introduction of the cloudy ion exchange membrane, which can be taken as an evaluation approach to determine the photoelectric catalytic activity of the modified TiO₂/Ti catalyst.Using the anodic oxidation method, the boron-doped TiO₂/Ti catalyst was prepared in the H2SO4 electrolyte solution mixed with the H3BO3, whose technique parameters were optimized by using ultraviolet visible diffusion reflection spectrum, AFM, XRD and some other analyzing methods, and as well as the results of the photoelectric catalysis tests.TiO₂/Ti catalyst prepared by the anodic oxidation was modified by Pt for preparing Pt-TiO₂/Ti catalyst through light photoreduction in the hexachloroplat- inic acid (Pt-TiO₂(R)) and the ion sputtering method (Pt-TiO₂(S)). The orthogonal testing method was used to optimize the condition of light photoreduction and the ion sputtering method. Pt-TiO₂(R) and Pt-TiO₂(S) catalysts prepared under the best condition were compared. The results indicate that the photoelectric catalytic activity of Pt-TiO₂(S) surpasses that of Pt-TiO₂(R). The optimized B-doped TiO₂/Ti catalyst and Pt-TiO₂ (S) catalyst were compared further, Considering the organic matter degradation efficiency and the preparation cost, it is found that the B-doped TiO₂/Ti catalyst can reduce the cost, the preparation technique is simple and this kind of doping on the substrate ensures good adhesion between the substrate and the films and the excellent machine capability and the long service life as well. Therefore, B-doped TiO₂/Ti catalyst was selected as the catalyst in the study of the humic acid degradation system.The adsorption rule of the humic acid on the B-doped TiO₂/Ti catalyst was conducted firstly and the best adsorption condition was optimized, which is helpful for the further photoelectric catalytic reaction. The experimental result indicates that the adsorption process of humic acid on B-doped TiO₂/Ti catalyst is the exothermic process, and meantime pH, the initial concentration, the sur-bias are the key factors to the adsorption effect.In the photoelectric catalysis and oxidation reaction system, the influences of the ultraviolet lamp power, the initial concentration of reactant, film catalyst area, sur-bias and other factors on the photoelectric catalysis degradation dynamics process of the humic acid were systematically studied; the related dynamic equation was established. The findings indicate that the order of factors affecting the humic acid photoelectric catalysis degradation speed ranges from the strong to the weak is: Ultraviolet lamp power > membrane electrode area > initial concentration of the humic acid > sur-bias.Through the structure analysis of the intermediary and the final products during the process of photoelectric catalysis degradation of humic acid through ion chromatograph, three dimensional fluorescence spectrum and GC-MS, the photoelectric catalysis degradation mechanism of humic acid was discussed. During the process of the photoelectric catalysis degradation of the humic acid, the macro-molecule organic matter is activated by the hydroxyl free radical under the ultraviolet ray, it gradually takes on a series of redox reaction, such as some groups and bases takings off, breaking, ring-splitting and so on, finally, produces small molecular matter like carboxylic acid, as well as inorganic small molecular matter like CO2 and H2O and so on.