Prepapation Of Nanometer Multi-Photocatalysts And Its Applications In Printing And Dyeing Wastewater

As poisonous and complicated of chemical composition of printing and dyeing wastewater, the degradation and treatment of them is a very difficult problem in the field of wastewater treatment. Photocatalytic oxidation of water contaminants with semiconductors has been reported as one of more promising remediation technologies for complete mineralization of undesirable organic contaminants, particularly toxic and unbiodegradable organic compounds. TiO2 has been shown to be an excellent photocatalyst owing to its stable chemical characteristics and low price, etc. However, due to its low reaction rate and narrow range of available spectrum, photocatalytic oxidation is almost unindustrialized in wastewater treatment. In order to improve the photocatalytic activity and extend energy range of photo-excitation, expensive metal (Ru) was deposit for amend photocatalytic activity of TiO2 in this thesis.1. Preparation and structural characterization of photocatalystRuO2/TiO2 and RuO2/La2O3/TiO2 were prepared by Sol-gel-immersion method. The structure and morphology of catalysts were characterized by means of XRD and TEM. The results indicated that the average particle size of catalysts was below 20nm and anatase TiO2 transformed to rutile TiO2 with increase of calcinations temperature. The percent of anatase TiO2 was about 100% at the calcinations temperature of 500C for 2h.2. Photocatalytic degradation experimentsThe photocatalytic activity of multi-photocatalyst was evaluated by the photodegradation of Direct Fast Blank G and Direct Fast Brown, and the effects of various conditions on the photocatalytic characteristics were investigated. The experimental results were as follows:(1) Photodegradation system of RuO2/TiO2: when addition of RuO2 0.16%, calcinations temperature 500C , amount of photocatalyst 5g/L, air flow rate 300 mL/min, initial pH 5.05, mercury lamp as light source, Direct Fast Blank G was degraded 97.6% in 30min.The results showed that the degradation reaction of the Direct Fast Blank G almost followed Langmuir-Hinshehwood model, and the reaction was the apparent first order. The reaction rate constant k and the absorption constant K were determined to be 4.94x10-3 mmol (L min)-1 and 14.22L mmol-1 respectively. The photocatalytic activity of used photocatalyst declined less than 3 percentage when compared with unused,'so it could be used repeatedly.(2) Photodegradation system of RuO2/La2O3/TiO2: (1) Degradation of Direct Fast Blank G: addition of RuO2 0.16% , calcinations temperature 500C , amount of photocatalyst 3g/L, air flow rate 300 mL/min> initial pH 7.32, mercury lamp as light source, the groups of visible spectrum were degraded in 40min, and the absorption spectrum from 200nm to 700nm were almost zore in 60min, this result indicates that the dye has been degraded completely. Compared with single nanosized TiO2, activity of multi-photocatalyst promoted 1.2 times. The half-degradation period by RuO2 /La2O3 /TiO2 been cut down 5min than RuO2/TiO2. (2) Degradation of Direct Fast Brown: addition of RuO2 0.12%, calcinations temperature 500C,amount of photocatalyst 3g/L, air flow rate 100 mL/min, initial pH 8.98, mercury lamp as light source, the degraded efficiency was 97.6% in 30min, and absorption constant k=0,206min-1,t1/2=3.37 min. The degraded rate improved obviously when addition of H2O2 to the system of RuO2/La2O3/TiO2 photocatalytic degradation.(3) Degradation of real printing and dyeing wastewater: By using of RuO2/TiO2 photocatalytic degradation system, the photocatalytic degradation of the real printing and dyeing wastewater (the value of initiation Chromaticity: 10000, CODCr value: 2614mg/L) was carried out for 120min, the results showed that the Chromaticity and CODCr value were reduced to be 99.2% and 97.6%, respectively.