Photodegradation Of The Dye Pollutions Using TiO₂ As Catalysis: Mechanism And Kinetic Investigation

With the rapid development of dyestuff industry,the number and the variety of dyestuff have increased day by day.The quantity and the type of dye have increased gradually.The environmental pollution taken by dye waste water has stepped up in the meanwhile.The wastewater with high color degree from print and dye plants is considered as one of the most hazardous industrial wastewater.It contains organic compounds which are more difficult to be biodegraded.The dyeing wastewater has become an important subject in the environmental protection and science research. The photocatalytic degradation of dyeing wastewater has been a subject to a wide range of investigations during the past decades.However,the photocatalytic degradation process is still uncertain due to the complexity of the dye molecule.One of the major problems is the difficulty of detecting the intermediates clearly.The main contents of this paper as follows:(1)The photocatalytic degradation of azo dye Alizarin Yellow R in water solution was investigated in the homemade reactor.The varies of the possible intermediates during degradation process were monitored with HPLC,LC-MS, GC-MS.The possible mechanism of Alizarin Yellow R photocatalytic degradation is proposed.(2)Quantum chemical calculations were performed for a better understanding of the reaction mechanism of photocatalytic degradation Alizarin Yellow R.On the basis of the optimal geometry conformation of Alizarin Yellow R molecule obtained at MOPAC/PM3 level,the charges value and the bond length were calculated.The MOPAC/PM3 calculation results indicated that the negative point charge on the carboxyl oxygen atoms were-0.57272 and -0.64224 and the C-C bond connected benzene ring with carboxyl group was highly unstable.The decarboxylation reaction was in accordance with the result of MOPAC/PM3 calculation.(3)In TiO₂ suspension system,the kinetic of photocatalytic degradation about thirteen kinds of dyes were studied.The kinetics study(catalyst dosage:1.0 g·L^-1, radiation intensity:2350μw·cm^-2)showed that the degradation of dyes at different initial concentration were congruent with the Langmuir-Hinshclwood(L-H)model.The innovation of this paper as follow:The alizarin yellow R reaction mechanism is studied by using LC-MS,G-C-MS detection of the intermediate product combinate with quantum chemical calculations.The real-time monitoring method was used to get kinetic data of thirteen kinds of different dyes.