Synergistic Photocatalytic Degradation Of Typical Pharmaceutical Pollutants By Precious Metal Supported Tio2 With Electron Capture Agent

In recent years, environmental problems caused by medical waste are more and more serious, combined with the strong oxidizing ability of the TiO₂ photocatalytic method, we have system studied of adding different electron capture agents (H₂O₂, KBrO₃, K₂S₂O₈) Collaborative TiO₂ loaded with precious metals photocatalytic degradation of typical medical waste water pollutants contained phenol, pyridine, nitrobenzene,β-lactam antibiotic amoxicillin.We loaded the precious metal on the surface of anatase TiO₂ using light deposition method, and then characterized by a variety of means to characterize their properties. UV-vis diffuse reflectance spectra showed that: in the UV region, the light absorbed by TiO₂ or M/TiO₂ is not very different, in the visible region, the absorption from strong to weak as: Au/TiO₂ > Ru/TiO₂ > Ag/TiO₂ > Pt/TiO₂ > Ir/TiO₂ > Pd/TiO₂ > Rh/TiO₂ > TiO₂; BET analysis showed that: loading all kinds of precious metals did not produce significant effects on the specific surface area of TiO₂, for the load of precious metals rarely and well distribution;Scanning electron microscopy and EDS analysis showed that: the precious metal can be extremely dispersed on the surface of TiO₂ by the light deposition method and inhibit the agglomeration of the nanosized precious metal to get a good dispersion and uniform distribution.We have studied the photocatalytic degradation of typical medical waste water pollutants phenol by adding electron capture agents collaborative TiO₂ loaded with precious metals. The results showed that the most favorable electron capture agents was H₂O₂; when the different precious metals loading on TiO₂ and H₂O₂ was added, the activity order of phenol removal was: Ag/TiO₂ > Ir/TiO₂ > Pd/TiO₂ > Rh/TiO₂ > Pt/TiO₂ > Ru/TiO₂ > Au/TiO₂. The favorable loading amount of the best precious metal Ag was 0.5%; the optimal dosage of catalyst was 0.02g; the best dosage of H₂O₂ was 50mM;the optimal pH was 5. Under these optimal conditions, the photocatalytic degradation rate reachs 57% in 3 hours, increased by 35% compared with the degradation rate of TiO₂ + UV system.We have studied the photocatalytic degradation of typical medical waste water pollutants pyridine by adding electron capture agents collaborative TiO₂ loaded with precious metals. The results showed that the most favorable electron capture agents was KBrO₃; when the different precious metals loading on TiO₂ and KBrO₃ was added, the activity order of pyridine removal was: Ag/TiO₂ > Au/TiO₂ > Pd/TiO₂ > Pt/TiO₂ TiO₂ > Ir/TiO₂ > Rh/TiO₂ Ru/TiO₂. The favorable loading amount of the best precious metal Ag was 0.5%; the optimal dosage of catalyst was 0.02g; the best dosage of KBrO₃ was 10mM;the optimal pH was 9. Under these optimal conditions, the photocatalytic degradation rate reachs 62% in 3 hours, increased by 23% compared with the degradation rate of TiO₂ + UV system.We have studied the photocatalytic degradation of typical medical waste water pollutants nitrobenzene by adding electron capture agents collaborative TiO₂ loaded with precious metals. The results showed that the most favorable electron capture agents was KBrO₃; when the different precious metals loading on TiO₂ and KBrO₃ was added, the activity order of nitrobenzene removal was:Au/TiO₂ > Ag/TiO₂≈TiO₂ > Ir/TiO₂ > Ru/TiO₂ > Pd/TiO₂ > Pt/TiO₂ > Rh/TiO₂. The favorable loading amount of the best precious metal Au was 0.1%; the optimal dosage of catalyst was 0.02g; the best dosage of KBrO₃ was 5mM;the optimal pH was 3. Under these optimal conditions, the photocatalytic degradation rate reachs 95% in 6 hours, increased by 17% compared with the degradation rate of TiO₂ + UV system.We have studied the photocatalytic degradation of typical medical waste water pollutantsβ-lactam antibiotics amoxicillin by adding electron capture agents collaborative TiO₂ loaded with precious metals. The results showed that the most favorable electron capture agents was KBrO₃; when the different precious metals loading on TiO₂ and KBrO₃ was added, the activity order of amoxicillin removal was: Rh/TiO₂ > Pd/TiO₂ > Ag/TiO₂ > Au/TiO₂ Ir/TiO₂ > TiO₂ > Pt/TiO₂ > Ru/TiO₂. The favorable loading amount of the best precious metal Rh was 0.1%; the optimal dosage of catalyst was 0.03g; the best dosage of KBrO₃ was 0.5mM;the optimal pH was 5. Under these optimal conditions,the photocatalytic degradation rate reachs 100% in 2 hours, increased by 80% compared with the degradation rate of TiO₂ + UV system.Finaly, for each pollutant were carried out three different comparative experiments of photocatalytic degradation: "without electron scavenger, TiO₂ withnot precious metals "; "with electron capture agent, TiO₂ withnot precious metals "; "with electron capture agent, TiO₂ loaded with precious metals ". The results show that for phenol, loading properly amount of Ag on TiO₂ and adding right amount of H₂O₂ can significantly increase the degradation rate of TOC contaminants; while for the other three pollutants, adding TiO₂ electron capture agent and load on precious metals does not increase TOC degradation rate, but it also can promote the pollutants to the transformation of small molecule intermediates. Kinetic analysis showed that three kinds of catalyst systems are consistent with the first order kinetic model, following the first order reaction rule, and the reaction rate constant K gradually increase, that add an electron capture agent and load the precious metals indeed effectively improve the photocatalytic reaction rate.