Ferrate(VI) oxidation of endocrine disruptors and antimicrobials in water

Author name used in this publication: X. Z. LiAccepted ManuscriptPublishe

REDUCTIVE DECHLORINATION OF CHLORINATED HYDROCARBONS IN AQUEOUS-SOLUTIONS CONTAINING FERROUS AND SULFIDE IONS

[[abstract]]©1992 Elsevier - The transformation of volatile chlorinated hydrocarbons in aqueous phase containing free ferrous and sulfide ions with and without light irradiation were investigated to evaluate the effect of these reducing ions on the dechlorination of chlorinated hydrocarbons. In the presence of the ferrous ion alone, 84% of the original carbon tetrachloride (CT) was transformed to chloroform within 33 days, and a removal efficiency of 99% was reached when the solution was irradiated by visible light. However, carbon tetrachloride did not appear to be reactive in other media containing sulfide and/or bound ferrous ions. 1,1,1-trichloroethane and tetrachloroethylene were less susceptible than carbon tetrachloride to the reductive dechlorination. No transformation was observed for these two compounds in different types of media in 33 days. Oxidation-reduction potential (ORP) measurements showed that carbon tetrachloride could be depleted only when ORP of the environment was below 360 mV(relative to standard hydrogen electrode). This study indicates that free ferrous ion is an active reducing agent for the dechlorination of CT, but has little effect on the transformation of 1,1,1-trichloroethane and tetrachloroethylene, whereas, free sulfide and bound ferrous ions do not appear to have the capability of dechlorination for these heavily chlorinated hydrocarbons.[[department]]醫環

The influence of pH and cadmium sulfide on the photocatalytic degradation of 2-chlorophenol in titanium dioxide suspensions

[[abstract]]©2001 Elsevier - The influence of pH and cadmium sulfide on the photocatalytic degradation of 2-chlorophenol (2-CP) in titanium dioxide suspensions was investigated to evaluate the feasibility of mixed semiconductors on the photodegradation of chlorinated organics in aqueous solution. Apparent first-order rate constants (k(obs)) and initial rate constants were used to evaluate the degradation efficiency of 2-CP. Higher degradation efficiency of 2-CP was observed at higher pH values. The apparent pseudo-first order rate constant was 0.036 min(-1) at pH 12.5 in TiO2/UV system, while a 2- to 9-fold decrease in k(obs) was observed over the pH range of 2.59.5. The addition of phosphate buffer solutions at different pH values have different effects on the degradation of 2-CP. H2PO4- has little effect on the photodegradation of 2-CP, while HPO42- could inhibit the photodegradation efficiency of 2-CP. Chlorocatechol, hydroquinone, benzoquinone and phenol were identified as the predominant aromatic intermediates for the photocatalytic degradation of 2-CP. Moreover, less aromatic intermediates at higher pH were observed. Direct oxidation contributed significantly to the photodegradation of 2-CP. An addition of a semiconductor decreased the initial and apparent first-order rate constants of 2-CP. The cutoff of wavelength of 320 nm could diminish the contribution of direct photolysis of 2-CP. The combination of cadmium sulfide and titanium dioxide can lead to an enhanced rate of disappearance of 2-CP compared to those in single semiconductor system. A 1.2 to 2.5-fold increase in rate constant in coupled semiconductor system relative to the single semiconductor system was obtained.[[fileno]]2060215010002[[department]]醫環

Relationship between electron donor and microorganism on the dechlorination of carbon tetrachloride by an anaerobic enrichment culture

[[abstract]]©2000 Elsevier - An investigation involving the supplement of different concentrations of substrates and microorganisms was carried out under anaerobic condition to assess the feasibility of bioremediation of carbon tetrachloride (CCl4) with the amendment of low concentrations of auxiliary substrate and microorganisms. The concentrations of substrate and microorganisms ranged from 10 to 100 mg/l and from 3.7 x 10(4) to 3.7 x 10(6) cell/ml, respectively. The biotransformation rate of CCl4 increased progressively with the increase in the concentrations of the substrate and microorganisms. In the low biomass-amended system (3.7 x 10(4) cells/ml), 28-71% and 57-96% of CCl4 removals were exhibited when 10-100 mg/l of acetate or glucose was supplemented, respectively, whereas nearly complete degradation of CCl4 was observed in the heavily inoculated systems (3.7 x 10(6) cells/ml). An addition of electron donor in the low microbial. activity batches enhanced greater efficiency in dechlorination than in the high microbial activity batches. The second-order rate constants ranged from 0.0059 to 0.0092 1/mg/day in high biomass input system, while a two- to four-fold increase in rate constant was obtained in the low microbial activity system. This study indicates that biomass was the more important environmental parameter than substrate affecting the fate of CCl4. The addition of auxiliary substrates was effective only in low biomass-amended batches (0.56 mg-VSS/l) and diminished inversely with the increase of microbial concentration.[[fileno]]2060215010015[[department]]醫環