RESUMO
The rate constants of sulfamethoxazole (SMX) degradation by ozonation and UV(254) radiation were investigated under various parameters including influent ozone gas concentration, initial SMX concentration, UV light intensity, ionic strength, water quality in terms of varying anions (bicarbonate, sulfate and nitrate), humic acid (HA) and pH. The results indicated that the removal of SMX by ozonation and UV(254) radiation fitted well to a pseudo first-order kinetic model and the rate constants were in the range of (0.9-9.8)×10(-3) and (1.7-18.9)×10(-3) s(-1), respectively. The second-order rate constants of SMX with ozone (ko(3)), under varying operational parameters, were also determined and varied in the range of (0.60-3.38)±0.13×10(5)M(-1) s(-1). In addition, SMX degradation through UV pretreatment followed by ozonation in the presence of HA was proved to be an effective method which can remove SMX with a low ozone dose. The results suggested that ozonation of SMX was more affected by concentration of influent ozone gas, alkalinity, and HA, while incident UV light intensity, pH, and HA were the dominant factors influencing UV degradation of SMX.
Assuntos
Anti-Infecciosos/química , Sulfametoxazol/química , Eliminação de Resíduos Líquidos , Poluentes Químicos da Água/química , Purificação da Água , Cromatografia Líquida de Alta Pressão , Substâncias Húmicas/análise , Concentração de Íons de Hidrogênio , Cinética , Concentração Osmolar , Ozônio/química , Fotólise , Raios Ultravioleta , Qualidade da ÁguaRESUMO
In this paper, the treatment of real groundwater samples contaminated with gasoline components, such as benzene, toluene, ethylbenzene, and xylene (BTEX), methyl tert-butyl ether (MTBE), tert-butyl alcohol (TBA), and other gasoline constituents in terms of total petroleum hydrocarbons as gasoline (TPHg) by an ozone/UV process was investigated. The treatment was conducted in a semi-batch reactor under different experimental conditions by varying ozone gas dosage and incident UV light intensity. The groundwater samples contained BTEX compounds, MTBE, TBA, and TPHg in the ranges of 5-10000, 3000-5500, 80-1400, and 2400-20000 microgl(-1), respectively. The ozone/UV process was very effective compared to ozonation in the removal of the gasoline components from the groundwater samples. For the various gasoline constituents, more than 99% removal efficiency was achieved for the ozone/UV process and the removal efficiency for ozonation was as low as 27%. The net ozone consumed per mol of organic carbon (from BTEX, MTBE, and TBA) oxidized varied in the range of 5-60 for different types of groundwater samples treated by the ozone/UV process. In ozonation experiments, it was observed that the presence of sufficient amount of iron in groundwater samples improved the removal of BTEX, MTBE, TBA, and TPHg.
Assuntos
Carcinógenos Ambientais/isolamento & purificação , Gasolina , Ozônio/química , Raios Ultravioleta , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Benzeno/química , Benzeno/isolamento & purificação , Derivados de Benzeno/química , Derivados de Benzeno/isolamento & purificação , Carcinógenos Ambientais/química , Éteres Metílicos/química , Éteres Metílicos/isolamento & purificação , Tolueno/química , Tolueno/isolamento & purificação , Poluentes Químicos da Água/química , Xilenos/química , Xilenos/isolamento & purificação , terc-Butil Álcool/química , terc-Butil Álcool/isolamento & purificaçãoRESUMO
A kinetic model that describes the removal of organic pollutants by an ozone/UV process is described. Oxalic acid, which reacts with a very low rate constant with ozone and relatively high rate constant with hydroxyl radical (OH*), was used as the probe chemical to model the process. The model was verified by experimental data on concentrations of oxalic acid and hydrogen peroxide (H202) under various experimental conditions, i.e., ozone gas dosage, UV light intensity, and varying oxalic acid concentrations.