Herbicides are chemical compounds capable of killing or inhibiting the growth of certain plants and they have been frequently detected in natural waters. Advanced treatments, including those using ozone, have been use...Herbicides are chemical compounds capable of killing or inhibiting the growth of certain plants and they have been frequently detected in natural waters. Advanced treatments, including those using ozone, have been used in order to remove herbicides from different types of water with good treatment efficiency. The efficiency of ozonation, an oxidative process, in the removal of persistent compounds is affected by several factors, such as pH and the concentration of the contaminant. The compound metribuzin, the herbicide investigated in this study, is persistent and mobile in the environment with a high potential for transport through soils and thus it can reach the groundwater. In this context, the objective of this study was to evaluate the effect of different pH conditions (2.5, 5.5 and 12.0) and initial concentrations of metribuzin (20, 50 and 100 ppm) on the removal of this herbicide from water using the ozonation process. In order to identify the possible effect of these two variables on the ozonation treatment, the concentration of metribuzin was determined by spectrophotometry UV-vis spectrophotometer. The results were used to evaluate the best conditions for the ozonation treatment. The ozonation conditions which provided the highest metribuzin removal efficiency (86.5% ± 0.3%) were pH 12.0 and an initial metribuzin concentration of 20 ppm. The findings indicate that oxidation with ozone is effective for the removal of metribuzin from aqueous solutions under the conditions studied.展开更多
Propranolol hydrochloride can be considered a persistent and bioaccumulative pharmaceutical in the environment.This drug and its by-products are potentially toxic and have adverse effects,since these compounds have be...Propranolol hydrochloride can be considered a persistent and bioaccumulative pharmaceutical in the environment.This drug and its by-products are potentially toxic and have adverse effects,since these compounds have been associated with endocrine-disrupting effects,reproductive deficiencies,embryo abnormalities and pericardial oedema.TiO_(2)–La 0.05%–carboxymethyl-β-cyclodextrin(CMCD)nanoparticles were successfully prepared by a simple two-step method,which consists of sonification and functionalization.The characterization analyses reveal that lanthanum is dispersed on the semiconductor surface,probably forming Ti–O–La bonds,which can induce oxygen vacancies and surface defects that effectively restrain the recombination of photogenerated electron/holes pairs.The efficiency of TiO_(2)–La 0.05%–CMCD samples in degradation of propranolol under UV-light irradiation is higher than that of pristine TiO_(2) within 20 min reaction,probably due to complex formation between theβ-blocker and the oligosaccharide,which allows us to propose a photocatalytic mechanism based on the formation of intermediates and competition of these compounds to the radicals and CMCD cavities.展开更多
文摘Herbicides are chemical compounds capable of killing or inhibiting the growth of certain plants and they have been frequently detected in natural waters. Advanced treatments, including those using ozone, have been used in order to remove herbicides from different types of water with good treatment efficiency. The efficiency of ozonation, an oxidative process, in the removal of persistent compounds is affected by several factors, such as pH and the concentration of the contaminant. The compound metribuzin, the herbicide investigated in this study, is persistent and mobile in the environment with a high potential for transport through soils and thus it can reach the groundwater. In this context, the objective of this study was to evaluate the effect of different pH conditions (2.5, 5.5 and 12.0) and initial concentrations of metribuzin (20, 50 and 100 ppm) on the removal of this herbicide from water using the ozonation process. In order to identify the possible effect of these two variables on the ozonation treatment, the concentration of metribuzin was determined by spectrophotometry UV-vis spectrophotometer. The results were used to evaluate the best conditions for the ozonation treatment. The ozonation conditions which provided the highest metribuzin removal efficiency (86.5% ± 0.3%) were pH 12.0 and an initial metribuzin concentration of 20 ppm. The findings indicate that oxidation with ozone is effective for the removal of metribuzin from aqueous solutions under the conditions studied.
基金Project supported by the Coordination for the Improvement of Higher Education Personnel (CAPES)。
文摘Propranolol hydrochloride can be considered a persistent and bioaccumulative pharmaceutical in the environment.This drug and its by-products are potentially toxic and have adverse effects,since these compounds have been associated with endocrine-disrupting effects,reproductive deficiencies,embryo abnormalities and pericardial oedema.TiO_(2)–La 0.05%–carboxymethyl-β-cyclodextrin(CMCD)nanoparticles were successfully prepared by a simple two-step method,which consists of sonification and functionalization.The characterization analyses reveal that lanthanum is dispersed on the semiconductor surface,probably forming Ti–O–La bonds,which can induce oxygen vacancies and surface defects that effectively restrain the recombination of photogenerated electron/holes pairs.The efficiency of TiO_(2)–La 0.05%–CMCD samples in degradation of propranolol under UV-light irradiation is higher than that of pristine TiO_(2) within 20 min reaction,probably due to complex formation between theβ-blocker and the oligosaccharide,which allows us to propose a photocatalytic mechanism based on the formation of intermediates and competition of these compounds to the radicals and CMCD cavities.
