Wastewater containing Cr(VI) treatment using solar tubular reactor.

The hexavalent chromium, Cr(VI), which is generated in the electroplating process, is toxic to most organisms and potentially harmful to human health. The method generally used for remediation of wastewater containing Cr(VI) employs chemicals with high toxicity. This work proposes an alternative technology for the treatment of these wastewaters, based on photochemical reduction of Cr(VI) by alcohols under radiation, which is environmentally sustainable and economically viable. Initially, a batch reactor in laboratory scale was used to determine the best experimental conditions and its specific reaction rate was calculated. Based on these results, a tubular reactor (artificial radiation and sunlight) was designed and built in semi-pilot scale. Tests were carried out with real wastewater from an electroplating industry containing Cr(VI). Tests conducted under sunlight showed a higher total Cr(VI) reduction than the tests with artificial radiation. The remediation of Cr(VI) from wastewater was 86.7% after 6 h of reaction under sunlight, indicating the high efficiency of the developed process.

Photocatalytic degradation of rosuvastatin: analytical studies and toxicity evaluations.

Photocatalytic degradation of rosuvastatin, which is a drug that has been used to reduce blood cholesterol levels, was studied in this work employing ZnO as catalyst. The experiments were carried out in a temperature-controlled batch reactor that was irradiated with UV light. Preliminary the effects of the photocatalyst loading, the initial pH and the initial rosuvastatin concentration were evaluated. The experimental results showed that rosuvastatin degradation is primarily a photocatalytic process, with pseudo-first order kinetics. The byproducts that were generated during the oxidative process were identified using nano-ultra performance liquid chromatography tandem mass spectrometry (nano-UPLC-MS/MS) and acute toxicity tests using Daphnia magna were done to evaluate the toxicity of the untreated rosuvastatin solution and the reactor effluent.

Wastewater remediation using a spiral shaped reactor for photochemical reduction of hexavalent chromium.

The hexavalent chromium contained in wastewater of some industries is toxic to most microorganisms and potentially harmful to human health. The application of photochemical reduction of Cr(VI) in the treatment of wastewater from the electroplating industry was studied, and a continuous reactor in spiral shape made of borosilicate was designed and constructed (SSR). The statistical model of a circumscribed central composite design (CCCD) was used to investigate the influence of the amount of ethanol and the initial concentration of hexavalent chromium on total Cr(VI) reduction. A total Cr(VI) reduction of 46.0% was achieved under the optimal conditions established by the experimental design, using a synthetic Cr(VI) solution. In addition, the photochemical reduction of Cr(VI) follows pseudo first-order kinetics. The SSR exhibited similar behavior to that of the plug flow reactor (PFR), and presented higher photonic efficiency than the batch reactor. Finally, the designed reactor was effective when applied to real wastewater, showing a total Cr(VI) reduction of 51.8%, and its configuration is suitable for scale up.

Reduction of hexavalent chromium: photocatalysis and photochemistry and their application in wastewater remediation.

Hexavalent chromium present in wastewater discharge of galvanic industries is toxic to most microorganisms and potentially harmful to human health. This work examines the photochemical reduction of Cr(VI) with ethanol under ultraviolet (UV) and visible radiation, and photocatalytic reduction of Cr(VI) with TiO2 in the presence of ethanol under UV radiation. By means of different experimental designs, this study investigates the influence of the initial pH, ethanol amount, catalyst concentration and initial Cr(VI) concentration on total Cr(VI) reduction. The results obtained showed that photochemistry with ethanol under UV radiation (96.10%) was more efficient than photochemistry with ethanol under visible light (48.07%). Furthermore, photocatalysis with TiO2 in the presence of ethanol under UV radiation showed high values of total Cr(VI) reduction: 94.15%, under the optimal conditions established by the experimental design. Finally, experiments were carried out with wastewater discharge from an electroplating plant in its original concentration, and higher values of total Cr(VI) reduction were observed.