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Highly efficient method for oxidation of dissolved hydrogen sulfide in water, utilizing a combination of UVC light and dissolved oxygen
摘要： Hydrogen sul?de is a hazardous contaminant that may appear in well-water and in sewage streams. Here we present a very e?cient way for the removal of H2S from well-water, based on combining UVC light and oxygen. The method was tested with H2S-enriched tap water as well as with natural well water, both of which containing up to 20 mg/L of H2S. A conversion of up to 90% was obtained within a residence time of no more than a few minutes. The quantum e?ciency, de?ned as the ratio between the number of removed H2S molecules to the number of impinging photons, was found to be as high as 70%, depending on conditions. The main product was found to be sulfate, without the appearance of elemental sulfur, i.e. with no major change in turbidity. The absence of sulfur in the outlet stream in of large importance when treating H2S-containing well-water, since it omits the need for posttreatment removal of particles. Results are explained by the excitation of HS- species, following by formation of polysul?de anions that readily react with any formed elemental sulfur, eventually yielding sulfate ions.
关键词： AOP,Water treatment,Sulfate,Hydrogen sul?de,Oxidation
更新于2025-09-23 15:23:52
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From micro to macro-contaminants: The impact of low-energy titanium dioxide photocatalysis followed by filtration on the mitigation of drinking water organics
摘要： This study evaluated strategies targeting macro- and micro-organic contaminant mitigation using low-energy titanium dioxide photocatalysis. Energy inputs of 1, 2, and 5 kWh m-3 resulted in incomplete oxidation of macro-organic natural organic matter, signified by greater reductions of UV254 and specific ultraviolet UV absorbance (SUVA) in comparison to dissolved organic carbon (DOC). The rate of UV254 removal was 3 orders of magnitude greater than the rate of DOC degradation. Incomplete oxidation improved operation of downstream filtration processes. Photocatalysis at 2 kWh m-3 increased the bed life of downstream granular activated carbon (GAC) filter by 340% relative to direct filtration pretreatment. Likewise, photocatalysis operated ahead of microfiltration decreased fouling, resulting in longer filter run times. Using 2 kWh m-3 photocatalysis increased filter run time by 36 times in comparison to direct filtration. Furthermore, levels of DOC and UV254 in the membrane permeate improved (with no change in removal across the membrane) using low-energy photocatalysis pretreatments. While high-energy UV inputs provided high levels of removal of the estrogenic micro-organics estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethynlestradiol (EE2), low-energy photocatalysis did not enhance removal of estrogens beyond levels achieved by photolysis alone. In the cases of E1 and E3, the addition of TiO2 as a photocatalyst reduced degradation rates of estrogens compared to UV photolysis. Overall, process electrical energy per order magnitude reductions (EEOs) greatly improved using photocatalysis, versus photolysis, for the macro-organics DOC, UV254, and SUVA; however, energy required for removal of estrogens was similar between photolysis and photocatalysis.
关键词： granular activated carbon (GAC),estrogens,UV photolysis,dissolved organic carbon (DOC),advanced oxidation process (AOP),natural organic matter (NOM)
更新于2025-09-23 15:21:01
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Normal boundary intersection applied in the scale-up for the treatment process of Eriochrome Black T through the UV/TiO2/O3 system
摘要： Minimizing the variability of any process can become a way to reduce costs and at the same time keep the process stable. The use of the Normal Boundary Intersection (NBI) algorithm to construct the Pareto frontier can be applied to a better choice of a particular setup that can give the process a better response and less variability. The objective of this research is to propose the modelling and optimization for the maximum removal of the Chemical Oxygen Demand (COD) and the minimization of the variance associated the COD removal, to the UV/TiO2/O3 process, in the treatment of Eriochrome Black T. The factors studied in the COD removal were: pH, ozonator power, ozone ?ow and reaction time. The process of modelling used the response surface through the Central Compound Design (CCD) arrangement. In addition to the optimization, a Pareto Frontier using the NBI algorithm was utilized. The optimized results showed a COD removal of 33.7 ± 1.29 obtained X* = [7.7; 160 W; 5.6 L min?1; 22.6 min]. The con?rmation of this point belonging to the Pareto frontier from the validation of the method was performed within a 95% con?dence interval, the number of experiments being determined from the power sample size, comparing the ratio between the variances, weights w1 = 1 and w2 = 0.45.
关键词： Optimization,Eriochrome Black T,AOP
更新于2025-09-19 17:15:36
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Removal of Carbofuran in aqueous solution by using UV-irradiation/hydrogen peroxide
摘要： Pesticide residues in natural water are one of the biggest environmental problems. carbofuran is an insecticide widely used in agricultural activities and it is easily biodegradable. Although this compound has a relatively short lifetime in soils and its persistence in the environment varies from one to several weeks. For this reason, the elimination of carbofuran residual from contaminated waters using suitable technique is of environmental interest. The aim of this study to investigate the synergetic effect of UV and UV with hydrogen peroxide on the degradation of carbofuran in aqueous solution. 50 mgL-1 aqueous solutions of carbofuran (CBF) were prepared. The solutions were exposed to various UV irradiation times. The irradiation time varied from (15-240 min). Hydrogen peroxide was set at 4.8 mM as a minimum concentration level. To follow the degradation percent, formaldehyde concentration, and to identify the intermediates by-products, GC-MS, IC, and UV-Visible spectrophotometer were used. The pH, total acidity, and dissolved oxygen values were determined before and after treatment with UV irradiation with/without hydrogen peroxide. Depending on the results obtained the mechanism pathway (degradation) was suggested. The complete removal of carbofuran in aqueous solution took place at 180 min in the presence of H2O2.
关键词： advanced oxidation processes (AOP’s),hydrogen peroxide effect,Carbofuran,UV/H2O2
更新于2025-09-10 09:29:36