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Sensitive spectrophotometric determination of trace-level Co2+ in water based on acetate enhanced catalysis of Co2+
摘要： A sensitive spectrophotometric method was developed for the determination of trace-level Co2+ in water based on the acetate enhanced catalytic decolorization of methylene blue (MB) with Co2+ as a catalyst and peroxymonosulfate (PMS) as an oxidizing agent. This indirect spectrophotometric method was easy to operate due to the strong absorption of MB at a maximum absorption wavelength of 664 nm with a molar absorptivity of 5.88 × 104 L mol?1 cm?1. Under the selected reaction conditions of 10.0 mg L?1 MB, 60.0 mg L?1 PMS and 100.0 mg L?1 Ac?, the depletion extent of MB was linearly correlated with the concentration of Co2+ from 0.20 to 7.0 μg L?1 (R2 = 0.986) and then from 7.0 to 50.0 μg L?1 (R2 = 0.991), with a detection limit (3 s/k) of 0.10 μg L?1. It was found that this method possessed excellent anti-interference capability to various coexisting ions including similar transitional metals. The developed method was used to determine the Co2+ concentration in practical samples with satisfactory results.
关键词： Spectrophotometry,Methylene blue,Catalytic decolorization,Acetate,Trace-level Cobalt
更新于2025-11-19 16:56:35
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Sequential anaerobic and electro-Fenton processes mediated by W and Mo oxides for degradation/mineralization of azo dye methyl orange in photo assisted microbial fuel cells
摘要： The intensification of the degradation and mineralization of the azo dye methyl orange (MO) in contaminated water with simultaneous production of renewable electrical energy was achieved in photo-assisted microbial fuel cells (MFCs) operated sequentially under anaerobic - aerobic processes, in the presence of Fe(III) and W and Mo oxides catalytic species. In this novel process, the W and Mo oxides deposited on the graphite felt cathodes accelerated electron transfer and the reductive decolorization of MO. Simultaneously, the mineralization of MO and intermediate products was intensified by the production of hydroxyl radicals (HO?) produced by (i) the photoreduction of Fe(III) to Fe(II), and by (ii) the reaction of the photochemically and electrochemically produced Fe(II) with hydrogen peroxide, which was produced in-situ during the aerobic stage. Under anaerobic conditions, the reductive decolorization of MO was driven by cathodic electrons, while the partial oxidation of the intermediates proceeded through holes oxidation, producing N,N-dimethyl-p-phenylenediamine. In contrast, under aerobic conditions superoxide radicals (O2?-) were predominant to HO?, forming 4-hydroxy-N,N-dimethylaniline. In the presence of Fe(III) and under aerobic conditions, the oxidation of the intermediate products driven by HO? superseded that of O2?-, yielding phenol and amines, via the oxidation of 4-hydroxy-N,N-dimethylaniline and N,N-dimethyl-p-phenylenediamine. These sequential anaerobic and electro-Fenton processes led to the production of benzene and significantly faster oxidation reactions, compared to either the anaerobic or the aerobic operation in the presence of Fe(III). Complete degradation and mineralization (96.8 ± 3.5%) of MO (20 mg/L) with simultaneous electricity production (0.0002 kWh/kg MO) was therefore achieved with sequential anaerobic (20 min) - aerobic (100 min) operation in the presence of Fe(III) (10 mg/L). This study demonstrates an alternative and environmentally benign approach for efficient remediation of azo dye contaminated water with simultaneous production of renewable energy.
关键词： azo dye,decolorization,photo-assisted microbial fuel cells,electro-Fenton,mineralization
更新于2025-09-23 15:23:52
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Graphite Supported Stainless-Steel Electrode for the Degradation of Azo Dye Orange G by Fenton Reactions: Effect of Photo-Irradiation
摘要： An electrode, stainless steel supported on graphite, was used for the degradation of hazardous organic compounds, azo dye Orange G (OG), using the photoelectro- Fenton (PEF) process. Results showed that the applied current controlled the electrogeneration rate of both ferrous ion and hydrogen peroxide, which in turn affected the dye degradation kinetics. At an applied current density of 45 μA cm?2, the SS-graphite electrode yielded a molar ?H2O2(cid:2)=?Fe2t(cid:2) ratio of 3.6, which was optimal for dye degradation. Under otherwise identical conditions, UV irradiation significantly enhanced OG degradation, i.e., PEF is more effective than electro-Fenton (EF) process. At the optimal applied current density of 45 μA cm?2, or optimal molar ?H2O2(cid:2)=?Fe2t(cid:2) of 3.6, OG decolorization and total organic carbon removal were 83% (in 3 h) and 55% (in 7 h), versus 75% (in 3 h) and 20% (in 7 h) by PEF and EF, respectively. OG degradation by both PEF and EF processes followed the pseudo first-order kinetics, which suggested the major role of OH radical in OG decolorization.
关键词： Stainless steel,Graphite,Orange G,Photo-electro-Fenton (FEF),Steady-state approximation,Decolorization
更新于2025-09-23 15:21:01
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Toward Concurrent Organics Removal and Potential Hydrogen Production in Wastewater Treatment: Photoelectrochemical Decolorization of Methylene Blue over Hematite Electrode in the Presence of Mn(II)
摘要： A sustainable system capable of simultaneous removal of organic contaminants and hydrogen generation in wastewater treatment operation was studied using hematite electrode in the presence of Mn(II), PEC-Mn(II), as a proof of concept. The photoelectrochemical (PEC) system exhibited methylene blue (MB) decolorization threefold faster than that of photo-Fenton processes and yielded comparable photocurrent density to relative to the control system, i.e., PEC water splitting in the absence of MB at otherwise identical operation conditions. Furthermore, the advantages of PEC-Mn(II) system were no H2O2 addition, hydrogen production potential, and ease in Mn(II) separation via the formation of MnO2 precipitates during wastewater treatment operations. The PEC-Mn(II) process is a promising and sustainable approach toward wastewater treatment with the capability of concurrent photochemical energy generation. Moreover, the PEC-Mn(II) process can be an emerging energy-from-wastewater alternative in addition to other systems such as microbial fuel cell and anaerobic digestion.
关键词： Wastewater Treatment,Decolorization,Sustainability,Photoelectrochemical,Hydrogen production
更新于2025-09-10 09:29:36
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Photocatalytic Decolorization of Cobalamin in Aqueous Suspensions of TiO2 and ZnO Under Solar Irradiation
摘要： Photolysis and photocatalysts treatments of aqueous solution of cobalamin were carried out over a suspension of titanium dioxide and zinc oxide. Heterogeneous photocatalytic processes applied under natural weathering conditions, in the presence of solar radiation show a promising degradation capability. Under solar radiation a complete removal of color was achieved in a relatively short time of about 10 minutes, when ZnO was used and in 45 min when TiO2 was used. However, in the presence of artificial UV-light, complete decolorization of cobalamin was obtained in 20 min of irradiation when ZnO was used and in 60 min, when TiO2 was used at the same temperature. The results indicate that the degree of photocatalytic decolorization of cobalamin was obviously affected by different parameters such as, catalyst mass, type of catalyst and addition of H2O2.
关键词： Titanium dioxide,Zinc oxide,Cobalamin,Solar,Photocatalytic reactions,Decolorization efficiency
更新于2025-09-09 09:28:46
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Nanotechnology in Water and Wastewater Treatment || Photocatalytic Decolorization of Two Remazol Dyes Using TiO2 Impregnated Pumice Composite as Catalyst
摘要： This study, as a first attempt, aimed to evaluate photocatalytic decolorization of of two remazol dyes (blue and red) using TiO2 impregnated pumice composite catalyst. The SEM-EDX analysis showed that TiO2 nanoparticules were mostly impregnated on the pores of pumice with a ratio of 1.60% Ti. A 97.8% and 97.6% of color removal was achieved for RB and RR at pH 3, respectively, whereas those color removal percentages decreased to 57.4% and 53.9%, respectively, at pH 11 after 2 hours illumination. The color removal efficiencies of 97.8%, 82.7%, and 75.3% for RB dye and of 97.6%, 85.3%, and 84.0% for RR dye were observed after first, second, and third cycles reuse of the synthesized catalyst. Toxicity of photocatalytic treated samples of both dyes decreased below 50% after 90 and 120 minutes irradiation when they were diluted at 75%. This result indicate there is an urgent need to prolong the irradiation time and/or for increasing catalyst dose to completely remove toxicity in the undiluted samples.
关键词： TiO2 impregnated pumice composite,Remazol dyes,Photocatalytic decolorization,Toxicity,UV-A illumination
更新于2025-09-09 09:28:46