Search

Diclofenac sodium was extensively used for treating arthritis, osteoarthritis and skeletal muscular injuries, which ultimately caused troubles for aquatic organisms as well as human beings. In this study, homogeneous catalytic advanced oxidation processes, including Fe2+/persulfate, Fe2+/peroxymonosulfate and Fe2+/H2O2, were used for the degradation of diclofenac sodium in water, without using UV-C light. About 89, 82 and 54% DCF sodium was decomposed by Fe2+/persulfate, Fe2+/peroxymonosulfate and Fe2+/H2O2, respectively, in 60 min. The degradation of diclofenac sodium followed the pseudo first-order kinetics, in all cases. The degradation efficiency of diclofenac sodium was significantly affected in the presence of various anions, such as NO3−, HCO3− and SO42−. The mineralization studies revealed 62, 45 and 32% total carbon removal by Fe2+/persulfate, Fe2+/peroxymonosulfate and Fe2+/H2O2, respectively, in 60 min. In addition, the degradation byproducts of diclofenac sodium were determined by FTIR analysis. The results revealed that the Fe2+/oxidant system, particularly Fe2+/persulfate, was a promising technology for the elimination of toxic pharmaceuticals, such as diclofenac sodium, from the water environment. [ABSTRACT FROM AUTHOR]

The removal of water pollutants by photocatalysis is a promising technique, mainly due to its environmentally friendly and sustainable nature. In this study, the degradation of a recalcitrant organic pollutant, malachite green (MG), was investigated in water by a microstructured silver oxide photocatalyst. The silver oxide (Ag2O) microparticles (MPs) were synthesized by a low-cost, green method, mediated by green tea leaves extract. The surface, morphological and optical properties of the synthesized Ag2O MPs were determined by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-visible) spectrophotometry. The synthesized Ag2O MPs showed good photoactivity, represented by 83% degradation of malachite green (MG) ([C]0 = 0.4 mM, Ag2O loading = 0.1 g L−1) at neutral pH, in 3 h. Persulfate ions (PS) showed a strong synergistic effect on the efficiency of solar/Ag2O photocatalysis, represented by complete MG removal in 15 min, in the presence of 1.6 mM PS. The results revealed that solar/Ag2O, particularly solar/Ag2O/PS photocatalysis is a promising method for the elimination of toxic organic pollutants, such as malachite green, from the water environment. [ABSTRACT FROM AUTHOR]

Nitrogen-doped titanium dioxide (N-TiO 2) nanoparticles were prepared using a modified sol-gel method. The as-prepared nanoparticles were characterized by state-of-the-art techniques for their optical, structural and morphological properties. The crystallite size, surface area and bandgap energy of reference TiO 2 and N-TiO 2 nanoparticles were found to be 16.1 and 10.9 nm, 83.6 and 131.8 m2 g−1 and 3.23 and 2.89 eV, respectively. The photocatalytic activities, in terms of 2,4-dichlorophenol (2,4-DCP) degradation, of reference TiO 2 and N-TiO 2 were found to be 46.9% and 65.4% at 120 min of treatments under UV light irradiation and 21.5% and 77.6% at 240 min of treatment under visible light irradiation, employing 153.4 µM 2,4-DCP, 1 g/L photocatalyst dosage, and pH 5.6. Interestingly, considerable H 2 production rate (i.e., 386 μmol h−1 g−1) was observed for visible/N-TiO 2 system in presence of 0.2 wt% Pt. The study revealed that visible/N-TiO 2 photocatalytic system can be used as an economically viable technology for environmental sustainability. [Display omitted] • Kinetic and mechanistic studies of 2,4-dichlorophenol were performed by visible/N-TiO 2 system. • 82.4% reduction in toxicity of 2,4-dichlorophenol solution was achieved by visible/N-TiO 2. • The rate of H 2 production was 386 μmol h−1 g−1 by using visible/0.2 wt% Pt/N-TiO 2 system. • Visible/N-TiO 2 is an economic and promising technology for environmental sustainability. • A waste to energy concept towards circular economy [ABSTRACT FROM AUTHOR]

[Display omitted] • Removal of lindane was studied by visible and simulated solar light-assisted S-TiO 2. • Efficiency of S-TiO 2 photocatalysis dramatically increased in the presence of HSO 5 −. • Operational parameters such as pH, concentration of lindane and HSO 5 − were optimized. • Degradation mechanism was proposed based on identified intermediates and final products. • S-TiO 2 photocatalysis is an effective AOP to treat lindane contaminated waters. Organochlorine pesticides (OCPs) are toxic and the most potent endocrine disrupting chemicals in the environment. Most OCPs are resistant towards oxidation by OH due to presence of electron-withdrawing chlorine group in their molecular structures. Here, we investigated a visible and simulated solar light-assisted sulfur doped TiO 2 (S-TiO 2)/peroxymonosulfate (HSO 5 −) process to eliminate a selected OCP, lindane. Initially, visible and simulated solar light-assisted S-TiO 2 photocatalysis resulted in 31.0 and 63.4% removal of lindane (C 0 = 1.0 μM), respectively in 6 h. The photocatalytic activity of S-TiO 2 was dramatically increased in the presence of 0.2 mM HSO 5 −, leading to 68.2 and 99.9% lindane removal under visible and simulated solar light illumination, respectively in 6 h. The observed pseudo first-order rate constant for simulated solar light-assisted S-TiO 2 /HSO 5 − decreased with increasing initial concentration of lindane, corresponding to 8.98 × 10−1, 6.58 × 10−1 and 3.84 × 10−1 h−1 at [lindane] 0 of 0.5, 1.0 and 2.0 μM, respectively. The degradation kinetics were significantly affected by solution pH, leading to 88.2, 99.9 and 71.4% removal of lindane in 6 h at pH 4.0, 5.8 and 8.0, respectively. S-TiO 2 film exhibited a high mechanical strength with only 3.3% loss of efficiency after four repeated cycles. Based on the detected reaction intermediates, a possible reaction mechanism was proposed, suggesting dechlorination, dehydrogenation, and hydroxylation via OH, SO 4 − and O 2 − attack. The results suggest that visible and simulated solar light-assisted S-TiO 2 /HSO 5 − is a promising alternative for treatment of water contaminated with most OCPs. [ABSTRACT FROM AUTHOR]

• Degradation of lindane by UV/persulfate based AOPs was investigated. • Mechanism involved H-abstraction by SO 4 •− accompanied by C-Cl bond cleavage via UV-C. • Both less and more toxic by-products than lindane were produced, but vanished at high UV dose. • Natural organic matter and inorganic ions considerably affect degradation efficiency. • H 2 O 2 had significant synergistic effects on UV/persulfate process. Sulfate radical-advanced oxidation processes (SR-AOPs) are emerging technologies for decomposing organic pollutants in water. This study investigated the efficiency of UV/persulfate (UV/S 2 O 8 2−) process to degrade lindane in water, showing 93.2% lindane removal ([lindane] 0 = 3.43 μM, [S 2 O 8 2−] 0 = 100 μM) at a UV fluence of 720 mJ/cm2. The lindane degradation followed first order kinetics and mechanistic studies suggested H-abstraction by SO 4 •− and Cl removal via C-Cl bond cleavage by UV-C light. Toxicity assessment using ECOSAR program showed toxicity gradually decreased and eventually no significant toxicity remained when all by-products vanished at high UV dose. Removal efficiency of lindane decreased from 93.2% to 38.4, 45.5, 56.0, 84.3 and 88.6%, by adding 1.0 mg/L humic acid or 1.0 mM CO 3 2−, HCO 3 −, Cl− or SO 4 2−, respectively. Coupling of H 2 O 2 with UV/S 2 O 8 2− showed a significant synergistic effect with 99.0% lindane removal at a UV fluence of 600 mJ/cm2, using [S 2 O 8 2−] 0 = [H 2 O 2 ] 0 = 50 μM while UV/H 2 O 2 resulted in only 36.6% lindane removal ([lindane] 0 = 3.43 μM, [H 2 O 2 ] 0 = 100 μM) at a UV fluence of 720 mJ/cm2. The results indicate that SR-AOP has potential for consideration as a remedial technology to treat persistent chlorinated pesticides such as lindane in contaminated water. [ABSTRACT FROM AUTHOR]

Organochlorine compounds (OCs) are very toxic, highly persistent, and ubiquitous contaminants in the environment. Degradation of lindane, a selected OC, by simulated solar light-activated TiO2 (SSLA-TiO2) photocatalysis was investigated. The film types of the TiO2 photocatalyst were prepared using a dip-coating method. The physical properties of the films were investigated using X-ray diffraction, transmission electron microscopy, and environmental scanning electron microscopy. The SSLA-TiO2 photocatalysis led to a lindane removal of 23% in 6 h, with 0.042 h−1 of an observed pseudo first-order rate constant (kobs). The SSLA-TiO2 photocatalysis efficiency was greatly enhanced by adding hydrogen peroxide (H2O2), persulfate (S2O82−), or both combined, corresponding to a 64%, 89%, and 99% lindane removal in the presence of 200 µM of H2O2, S2O82−, or equimolar H2O2-S2O82−, respectively. The hydroxyl and sulfate radicals mainly participated in lindane degradation, proven by the results of a radical scavenger study. The degradation kinetics were hindered in the presence of the water constituents, indicated by a 61%, 35%, 50%, 70%, 88%, and 91% degradation of lindane in 6 h, using a SSLA-TiO2/S2O82−/H2O2 photocatalysis system containing 1.0 mg L−1 humic acid (HA), or 1 mM of CO32−, HCO3−, NO3−, SO42−, and Cl−, respectively. The TiO2 film demonstrated high reusability during four runs of lindane decomposition experiments. The SSLA-TiO2/S2O82−/H2O2 photocatalysis is very effective for the elimination of a persistent OC, lindane, from a water environment. [ABSTRACT FROM AUTHOR]

• Eosin modified TiO 2 film with co-exposed {001} and {101} facets was synthesized. • Sulfite/Eosin-TiO 2 system was used as SO 4 − based Advanced Oxidation Process. • Degradation of PABA was performed by sulfite/Eosin-TiO 2 /solar system. • Under visible light irradiation, Eosin-TiO 2 showed appreciable H 2 production rate. • Solar/Eosin-TiO 2 (/SO 3 2–) is a promising method for environmental sustainability. Owing to the increasing photosensitivity and DNA damage properties of para -aminobenzoic acid (PABA), concerns have been raised over the exposure of humans to PABA. Solar light-driven photocatalysis (SPC) provides a promising solution for the effective removal of organic pollutants especially when directed towards sulfate radical (SO 4 −) production. Herein, we have developed a sulfite-enhanced SPC using Eosin-Y sensitized TiO 2 /Ti film as a photocatalyst. The removal efficiency of PABA was enhanced by coupling Eosin-Y with TiO 2 /Ti film as revealed from 23.6 and 48.9 % PABA degradation by reference-TiO 2 /solar and Eosin-TiO 2 /solar, respectively. The apparent rate constant of PABA degradation by Eosin-TiO 2 was improved by 4.7 times in presence of 5 mM sulfite. Interestingly, Eosin-TiO 2 showed appreciable H 2 production rate under visible light illumination. Solar/sulfite/Eosin-TiO 2 system is a promising technology for environmental sustainability by using the renewable solar energy and air pollutants since sulfite is a waste from flue gas desulfurization process. [ABSTRACT FROM AUTHOR]