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The gamma irradiation was investigated for potential removal of endosulfan sulfate, an emerging water pollutant and central nervous system disruptor. A removal efficiency of 99.5% of initially 1.30 μM endosulfan sulfate was observed at an absorbed dose of 1020 Gy. Aqueous electron (eaq(-)) was found to play primary role in the removal of endosulfan sulfate which was possibly due to greater reactivity of eaq(-) with endosulfan sulfate, considering the second-order rate constant of 8.1×10(9) and 3.4×10(10) M(-1) s(-1) for hydroxyl radical (·OH) and eaq(-), respectively, with endosulfan sulfate. The removal efficiency of endosulfan sulfate was affected by the pH of aqueous solution, with observed removal efficiency of 99.5%, 98.3% and 31.3% at pH 6.2, pH 10.0, and pH 2.6, respectively. The efficiency was also influenced by inorganic anions and humic acid in the order of nitrate>nitrite>bicarbonate>carbonate ≃ humic acid. The initial degradation rate increased while degradation constant decreased with increasing initial concentrations of endosulfan sulfate. The degradation pathways showed that oxidative pathway was initiated at the SO2 bond while reductive pathways at the chlorine attached to the ring of endosulfan sulfate. The mass balance showed removal of 98% chloride and 72% sulfate ions from endosulfan sulfate at an absorbed dose of 1020 Gy. The removal of endosulfan sulfate followed by subsequent loss of by-products under extended treatment showed that gamma irradiation is potential technique for the remediation of organic pollutants from a water environment., (Copyright © 2014. Published by Elsevier Ltd.)

This study explored the efficiency of UV-C-based advanced oxidation processes (AOPs), i.e., UV/S2O8(2-), UV/HSO5(-), and UV/H2O2 for the degradation of endosulfan, an organochlorine insecticide and an emerging water pollutant. A significant removal, 91%, 86%, and 64%, of endosulfan, at an initial concentration of 2.45 μM and UV fluence of 480 mJ/cm(2), was achieved by UV/S2O8(2-), UV/HSO5(-), and UV/H2O2 processes, respectively, at a [peroxide]0/[endosulfan]0 molar ratio of 20. The efficiency of these processes was, however, inhibited in the presence of radical scavengers, such as alcohols (e.g., tertiary butyl alcohol and isopropyl alcohol) and natural organic matter (NOM). The inhibition was also influenced by common inorganic anions in the order of nitrite > bicarbonate > chloride > nitrate ≈ sulfate. The observed pseudo-first-order rate constant decreased while the degradation rate increased with increasing initial concentration of the target contaminant. The degradation mechanism of endosulfan by the AOPs was evaluated revealing the main by-product as endosulfan ether. Results of this study suggest that UV-C-based AOPs are potential methods for the removal of pesticides, such as endosulfan and its by-products, from contaminated water., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The oxidative degradation of CV dye in aqueous media has been evaluated using Fenton (Fe2+/H2O2) and photo-Fenton (Fe2+/H2O2/UV) processes. Various operational parameters like H2O2 dosages, Fe2+ dosages and [CV]0 were optimized of both Fenton and photo-Fenton processes for the removal of CV dye from aqueous media. Kinetic results indicated that photo-Fenton process (kobs=0.0097 min−1, t1/2=71.45 min) is more effective than Fenton process (kobs=0.0074 min−1, t1/2=93.66 min). Second order rate constant of ˙OH radical with CV dye was calculated to be 3.96×109 M−1s−1. De-methylated organic intermediates of CV dye detected by LC-MS and some other intermediates like CH3COO−, HCOO−, NH4+ and Cl− were identified by ion-chromatography. [ABSTRACT FROM AUTHOR]

Removal of chlorendic acid, an emerging water pollutant and potential carcinogenic, was investigated by gamma radiation in the absence and presence of peroxymonosulfate (PMS, HSO 5 − ). The removal of chlorendic acid (1.40 μM initial concentration) by gamma radiation was promoted with PMS, i.e., 95% compared to 82% in the absence of PMS, at an absorbed dose of 1000 Gy. The removal of chlorendic acid by gamma-ray/PMS process was due to OH and SO 4 − . Second-order rate constants of 5.90 × 10 9 , 1.75 × 10 9 , and 2.05 × 10 9 M −1 s −1 for chlorendic acid with e aq − , OH, and SO 4 − , respectively, were determined. The removal efficiency of chlorendic acid was promoted with increasing initial PMS concentration and decreasing initial target contaminant concentration. The removal of chlorendic acid by gamma-ray/PMS was inhibited in the presence of CO 3 2− , NO 2 − , p -CBA, m -TA, and alcohols. The presence of Fe 2+ , Cu + , and Fe 3+ with gamma-ray/PMS promoted removal efficiency of chlorendic acid from 78% to 99, 94, and 89%, respectively, at 592 Gy. The degradation of chlorendic acid by OH and SO 4 − was found to be initiated at the carboxylate group as could be revealed from nature of the transformation by-products. Nevertheless, this study concluded that gamma-ray/PMS is of practical importance in treatment of natural water containing chlorendic acid, as potential detoxification of chlorendic acid solution can be revealed from 83% loss of chloride ion at 3000 Gy. In addition, gamma-ray/PMS process achieved efficient removal of chlorendic acid even in the presence of commonly found inorganic ions in natural water. [ABSTRACT FROM AUTHOR]

Conventional titanium dioxide (TiO2) materials can be activated only by ultraviolet (UV) light, which is only 4-5% of the whole solar spectrum. As a result, visible light (vis)-active TiO2-based photocatalysts have recently received significant attention in the field of TiO2 photocatalytic treatment and purification of water and air. This study reports the preparation of UV-visible light-active phosphorous (P)-doped, fluorine (F)-doped, and PF-co-doped anatase TiO2 nanoparticles via an innovative sol-gel method. Prepared nanoparticles were characterized by UV-vis diffuse reflectance spectroscopy, X-ray diffraction analysis, Raman spectroscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy (FTIR), and porosimetry analysis. Synthesized materials exhibited improved structural properties, including high surface area, small crystallite size, reduced band gap energy, mesoporous structure, and high porosity. Due to doping with P and F, light absorption of TiO2 in the visible light region was efficiently enhanced with effective band gap energy of 2.70 eV. Brunauer-Emmett-Teller (BET) surface area for PF-co-doped, P-doped, F-doped, and reference TiO2 nanoparticles was 212.0, 175.0, 88.8, and 79.7 m2/g, respectively. PF-co-doped TiO2 showed the highest photocatalytic degradation of atrazine, which could be attributed to the beneficial effects including small crystallite size, high BET surface area, and light absorption in UV-visible region, induced by co-doping of TiO2 with P and F. Finally, reaction intermediates were determined, which confirms the photocatalytic degradation of atrazine using the synthesized catalysts under UV-visible light illumination. [ABSTRACT FROM AUTHOR]

Water is obligatory for sustaining life on Earth. About 71% of the Earth's surface is covered in water. However, only one percent of the total water is drinkable. The presence of contaminants in wastewater, surface water, groundwater, and drinking water is a serious threat to human and environmental health. Their toxic effects and resistance towards conventional water treatment methods have compelled the scientific community to search for an environmentally friendly method that could efficiently degrade toxic contaminants. In this regard, visible light active photocatalysts have proved to be efficient in eliminating a wide variety of water toxins. A plethora of research activities have been carried out and significant amounts of funds are spent on the monitoring and removal of water contaminants, but relatively little attention has been paid to the degradation of persistent water pollutants. In this regard, nanoparticles of doped ZnO are preferred options owing to their low recombination rate and excellent photocatalytic and antimicrobial activity under irradiation of solar light. The current article presents the roles of these nanomaterials for wastewater treatment from pollutants of emerging concern. [ABSTRACT FROM AUTHOR]

The removal of brilliant green (BG), a toxic organic and cationic dye, has been examined by UV/S 2 O 8 2− (PS), UV/HSO 5 − (PMS) and UV/H 2 O 2 processes. BG showed insignificant direct photolysis at 254 nm (i.e., 8.6% after 30 min). However, enhanced BG degradation was observed in UV/PS, UV/PMS and UV/H 2 O 2 systems as revealed from 63.1, 47.0 and 34.8% BG degradation, respectively, at 30 min of reaction time, using 0.05 mM BG and 1.0 mM oxidant initial concentration. The bimolecular rate constants of OH and SO 4 − with BG were determined to be 2.35 × 10 9 and 2.21 × 10 9 M −1 s −1 , respectively. Electrical energy per order (EE/O) values for UV/PS, UV/PMS and UV/H 2 O 2 processes were calculated to be 5.4, 6.8, and 7.8 KWh/m 3 /order, respectively. The addition of humic acid (HA) and inorganic anions inhibited the degradation of BG by UV/PS in the order of NO 2 −  > HA > HCO 3 −  > Cl −   > NO 3 −  ≈ SO 4 2− . The results of frontier electron densities (FEDs) showed that C-atom holding the three rings (C7), and C-atoms at para positions to N-alkyl groups of the two rings (C4 and C14) are the predominant sites for radical addition. Furthermore, nine degradation products (DPs) of BG were detected experimentally using LC/MS/MS. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synergistic HC/SPC/O 3 process for degradation of emerging environmental pollutants. • Superior performance of HC/SPC/O 3 comparing to HC/H 2 O 2 /O 3. • Improvement of sustainability and process safety of AOPs by percarbonate oxidant. • Green advanced oxidation based on cavitation phenomenon. • Importance of hydrodynamic cavitation in activation of oxidants. Hydrodynamic cavitation (HC) was employed to activate sodium percarbonate (SPC) and ozone (O 3) to degrade recalcitrant 1,4-dioxane. The degradation efficiency > 99 % with a rate constant of 4.04 × 10−2 min−1 was achieved in 120 min under the optimal conditions of cavitation number (C v) 0.27, pH 5, molar ratio of oxidant to pollutant (r ox) 8, ozone dose of 0.86 g h−1 under 25 ± 2 °C with initial concentration of 1,4-dioxane 100 ppm. The application of HC with SPC/O 3 increased the degradation efficiency by 43.32 % in 120 min, confirming a synergistic effect between the coupled processes. In addition, the degradation efficiency of 1,4-dioxane in HC/SPC/O 3 was superior as compared to HC/H 2 O 2 /O 3 , suggesting that the presence of SPC has a significant role in degradation of 1,4-dioxane. Radical quenching experiment revealed highest contribution of hydroxyl (HO) radicals in the degradation of 1,4-dioxane among carbonate (CO 3 −) and superoxide (O 2 −) radicals. The presence of co-existing anions resulted in an inhibitory effect in the following order: SO 4 2− > NO 3 − > Cl−. Based on GC–MS analysis, ethylene glycol diformate (EGDF) was detected as the main degradation product of 1,4-dioxane. The observed intermediate supports the radical route of 1,4-dioxane oxidation, which involves H-abstraction, ΔC-C splitting at the α-C position, subsequent dimerization, fragmentation and mineralization. Electric energy per order (E EO) for best process was 102.65 kWh·m−3·order−1. Total cost of treatment was estimated as approx. 12 USD/m3. These findings confirmed the SPC as an efficient, environmentally-friendly alternative to H 2 O 2 and broadened the scope of HC-based AOPs for water and wastewater treatment. [ABSTRACT FROM AUTHOR]

• Highly stable and solar light responsive Bi-TiO 2 was synthesized. • The doping of Bi3+ induced Ti3+ and oxygen vacancy in the TiO 2 lattice. • The photocatalytic efficiency of TBi5 was enhanced by coupling with HSO 5 −. • SO 4 − and OH were dominant species involved in the degradation of FLU. • The contribution rate of SO 4 − was calculated to be 89% in the degradation of FLU. The present study is focused on the synthesis of a novel solar light responsive bismuth doped titania (Bi-TiO 2) through a facile so-gel technique by applying various wt% of Bi. The as-synthesized Bi-TiO 2 showed superior photocatalytic performance than un-doped TiO 2 towards degradation of flumequine (FLU) under solar light irradiation. The as-synthesized material was thoroughly characterized to examine its structure, morphology and chemical states. The EPR analysis revealed the existence of Ti3+ ion and oxygen vacancy, which is created due to Bi-doping. The as-synthesized Bi-TiO 2 with 5 wt% Bi (TBi5) showed excellent photocatalytic performance as compared to their counterparts. The photocatalytic activity of TBi5 was further improved when added with peroxymonosulfate (HSO 5 −) and increased with increasing [HSO 5 −] 0. The mechanistic investigation and radical scavenging studies revealed that OH and SO 4 − are involved in the degradation of FLU by the as-synthesized material. The bimolecular rate constants of OH and SO 4 − were calculated to be 9.1 × 109 M−1s−1 and 8.5 × 109 M−1s−1, respectively. The photocatalytic performance of the as-synthesized TBi5 coupled with HSO 5 − under solar light irradiation towards degradation of FLU in Milli-Q water (MW), tape water (TW) and synthetic wastewater (SWW) was 92, 82 and 70% with k app values of 0.093, 0.085 and 0.066 min−1, respectively. Furthermore, the degradation pathways of FLU were predicted on the basis of its degradation products (DPs). The high mineralization of FLU as well as the evaluation of non-toxic DPs suggests that solar light/TBi5/HSO 5 − is a promising advanced oxidation process for the future wastewater treatment applications. [ABSTRACT FROM AUTHOR]