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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]

Abstract This study presents the synthesis of a novel Mn2+ and Co2+ co-doped TiO 2 (Mn-Co-TiO 2) for the photocatalytic degradation of enoxacin (ENX) under solar light irradiation. The as-synthesized photocatalysts were fully characterized by X-ray diffraction (XRD) analysis, field emission-scanning electron microscopy (FE-SEM), and UV-diffuse reflectance spectroscopy (UV-DRS). The structural appearance of the Mn-Co-TiO 2 suggests porous cylindrical type morphology. Moreover, the co-doping of Mn2+ and Co2+ has successfully reduced the band gap of TiO 2 from 2.81 eV to 2.10 eV. Applying Langmuir Hinshelwood kinetic model, the photocatalytic degradation of ENX by Mn-Co-TiO 2 followed pseudo-first-order kinetics. A total of twelve (12) DPs of ENX were identified by UPLC/MS-MS. The natural water constituents such as CO 3 2−, HCO 3 −, Cl− and Fe3+ had great influence on the photocatalytic degradation of ENX by Mn-Co-TiO 2 under solar light irradiation. The as-synthesized Mn-Co-TiO 2 showed appreciable results for the photocatalytic degradation of ENX in synthetic wastewater (SWW) and real wastewater (RWW) samples. Furthermore, the toxicity assessment of ENX and its DPs towards aquatic organisms (i.e., fish, daphnia and green algae) was measured which are helpful for the practical implementation of this technology for wastewater treatment. The Mn-Co-TiO 2 materials also showed good peroxidase-like activity towards the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H 2 O 2 and followed Michaelis-Menten kinetics. Graphical abstract Unlabelled Image Highlights • Efficient Solar light driven photocatalysis of Enoxacin. • Narrowing the band gap of TiO 2 by co-doping with Mn2+ and Co2+ • Total of twelve (12) new photocatalytic degradation byproducts of ENX were found. • Toxicity assessment revealed that some of the degradation byproducts are more toxic than ENX. • Additional peroxidase like activity of Mn/Co-TiO 2 was found. [ABSTRACT FROM AUTHOR]

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]

The present study elaborates the removal of endosulfan, an emerging water pollutant and potential carcinogenic, in aerated solution. The influence of Cl, NO, NO, CO, HCO, SO, and humic acid was assessed on the radiolytic degradation of endosulfan. A strong inhibition on the radiolytic degradation of endosulfan was observed in the presence of NO, NO, and SO. Instead, a slight increase in the removal efficiency of endosulfan was observed at high concentrations of CO and HCO. The formation of CO in radiolytic degradation of endosulfan in the presence of CO and HCO was demonstrated by adding SO that rapidly react with CO. The results indicate that CO formed from the reactions of CO and HCO and commonly found in natural water can play an important role in the degradation of endosulfan and other sulfur containing electron-rich compounds. The study showed faster degradation of endosulfan at lower concentration compared to high concentration and removal was found to follow pseudo-first-order kinetic. Endosulfan ether was found as the main degradation product and degradation pathway was found to be initiated at the S=O bond of endosulfan. The efficiency of gamma irradiation in the removal of endosulfan was examined in terms of formation of short chain organic acids and chloride ion accumulation. [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]

• 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]

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]

In this study, activated carbon (AC) and nano-zerovalent copper (nZVCu) functionalized hydroxyapatite (HA) and alginate beads were synthesized and used for the removal of As3+ from aqueous solution. The characterization by X-ray diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, high resolution transmission electron microscopy, BET surface area analysis, thermogravimetric analysis, and Fourier transform infrared spectroscopy revealed successful formation of the AC/nZVCu/HA-alginate, nZVCu/HA-alginate, AC/HA-alginate, and HA-alginate beads. The scanning electron microscopy and surface analysis revealed the prepared beads to be highly mesoporous which led to the maximum adsorption of As3+, i.e., 13.97, 29.33, 30.96, and 39.06 mg/g by HA-alginate, AC/HA-alginate, nZVCu/HA-alginate, and AC/nZVCu/HA-alginate beads, respectively. The thermogravimteric analysis showed the nZVCu/HA-alginate beads to be highly stable while the AC composite beads as the least stable to heat treatment. The HA-alginate beads achieved 39% removal of As3+, however, removal efficiency was promoted to 95% by coupling AC and nZVCu with HA-alginate beads at a reaction time of 120 min. The removal of As3+ by the prepared AC & nZVCu coupled HA-alginate beads was promoted with increasing [As3+] 0 and [AC/nZVCu/HA-alginate] 0. The pH of aqueous solution significantly influenced the removal of As3+ by AC/nZVCu/HA-alginate beads and maximum removal was achieved at pH 5.8. Freundlich adsorption isotherm and pseudo-second-order kinetic models were found to best fit the removal of As3+ by the synthesized beads. The high performance of AC/nZVCu/HA-alginate beads in the removal of As3+ even after seven cyclic treatment as well as least leaching of Cu ions into aqueous solution suggest enhanced reusability and stability of HA-alginate beads by coupling with AC and nZVCu. The results suggest that the synthesized beads have good potential for the removal of As3+ from aqueous solutions. Image 1 • Characterization techniques proved nZVCu and AC coupled HA-Alginate beads formation. • Coupling AC and nZVCu enhanced performance and reusability of HA-Alginate beads. • Removal of As3+ best fitted Freundlich isotherm and pseudo-second-order models. • Removal of As3+ was significantly affected by the pH of aqueous solution. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Highly stable nZVMn was synthesized by chemical reduction method. • Addition of S 2 O 8 2− promoted the performance of nZVMn. • Second-order rate constants of CIP with OH and SO4 − were calculated. • Proposed pathways for conversion of CIP into TPs were developed. • Acute and chronic toxicities of CIP and its TPs were evaluated. Abstract Nano zerovalent manganese (nZVMn, Mn0) materials have been synthesized in this study and used for degradation of ciprofloxacin (CIP), an emerging water pollutant. The investigation of physiological characteristics of Mn0 by different characterization techniques proved successful formation of Mn0 by the chemical reduction method and found it to be highly crystalline. The Mn0 was highly efficient and resulted in 63% degradation of CIP using [CIP] 0 = 10 mg/L and [Mn0] 0 = 1.0 g/L at a reaction time of 80 min. Addition of S 2 O 8 2− to Mn0 promoted removal efficiency of CIP from 63 to 95% at a reaction time of 80 min using the conditions of [CIP] 0 = 10 mg/L, [Mn0] 0 = 1.0 g/L, and [S 2 O 8 2−] 0 = 50 mg/L. The presence of OH and SO 4 − scavengers inhibited the degradation of CIP by Mn0/S 2 O 8 2−. The comparable second-order rate constants of CIP with OH and SO 4 − were calculated to be 2.35 × 109 and 2.10 × 109 M−1 s−1, respectively. High S 2 O 8 2− and Mn0 concentrations and low pH accelerated the degradation of CIP. However, removal efficiency of CIP by Mn0 with the added S 2 O 8 2− was inhibited using high CIP concentration, high pH, inorganic anions, and NOM. Degradation pathways from OH and SO 4 − based degradation of CIP were developed. Acute and chronic toxicities of CIP and its products were estimated, showing the final product to be non-toxic. The as-synthesized Mn0 was found to be stable as well as environmentally friendly for treating CIP. This study suggests that Mn0 with the added S 2 O 8 2− is a promising alternative for potential remediation and detoxification of CIP and other emerging water pollutants. [ABSTRACT FROM AUTHOR]

In this study, solar light responsive Bi 3+ and Fe 2+ doped ZnO were synthesized and used for photocatalytic degradation of norfloxacin (NOR), an emerging water pollutant. Analysis with Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and UV–vis diffuse reflectance spectroscopy (DRS) confirmed coupling of dopants (i.e., Bi 3+ and Fe 2+ ) or co-dopants (Bi 3+ /Fe 2+ ) with ZnO and suggested small narrow size as well as highly crystalline and porous nature of the doped ZnO. Metal ions doping lowered band gap energy and inhibited recombination of electron-hole pair in the as-synthesized ZnO. Consequently, BiFe-ZnO showed enhanced photocatalytic activity and reusability, giving 80% removal of NOR as compared to 36% by un-doped ZnO at a reaction time of 120 min. The analysis with photoluminescence (PL) technique verified high yield of OH from solar light activation of BiFe-ZnO compared to Bi-ZnO, Fe-ZnO and ZnO. Performance of the as-prepared photocatalysts was promoted with the added HSO 5 − and increased with increasing [HSO 5 − ] 0 . Degradation of NOR by BiFe-ZnO with the added HSO 5 − was due to OH and SO 4 − and NOR showed high reactivity with OH and SO 4 − . The removal efficiency of NOR was inhibited using OH and SO 4 − scavengers. Photocatalytic activity of the as-synthesized photocatalysts with the added HSO 5 − was highly dependent on [NOR] 0 , [pH] 0 , co-existing ions, and natural organic matter. Degradation pathways were suggested from the pattern of NOR degradation and identified transformation products. The mineralization of NOR as well as formation of non-toxic end product suggests co-doped ZnO with added HSO 5 − to be a potential technology for treating antibiotics contaminated water. [ABSTRACT FROM AUTHOR]

Norfloxacin (NOR), an important antibiotic used for the treatment of different infections which is reportedly causing huge quantity of water pollution and severe environmental issues. In this study, biochar prepared from Phoenix dactylifera roots biomass (PB) and composited with mesoporous nano-zerovalent cerium (nZVCe) was used for treatment of NOR solutions. The various characterization and treatment studies showed successful formation of the nZVCe and PB composite. The nZVCe was found to improve physiological characteristics and catalytic efficiency of PB. The nZVCe/PB composite caused 52% removal of NOR as compared to 23% by the individual PB. The use of peroxydisulfate (PDS) with PB and nZVCe/PB showed further improvement in the removal of NOR and caused 58 and 84% removal efficiencies of NOR by PB/PDS and nZVCe/PB/PDS, respectively. The use of PDS with PB and nZVCe/PB was found to yield ●OH and SO 4 ●– which improved degradation of NOR, however, addition of ●OH and SO 4 ●– scavengers impeded NOR degradation. The PB was found to have several oxygen functional groups which decomposed PDS into ●OH and SO 4 ●–. The nZVCe/PB showed high recovery, reusability, and stability and caused high removal of NOR even at fifth cycle of treatment both in the absence and presence of PDS. The treatment of NOR by nZVCe/PB-catalyzed PDS showed encouraging results under different pH, and varying concentrations of PDS, nZVCe/PB, and NOR as well as in real water samples which suggest potential practical applications of NOR contaminated water. Degradation of NOR resulted into several products and the resulting final product proved to be non-toxic. [Display omitted] • nZVCe and biochar composite was prepared and nZVCe improved properties of biochar. • Biochar and nZVCe/PB effectively decomposed PDS into.●OH and SO 4 ●–. • Radical scavengers inhibited role of.●OH and SO 4 ●– in degradation of norfloxacin. • The PB and nZVCe/PB effectively degraded norfloxacin in real water also. • The composite of biochar and nZVCe showed enhanced stability and reusability. [ABSTRACT FROM AUTHOR]

Textile industries contribute to water pollution through synthetic dye discharge. This study explores the use of natural bio-coagulants to remove acid dyes from wastewater, investigating factors like pH, coagulant dose, dye concentration, contact time, and temperature for optimal results. The optimum pH and coagulants capabilities of (CAAPP, CAAPH, CBAGL, CBAPP and CBAPH) were 3 (49.6 mg/g), 3 (42.5 mg/g), 3 (38.9 mg/g), 4 (35.7 mg/g), 4 (34.1 mg/g), and 4 (29.4 mg/g) respectively, while treating of selected BRF-221 dyes from water solution. The acidic range (3–4) was found to have the best pH for the maximal coagulation, and the optimal dose were found to be 0.05 g/50 mL. The equilibrium was attained within 45–60 min for all coagulants. After 60 min of shaking, the maximum coagulation capacities (21.9, 21.02, 16.5, 27.9, 25.3, and 23.4 mg/g) of several coagulant composites (CAAGL, CAAPP, CAAPH, CBAGL, CBAPP, CBAPH) were determined. The initial BRF-221 dye concentration in the range of 10–200 mg/L was considered as optimum for gaiting maximum elimination of dye using different coagulants. At a dye value of 100 mg/L of BRF-221, maximal coagulation capacities CAAGL (179.19 mg/g), CAAPP (166.06 mg/g), CAAPH (141.60 mg/g), and CBAGL (126.49 mg/g), CBAPP (113.9 mg/g), CBAPH (93.08 mg/g) were attained. The study found 35 °C to be the optimal temperature for maximum acid dye removal using bio-coagulants. Increasing temperature reduced coagulation capacity, indicating an exothermic process. Freundlich and Langmuir isotherms showed suitability for pseudo-first-order and pseudo-second-order kinetics in biosorption. Thermodynamic parameters were assessed for process feasibility. Effective coagulants demonstrated sensitivity to electrolyte variations. In column studies, adjusting parameters achieved maximum coagulation efficiency for removing BRF-221 dyes. The study successfully applied optimal parameters to remove real textile effluents at a practical scale. SEM, FT-IR, BET and XRD characterized coagulants, providing insights into stability and morphology. [Display omitted] • Maximal coagulation capacities of Reactive Blue BRF-221 ranges from 93.08 mg/g to 179.19 mg/g. • Freundlich and Langmuir isotherms demonstrated excellent suitability for biosorption. • Higher temperatures decreased coagulation efficiency, suggesting an exothermic process. • Green Hybrid Coagulants offer cost-effectiveness, and exceptional sorption capacity. • Surfactants and detergents greatly hindered BRF-221 dye coagulation in water. [ABSTRACT FROM AUTHOR]

• The nZVMn/PBC showed high activity in adsorptive and oxidative removal of Congo-red. • The physical properties of biochar were improved with the coupling of nZVMn. • The nZVMn/PBC-catalyzed H2O2 into ●OH that caused oxidative removal of Congo-red. • Congo-red removal was promoted with the high dose of adsorbent and H2O2. • Degradation pathways of Congo-red in ●OH-mediated oxidative system were proposed. Congo-red (CR), a precursor of textile products and a contaminant of great concern, has contaminated aquatic environments. Here, we explored the synthesis of mesoporous nano-zerovalent manganese (nZVMn) and Phoenix dactylifera leaves biochar (PBC) composite for the removal of CR from water. The nZVMn/PBC adsorbed 117.647 mg/g of CR versus 25.316 mg/g by PBC at [CR] 0 = 20 mg/L and [PBC] 0 = [nZVMn/PBC] 0 = 500 mg/L. Variation of [nZVMn/PBC] 0 , [CR] 0 and pH influenced the adsorption of CR. Freundlich adsorption isotherm and pseudo-first-order kinetic models best fitted CR adsorption. The H 2 O 2 coupling with nZVMn/PBC promoted removal of CR possibly due to the formation of hydroxyl radical (●OH) and caused 95 % removal of CR versus 77 % by nZVMn/PBC alone. The ●OH scavengers inhibited the removal of CR. The nZVMn/PBC showed a good reusability and efficient removal of CR up to the seventh cycle of treatment. Results reveal that nZVMn improved performance, thermal stability and reusability of biochar. Degradation products from ●OH-mediated degradation of CR were studied by ultraperformance liquid chromatography with mass spectrometric detector to establish degradation pathways. The ion-chromatographic analysis showed the formation of non-toxic inorganic acetate product, which suggests high potential of the newly fabricated adsorbent in the removal of CR. [ABSTRACT FROM AUTHOR]

• Congo-red dye and its DPs were found highly toxic. • Gamma-ray with the added H 2 O 2 and S 2 O 8 2− efficiently degraded CR. • Reactivity of congo-red dye with OH and SO 4 − were calculated. • Proposed degradation pathways of CR were developed from the DPs evolved. Gamma radiation has received increasing attention due to their high potential in degradation of recalcitrant pollutants. Thus in the present study, gamma radiation was used for degradation of congo-red (CR) dye, a highly toxic and carcinogenic pollutant, in the presence of H 2 O 2 and S 2 O 8 2−. The CR was significantly degraded by gamma radiation (i.e., 53%), however, presence of H 2 O 2 and S 2 O 8 2− promoted degradation of CR to 98 and 87%, respectively, at 1184 Gy absorbed dose. The radical scavengers and electron spin resonance studies revealed that gamma radiation decompose H 2 O 2 and S 2 O 8 2− into OH and SO 4 − and both OH and SO 4 − caused degradation of CR. The CR showed high reactivity, i.e., 3.25 × 109 and 8.50 × 108 M−1 s−1 with OH and SO 4 −, respectively, and removal of CR was inhibited in the presence of OH and SO 4 − scavengers. The removal of CR was promoted with elevating initial concentrations of H 2 O 2 and S 2 O 8 2− and decreasing initial concentrations of CR. pH of aqueous solution also significantly influenced removal of the dye. The proposed degradation pathways of CR were established from the OH mediated degradation of CR and nature of identified degradation products. The greater mineralization of CR, formation of small molecular mass degradation product, and decline in concentration of acetate after extended treatment suggest the gamma-ray mediated peroxide based process to be a promising alternative for potential degradation of CR. [ABSTRACT FROM AUTHOR]

Chlorpyrifos (CPY), an organophosphate pesticide is largely used throughout the world on different crops for the control of pests and causes severe health and environmental issues. In this study, highly efficient, crystalline, and nm-rang sized zerovalent zinc (nZVZn) catalyst was synthesized and used for removal of chlorpyrifos at semi-pilot scale. The nZVZn showed high activity and caused 55% removal of CPY at 90 min time under the conditions of [CPY] 0 = 10 mg/L, [nZVZn] 0 = 1.0 g/L, and flow rate of the reactor = 0.2 L/min. Using identical conditions of [CPY] 0 , [nZVZn] 0 and flow rate, the use of peroxymonosulfate (PMS) promoted the performance of nZVZn and caused 99.5% removal of CPY at [PMS] 0 = 40 mg/L. The electron spin resonance (ESR) spectroscopy studies revealed that nZVZn catalyzed PMS reactions yield hydroxyl and sulfate radicals that degraded CPY and removal of CPY was suppressed by applying radical scavengers. The nZVZn catalyzed PMS based removal of CPY was optimum at high [PMS] 0 , [nZVZn] 0 and low pH of solution. The flow rate of the pilot plant reactor also influenced the degradation efficiency of CPY. High pH of solution, high [CPY] 0 as well as use of alcohols, NOM, and some inorganic ions inhibited removal of CPY by nZVZn catalyzed PMS. The analysis of degradation products (DPs) of CPY were used to propose degradation pathways of CPY. The high TOC removal of CPY, low leaching of Zn2+ from Zn0 into aqueous solution, and toxicity reduction of CPY suggest the nZVZn catalyzed PMS process to be highly effective and environmental benign for treatment of CPY. Image 1 • Nano zerovalent zinc was used for removal of chlorpyrifos at semi-pilot scale. • Removal of chlorpyrifos by zerovalent zinc was promoted by peroxymonosulfate. • Hydroxyl and sulfate radical rate constants with chlorpyrifos were calculated. • Proposed degradation pathways of chlorpyrifos were suggested. • Toxicities of treated chlorpyrifos solutions and zinc ion leaching were evaluated. [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]

Ciprofloxacin (CIP) is a widespread emerging water pollutant and thus its removal from aquatic environment is vital. The use of Fe3+/H2O2 and Fe2+/H2O2 resulted in 38 and 64% removal of CIP (8.0 ppm), respectively, within 80 min reaction time (pH 5.8, [H2O2]0 = 80 ppm, and [iron]0 = 20 ppm). Low pH, high temperature, high dose of H2O2 and Fe2+, and low CIP concentration facilitated removal of CIP. The radical scavenger studies proved in situ generated OH to be involved primarily in the removal of CIP. The effect of temperature was used to estimate enthalpy and activation energies of the removal of CIP. At 800 min reaction time, the Fe2+/H2O2 resulted in 54% mineralization of CIP using 16.0 ppm [CIP]0, 320.0 ppm [H2O2]0, and 40.0 ppm [Fe2+]0. The potential degradation pathways of CIP established from the degradation of CIP by OH and products evolved was found to be initiated at C6 through the loss of fluoride ion. The acute and chronic toxicities of CIP and its degradation products were estimated with the final product found to be non-toxic. The results suggest that Fe2+/H2O2-mediated AOPs have high potential for degradation as well as toxicity elimination of CIP and its degradation products. [ABSTRACT FROM AUTHOR]

Carbamazepine (CBZ), a widely used antiepileptic drug, was removed by UV–254 nm based advanced oxidation processes. CBZ was found to be stable under sole UV, however, removal of CBZ was promoted using Fe3+ and Fe2+ with UV. Further, removal efficiency of CBZ was significantly enhanced by coupling H2O2 with UV and Fe3+/Fe2+. At 3600 mJ cm−2, 7.5, 60.2, 74.3 and 90.6% CBZ degradation was achieved in UV, UV/H2O2, UV/H2O2/Fe3+ and UV/H2O2/Fe2+, using CBZ, H2O2, Fe2+ and Fe3+ at 21.16, 1060.00, 17.91 and 17.91 μM, respectively. Higher CBZ degradation in the presence of H2O2 was attributed to HO whose second-order rate constant with CBZ was calculated to be (8.83 ± 0.27) × 109 M−1 s−1. Removal of CBZ by UV/H2O2/Fe2+ system was optimum at pH 3.0, as 80.8, 90.6 and 70.4% CBZ degradation was observed at pH 2.0, 3.0 and 6.5, respectively. The removal of CBZ by UV/H2O2/Fe2+ was retarded in the presence of Cl− and humic acid as revealed from 84.5 and 56.7% CBZ degradation in the presence of Cl− and humic acid, respectively, compared to 90.6% in their absence at 3600 mJ cm−2. The CBZ degradation products were found to be less toxic than the parent compound, suggesting important role of UV-assisted AOPs in efficient removal and toxicity reduction of CBZ and their degradation products. [ABSTRACT FROM AUTHOR]

• The presence of H 2 O 2 with iron promoted the removal of CIP. • The presence of OH scavengers inhibited removal of CIP by Fe2+/H 2 O 2. • Mineralization of CIP by Fe2+/H 2 O 2 -mediated AOPs was explored. • Potential pathways for conversion of CIP into degradation products were developed. • Acute and chronic toxicities of CIP and its degradation products were estimated. Ciprofloxacin (CIP) is a widespread emerging water pollutant and thus its removal from aquatic environment is vital. The use of Fe3+/H 2 O 2 and Fe2+/H 2 O 2 resulted in 38 and 64% removal of CIP (8.0 ppm), respectively, within 80 min reaction time (pH 5.8, [H 2 O 2 ] 0 = 80 ppm, and [iron] 0 = 20 ppm). Low pH, high temperature, high dose of H 2 O 2 and Fe2+, and low CIP concentration facilitated removal of CIP. The radical scavenger studies proved in situ generated OH to be involved primarily in the removal of CIP. The effect of temperature was used to estimate enthalpy and activation energies of the removal of CIP. At 800 min reaction time, the Fe2+/H 2 O 2 resulted in 54% mineralization of CIP using 16.0 ppm [CIP] 0 , 320.0 ppm [H 2 O 2 ] 0 , and 40.0 ppm [Fe2+] 0. The potential degradation pathways of CIP established from the degradation of CIP by OH and products evolved was found to be initiated at C 6 through the loss of fluoride ion. The acute and chronic toxicities of CIP and its degradation products were estimated with the final product found to be non-toxic. The results suggest that Fe2+/H 2 O 2 -mediated AOPs have high potential for degradation as well as toxicity elimination of CIP and its degradation products. [ABSTRACT FROM AUTHOR]

• Degradation of carbamazepine was investigated in UV-assisted AOPs. • Carbamazepine was recalcitrant to sole UV but susceptible to UV/H 2 O 2 /Fe2+ oxidation. • Second order rate constant of carbamazepine with OH was (8.83 ± 0.27) × 109 M−1 s−1. • The UV/H 2 O 2 /Fe2+ treatment was efficient in toxicity reduction of CBZ. • Degradation mechanism was proposed from identified degradation products. Carbamazepine (CBZ), a widely used antiepileptic drug, was removed by UV–254 nm based advanced oxidation processes. CBZ was found to be stable under sole UV, however, removal of CBZ was promoted using Fe3+ and Fe2+ with UV. Further, removal efficiency of CBZ was significantly enhanced by coupling H 2 O 2 with UV and Fe3+/Fe2+. At 3600 mJ cm−2, 7.5, 60.2, 74.3 and 90.6% CBZ degradation was achieved in UV, UV/H 2 O 2 , UV/H 2 O 2 /Fe3+ and UV/H 2 O 2 /Fe2+, using CBZ, H 2 O 2 , Fe2+ and Fe3+ at 21.16, 1060.00, 17.91 and 17.91 μM, respectively. Higher CBZ degradation in the presence of H 2 O 2 was attributed to HO whose second-order rate constant with CBZ was calculated to be (8.83 ± 0.27) × 109 M−1 s−1. Removal of CBZ by UV/H 2 O 2 /Fe2+ system was optimum at pH 3.0, as 80.8, 90.6 and 70.4% CBZ degradation was observed at pH 2.0, 3.0 and 6.5, respectively. The removal of CBZ by UV/H 2 O 2 /Fe2+ was retarded in the presence of Cl− and humic acid as revealed from 84.5 and 56.7% CBZ degradation in the presence of Cl− and humic acid, respectively, compared to 90.6% in their absence at 3600 mJ cm−2. The CBZ degradation products were found to be less toxic than the parent compound, suggesting important role of UV-assisted AOPs in efficient removal and toxicity reduction of CBZ and their degradation products. [ABSTRACT FROM AUTHOR]

Desethyl-atrazine (DEA) and desisopropyl-atrazine (DIA) are the two major degradation by-products of atrazine (a suspected human carcinogen and endocrine disrupting herbicide), and show an equal toxicity to their parent compound. This study investigated the degradation of DEA and DIA with OH and SO 4 − generated from the activation of peroxides, i.e., persulfate (S 2 O 8 2− ), peroxymonosulfate (HSO 5 − ) and hydrogen peroxide (H 2 O 2 ), by UV-254 nm radiation in the presence or absence of Fe 2+ . Quantum yields of DEA and DIA were independent of pH (3.0–11.0). The higher quantum yield of reactive radicals from UV/S 2 O 8 2− , i.e., 1.8 compared to 1.04 for UV/HSO 5 − and 1.0 for UV/H 2 O 2 , resulted in greater efficiency of UV/S 2 O 8 2− for both DEA and DIA degradation. The second-order rate constants of DEA and DIA with SO 4 − were calculated to be (6.42 ± 0.12) × 10 8 and (1.70 ± 0.30) × 10 9 M −1 s −1 , and that with OH were (1.14 ± 0.09) × 10 9 and (2.22 ± 0.44) × 10 9 M −1 s −1 , respectively, suggesting a strong impact of side chains toward radical reactions. Fe 2+ promoted slightly the activation of the examined peroxides at pH 7.4. Presence of organic matter and alkalinity in field water samples negatively influenced the efficiency of UV/S 2 O 8 2− . Based on the identified degradation by-products by GC–MS, potential degradation pathways were proposed for both compounds. The results obtained suggested that DEA and DIA can be efficiently removed from the contaminated water by OH and SO 4 − based-AOPs. [ABSTRACT FROM AUTHOR]

Bromate, a potential carcinogen, is a well known highly persistent and environmentally recalcitrant contaminant. UV-254/sulfite-based advanced reductive pathways (ARPs) were proposed to eliminate bromate successfully from water. Experiments with N 2 , N 2 O, 2-chlorophenol, inorganic ions, and different pH (highly acidic to highly basic) proved that UV-254/sulfite successfully provides aqueous electron that effectively participate in bromate removal from water. Significant removal, 86%, of initially 39.0 µM bromate was achieved by UV-254/sulfite under conditions that dominate aqueous electron based pathways. The high second-order rate constant of 5.3 × 10 9 M −1 s −1 determined proved high reactivity of aqueous electron with bromate. The kinetic and removal efficiency of bromate showed linear relationship with the rate of aqueous electron formation. An increase in kinetic and removal efficiency of bromate was observed with increasing initial sulfite concentration and decreasing bromate concentration. The impacts of different initial concentrations of the typical ions commonly found in water were studied in detail to extend the UV-254/sulfite-based process for potential practical applications. The lower molar absorptivity of bromate at 254 nm determined proved insignificant removal of bromate under direct photolysis. The impacts of initial sulfite concentration on removal of bromate in UV-254/sulfite-based process also minimized role of direct photolysis. The cost evaluation and rapid decomposition of bromate into bromide proved UV-254/sulfite-based ARPs to be economical and highly rewarding in efficient decomposition of bromate and other inorganic oxyhalides. [ABSTRACT FROM AUTHOR]

[Display omitted] • Different peroxides-based oxidative pathways were compared towards NOR degradation. • The peroxide HSO 5 − performed best in the degradation of NOR under UV-C and Fe2+. • The peroxides yield ●OH and SO 4 ●− under activation by UV-C and Fe2+ activation. • The ●OH and SO 4 ●− scavengers inhibited degradation of NOR. • Degradation products and ecotoxicities of NOR as well as its DPS were estimated. The removal of norfloxacin (NOR), a widely used pharmaceutical and emerging water pollutant, was studied using UV-C and Fe2+ catalyzed peroxides-based oxidative processes (e.g., UV-C/Fe2+/H 2 O 2 , UV-C/Fe2+/S 2 O 8 2− and UV-C/Fe2+/HSO 5 −) and compared with UV-C and UV-C/Fe2+. The UV-C and UV-C/Fe2+ degraded NOR to 38 and 55 %. However, use of peroxides, i.e., H 2 O 2 , S 2 O 8 2−, HSO 5 − with UV-C and UV-C/Fe2+ promoted NOR %degradation to 75, 83, and 90 % using [peroxides] 0 = 50 mg/L, [Fe2+] 0 = 1 mg/L, and [NOR] 0 = 10 mg/L, respectively. The significant impact of peroxides on NOR degradation was due to their decomposition into ●OH and SO 4 ●− which showed high activity towards NOR degradation. The ●OH and SO 4 ●− formation from peroxides decomposition and their contribution in NOR degradation was verified by different scavenger studies. Among the UV-C/Fe2+/peroxides processes, UV-C/Fe2+/HSO 5 − showed better performance. The changing concentrations of peroxides, Fe2+, and NOR affected degradation of NOR. The use of different pH and inorganic anions also influenced NOR degradation. The degradation pathways of NOR were established and analyzed acute as well as chronic toxicities of NOR and its DPs. [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]