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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]

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 Removal of cadmium (Cd2+), a highly toxic heavy metal, from aqueous solutions was investigated using nano zerovalent iron (Fe0). Cadmium was efficiently removed by Fe0, although reactivity and reusability of Fe0 was significantly promoted by coupling with bismuth (Bi). At a reaction time of 20 min, 85% and 96% Cd2+ was removed by Fe0 and Bi/Fe0, respectively, at first cycle using [Cd2+] 0 = 10 mg/L and [Fe0] 0 = [Bi/Fe0] 0 = 1.0 g/L. However, Cd2+ removal efficiency was reduced to 12% and 80% at sixth cycle by Fe0 and Bi/Fe0, respectively. The X-Ray diffraction and energy dispersive X-Ray spectroscopy analysis proved successful formation of Fe0 by the chemical reduction method and also confirmed coupling of Bi with Fe0 to form bimetallic Bi/Fe0. The oxidation of Fe0 and Bi/Fe0 yielded electron that played significant role in the conversion of toxic Cd2+ into non-toxic Cd0. The reactivity of electron with Cd2+ was calculated to be 4.3 × 109 M−1 s−1. The pH of solution showed pronounced effects on the reactivity of both Fe0 and Bi/Fe0. Removal of Cd2+ by both Fe0 and Bi/Fe0 followed pseudo-first-order kinetic model. The conversion of Cd2+ into non-toxic Cd0 proved Fe0 and Bi/Fe0 to be highly efficient and rewarding in detoxification of Cd2+ and other toxic metals in aqueous environments. Graphical abstract Unlabelled Image Highlights • Bi was successfully coupled with Fe0 using chemical reduction method. • The Bi coupled Fe0 displayed greater reactivity, stability, and reusability. • Second-order rate constant of hydrated electron with Cd2+ was estimated. • pH of aqueous solution significantly influenced efficiency of Fe0 and Bi/Fe0. [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]

• 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]

The drug resistant bacteria and textile contaminations of water cause different sever health problem throughout the world. To overcome this issue, new environmental benign materials and methods are needed. Plant metabolites directed synthesis of nanoparticles is considered eco-friendly and easy in synthesis. Therefore, it was explicit for the synthesis of AgNPs. The prepared AgNPs were evaluated for antibacterial, antioxidant, photo-catalytic and electrochemical degradation properties as well as toxicity of degradation products on aquatic life. X-Ray Photoelectron Spectroscopy (XPS) has been used for analyzing the surface chemistry of prepared AgNPs. The particle size determines the interaction of nanoparticles with pathogens. Both Gram positive and negative bacteria ( Escherichia coli and Staphylococcus areous ) are used to determine the anti-microbial potency of the green synthesized AgNPs. The synthesized silver nanoparticles showed significant anti-bacterial applications against B. subtilus and S. aureus. The anti-oxidant applications of AgNPs also studied on comparison with vitamin C. The toxicity of the phenolic Azo dyes (PDA) has been studied against Fish, Daphnia and Green Algae . The electrode potential was studied in the electrochemical redox reaction of hydroxy phenol in aqueous media. Simple electrolyte was used to determine the current efficiency. For the stability of electrode multi cyclic voltammetry was also studied during redox reaction, which showed stability under the potential 0.4 to 0.2 V. [ABSTRACT FROM AUTHOR]

A highly efficient, quick and environmentally benign protocol has been adopted to synthesize AuNPs using the plant extract of Sueda fruciotosa . UV–vis spectroscopy, XRD, HRTEM, SEM and FTIR were used to characterize the prepared AuNPs. Different concentrations of plant extract were used to optimize the size, morphology and distribution of AuNPs. AuNPs were of small size and spheroid in shape at lower concentration. AuNPs showed a surface plasmon resonance at 443 nm. According to HRTEM the average size of AuNPs was 6–8 nm. The AuNPs were appraised for their photo degradation activity on methylene blue (MB) as an experimental substrate. Photo-catalytic activity of AuNPs was found to be dependent on the concentration of catalyst, irradiation time, size and aggregation of AuNPs. Furthermore, AuNPs exhibited an excellent electro-catalytic activity. The sensitivity of modified AuNPs was also studied for phenolic Azo dyes (PAD) which showed its good degradation activity. These gold nanoparticles found to be significantly applicable in the field of electrochemistry, sensors, catalysis, nano-devices, treatment of waste water and conversion of toxic agents into less toxic compound. [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]

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]

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]

This study investigated iron-mediated oxidative processes for the photochemical degradation of endosulfan, a chlorinated insecticide and central nervous system disruptor. At UV fluence of 360 mJ/cm 2 , 52.4% and 32.0% removal of 2.45 μM initial endosulfan was observed by UV/Fe 3+ and UV/Fe 2+ processes, respectively, at an initial concentration of 17.8 μM iron. The degradation of endosulfan by UV/Fe 3+ or UV/Fe 2+ was dramatically enhanced by adding peroxide (i.e., H 2 O 2 , S 2 O 8 2− or HSO 5 − ). Among the UV/peroxide/Fe processes, the highest degradation efficiency of 99.0% at UV fluence of 360 mJ/cm 2 was observed by UV/HSO 5 − /Fe 2+ with 2.45 μM [endosulfan] 0 , 17.8 μM [Fe 2+ ] 0 , and 49.0 μM [HSO 5 − ] 0 . The observed degradation rate constant of endosulfan was promoted either by increasing [Fe 2+ ] 0 and/or [peroxide] 0 or by decreasing [endosulfan] 0 , while the initial degradation rate of endosulfan increased with increasing [Fe 2+ ] 0 , [peroxide] 0 , or [endosulfan] 0 . At UV fluence of 6000 mJ/cm 2 , 45.0% mineralization as represented by the decrease in total organic carbon content was observed by UV/HSO 5 − /Fe 2+ at 9.80 μM [endosulfan] 0 , 980 μM [HSO 5 − ] 0 , and 17.8 μM [Fe 2+ ] 0 . The major by-product of endosulfan was observed in all cases to be endosulfan ether which was further degraded with an extended reaction time. The results suggest that iron-mediated advanced oxidation processes (AOPs) have a high potential for the removal of endosulfan and its by-product from contaminated water. [ABSTRACT FROM AUTHOR]

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 (e aq − ) was found to play primary role in the removal of endosulfan sulfate which was possibly due to greater reactivity of e aq − 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 e aq − , 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 SO 2 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. [ABSTRACT FROM AUTHOR]

This study reported Fe doped zinc oxide (Fe-ZnO) synthesis to degrade chlorpyrifos (CPY), a highly toxic organophosphate pesticide and important sources of agricultural wastes. Fourier transform infrared, X-ray diffraction, scanning electron microscope, and energy-dispersive X-ray spectroscopic analyses showed successful formation of the Fe-ZnO with highly crystalline and amorphous nature. Water collected from agricultural wastes were treated with Fe-ZnO and the results showed 67% degradation of CPY by Fe-ZnO versus 39% by ZnO at 140 min treatment time. Detail mechanism involving reactive oxygen species production from solar light activated Fe-ZnO and their role in degradation of CPY was assessed. Use of H 2 O 2 , peroxydisulfate (S 2 O 8 2−) and peroxymonosulfate (HSO 5 −) with Fe-ZnO under solar irradiation promoted removal of CPY. The peroxides yielded hydroxyl (OH) and sulfate radical (▪) under solar irradiation mediated by Fe-ZnO. Effects of several parameters including concentration of pollutant and oxidants, pH, co-existing ions, and presence of natural organic matter on CPY degradation were studied. Among peroxides, HSO 5 − revealed to provide better performance. The prepared Fe-ZnO showed high reusability and greater mineralization of CPY. The GC-MS analysis showed degradation of CPY resulted into several transformation products (TPs). Toxicity analysis of CPY as well as its TPs was performed and the formation of non-toxic acetate imply greater capability of the treatment technology. [Display omitted] • Fe doped ZnO was successfully synthesized by sol-gel method. • Fe doping and use of peroxides synergistically promoted performance of ZnO. • Degradation of chlorpyrifos was inhibited by h vb + and OH scavengers. • Second-order rate constants of chlorpyrifos with OH and ▪ were calculated. • Toxicities of chlorpyrifos and its transformation products were estimated. [ABSTRACT FROM AUTHOR]

Extensive research has been conducted on controlling carbon dioxide (CO 2), sulfur oxides (SO x), and nitrogen oxides (NO x) emissions in recent years with increasing environmental awareness. The primary contributor to climate change is the exponentially growing anthropogenic CO 2 , NO x, and SO x in the air from various energy and industrial sectors. Hence, several pre-combustion and post-combustion processes to mitigate these gases have been introduced and implemented. Despite the benefits of CO 2 , SO x , and NO x abatement technologies, researchers still have major challenges to deal with. While the removal efficiencies, operational costs, and resulting byproducts of conventional removal technologies are being improved, new technologies are also emerging. As it is evident from the current abundant reserves of coal that it will continue to be in a significant position among the principal sources of energy for more than a decade, the research for the reduction of CO 2 , NO x, and SO x is inevitable to save future generations from the harmful impacts of these pollutants. This review paper summarizes the progress of different emission control technologies at the plant level and introduces emerging technologies that are environment friendly. [Display omitted] • NO x , SO x and CO 2 emissions from fuel combustion and industries are of significant concern. • Several pre and post combustion processes have been devised to control emissions. • Adsorption, absorption, and membrane technologies for CO 2 capture have been promising. • For NOx reduction, SNCR process has relatively low capital and operational cost. • WFGD technology is the most extensively utilized process for SOx control. [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]

Abstract In the present study the synthesis of an inexpensive solar light responsive Co2+ and Fe3+ co-doped TiO 2 (Co Fe TiO 2) for efficient photocatalytic degradation of ofloxacin (OFL) in addition to its excellent activity as peroxidase mimics has been reported. The as-synthesized material was fully investigated morphologically and structurally by X-ray diffraction (XRD) analysis, field emission-scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) and UV diffuse reflectance spectroscopy (UV-DRS). The morphology of the as-synthesized Co Fe TiO 2 appeared to be more dispersed, porous and uniform. The UV-DRS analysis showed that the band gap of the as-synthesized TiO 2 , Fe TiO 2 , Co TiO 2 , Co Fe TiO 2 was measured as 3.31, 3.22, 3.15 and 3.04 eV, respectively. The pilot scale experiments were conducted in a simple non-concentrating solar photoreactor by using the as-synthesized Co Fe TiO 2 having total volume of 5 L. To synergize the photocatalytic process the photocatalytic reactor was added with peroxymonosulfate (HSO 5 −). The effect of various process parameters like [HSO 5 −] 0 , flow rate and [Co Fe TiO 2 ] 0 were optimized. The assessment of degradation products (DPs) of OFL and then their toxicity analysis suggested the as-synthesized Co Fe TiO 2 provides a safe route for the solar light induced photocatalytic degradation of OFL. The as-synthesized Co-Fe TiO 2 was also applied as novel peroxidase mimetic that can catalyze 3,3′,5,5′-tetramethylbenzidine (TMB) when H 2 O 2 serves as oxidant. The results showed that the color response and the peroxidase like response of Co Fe TiO 2 highly rely on the concentration of H 2 O 2 and thus the as-synthesized material can successfully be applied for the calorimetric sensing of H 2 O 2. Graphical abstract Unlabelled Image Highlights • Solar light driven photocatalysis of ofloxacin at pilot scale level. • Lowering the band gap of TiO 2 by co-doping with Co2+ and Fe3+. • Fifteen (15) new photocatalytic degradation byproducts of OFL were found. • Toxicity assessment revealed that some of the DPs are more toxic than OFL. • In situ peroxidase like behavior of Co Fe TiO 2 was found. [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]

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]

• 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]

Highlights: [•] Degradation of atrazine was investigated in UV, UV/H2O2, UV/HSO5 − and UV/S2O8 2− AOPs. [•] UV/S2O8 2− process was found to be more efficient as well as more economical. [•] The pH affected UV/S2O8 2− but had no significant influence on UV, UV/H2O2 and UV/HSO5 −. [•] Second order rate constants of atrazine with SO4 − and OH were found to be comparable. [•] Degradation mechanism was investigated by GC–MS and LC–MS/MS analysis. [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]

Abstract: The degradation of atrazine, a widely used endocrine disrupting, carcinogenic and persistent herbicide, was investigated by photo-Fenton and photo-Fenton-like advanced oxidation technologies (AOTs): UV/H2O2/Fe2+, UV//Fe2+ and UV//Fe2+. The study was carried out at two pH value conditions, i.e., pH 3.0 and pH 5.8. At pH 3.0, UV//Fe2+ was found to be the most efficient technology whereas UV//Fe2+ was observed to be the most effective at pH 5.8. The degradation of atrazine followed pseudo-first-order reaction with the highest observed rate constant of 2.00×10−2 cm2/mJ in UV//Fe2+ system at the initial concentrations of 4.64μM atrazine, 46.4μM (PMS) and 35.81μM Fe2+. The UV fluence required for the complete removal of 4.64μM atrazine at initially 92.80μM of oxidant and 8.95μM of Fe2+ concentrations at pH 3.0 was found to be 480, 720 and 960mJ/cm2 in UV//Fe2+, UV//Fe2+ and UV/H2O2/Fe2+ systems, respectively. Humic and fulvic acids were found to negatively impact the degradation of atrazine. The removal of TOC was not significant unless a high UV fluence was applied. At an initial concentration of 18.56μM atrazine, 1856.00μM oxidant and 17.91μM Fe2+, a 62.94%, 47.10% and 44.09% decrease in TOC was achieved at a UV fluence of 6000mJ/cm2 in UV/PS/Fe2+, UV/PMS/Fe2+ and UV/H2O2/Fe2+ systems, respectively. Nevertheless, it is suggested in this study that photo-Fenton and photo-Fenton-like technologies are capable of removing atrazine from water efficiently. [Copyright &y& Elsevier]