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The present study is focused on the synthesis of zero-valent iron/cellulose acetate (Fe0-x/CA) membranes by phase inversion route for the activation of peroxymonosulfate (PMS). The generated •OH and SO4•− effectively degraded methylene blue (MB) dye in water to give comparatively non-toxic byproducts. The SEM investigations revealed that Fe0 nanoparticles are evenly dispersed into the CA membrane resulting in decline of agglomeration and enhancing the roughness of the composite surface. Moreover, the catalytic degradation of MB demonstrated that M5-alone showed 85% and was further boosted to 97% when coupled with PMS (M5/HSO5−). The catalytic degradation of degradation of MB by M5/HSO5− membrane system in acidic, neutral, and basic media indicated that the degradation was 99.5%, 98.0%, 97.0%, 86.0% and 70.0% when the pH of the medium was 3, 5, 7, and 11, respectively. Furthermore, the degradation performance of M5/HSO5− membrane system was evaluated in de-ionized water (DIW), tape water (TPW) and industrial wastewater (IWW) and the results indicated that MB catalytic degradation was in the order of DIW (97%) > TPW (84%) > IWW (68%). Besides, various parameters like water flux permeability, contact angle, porosity, and fouling performance were also investigated. In addition, the degradation products were evaluated, and the degradation pathways were proposed accordingly. [ABSTRACT FROM AUTHOR]

Advanced oxidation/reduction processes (AO/RPs) are considered as effective water treatment technologies and thus could be used to solve the problem of water pollution. These technologies of wastewater treatment involve the production of highly reactive species such as •OH, H•, e−aq, SO4•−, and SO3•−. These radicals can attack the targeted contaminants present in aqueous media and result in their destruction. The efficiency of AO/RPs is highly affected by various operational parameters such as initial concentration of contaminant, solution pH, catalyst amount, intensity of light source, nature of oxidant and reductant used, and the presence of various ionic species in aquatic media. Among AO/RPs, the solar light-based AO/RPs are most widely used nowadays for contaminant removal from aqueous media because of their high environmental friendliness and cost effectiveness. By using these techniques, almost all types of pollutants can be easily removed from aquatic media within short intervals of time, and hence, the problem of water pollution can be solved effectively. This review focuses on various AO/RPs used for wastewater treatment. The effects of different operational parameters that affect the efficiency of these processes toward contaminant removal have been discussed. Besides, challenges and future recommendations are also briefly provided for the researchers in order to improve the efficiency of these processes. [ABSTRACT FROM AUTHOR]

Present study focused on the green nanocomposites synthetization to treat textile wastewater and its reusability for agriculture crops. Punica granatum (leaves and peels) and biomass (almond shells, sugar cane bagasse, eggshells) are used for synthesis of zinc oxide nanocomposites (PGL-ZnO), copper nanocomposites (PGP-Cu) and iron nanocomposites (PGL-Fe). It is characterized by scanning electron microscope, Fourier-transform infrared spectroscopy, X-ray powder diffraction and Brunauer–Emmett–Teller. The highest adsorption efficiency of all synthesized nanocomposites was accomplished at pH 2 which is acidic, 0.01 g dose, 50 mg/L initial dye concentration and 90 min contact time at 40 °C temperature. The highest adsorption proficiency Punica granatum = 18 < Zinc Oxide nanocomposites = 78 < Iron nanocomposites = 65 < Copper nanocomposites = 85 mg/g of all synthesized nanocomposites was obtained. The model Freundlich showed good fitness results which indicate complex nanocomposites nature. The 1st order showed best results on fitness of isotherm on kinetic data and rate constants determined the best fitness of model. The negative value of ΔHo and ΔSo of nanocomposites exhibited the exothermic nature and decrease in disorderness of adsorption process for dye exclusion. When values of Δ G o is positive then the reaction is spontaneous. Desorption of acidic dye from maximum efficient nanocomposites was 99 mg/g using eluent. Hence, it was determined that these nanocomposites serve as the novel, feasible, cost-effective, ecofriendly, and bio recyclability for treating acid dye-containing wastewater. [ABSTRACT FROM AUTHOR]

This study is focused on synthesis of highly efficient Titania/reduced Graphene Oxide (TiO2/rGO) nanocomposites by means of simple hydrothermal technique. The TiO2/rGO were synthesized in different ratios of 0.5, 1.0, 2.0, and 3% by varying the concentration of rGO while the concentration of TiO2 was kept constant and the obtained samples were designated as TrG0.5, TrG1, TrG2, and TrG3 respectively. Different characterization techniques (SEM, TEM, HRTEM, XRD, EDX, TGA, UV-DRS, PL, EIS, and BET) showed high crystallinity, small crystallite size (18.4 nm), high thermal stability, high purity, low band gap energy (Eg = 3.12 eV), and high surface area (65.989 m2/g) for the as-synthesized TiO2/rGO nanocomposite. The efficiencies of TiO2/rGO were determined in terms of brilliant green (BG) dye degradation in aqueous media under UV light. The results revealed that 2% TiO2/rGO (TrG2) showed high efficiency for BG degradation with the kapp of 0.023 min−1 compared to TiO2 alone (kapp of 0.006 min−1). The rate of BG degradation was further synergised by the addition of peroxymonosulfate (PMS) to the system. The degradation of BG was improved to 99.4% by the incorporation of PMS in aqueous media compared to TrG2 alone. Furthermore, the degradation of BG was also examined in various media (neutral, acidic, and basic). The results revealed that by increasing pH of the medium from 3.85 to 8.2 the degradation of BG was enhanced from 99.4 to 99.9% with the corresponding kapp of 0.0602 min−1. Moreover, the photocatalytic degradation of BG followed the pseudo-first-order kinetics. Radical scavenging experiments showed that ●OH and SO4●– were the main species responsible for the degradation of BG under UV light. Besides, for determining the efficiency of as-synthesized TrG2/PMS system, the degradation of BG was also performed in various water types (distilled water, tape water, synthetic wastewater, and industrial wastewater). The degradation products (DPs) of BG and their corresponding pathways were proposed, accordingly. [ABSTRACT FROM AUTHOR]

Binary composite of zerovalent iron and titanium dioxide (Fe0/TiO2) was synthesized for the catalytic removal of dichlorophene (DCP) in the presence of peroxymonosulfate (PMS). The as-prepared composite (Fe0/TiO2) exhibits synergistic effect and enhanced properties like improved catalytic activity of catalyst and greater magnetic property for facile recycling of catalyst. The results showed that without addition of PMS at reaction time of 50 min, the percent degradation of DCP by TiO2, Fe0, and Fe0/TiO2 was just 5%, 11%, and 12%, respectively. However, with the addition of 0.8 mM PMS, at 10 min of reaction time, the catalytic degradation performance of Fe0, TiO2, and Fe0/TiO2 was significantly improved to 82%, 18%, and 88%, respectively. The as-prepared catalyst was fully characterized to evaluate its structure, chemical states, and morphology. Scanning electron microscopy results showed that in composite TiO2 causes dispersion of agglomerated iron particles which enhances porosity and surface area of the composites and X-ray diffraction (XRD), energy dispersive X-ray (EDX), and Fourier-transform infrared (FTIR) results revealed successful incorporation of Fe0, and oxides of Fe and TiO2 in the composite. The adsorption–desorption analysis verifies that the surface area of Fe0/TiO2 is significantly larger than bare Fe0 and TiO2. Moreover, the surface area, particle size, and crystal size of Fe0/TiO2 was surface area = 85 m2 g−1, particle size = 0.35 μm, and crystal size = 0.16 nm as compared to TiO2 alone (surface area = 22 m2 g−1, particle size = 4.25 μm, and crystal size = 25.4 nm) and Fe0 alone (surface area = 65 m2 g−1, particle size = 0.9 μm, and crystal size = 7.87 nm). The as-synthesized material showed excellent degradation performance in synthesized wastewater as well. The degradation products and their toxicities were evaluated and the resulted degradation mechanism was proposed accordingly. The toxicity values decreased in order of DP1 > DP5 > DP2 > DP3 > DP4 and the LC50 values toward fish for 96-h duration decreased from 0.531 to 67.2. This suggests that the proposed technology is an excellent option for the treatment of antibiotic containing wastewater. [ABSTRACT FROM AUTHOR]

In this work, bismuth-doped titania (BixTiO2) with improved oxygen vacancies was synthesized by sol-gel protocol as a novel peroxymonosulfate (PMS, HSO5−) activator. HSO5− and adsorbed oxygen molecules could efficiently be transformed into their respective radicals through defect ionization to attain charge balance after their trapping on oxygen vacancies of the catalyst. XRD study of BixTiO2 with 5 wt% Bi (5BiT) revealed anatase, crystalline nature, and successful doping of Bi into TiO2 crystal lattice. The particle size obtained from BET data and SEM observations was in good agreement. PL spectra showed the formation rates of •OH by 3BiT, 7BiT, 5BiTC, and 5BiT as 0.720, 1.200, 1.489, and 2.153 μmol/h, respectively. 5BiT catalyst with high surface area (216.87 m2 g−1) and high porosity (29.81%) was observed the excellent HSO5− activator. The catalytic performance of 0BiT, 3BiT, 5BiT, and 7BiT when coupled with 2 mM HSO5− for recalcitrant flumequine (FLU) removal under dark was 10, 27, 55, and 37%, respectively. Only 5.4% decrease in catalytic efficiency was observed at the end of seventh cyclic run. Radical scavenging studies indicate that SO4•− is the dominant species that caused 62.0% degradation. Moreover, strong interaction between Bi and TiO2 through Bi-O-Ti bonds prevents Bi leaching (0.081 mg L−1) as shown by AAS. The kinetics, degradation pathways, ecotoxicity, and catalytic mechanism for recalcitrant FLU were also elucidated. Cost-efficient, environment-friendly, and high mineralization recommends this design strategy; BixTiO2/HSO5− system is a promising advanced oxidation process for the aquatic environment remediation. [ABSTRACT FROM AUTHOR]

In this study, for the first-time, aqueous solution of Acid Fuchsin (AF) was spectrophotometrically evaluated as a possible chemical dosimeter for food irradiation dosimetry at low dose ranges. A 50 µM solution of AF at natural pH was gamma irradiated and absorbance of the solution was measured at λmax (i.e., 543 nm) in addition to other wavelengths (490, 510, 549 and 564 nm). The response of AF dosimeter was investigated by plotting various variables, i.e., absorbance (A), − log A, change in absorbance (∆A), log Ao/Ai and absorbance % (A %) against absorbed dose. The response plots suggested that the beneficial dose range of AF solution in water was up to 0.82 kGy when absorbance (A), change in absorbance (ΔA) and absorbance % (A %) were extrapolated against absorbed dose. Though, the response was linear and beneficial absorbed dose range was extended up to 1.65 kGy, when − log A and log Ao/Ai were plotted against absorbed dose. It was concluded from pre- and post-irradiation stability studies of AF dosimeter that it should be protected from light and heat during handling and storage. For detection of the reactive specie involved in the bleaching of AF dye the AF dye solution was saturated with O2, N2 and N2O gases. [ABSTRACT FROM AUTHOR]

For the first time, chloroform and 2-butanol were used as solvent systems for the preparation of ZrO2-PANI and CeO2-PANI composites. Solubility of the synthesized composites was studied in chloroform, N-methyl-2-pyrrolidinone (NMP), and in mixture of toluene + 2-propanol (2:1). XRD and cyclic voltammetry data showed that the ZrO2-PANI and CeO2-PANI composites possess both crystalline and amorphous domains indicating some sort of conductivity. TGA results showed that ZrO2-PANI composite have a better thermal stability than pure PANI; however, CeO2-PANI composite has lower thermal stability than pure PANI. The conjugated unsaturated structure of PANI is responsible for the enhanced photocatalytic properties of ZrO2-PANI and CeO2-PANI. Photocatalytic results showed that, at photolysis time of 60 min, rhodamine B (RhB) dye was degraded up to 34 and 35% by ZrO2-PANI and CeO2-PANI, respectively. The degradation products of RhB were quantified by LC-MS and GC-MS, and accordingly, a detailed pathway was proposed. [ABSTRACT FROM AUTHOR]

Protonation plays an important role in the redox reactions. We observed this leading role during the reduction of [FeIII(phen)2(CN)2]+ by FcCOMe and FcCHOHMe. The kinetic data showed that the reaction(s) followed a complex kinetics due to the formation of protonated acetylferrocene (FcC+OHMe), and or, protonated α-methylferrocenemethanol (FcCHO+H2Me) in aqueous dioxane (80% v/v). Our results helped us to conclude that the reactions were completed in three phases. An overall zeroth order was observed in the first phase of the reactions. In the second phase, the kinetic data showed an overall second order reaction. The third phase was a complex phase where the rate of redox reactions and the insolubility of the neutral product ([FeII(phen)2(CN)2]) competed with each other. We studied the effect of different factors to identify the reacting entities, which take part in the rate-determining step of each reaction in the second phase. Consequently, we determined the effects of selected factors upon the observed pseudo-first order rate constant(s) (k′ obs) of each reaction. The value of k′ obs increased upon addition of protons in the reaction mixture in case of FcCOMe, and it decreased during the oxidation of FcCHOHMe. Meanwhile, upon enhancing the ionic strength, we observed an increase in k′ obs for FcCOMe, and no change in the value of k′ obs during the reaction of FcCHOHMe. However, a decrease in k′ obs was noticed upon increasing the dielectric constant of the reaction mixture when the reductant was FcCOMe, and no effect was observed in case of FcCHOHMe. Together, these results suggested oxidation of FcC+OHMe and FcCHOHMe in the slow-step, and FcCOMe and FcCHO+H2Me during the fast-step. We refined our results by estimating the thermodynamic parameters of activation. The low values of activation energy and enthalpy of activation confirmed that the reduction of [FeIII(phen)2(CN)2]+ hardly depends upon temperature when the reducing agent is FcCOMe. The outcomes justified that the rate of reaction depends upon the unsaturated FcC+OHMe. This intermediate species contain a ‘carbonium ion’, which is very reactive and energetic. We obtained comparatively high values of the activation energy and enthalpy of activation for the reaction between [FeIII(phen)2(CN)2]+ and FcCHOHMe. The results show that FcCHOHMe is a saturated and stable compound that leads the slow-step and controls the rate of reaction. [ABSTRACT FROM AUTHOR]

This study reports the efficiency of gamma-ray irradiation to degrade quinolone antibiotic, norfloxacin, in aqueous solution. Laboratory batch experiments were conducted to determine the 'pseudo-first' order degradation kinetics of norfloxacin in the concentration ranges of 3.4-16.1 mg L by gamma-ray irradiation. The dose constant was found to be dependent on the initial concentration of norfloxacin and gamma-ray irradiation dose rate ( D). The saturation of norfloxacin sample solutions with N, air or NO, and the presence of tert-butanol and 2-propanol showed that OH played more crucial role in the degradation of norfloxacin. The second order rate constants of OH, e, and H with norfloxacin were calculated to be 8.81 × 10, 9.54 × 10, and 1.10 × 10 M s, respectively. The effects of various additives including CO, HCO, NO, NO, and thiourea and the pH of the medium on the degradation of norfloxacin were also investigated. Norfloxacin degradation was lower in surface water and wastewater than in ultrapure water. Several degradation byproducts of norfloxacin were identified from which the possible degradation pathway was proposed. [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]