RESUMO
ß-lactam antibiotics, extensively used worldwide, pose significant risks to human health and ecological safety due to their accumulation in the environment. Recent studies have demonstrated the efficacy of transition metal-activated sulfite systems, like Fe(â ¢)/HSO3-, in removing PPCPs from water. However, research on their capability to degrade ß-lactam antibiotics remains sparse. This paper evaluates the degradation of 14 types of ß-lactam antibiotics in Fe(â ¢)/HSO3- system and establishes a QSAR model correlating molecular descriptors with degradation rates using the MLR method. Using cefazolin as a case study, this research predicts degradation pathways through NPA charge and Fukui function analysis, corroborated by UPLC-MS product analysis. The investigation further explores the influence of variables such as HSO3- dosage, substrate concentration, Fe(â ¢) dosage, initial pH and the presence of common seen water matrices including humic acid and bicarbonate on the degradation efficiency. Optimal conditions for cefazolin degradation in Fe(â ¢)/HSO3- system were determined to be 93.3 µM HSO3-, 8.12 µM Fe(â ¢) and an initial pH of 3.61, under which the interaction of Fe(â ¢) dosage with initial pH was found to significantly affect the degradation efficiency. This study not only provides a novel degradation approach for ß-lactam antibiotics but also expands the theoretical application horizon of the Fe(â ¢)/HSO3- system.
RESUMO
This study provided an in-depth understanding of enhanced algae inactivation by combining ultraviolet and peracetic acid (UV/PAA) and selecting Microcystis aeruginosa as the target algae species. The electron paramagnetic resonance (EPR) tests and scavenging experiments provided direct evidence on the formed reactive species (RSs) and indicated the dominant role of RSs including singlet oxygen (1O2) and hydroxyl (HOâ¢) and organic (ROâ¢) radicals in algae inactivation. Based on the algae inactivation kinetic model and the determined steady-state concentration of RSs, the contribution of RSs was quantitatively assessed with the second-order rate constants for the inactivation of algae by HOâ¢, ROâ¢, and 1O2 of 2.67 × 109, 3.44 × 1010, and 1.72 × 109 M-1 s-1, respectively. Afterward, the coexisting bi/carbonate, acting as a shuttle, that promotes the transformation from HO⢠to RO⢠was evidenced to account for the better performance of the UV/PAA system in algae inactivation under the natural water background. Subsequently, along with the evaluation of the UV/PAA preoxidation to modify coagulation-sedimentation, the possible application of the UV/PAA process for algae removal was advanced.
Assuntos
Poluentes Químicos da Água , Purificação da Água , Raios Ultravioleta , Ácido Peracético/farmacologia , Água , Peróxido de Hidrogênio , OxirreduçãoRESUMO
Environmental-friendly and low-cost catalysts for peracetic acid (PAA) activation are vital to promote their application for micropollutant degradation in water. In this study, powdered activated carbon (PAC) was reported to improve the degradation of sulfamethoxazole (SMX). The improvement of SMX degradation in the PAC/PAA system was expected to be because of the PAA activation rather than the co-existing H2O2 activation. Non-radical oxidation pathways, including the mediated electron-transfer process and singlet oxygen (1O2), were evidenced to play the dominant roles in the degradation of micro-organic pollutants. The graphitization of PAC, persistent free radicals, and electron-donating groups like C-OH were proposed to contribute to the activation of PAA. High SMX degradation could be achieved in the acidic and neutral conditions in the PAC/PAA system. Overall, higher dosages of PAC (0-0.02 g/L) and PAA (0-100 µM) benefited the degradation of SMX. The presence of HCO3- could lower the SMX degradation significantly, while Cl-, PO43-, and humic acid (HA) only reduced the SMX degradation efficiency a little. Overall, this study offered an efficient non-radical PAA activation method using PAC, which can be effectively used to degrade micro-organic pollutants.
Assuntos
Ácido Peracético , Poluentes Químicos da Água , Sulfametoxazol , Peróxido de Hidrogênio , Carvão Vegetal , OxirreduçãoRESUMO
Chemical oxidation using peracetic acid (PAA) can be enhanced by activation with the formation of reactive species such as organic radicals (R-Oâ¢) and HOâ¢. Thermal activation is an alternative way for PAA activation, which was first applied to degrade micropollutants in this study. PAA is easily decomposed by heat via both radical and nonradical pathways. Our experimental results suggest that a series of reactive species including R-Oâ¢, HOâ¢, and 1O2 can be produced through the thermal decomposition of PAA. Sulfamethoxazole (SMX), a typical sulfa drug, can be effectively removed by the thermoactivated PAA process under conditions of neutral pH. R-O⢠including CH3C(O)O⢠and CH3C(O)OO⢠has been shown to play a primary role in the degradation of SMX followed by direct PAA oxidation in the thermoactivated PAA process. Both higher temperature (60 °C) and higher PAA dose benefit SMX degradation, while coexisting H2O2 inhibits SMX degradation in the thermoactivated PAA process. With a variation of solution pH, conditions near a neutral value show the best performance of this process in SMX degradation. Based on the identified intermediates, transformation of SMX was proposed to undergo oxidation of the amine group and oxidative coupling reactions. This study definitively illustrates the PAA decomposition pathways at high temperature in aquatic solution and addresses the possibility of the thermoactivated PAA process for contaminant destruction, demonstrating this process to be a feasible advanced oxidation process.
Assuntos
Sulfametoxazol , Poluentes Químicos da Água , Peróxido de Hidrogênio , Oxirredução , Ácido PeracéticoRESUMO
An advanced oxidation process of combining cobalt and peracetic acid (Co/PAA) was developed to degrade sulfamethoxazole (SMX) in this study. The formed acetylperoxy radical (CH3CO3â¢) through the activation of PAA by Co (Co2+) was the dominant radical responsible for SMX degradation, and acetoxyl radical (CH3CO2â¢) might also have played a role. The efficient redox cycle of Co3+/Co2+ allows good removal efficiency of SMX even at quite low dosage of Co (<1 µM). The presence of H2O2 in the Co/PAA process has a negative effect on the degradation of SMX due to the competition for reactive radicals. The SMX degradation in the Co/PAA process is pH dependent, and the optimum reaction pH is near-neutral. Humic acid and HCO3- can inhibit SMX degradation in the Co/PAA process, while the presence of Cl- plays a little role in the degradation of SMX in this system. Although transformation products of SMX in the Co/PAA system show higher acute toxicity, the low Co dose and SMX concentration in aquatic solution can efficiently weaken the acute toxicity. After reaction in the Co/PAA process, numerous carbon sources that could be provided for bacteria and algae growth can be produced, suggesting that the proposed Co/PAA process has good potential when combined with the biotreatment processes.
Assuntos
Sulfametoxazol , Poluentes Químicos da Água , Cobalto , Peróxido de Hidrogênio , Oxirredução , Ácido PeracéticoRESUMO
Combined sewer overflows (CSOs) introduce microbial contaminants into the receiving water bodies, thereby posing risks to public health. This study systematically investigated the disinfection performance and mechanisms of the combined process of ultraviolet and peracetic acid (UV/PAA) in CSOs with selecting Escherichia coli (E. coli) as a target microbial contaminant. The UV/PAA process exhibited superior performance in inactivating E. coli in simulated CSOs compared with UV, PAA, and UV/H2O2 processes. Increasing the PAA dosage greatly enhanced the disinfection efficiency, while turbidity and organic matter hindered the inactivation performance. Singlet oxygen (1O2), hydroxyl (â¢OH) and organic radicals (ROâ¢) contributed to the inactivation of E. coli, with â¢OH and RO⢠playing the prominent role. Variations of intracellular reactive oxygen species, malondialdehyde, enzymes activities, DNA contents and biochemical compositions of E. coli cells suggested that UV/PAA primarily caused oxidative damage to intracellular molecules rather than the damage to the lipids of the cell membrane, therefore effectively limited the regrowth of E. coli. Additionally, the UV/PAA process displayed an outstanding performance in disinfecting actual raw CSOs, achieving a 2.90-log inactivation of total bacteria after reaction for 4 min. These results highlighted the practical applicability and effectiveness of the UV/PAA process in the disinfection of CSOs.
Assuntos
Desinfecção , Escherichia coli , Ácido Peracético , Esgotos , Raios Ultravioleta , Desinfecção/métodos , Ácido Peracético/farmacologia , Escherichia coli/efeitos dos fármacos , Esgotos/microbiologia , Oxirredução , Espécies Reativas de Oxigênio/metabolismoRESUMO
Aqueous suspensions of Microcystis aeruginosa were preoxidized with either ozone or permanganate and then subjected to chlorination under conditions simulating drinking water purification. The impacts of the two oxidants on the algal cells and on the subsequent production of dissolved organic matter and disinfection byproducts were investigated. Preozonation dramatically increased disinfection byproduct formation during chlorination, especially the formation of haloaldehydes, haloacetonitriles, and halonitromethanes. Preoxidation with permanganate had much less effect on disinfection byproduct formation. Preozonation destroyed algal cell walls and cell membranes to release intracellular organic matter (IOM), and less than 2.0% integrated cells were left after preozonation with the dosage as low as 0.4 mg/L. Preoxidation with permanganate mainly released organic matter adsorbed on the cells' surface without causing any damage to the cells' integrity, so the increase in byproduct formation was much less. More organic nitrogen and lower molecular weight precursors were produced in a dissolved phase after preozonation than permanganate preoxidation, which contributes to the significant increase of disinfection byproducts after preozonation. The results suggest that permanganate is a better choice than ozone for controlling algae derived pollutants and disinfection byproducts.
Assuntos
Desinfecção , Halogenação , Compostos de Manganês/farmacologia , Microcystis/citologia , Microcystis/efeitos dos fármacos , Óxidos/farmacologia , Ozônio/farmacologia , Água/química , Aminas/análise , Aminoácidos/análise , Carbono/análise , Floculação/efeitos dos fármacos , Compostos de Manganês/química , Microcystis/metabolismo , Peso Molecular , Compostos de Nitrogênio/análise , Oxirredução/efeitos dos fármacos , Óxidos/química , Purificação da ÁguaRESUMO
The reaction between ferrous iron (Fe(II)) with peroxymonosulfate (PMS) generates reactive oxidants capable of degrading refractory organic contaminants. However, the slow transformation from ferric iron (Fe(III)) back to Fe(II) limits its widespread application. Here, we added hydroxylamine (HA), a common reducing agent, into Fe(II)/PMS process to accelerate the transformation from Fe(III) to Fe(II). With benzoic acid (BA) as probe compound, the addition of HA into Fe(II)/PMS process accelerated the degradation of BA rapidly in the pH range of 2.0-6.0 by accelerating the key reactions, including the redox cycle of Fe(III)/Fe(II) and the generation of reactive oxidants. Both sulfate radicals and hydroxyl radicals were considered as the primary reactive oxidants for the degradation of BA in HA/Fe(II)/PMS process with the experiments of electron spin resonance and alcohols quenching. Moreover, HA was gradually degraded to N2, N2O, NO2 (−), and NO3 (−), while the environmentally friendly gas of N2 was considered as its major end product in the process. The present study might provide a promising idea based on Fe(II)/PMS process for the rapid degradation of refractory organic contaminants in water treatment.
Assuntos
Hidroxilamina/química , Ferro/química , Compostos Orgânicos/química , Peróxidos/química , Poluentes Químicos da Água/química , Ácido Benzoico/química , Espectroscopia de Ressonância de Spin Eletrônica , Sequestradores de Radicais Livres/química , Concentração de Íons de Hidrogênio , Oxidantes/química , Oxirredução , Fatores de TempoRESUMO
The hydroxylamine-enhanced Fe(II)/peracetic acid (PAA) process is a promising advanced oxidation process (AOP) with the generation of reactive species (RS) including ROâ¢, â¢OH and Fe(IV). Nevertheless, it is still challenging to identify which RS is the major intermediate oxidant, and the reasons why the optimal condition is pH 4.5 rather than 3.0 are also unclear. Herein, the generation of RS and their contribution to the degradation of three micro-pollutants were explored. The quenching experiments and pseudo first-order kinetic model demonstrated that RO⢠rather than the other two RS were predominant. Then the overall generation and evolution pathways of RS were depicted. The elevation of pH (3.0-4.5) would accelerate the Fe(II)/Fe(III) redox cycle through the enhanced reduction of Fe(III) by hydroxylamine and induce the conversion of Fe(IV) to ROâ¢, which benefited naproxen degradation. While the adverse Fe(III) precipitation would dominate the reduced degradation performance with the solution pH higher than 4.5. The elevation of PAA and Fe(II) dosages sped up the PAA activation, while excess hydroxylamine could consume the formed RS and exhibited an inhibitory effect. This study helps further understand the role of HA and differentiate the contribution of RS in the emerging PAA-based AOPs.
Assuntos
Poluentes Ambientais , Poluentes Químicos da Água , Compostos Férricos , Compostos Ferrosos , Peróxido de Hidrogênio , Concentração de Íons de Hidrogênio , Hidroxilamina , Hidroxilaminas , Ferro , Naproxeno , Oxidantes , Oxirredução , Ácido PeracéticoRESUMO
In this study, Fe(â ¡)/peracetic acid (PAA) and Fe(â ¡)/sodium hypochlorite (NaClO) systems were applied as the combined preoxidation and coagulation process to enhance algae removal. A high removal rate of algae and turbidity could be achieved, with most algal cells keeping intact when adding reasonable concentrations of PAA and NaClO to enhance Fe(â ¡) coagulation. The variations of chlorophyll a, malondialdehyde, and intracellular reactive oxygen species suggested that moderate oxidation with only destroying surface-adsorbed organic matter rather than cell integrity was realized. The generated organic radicals, Fe(â £), and hydroxy radical played the major roles in the Fe(â ¡)/PAA system for the moderate oxidation of algal cells, but direct oxidation by NaClO rather than producing reactive species in the Fe(â ¡)/NaClO process contributed to the preoxidation. Concurrently, the in-situ formed Fe(â ¢) greatly promoted the agglomerating and settling of algae. The analysis of cell integrity, biochemical compositions, and fluorescence excitation-emission matrices spectra demonstrated that excess NaClO but not PAA would seriously damage the algal cells. This might be because that NaClO would directly oxidize the cell wall/membrane, while PAA mainly permeates into the cell to inactivate algae. These results suggest that Fe(â ¡)/PAA is an efficient strategy for algae-laden water treatment without serious algae lysis.
Assuntos
Hipoclorito de Sódio , Purificação da Água , Hipoclorito de Sódio/farmacologia , Hipoclorito de Sódio/química , Ácido Peracético/farmacologia , Compostos Férricos , Clorofila A , Oxirredução , Purificação da Água/métodos , Compostos Ferrosos/químicaRESUMO
The sulfite(S(IV))-based advanced oxidation process has attracted significant attention in removing As(III) in the water matrix for its low-cost and environmental-friendly. In this study, a cobalt-doped molybdenum disulfide (Co-MoS2) nanocatalyst was first applied to activate S(IV) for As(III) oxidation. Some parameters including initial pH, S(IV) dosage, catalyst dosage, and dissolved oxygen were investigated. The experiment results show that >Co(II) and >Mo(VI) on the catalyst surface promptly activated S(IV) in the Co-MoS2/S(IV) system, and the electron transfer between Mo, S, and Co atoms accelerated the activation. SO4â¢- was identified as the main active species for As(III) oxidation. Furthermore, DFT calculations confirmed that Co doping improved the MoS2 catalytic capacity. This study has proven that the material has broad application prospects through reutilization test and actual water experiments. It also provides a new idea for developing bimetallic catalysts for S(IV) activation.
RESUMO
To explore effective therapeutic strategy on nonalcoholic fatty liver disease (NAFLD), the amphiphilic oligochitosan derivative containing ursodeoxycholic acid (UDCA) was synthesized and named as UBC, which could self-assemble and encapsulate exenatide (Exe) to obtain Exe-UBC nano-vesicle. Exe-UBC could be uptaken by fatty-acid cultured cells and release UDCA and Exe responsive to the high esterase concentration. In vitro experiments demonstrated that Exe-UBC activated the expression level of SIRT1 with inhibited expression of PGC-1ß and PPAR-γ and consequently exerted synergistic bioaction immediately on reducing lipidosis. After a month of Exe-UBC treated through intravenous injection, the body weight of high-fat diet feeding C57BL/6 mice recovered to ordinary level, and their lipid contents in the liver declined significantly. The recovery in hepatic function indexes like TG, AST, and ALT further revealed the superiority of Exe-UBC vesicles. These results suggested that the co-delivery of UDCA and Exe via Exe-UBC could be a potent platform for NAFLD treatment.
Assuntos
Hepatopatia Gordurosa não Alcoólica , Animais , Quitosana , Dieta Hiperlipídica , Exenatida/farmacologia , Fígado , Camundongos , Camundongos Endogâmicos C57BL , Hepatopatia Gordurosa não Alcoólica/tratamento farmacológico , Hepatopatia Gordurosa não Alcoólica/metabolismo , Oligossacarídeos , Sirtuína 1/metabolismo , Sirtuína 1/farmacologia , Sirtuína 1/uso terapêutico , Ácido Ursodesoxicólico/metabolismo , Ácido Ursodesoxicólico/farmacologia , Ácido Ursodesoxicólico/uso terapêuticoRESUMO
The inactivation of algae by a combined process of peracetic acid and ultraviolet irradiation (UV/PAA) was systematically investigated by choosing Microcystis aeruginosa as the reference algal species. Both hydroxyl (HOâ¢) and organic radicals (ROâ¢) contributed to the cell integrity loss and RO⢠played the dominant roles. The algae inactivation kinetics can be well fitted by the typical Hom model, showing that the inactivation kinetic curves followed a type of shoulder and exponential reduction. The initial shoulder might be induced by the protection from the cell wall. Although the results from the cell morphology, UV-vis spectra and fluorescence excitation-emission matrices analysis suggested the cell lysis and the release of algal organic matter (AOM) in the UV/PAA process, the AOM could be subsequently degraded. Humic acid (1 - 5 mg/L) inhibited the algal cell inactivation, and the presence of chloride (0.5 - 2 mM) had little effect on the cell viability reduction. However, the addition of bicarbonate (1 - 5 mM) promoted cell integrity loss. The UV/PAA process displayed better performance under the natural water background, demonstrating the extensive potential for the practical application of this approach. This study suggests that the UV/PAA process is an effective strategy for algae inactivation.
Assuntos
Microcystis , Purificação da Água , Radical Hidroxila , Ácido Peracético/farmacologia , Raios UltravioletaRESUMO
The Fenton system generates reactive species with high oxidation potential such as hydroxyl radicals (HO(â¢)) or ferryl via the reaction between Fe (II) and H2O2. However, a number of drawbacks limit its widespread application including the accumulation of Fe (III) and the narrow pH range limits, etc. The aim of this study is to propose a much more efficient Fenton-HA system which is characterized by combining Fenton system with hydroxylamine (NH2OH), a common reducing agent, to relieve the aforementioned drawbacks, with benzoic acid (BA) as the probe reagent. The presence of NH2OH in Fenton's reagent accelerated the Fe (III)/Fe (II) redox cycles, leading to relatively steady Fe (II) recovery, thus, increased the pseudo first-order reaction rates and expanded the effective pH range up to 5.7. The HO(â¢) mechanism was confirmed to be dominating in the Fenton-HA system, and the generation of HO(â¢) was much faster and the amount of HO(â¢) formed was higher than that in the classical Fenton system. Furthermore, the major end products of NH2OH in Fenton-HA system were supposed to be NO3(-) and N2O.
Assuntos
Compostos Férricos/química , Compostos Ferrosos/química , Peróxido de Hidrogênio/química , Hidroxilamina/química , Ferro/química , OxirreduçãoRESUMO
Degradation of tetrabromobisphenol A (TBBPA), an emerging micropollutant, by photo/Fe3+/sulfite process was investigated under different operational conditions and water matrices. 91% of TBBPA was efficiently degraded within 30 min in the Fe3+/sulfite system under sunlight irradiation when the initial pH was 6.0, which is much higher than that of TBBPA without irradiation (52%). The acceleration of radical generation and direct photolysis by photo irradiation were responsible for the enhanced TBBPA degradation. Although this process showed better performance on TBBPA degradation in weak acid conditions, the high removal efficiency was also achieved at near-neutral pH. HO, SO4- and direct photolysis contributed to TBBPA degradation. Direct photolysis and SO4- presented the dominant contribution. The degradation rate increased with elevating the Fe3+ dose (10-40 µM), but slightly decreased when the Fe3+ dose was further raised to 100 µM. Similarly, the degradation efficiency initially increased with increasing the sulfite dose (100-400 µM), but decreased when the sulfite concentration reached 1000 µM. Dissolved oxygen played a crucial role in TBBPA degradation, the presence of water matrices such as humic acid (0.8-4.0 mg/L), bicarbonate (0.5-10 mM) and chloride (0.5-10 mM) retarded TBBPA degradation. This study proposed a new efficient strategy to enhance TBBPA degradation in the Fe3+/sulfite process.
Assuntos
Bifenil Polibromatos , Poluentes Químicos da Água , Bifenil Polibromatos/análise , Sulfitos , Luz Solar , Poluentes Químicos da Água/análiseRESUMO
Sulfonamide antibiotics (SAs) are typical antibiotics and have attracted increasing concerns about their wide occurrence in environment as well as potential risk for human health. In this study, we applied a novel advanced oxidation process in SAs degradation by combining molybdenum sulfide and peracetic acid (MoS2/PAA). Reactive oxygen species (ROS) including HOâ, CH3C(O)Oâ, CH3C(O)OOâ, and 1O2 were generated from PAA by MoS2 activation and contributed to SAs degradation. The effects of initial pH, the dosages of PAA and MoS2, and humic acid for SAs degradation were further evaluated by selecting sulfamethoxazole (SMX) as a target SA in the MoS2/PAA process. Results suggested that the optimum pH for SMX removal was 3, where the degradation efficiency of SMX was higher than 80% after reaction for 15 min. Increasing PAA (0.075-0.45 mM) or MoS2 (0.1-0.4 g/L) dosages facilitated the SMX degradation, while the presence of humic acids retarded the SMX removal. This MoS2/PAA process also showed good efficiencies in removing other SAs including sulfaguanidine, sulfamonomethoxine and sulfamerazine. Their possible degradation pathways were proposed based on the products identification and DFT calculation, showing that apart from the oxidation of amine groups to nitro groups in SAs, MoS2/PAA induced SO2 extrusion reaction for SAs that contained six-membered heterocyclic moieties.
Assuntos
Ácido Peracético , Poluentes Químicos da Água , Antibacterianos , Dissulfetos , Humanos , Peróxido de Hidrogênio , Molibdênio , Oxirredução , Sulfametoxazol , SulfonamidasRESUMO
In this study, the effects of UV/chlorine pretreatment on ultrafiltration (UF) membrane fouling derived from different fractions of natural organic matter (NOM) were studied and compared. Three model organic compounds including humic acid (HA), sodium alginate (SA) and bovine serum albumin (BSA) were employed to represent different NOM fractions in natural surface water. The results suggest that membrane fouling induced from HA, SA and HA-SA-BSA mixture could be effectively mitigated by UV/chlorine pretreatment, which could be further improved by increasing the chlorine dose. Although UV irradiation alone severely aggravated BSA fouling, the addition of chlorine (0.0625 mM) to the pretreatment process could effectively avoid the fouling. The alleviation of membrane fouling is primarily ascribed to the reduction of molecular weight (MW) of organic compounds, and the decomposition of unsaturated organic species, thereby reducing the accumulation of organics on the membrane surface and pores. This is confirmed by the reduction of UV254 and fluorescent components in the feed solution and the increase of DOC in the permeate after UV/chlorine pretreatment. Membrane fouling during the filtration of untreated HA, SA, and HA-SA-BSA mixture was occupied by cake filtration and intermediate pore blocking, while UV/chlorine pretreatment led to the exacerbation of pore blocking at the initial filtration stage. The initial fouling mechanism of untreated BSA was mainly governed by complete blocking, which shifted to intermediate pore blocking after UV/chlorine pretreatment.
Assuntos
Ultrafiltração , Purificação da Água , Cloro , Substâncias Húmicas , Membranas ArtificiaisRESUMO
With the fast development of peroxymonosulfate (PMS)-dominating processes in drinking water and wastewater treatment, residual PMS is easy to come across chlorine as these processes are usually followed by secondary chlorine disinfection. The synergistic effect of PMS and chlorine on the degradation of micro-organic pollutants is investigated by selecting acetaminophen (ACT) as a reference compound for the first time in this study. Unlike conventional PMS or chlorine activation which generates reactive species such as hydroxyl radical (HOâ¢), sulfate radical (SO4â¢-), chlorine radical (Clâ¢), and singlet oxygen (1O2), the efficient ACT removal is attributed to the direct catalytic chlorination by PMS due to the significantly enhanced consumption of chlorine along with negligible change of PMS concentration at neutral condition, and the same reaction pathways in both PMS/chlorine and chlorine processes. The kinetic study demonstrates that ACT oxidation by PMS/chlorine follows second order reaction, and the degradation efficiency can be promoted at alkaline conditions with peak rate constants at pH 9.0-10.0. The presence of chloride can enhance the removal of ACT, while ammonium and humic acid significantly retard ACT degradation. Higher formation of selected disinfection by-products (DBPs) is observed in the PMS/chlorine process than in the sole chlorination. This study highlights the important role of PMS in organic pollutants degradation and DBPs formation during the chlorination process.
Assuntos
Poluentes Químicos da Água , Purificação da Água , Acetaminofen , Cloretos , Cloro , Desinfecção , Oxirredução , Peróxidos , Poluentes Químicos da Água/análiseRESUMO
Lanthanum molybdate/magnetite (M-La2(MoO4)3) with various LaCl3/Fe3O4 mass ratios was synthesized and optimized for selective phosphate removal from wastewater. M-La2(MoO4)3 (2:1) was selected on the basis of phosphate sorption capacity for further experiments and characterized by a variety of methods. The phosphate sorption kinetics, isotherms, and matrix effect were studied. The maximum sorption capacity at initial pH 7 indicates the possible applicability M-La2(MoO4)3 (2:1) in removing phosphate from the aquatic environment. Phosphate removal by M-La2(MoO4)3 (2:1) with high selectivity was achieved in the presence of other co-existing anions, while calcium and magnesium ions were found to inhibit the sorption process. The sorption isotherm study showed that Freundlich and Sips models fit better the Langmuir model, indicating that heterogeneous multilayer sorption was dominant during the phosphate sorption process. Sorption kinetic results showed that the pseudo-first-order kinetic model can describe well the phosphate sorption process by M-La2(MoO4)3 (2:1). Consecutive sorption-desorption runs showed that M-La2(MoO4)3 (2:1) could be reused for a few cycles. Simultaneous removal of phosphate and organic matter was achieved in real wastewater by using M-La2(MoO4)3 (2:1). The sorption mechanism was inner-sphere complexation.
Assuntos
Lantânio , Águas Residuárias , Adsorção , Óxido Ferroso-Férrico , Concentração de Íons de Hidrogênio , Cinética , Molibdênio , Fosfatos/análiseRESUMO
UV/persulfate (UV/PS) could effectively degrade algal cells and micro-organic pollutants. This process was firstly applied to remove Microcystis aeruginosa (M. aeruginosa) and 2,4,6-trichlorophenol (TCP) simultaneously in bench scale. Algal cells can be efficiently removed after 120 min reaction accompanied with far quicker removal of the coexisted TCP, which could be totally removed within 5 min in the UV/PS process. Both SO 4 ⢠- and HO⢠were responsible for algal cells and TCP degradation, while SO 4 ⢠- and HO⢠separately dominated TCP degradation and algal cells removal. Apart from the role of radicals ( SO 4 ⢠- and HOâ¢) for algal cells and TCP degradation, UV also played a role to some extent. Increased PS dose (0-4.5 mM) or UV intensity (2.71-7.82 mW/cm2) could enhance the performance of the UV/PS process in both TCP and algae removal. Although some intracellular organic matters can be released to the outside of algal cells due to the cell lysis, they can be further degraded by UV/PS process, which was inhibited by the presence of TCP. This study suggested the good potential of the UV/PS process in the simultaneous removal of algal cells and micro-organic pollutants.