Display omitted
•UV/chlorine process was applied to inactivate M. aeruginosa.•A kinetic model was developed to describe the mechanism for chlorine decay.•Flow cytometry and confocal laser scanning ...microscopy were used.•UV/chlorine pretreatment can improve coagulation of algae.
Inactivation of Microcystis aeruginosa by UV/chlorine process was investigated in this study. Chlorine decay with or without the presence of algal cells was modeled based on a kinetic model, and the second-order rate constant between chlorine and algal cells was determined to be 3.3 × 10−4 (mgC/L)−1 s−1. Flow cytometry as well as confocal laser scanning microscopy were used to characterize the cell integrity of M. aeruginosa. Results demonstrated that UV/chlorine pre-oxidation was responsible for the inactivation of M. aeruginosa, and the inactivation efficiency increased with the increasing dosage of chlorine. UV/chlorine process can significantly change the surface characteristics of M. aeruginosa and enhance the coagulation efficiency. Moreover, due to the destruction of algal cells, microcystin-LR would be released and then degraded during pre-oxidation, and the releasing endotoxin could be removed during subsequent coagulation-sedimentation process. This study suggests that UV/chlorine process might be a potential alternative for the pretreatment of cyanobacterial cells in treating cyanobacteria-laden water.
Extracellular organic matter (EOM) and intracellular organic matter (IOM) of Microcystis aeruginosa have been reported to contribute to the formation of carbonaceous disinfection by-products (C-DBPs) ...and nitrogenous disinfection by-products (N-DBPs). Little is known about DBPs formation from different molecular weight (MW) fractions, especially for N-nitrosodimethylamine (NDMA). This study fractionated EOM and IOM into several MW fractions using a series of ultrafiltration membranes and is the first to report on the C-DBPs and N-DBPs formation from chlorination and chloramination of different MW fractions. Results showed that EOM and IOM were mainly distributed in low-MW (<1 KDa) and high-MW (>100 KDa) fractions. Additionally, the low-MW and high-MW fractions of EOM and IOM generally took an important part in forming C-DBPs and N-DBPs, either in chlorination or in chloramination. Furthermore, the effects of pre-ozonation on the formation of DBPs in subsequent chlorination and chloramination were also investigated. It was found that ozone shifted the high-MW fractions of EOM and IOM into lower MW fractions and increased the C-DBPs and N-DBPs yields to different degrees. As low-MW fractions are more difficult to remove than high-MW fractions by conventional treatment processes, therefore, activated carbon adsorption, nanofiltration (NF) and biological treatment processes can be ideal to remove the low-MW fractions and minimize the formation potential of C-DBPs and N-DBPs. Moreover, the use of ozone should be carefully considered in the treatment of algal-rich water.
Display omitted
•Algal organic matters were fractionated into six molecular weight (MW) fractions.•Low-MW and high-MW fractions contributed to most disinfection by-products (DBPs).•Pre-ozonation shifted the high-MW to low-MW fractions and increased DBPs yields.
•CoFe2O4 MNPs tested as heterogeneous catalyst for the activation of oxone.•The catalytic performance was typically affected by several key operating parameters.•The catalyst exhibited good stability ...and easily recovered with excellent reusability.•Degradation pathway was proposed according to the results of LC-MS/MS analysis.
A magnetic nanoscaled catalyst cobalt ferrite (CoFe2O4) was successfully prepared and used for the activation of oxone to generate sulfate radicals for the degradation of diclofenac. The catalyst was characterized by transmission electron microscopy, X-ray diffractometry, Fourier transform infrared spectroscopy and vibrating sample magnetometer. The effects of calcination temperature, initial pH, catalyst and oxone dosage on the degradation efficiency were investigated. Results demonstrated that CoFe2O4-300 exhibited the best catalytic performance and almost complete removal of diclofenac was obtained in 15min. The degradation efficiency increased with initial pH decreasing in the pH range of 5–9. The increase of catalyst and oxone dosage both had the positive effect on the degradation of diclofenac. Moreover, CoFe2O4 could retain high degradation efficiency even after being reused for five cycles. Finally, the major diclofenac degradation intermediates were identified and the primary degradation pathways were proposed.
Advanced oxidation processes (AOPs) are ideal alternative to remove contaminants of emerging concern (CECs). Nitrate and nitrite commonly co-exist with CECs in surface water, groundwater, and ...agricultural runoffs, which impact the performance of AOPs. Interests in investigation on the impacts of nitrate/nitrite on CEC degradation in AOPs have grown exponentially, due to the participation of reactive nitrogen species (RNS). RNS as a daughter radical in AOPs, are generally formed from photolysis of nitrate/nitrite or reactions of nitrate/nitrite with hydroxyl radical. It was documented that nitrate/nitrite in photochemical AOPs could accelerate CEC degradation, while that in non-photochemical AOPs usually play an inhibitory role. Except the performance of AOPs, nitrate/nitrite present in AOPs also have significant impact on the degradation pathway of CECs, of which the typical one is the nitration/nitrosation of CECs. Formation of nitrated/nitrosated CEC products in AOPs is almost inevitable when nitrite is present in water, because RNS are typical nitrating/nitrosating agents. The nitrated/nitrosated products not only show higher toxicity, but have higher formation potential of nitro/nitroso disinfection byproducts. Therefore, nitrate/nitrite can be used as a source of hydroxyl radical and RNS in photochemical AOPs (especially at λ > 280 nm), and should be avoided in non-photochemical AOPs. Besides, using pretreatment to turn nitrite to nitrate is a useful method to reduce the formation of nitrated/nitrosated CECs. Overall, this critical review aims to summarize the all-round impacts of nitrate/nitrite on AOPs, and provide practical implications to better utilize the naturally present nitrate/nitrite.
Display omitted
•NO3−/NO2− enhances CEC degradation in photochemical AOPs (λ > 280 nm).•Photo induced decomposition of NO3−/NO2− leads to the nitr(os)ation of CECs.•NO2− play an important role in nitr(os)ation of CECs in non-photochemical AOPs.•Typical N-DBPs are generated from NO3−/NO2− when AOPs are set before disinfection.
•The APAP degradation exhibited a pseudo-first-order kinetics pattern well.•The Fe3O4 was stable without significant leaching of iron to water during reaction.•XPS and EPR results show that Fe2+Fe3+ ...cycle was answerable for radical generation.•The removal of APAP is a result of oxidation due to both OH• and SO4−•.
Magnetic nano-scaled particles Fe3O4 were studied for the activation of peroxymonosulfate (PMS) to generate active radicals for degradation of acetaminophen (APAP) in water. The Fe3O4 MNPs were found to effectively catalyze PMS for removal of APAP, and the reactions well followed a pseudo-first-order kinetics pattern (R2>0.95). Within 120min, approximately 75% of 10ppm APAP was accomplished by 0.2mM PMS in the presence of 0.8g/L Fe3O4 MNPs with little Fe3+ leaching (<4μg/L). Higher Fe3O4 MNP dose, lower initial APAP concentration, neutral pH, and higher reaction temperature favored the APAP degradation. The production of sulfate radicals and hydroxyl radicals was validated through two ways: (1) indirectly from the scavenging tests with scavenging agents, tert-butyl alcohol (TBA) and ethanol (EtOH); (2) directly from the electron paramagnetic resonance (ESR) tests with 0.1M 5,5-dimethyl-1-pyrrolidine N-oxide (DMPO). Plausible mechanisms on the radical generation from Fe3O4 MNP activation of PMS are proposed based on the results of radical identification tests and XPS analysis. It appeared that Fe2+Fe3+ on the catalyst surface was responsible for the radical generation. The results demonstrated that Fe3O4 MNPs activated PMS is a promising technology for water pollution caused by contaminants such as pharmaceuticals.
•The antipyrine decomposition exhibited a pseudo-first-order kinetics pattern well.•The kobs with irradiance or oxidant dosage presented a linear relationship well.•The kobs exhibit an exponential ...trend as a function of AP0 for three systems.•UV/H2O2 behaved best at pH 2.5–10, while UV/PS behaved best at pH 10.0–11.5.•Cost for chemicals was firstly taken into account in calculation of the EE/O values.
Degradation of antipyrine (AP) in water by three UV-based photolysis processes (i.e., direct UV, UV/H2O2, UV/persulfate (UV/PS)) was studied. For all the oxidation processes, the AP decomposition exhibited a pseudo-first-order kinetics pattern. Generally, UV/H2O2 and UV/PS significantly improved the degradation rate relevant to UV treatment alone. The pseudo-first-order degradation rate constants (kobs) were, to different degrees, affected by initial AP concentration, oxidant dose, pH, UV irradiation intensity, and co-existing chemicals such as humic acid, chloride, bicarbonate, carbonate and nitrate. The three oxidation processes followed the order in terms of treatment costs: UV/PS>UV>UV/H2O2 if the energy and chemical costs are considered. Finally, the AP degradation pathways in the UV/H2O2 and UV/PS processes are proposed. Results demonstrated that UV/H2O2 and UV/PS are potential alternatives to control water pollution caused by emerging contaminants such as AP.
► All the CBZ degradation followed the pseudo-first-order kinetics model. ► The best CBZ degradation can be achieved at different pH in the three oxidation systems. ► Coexisting anions produced ...different effect on the three oxidation systems. ► Persulfate can be applied as an alternative oxidant in water treatment.
This paper systematically investigated the performance of carbamazepine (CBZ) degradation oxone by UVC (253.7nm) irradiation in the presence of different common oxidants including peroxymonosulfate (PMS), hydrogen peroxide (H2O2) and persulfate (PS). The influence of oxidant dosage, initial CBZ concentrations, solution pH and coexisting inorganic anions was also evaluated. Results revealed that all the CBZ degradation followed the pseudo-first-order kinetics well. The degradation efficiency of the three UV-based processes was in the order of UV/PS>UV/H2O2>UV/PMS. The rate of CBZ degradation increased as the oxidant dosage increased and decreased as the initial CBZ concentrations increased. The maximum CBZ degradation occurred at pH 11, 3, 5 in UV/PMS, UV/H2O2 and UV/PS system, respectively. Both Cl− and CO32- can inhibit the CBZ degradation in UV/H2O2 and UV/PS system. However, adding Cl− and CO32- into UV/PMS system can increase CBZ degradation at different degrees. Comprehensively consideration of energy requirements, oxidant costs and affecting factors, UV/PS system was the most efficient and economic process for CBZ degradation and a promising technology for water treatment.
Display omitted
•Among different water quality components, TC degradation by UV/NH2Cl process was most greatly affected by addition of HCO3−.•Reactive chlorine species played a major role on TC ...degradation by UV/NH2Cl process in pH range of 6.0–8.0.•TC degradation in UV/NH2Cl process involved the hydroxylation, demethylation, dehydration and chlorine substitution.•Compared with chloramination, UV/NH2Cl treatment increased the NDMA formation.•The observed acute toxicity in chloramination and UV/NH2Cl oxidation was higher than UV photolysis.
The combination of UV and monochloramine (UV/NH2Cl) was investigated to eliminate tetracycline (TC) in water. The results indicated that TC degradation by UV/NH2Cl oxidation far exceeded that by UV photolysis and dark chloramination and these processes well fitted pseudo-first-order kinetics. With the increase of NH2Cl dosage, the pseudo-first-order rate constant (kobs) value increased linearly during TC chloramination, while the growth rate of kobs presented a gradual downward trend in UV/NH2Cl process. TC degradation by UV photolysis, dark chloramination and UV/NH2Cl oxidation displayed highly pH-dependent. As solution pH increased from 5.0 to 9.0, the TC removal increased during UV photolysis, while decreased during dark chloramination. For UV/NH2Cl process, the TC degradation showed a decreasing trend with increasing pH from 5.0 to 7.0, but further increasing pH to 9.0 presented an increasing trend. Reactive chlorine species acted as the major contributors to TC degradation in pH range of 6.0–8.0. TC degradation was not apparently affected after the introduction of HA and chloride, but was substantially accelerated in the presence of HCO3−. The proposed degradation pathways involved the hydroxylation, demethylation, dehydration and chlorine substitution processes. Compared with dark chloramination, the N-Nitrosodimethylamine (NDMA) generation was enhanced during TC oxidation by UV/NH2Cl process. The NDMA concentration increased with increasing solution pH from 6.0 to 8.0 and also elevated in the presences of humic acid (HA), nitrite, nitrate and ammonium during TC oxidation by chloramination and UV/NH2Cl. The results of acute toxicity test demonstrated that the toxicity of the reacted solution exhibited similar trends during dark chloramination and UV/NH2Cl treatment and was found to be obviously higher than UV photolysis.
•Thermally activated persulfate (TAP) technology can decompose CBZ efficiently.•Sulfate radicals play the primary role in TAP oxidation.•The best CBZ degradation can be achieved at acidic ...conditions.•Coexisting anions and cations exhibit opposite effect on the CBZ degradation.•Six intermediate products are identified using LC–MS/MS.
Sulfate radicals-based advanced oxidation processes have been applied in water treatment and in situ chemical oxidation. Batch experiments were conducted to investigate the influencing factors including persulfate dosage, initial carbamazepine (CBZ) concentrations, solution pH, coexisting inorganic anions and cations on the decomposition of CBZ using thermally activated persulfate (TAP) technology. The results showed that TAP oxidation was efficient process for the CBZ degradation in water. The generation of sulfate radicals was accounted for the CBZ degradation in TAP system. The CBZ degradation rate constant increased as persulfate dosage increased and decreased as the initial CBZ concentrations increased. The CBZ decomposition rate decreased with the increasing pH and the best degradation occurred at pH 3. The exception was the strong alkaline condition under which a higher CBZ degradation performance was achieved. Coexisting inorganic anions slowed down the CBZ degradation to different degrees and the inhibiting effect abided by the following order: CO32->HCO3->Cl->SO42->NO3-. In contrast, coexisting cations could significantly enhance the CBZ degradation, and the promoting effect was in the order of Fe2+>Cu2+>Fe3+. In this study, six major intermediate products were generated during the TAP oxidation.
Electronic skins (e‐skins) have gained tremendous attention in health monitoring and disease diagnosis. However, the accumulated sweat at the skin/e‐skin interface would compromise the comfort, ...reliability, and fidelity for long‐term monitoring. Here, inspired by the active liquid transport phenomenon in nature, a biomimetic gold/thermoplastic polyurethane/cellulose membrane (Au/TPU/CM) based e‐skin is reported that can “pump” perspiration from the interface immediately through the combination of gradient porosity and surface energy gradient. The resulting electrode possesses good conductivity (2.68 Ω sq–1), excellent flexibility (the resistance only fluctuated 1.1% and 0.4% after 10 000 bending cycles and 2500 tensile cycles, respectively), and outstanding water vapor transmission and water evaporation rate (2.2 and 7.1 times as much as that of cotton fabric, respectively). The ultrafast perspiration‐wicking capability not only improves the wearing comfort but also minimizes the measurement error of skin hydration and temperature due to perspiration, eliminates the risk of short circuit in sensor array, and reduces the noise level, significantly enhancing the accuracy and reliability of multimodal sensing in e‐skins. The design strategy may encourage more material and structure development in e‐skins with improved sweat tolerance.
This study leverages controlled liquid transport principles in biosystems in e‐skin design and achieves active and unidirectional transportation of sweat away from the skin through the construction of dual porosity and surface energy gradients, preventing signal degradation and wearing discomfort caused by perspiration accumulation.
