66 research outputs found

    Developing persulfate-activator soft solid (PASS) as slow release oxidant to remediate phenol-contaminated groundwater

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    The research objective was to develop a persulfate-activator soft solid (PASS) as a biodegradable slow-release oxidant to treat phenol-contaminated groundwater. PASS was prepared by graft copolymerization of acrylic acid (AA) and acrylamide (AM) onto 1% (w/v) sodium alginate mixed with 500 mg L−1 sodium persulfate and 5 mg L−1 ferrous sulfate. The physical and chemical properties of PASS were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, the water content and swelling ratio. Various variables, including the ratio of AA/AM, pH, temperature and the type of groundwater cations affecting PS release, were investigated. The maximum PS release in DI water was 98% in the ratio of PASS 1 (AA/AM, 75/25), 96% at pH 3, 83% at 25 °C, and 80% with Na+. The major factors controlling PS release were the AA/AM ratio and pH. PASS 1 can be stable in size and shape for 6–8 days and completely degraded within 34 days. The degradation rates of 10 mgL−1 phenol using PASS produced the highest kobs values for each variable at a ratio of PASS 1 (k = 0.1408 h−1), pH 7 (k = 0.1338 h−1), 25 °C (k = 0.1939 h−1), and Ca2+ (k = 0.1336 h−1). The temperature of the groundwater was key to driving the reaction between PS and phenol. PASS 1 was applied in simulated phenol-contaminated groundwater via horizontal tanks containing Ottawa sand. The results indicated 93.2% phenol removal within 72 h in a narrow horizontal flow tank and 41.7% phenol removal in a wide horizontal flow tank with aeration

    Developing a Slow-Release Permanganate Composite for Degrading Aquaculture Antibiotics

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    Copious use of antibiotics in aquaculture farming systems has resulted in surface water contamination in some countries. Our objective was to develop a slow-release oxidant that could be used in situ to reduce antibiotic concentrations in discharges from aquaculture lagoons. We accomplished this by generating a slow-release permanganate (SR-MnO4-) that was composed of a biodegradable wax and a phosphate-based dispersing agent. Sulfadimethoxine (SDM) and its synergistic antibiotics were used as representative surrogates. Kinetic experiments verified that the antibiotic-MnO4- reactions were first-order with respect to MnO4- and initial antibiotic concentration (second-order rates: 0.056–0.128 s-1 M-1). A series of batch experiments showed that solution pH, water matrices, and humic acids impacted SDM degradation efficiency. Degradation plateaus were observed in the presence of humic acids (\u3e20 mgL-1), which caused greater MnO2 production. A mixture of KMnO4/beeswax/paraffin (SRB) at a ratio of 11.5:4:1 (w/w) was better for biodegradability and the continual release of MnO4-, but MnO2 formation altered release patterns. Adding tetrapotassium pyrophosphate (TKPP) into the composite resulted in delaying MnO2 aggregation and increased SDM removal efficiency to 90% due to the increased oxidative sites on the MnO2 particle surface. The MnO4- release data fit the Siepmann–Peppas model over the long term (t \u3c 48 d) while a Higuchi model provided a better fit for shorter timeframes (t \u3c 8 d). Our flow-through discharge tank system using SRB with TKPP continually reduced the SDM concentration in both DI water and lagoon wastewater. These results support SRB with TKPP as an effective composite for treating antibiotic residues in aquaculture discharge water

    Dual Activation of Peroxymonosulfate Using MnFe\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e4\u3c/sub\u3e/g‑C\u3csub\u3e3\u3c/sub\u3eN\u3csub\u3e4\u3c/sub\u3e and Visible Light for the Efficient Degradation of Steroid Hormones: Performance, Mechanisms, and Environmental Impacts

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    Single activation of peroxymonosulfate (PMS) in a homogeneous system is sometimes insufficient for producing reactive oxygen species (ROS) for water treatment applications. In this work, manganese spinel ferrite and graphitic carbon nitride (MnFe2O4/g-C3N4; MnF) were successfully used as an activator for PMS under visible light irradiation to remove the four-mostdetected- hormone-contaminated water under different environmental conditions. The incorporation of g-C3N4 in the nanocomposites led to material enhancements, including increased crystallinity, reduced particle agglomeration, amplified magnetism, improved recyclability, and increased active surface area, thereby facilitating the PMS activation and electron transfer processes. The dominant active radical species included singlet oxygen (1O2) and superoxide anions (O2 •−), which were more susceptible to the estrogen molecular structure than testosterone due to the higher electron-rich moieties. The self-scavenging effect occurred at high PMS concentrations, whereas elevated constituent ion concentrations can be both inhibitors and promoters due to the generation of secondary radicals. The MnF/PMS/vis system degradation byproducts and possible pathways of 17β-estradiol and 17α-methyltestosterone were identified. The impact of hormone-treated water on Oryza sativa L. seed germination, shoot length, and root length was found to be lower than that of untreated water. However, the viability of both ELT3 and Sertoli TM4 cells was affected only at higher water compositions. Our results confirmed that MnF and visible light could be potential PMS activators due to their superior degradation performance and ability to produce safer treated water

    Dual Activation of Peroxymonosulfate Using MnFe\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e4\u3c/sub\u3e/g‑C\u3csub\u3e3\u3c/sub\u3eN\u3csub\u3e4\u3c/sub\u3e and Visible Light for the Efficient Degradation of Steroid Hormones: Performance, Mechanisms, and Environmental Impacts

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    Single activation of peroxymonosulfate (PMS) in a homogeneous system is sometimes insufficient for producing reactive oxygen species (ROS) for water treatment applications. In this work, manganese spinel ferrite and graphitic carbon nitride (MnFe2O4/g-C3N4; MnF) were successfully used as an activator for PMS under visible light irradiation to remove the four-mostdetected- hormone-contaminated water under different environmental conditions. The incorporation of g-C3N4 in the nanocomposites led to material enhancements, including increased crystallinity, reduced particle agglomeration, amplified magnetism, improved recyclability, and increased active surface area, thereby facilitating the PMS activation and electron transfer processes. The dominant active radical species included singlet oxygen (1O2) and superoxide anions (O2 •−), which were more susceptible to the estrogen molecular structure than testosterone due to the higher electron-rich moieties. The self-scavenging effect occurred at high PMS concentrations, whereas elevated constituent ion concentrations can be both inhibitors and promoters due to the generation of secondary radicals. The MnF/PMS/vis system degradation byproducts and possible pathways of 17β-estradiol and 17α-methyltestosterone were identified. The impact of hormone-treated water on Oryza sativa L. seed germination, shoot length, and root length was found to be lower than that of untreated water. However, the viability of both ELT3 and Sertoli TM4 cells was affected only at higher water compositions. Our results confirmed that MnF and visible light could be potential PMS activators due to their superior degradation performance and ability to produce safer treated water

    Adsorptive–Photocatalytic Performance for Antibiotic and Personal Care Product Using Cu\u3csub\u3e0.5\u3c/sub\u3eMn\u3csub\u3e0.5\u3c/sub\u3eFe\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e4\u3c/sub\u3e

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    The amount of antibiotics and personal care products entering local sewage systems and ultimately natural waters is increasing and raising concerns about long-term human health effects. We developed an adsorptive photocatalyst, Cu0.5Mn0.5Fe2O4 nanoparticles, utilizing co-precipitation and calcination with melamine, and quantified its efficacy in removing paraben and oxytetracycline (OTC). During melamine calcination, Cu0.5Mn0.5Fe2O4 recrystallized, improving material crystallinity and purity for the adsorptive–photocatalytic reaction. Kinetic experiments showed that all four parabens and OTC were removed within 120 and 45 min. We found that contaminant adsorption and reaction with active radicals occurred almost simultaneously with the photocatalyst. OTC adsorption could be adequately described by the Brouers–Sotolongo kinetic and Freundlich isotherm models. OTC photocatalytic degradation started with a series of reactions at different carbon locations (i.e., decarboxamidation, deamination, dehydroxylation, demethylation, and tautomerization). Further toxicity testing showed that Zea mays L. and Vigna radiata L. shoot indexes were less affected by treated water than root indexes. The Zea mays L. endodermis thickness and area decreased considerably after exposure to the 25% (v/v)-treated water. Overall, Cu0.5Mn0.5Fe2O4 nanoparticles exhibit a remarkable adsorptive–photocatalytic performance for the degradation of tested antibiotics and personal care products

    Enrofloxacin and Sulfamethoxazole Sorption on Carbonized Leonardite: Kinetics, Isotherms, Influential Effects, and Antibacterial Activity toward \u3ci\u3eS. aureus\u3c/i\u3e ATCC 25923

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    Excessive antibiotic use in veterinary applications has resulted in water contamination and potentially poses a serious threat to aquatic environments and human health. The objective of the current study was to quantify carbonized leonardite (cLND) adsorption capabilities to remove sulfamethoxazole (SMX)- and enrofloxacin (ENR)-contaminated water and to determine the microbial activity of ENR residuals on cLND following adsorption. The cLND samples prepared at 450oC and 850oC (cLND450 and cLND550, respectively) were evaluated for structural and physical characteristics and adsorption capabilities based on adsorption kinetics and isotherm studies. The low pyrolysis temperature of cLND resulted in a heterogeneous surface that was abundant in both hydrophobic and hydrophilic functional groups. SMX and ENR adsorption were best described using a pseudo-second-order rate expression. The SMX and ENR adsorption equilibrium data on cLND450 and cLND550 revealed their better compliance with a Langmuir isotherm than with four other models based on 2.3-fold higher values of qmENR than qmSMX. Under the presence of the environmental interference, the electrostatic interaction was the main contributing factor to the adsorption capability. Microbial activity experiments based on the growth of Staphylococcus aureus ATCC 25923 revealed that cLND could successfully adsorb and subsequently retain the adsorbed antibiotic on the cLND surface. This study demonstrated the potential of cLND550 as a suitable low-cost adsorbent for the highly efficient removal of antibiotics from water

    Spread of artemisinin resistance in Plasmodium falciparum malaria.

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    BACKGROUND: Artemisinin resistance in Plasmodium falciparum has emerged in Southeast Asia and now poses a threat to the control and elimination of malaria. Mapping the geographic extent of resistance is essential for planning containment and elimination strategies. METHODS: Between May 2011 and April 2013, we enrolled 1241 adults and children with acute, uncomplicated falciparum malaria in an open-label trial at 15 sites in 10 countries (7 in Asia and 3 in Africa). Patients received artesunate, administered orally at a daily dose of either 2 mg per kilogram of body weight per day or 4 mg per kilogram, for 3 days, followed by a standard 3-day course of artemisinin-based combination therapy. Parasite counts in peripheral-blood samples were measured every 6 hours, and the parasite clearance half-lives were determined. RESULTS: The median parasite clearance half-lives ranged from 1.9 hours in the Democratic Republic of Congo to 7.0 hours at the Thailand-Cambodia border. Slowly clearing infections (parasite clearance half-life >5 hours), strongly associated with single point mutations in the "propeller" region of the P. falciparum kelch protein gene on chromosome 13 (kelch13), were detected throughout mainland Southeast Asia from southern Vietnam to central Myanmar. The incidence of pretreatment and post-treatment gametocytemia was higher among patients with slow parasite clearance, suggesting greater potential for transmission. In western Cambodia, where artemisinin-based combination therapies are failing, the 6-day course of antimalarial therapy was associated with a cure rate of 97.7% (95% confidence interval, 90.9 to 99.4) at 42 days. CONCLUSIONS: Artemisinin resistance to P. falciparum, which is now prevalent across mainland Southeast Asia, is associated with mutations in kelch13. Prolonged courses of artemisinin-based combination therapies are currently efficacious in areas where standard 3-day treatments are failing. (Funded by the U.K. Department of International Development and others; ClinicalTrials.gov number, NCT01350856.)
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