Improved degradation of anthraquinone dye by electrochemical activation of PDS.

Electrochemical oxidation (EO) coupled with peroxydisulfate (PDS) activation as a synergistic wastewater treatment process (PDS/EO) was performed to degrade anthraquinone dye-Reactive Brilliant Blue (RBB) in aqueous solution. Introducing PDS into the EO improved the RBB removal than the sole PDS and conventional EO systems. The RBB could activate PDS to a certain degree by itself. By the comparison of various inorganic ions addition, it showed that adding NO3- as the background electrolyte was more effective than the systems using the Cl- and SO42-, respectively. In this PDS/EO-NO3- system, increasing PDS concentration (1-5 mmol L-1) and current density (5-10 mA cm-2) considerably promoted the degradation of RBB. The adjustment of the solution pH displayed that the acidic and neutral condition was beneficial to the RBB removal, and the synergistic effect was inverse ratio to the RBB initial concentration. Furthermore, the scavenger experiments verified that both SO4·- and HO· were the major active substances in the RBB decomposition, and other reactive oxygen species also had considerable contributions. Thereinto NO3- only act a catalytic agent to improve the generation of active matters in the PDS/EO-NO3-. Overall, the proposed synergistic process could serve as an efficient method for the degradation of anthraquinone dye.

Evaluation of antibiotic oxytetracycline removal in water using a gas phase dielectric barrier discharge plasma.

Degradation of oxytetracycline (OTC), a primary member of antibiotics in water, was performed by a gas phase dielectric barrier discharge (GPDBD) plasma reactor. The influences of operation conditions including applied voltages, air bubbling rates, initial OTC concentrations and initial pH values on OTC abatement were investigated respectively. The results showed that the decontamination process can be fitted by first order kinetics, and the removal ratio and rate were affected obviously by those parameters. After 20 min of discharge treatment, approximately 93.4% of OTC was removed under the experimental conditions: applied voltage of 7.5 kV, air flow rate of 1.0 L/min, initial OTC concentration of 100 mg/L, and initial pH of 5.0. In addition, TOC and COD removal efficiency reached 43.0% and 73.7% at the original pH 9.3, respectively. Furthermore, the amounts of hydrogen peroxide and ozone in aqueous were quantitatively measured to evaluate their roles during antibiotic removal, and the main function of hydroxyl radicals was demonstrated by the radicals scavenger test. At last, the analyses of UV-Vis spectra and HPLC-MS were employed to study the OTC elimination mechanism, and the possible decomposition pathway was proposed based on the speculated intermediates.

Photocatalytic activity of G-TiO2@Fe3O4 with persulfate for degradation of alizarin red S under visible light.

A composite photocatalyst combined with TiO2, graphite (G) and Fe3O4 was prepared by co-precipitation method. Then the G-TiO2@Fe3O4 was employed with persulfate (PS) to degrade alizarin red S (ARS) under visible light. The removal rate of ARS reached 100% after 60 min irradiation. The degradation rate constant of G-TiO2@Fe3O4/PS exhibited 20.8, 9.0 and 3.1 times than that of TiO2, G-TiO2 and G-TiO2@Fe3O4, respectively. The effects of photocatalyst dosage, mass ratios of graphite and Fe3O4 to TiO2, PS dosage, initial pH and ARS concentration on the degradation efficiency were investigated. The optimal removal efficiency of ARS was obtained when G-TiO2@Fe3O4 dosage was 0.25 g/L, G: TiO2 = 0.005, Fe3O4: TiO2 = 0.8, PS concentration was 6 mmol/L, initial pH = 3, and initial concentration of ARS was 100 mg/L. The SO4·- was demonstrated more important than O2- and·OH in the degradation of ARS. The intermediates and possible degradation pathways of ARS were discussed. Reuse and stability of G-TiO2@Fe3O4 were also tested, and 88.3% photocatalytic activity was maintained after five cycles. Therefore, the proposed G-TiO2@Fe3O4/PS not only had excellent photocatalytic activity, but also showed superior stability and reusability.

Elimination of humic acid in water: comparison of UV/PDS and UV/PMS.

Humic substances are polyelectrolytic macromolecules; their presence in water leads to many environmental problems without effective treatment. In this work, the elimination of humic acid (HA), a typical humic substance, has been examined through ultraviolet (UV) activation systems in the presence of peroxydisulfate (PDS) and peroxymonosulfate (PMS), respectively. The results indicated that 92.9% and 97.1% of HA were eliminated with rate constants of 0.0328 ± 0.0006 and 0.0436 ± 0.0011 min-1 with 180 and 60 min treatment times at pH 6 and 3 when adding 3 and 1 mmol L-1 oxidant during UV/PDS and UV/PMS, respectively; the corresponding electric energies per order were 0.0287 and 0.0131 kW h m-3. The HA removal was systematically investigated by varying different reaction parameters, including radical scavengers, persulphate dose, solution pH, and initial HA concentration, and by addition of various common ions. Moreover, the decomposition details were identified through the changes in the dissolved organic carbon, unique UV absorbances, and UV spectroscopic ratios. Furthermore, the destruction mechanism was verified by fluorescence spectroscopy, demonstrating that the HA structure was decomposed to small molecular fractions in the two UV/persulphate systems. In addition, the purification of HA by the two UV/persulphate processes was assessed in actual water matrices.

Fe3+-sulfite complexation enhanced persulfate Fenton-like process for antibiotic degradation based on response surface optimization.

To improve the cycle between Fe3+ and Fe2+ in persulfate (PS) Fenton-like system, sulfite (Na2SO3) was used as the iron complexing agent to enhance the degradation of sulfamethoxazole (SMX) antibiotic in water. Response surface methodology (RSM) was applied to regulate the operation parameters for the Fe3+/Na2SO3/PS synergistic system. Based on the RSM, the SMX could be completely degraded when the concentration of Fe3+, Na2SO3, and PS were 0.4, 0.5, and 2.5 mM, respectively. The result showed that the synergistic process represented a high Fe3+ utilization rate and SMX degradation efficiency. After 1 h reaction, 100.00% of SMX and 27.80% of total organic carbon were removed under the ambient conditions containing the initial SMX concentration of 10 µM and initial pH of 5.96. Free radical masking and electron spin-resonance tests proved that hydroxyl radical (HO) and oxysulfur radicals (SOx-, x = 3, 4, 5) were all played the significant role in the antibiotic removal, and the primary active radical was HO. The SMX decomposition pathways based on the formed intermediates was proposed through the high-performance liquid chromatography and mass spectrum analyses. The toxicity assessment prediction indicated that the toxicities of decomposed SMX byproducts were reduced after the coupling treatment.

Percarbonate promoted antibiotic decomposition in dielectric barrier discharge plasma.

A coupling technique introducing sodium percarbonate (SPC) into a dielectric barrier discharge (DBD) plasma was investigated to enhance the degradation of antibiotic tetracycline (TC) in aqueous. The dominant effects of SPC addition amount and discharge voltage were evaluated firstly. The experiments indicated that the moderate SPC dosages in the DBD presented an obvious synergistic effect, improving the TC decomposition efficiency and kinetics. Elevating the voltage was conducive for the promotion of antibiotic abatement. After 5 min treatment, the removal reached 94.3% at the SPC of 52.0 µmol/L and voltage of 4.8 kV for 20 mg/L TC. Especially the defined synergy factors were greater than one since the SPC being added, and the energy yield was increased by 155%. Besides, the function mechanism was explained by the hydrogen peroxide and ozone quantitative determinations and radical scavenger test, and the results confirmed that the collaborative method could increase the generation of reactive species, and the produced hydroxyl and superoxide radicals both played the significant roles for the TC elimination. Furthermore, the decomposition and mineralization of the synergism were verified by UV-vis spectroscopy, TOC and COD analyses, and the degradation byproducts and transformation pathways were identified based on the analysis of HPLC-MS finally.

Comparative study of persulfate oxidants promoted photocatalytic fuel cell performance: Simultaneous dye removal and electricity generation.

Introducing peroxymonosulfate (PMS) and peroxydisulfate (PDS) into the photocatalytic fuel cell (PFC) system were investigated by comparing the Reactive Brilliant Blue (KN-R) degradation and synchronous electricity production. The two persulfates (PS) themselves are strong oxidant, and could be activated and as electron sacrificial agent in the PFCs, facilitating the photoelectrocatalysis and expanding redox to the entire cell space. Hence, the two established PFC/PS systems manifested prominent cell performances, enhancing the KN-R decomposition and electric power production relative to the virgin PFC. Thereinto, the KN-R removal rate of PFC/PMS was faster than that of PFC/PDS, but an opposite trend appeared in the electricity generation. Besides, the cell performances of the two cooperative systems were evaluated at different operation conditions, including PS dosage, solution pH, and irradiation strength. Moreover, the dye elimination principle was explored by radicals scavenging experiment, and the consequence revealed that hydroxyl radical (HO•), sulfate radical (SO4•-) and singlet oxygen were chief active species in the PFC/PMS, and HO•, SO4•- and superoxide anion played the key roles in the PFC/PDS. Furthermore, the calculated economic indicator demonstrated that the economy of the two synergistic processes were greater than that of UV/PS and solo PFC, and the PFC/PDS was more cost-effective than PFC/PMS.

Facile Preparation and Enhanced Catalytic Properties of Self-Assembled Pd Nanoparticle-Loaded Nanocomposite Films Synthesized via the Electrospun Approach.

In recent years, people pay more attention to environmental pollution and the treatment of sewage has become the focus of recent research. Palladium nanoparticles have good catalytic properties but are easy to agglomerate. Therefore, we used the electrospinning technology to prepare a uniform composite nanofiber film based on polyacrylic acid (PAA) and polyvinyl alcohol (PVA), which demonstrated that they are good carriers of palladium nanoparticles to make the nanoparticles well dispersed. Furthermore, carbon nanotubes (CNTs) were added to increase the specific surface area of the composite nanofiber film and improve its mechanical properties. The successfully synthesized PAA/PVA/CNT-COOH@palladium nanoparticle (PdNP) composite fiber films were characterized by scanning electron microscopy, transmission electron microscopy, and thermogravimetry analysis. p-Nitrophenol and 2-nitroaniline were utilized as typical pollutants to further evaluate the catalytic performance of PAA/PVA/CNT-COOH@PdNP composite fiber films. The PAA/PVA/CNT-COOH@PdNP composite fiber films exhibited enhanced catalytic performance and could be reused for eight consecutive cycles. This work provided new clues for the preparation and application of composite electrospun film materials.

Self-Assembled Naphthylidene-Containing Schiff Base Anchored Polystyrene Nanocomposites Targeted for Selective Cu(II) Ion Removal from Wastewater.

Self-assembled composite adsorbents that combine the controllability of self-assembly with a mild operation process are promising for removal of heavy metal ions in wastewater. The design and preparation of functionalized composite adsorbent materials with multiple-site adsorption ability remain the most attractive in effectively removing heavy metal ions. Inspired by the macroporous structure of charged polystyrene (PS) resin and chelation of Schiff bases with heavy metal ions, smart composite adsorbents are constructed based on the combination and synergistic effect of multiple hydrophobic, π-π stacking, and electrostatic noncovalent interactions between polystyrene resin and naphthylidene-containing Schiff base (NSB). The resulting hybrid nanomaterials (PS-NSB) have uniform porous structures and well-defined and multiple target sites. These properties promote diffusion of the target ion, increase the binding site, and enhance the removal efficacy. This study offers a new strategy to harness a self-assembled Schiff base with integrated flexibility and multifunctions to enhance target metal ion specific binding and removal effects, highlighting opportunities to develop smart composite adsorbents.

Enhancing CaO2 fenton-like process by Fe(II)-oxalic acid complexation for organic wastewater treatment.

Hydrogen peroxide (H2O2) is used widely as Fenton's reagent for organic wastewater treatment. However, the application range of the optimum Fenton reaction is narrow, needing to adjust pH before and after treatment. Besides, the disproportionation of H2O2 and generated iron precipitation also confine the normal operation of Fenton method. To overcome the drawbacks of the traditional Fenton process, a Fe(II) catalyzed calcium peroxide (CaO2) Fenton-like process assisted by oxalic acid (OA) for aqueous organic pollutants degradation was proposed (Fe2+/OA/CaO2). The methyl orange (MO) as a typical organic pollutant, its removal performances by this Fe2+/OA/CaO2 system were evaluated. In the optimized conditions, 99% of MO was degraded within 15 min, and 38% mineralized after 180 min when the molar ratio of Fe2+: OA: CaO2 was 1: 2: 2 (Fe2+ = 1.5 mM). Radicals detection indicated that hydroxyl radical (HO•) was the main reactive species for the MO elimination. Furthermore, density functional theory calculation was in good agreement with the experimental results, which proved that the Fe2+/OA/CaO2 could improve the circulation between Fe2+ and Fe3+, promoting the oxygen reactive species generation and pollutant removal. The main intermediates were identified and the degradation pathways were proposed based on the results of the mass spectrum analysis, and the attack of HO• was suggested as the main function for the MO decomposition. The matrix effects of water constituents on the performance of Fe2+/OA/CaO2 were investigated, and the results showed that a certain amount of Cl-, NO3-, HCO3-, and HA affected the elimination than SO42-. Finally, the attempt of actual wastewater disposal indicated the synergistic system possessed good potential for future practical application.