Treatment of simulated wastewater containing Reactive Red 195 by zero-valent iron/activated carbon combined with microwave discharge electrodeless lamp/sodium hypochlorite

A comparative study of treatment of simulated wastewater containing Reactive Red 195 using zero-valent iron/activated carbon(ZVI/AC),microwave discharge electrodeless lamp/sodium hypochlorite(MDEL/NaClO) and the combination of ZVI/ACMDEL/NaClO was conducted.The preliminary results showed the two steps method of ZVI/AC-MDEL/NaClO had much higher degradation effciency than both single steps.The final color removal percentage was nearly up to 100% and the chemical oxygen demand reduction percentage was up to approximately 82%.The effects of operational parameters,including initial pH value of simulated wastewater,ZVI/AC ratio and particle size of ZVI were also investigated.In addition,from the discussion of synergistic effect between ZVI/AC and MEDL/NaClO,we found that in the ZVI/AC-MEDL/NaClO process,ZVI/AC could break the azo bond firstly and then MEDL/NaClO degraded the aromatic amine products effectively.Reversing the order would reduce the degradation effciency.

Enhanced ozonation degradation of atrazine in the presence of nano-ZnO： Performance, kinetics and effects

Enhanced ozonation degradation of atrazine(ATZ) with nano-ZnO(nZnO) as catalyst and the influences of the operational parameters have been investigated through semi-continuous experiments in this study. The results demonstrated that the combination of ozone(O_3) and nZnO showed an obvious synergetic effect and the ATZ degradation conformed to pseudo-first-order kinetics. An improvement of ATZ degradation efficiency by 41.8% and pseudo-first-order rate constant by more than a factor of four was obtained in the O_3/nZnO process after 5 min of reaction compared to O_3 alone. Meanwhile, the degradation efficiency of ATZ was gradually enhanced with increasing nZnO dosage and initial pH in the range from 3.0 to 8.0, and a higher amount of ATZ was degraded when the initial concentration of ATZ rose from 0.5 to 5 mg/L. Additionally, sulfate ion, chloride ion, nitrate ion and low concentrations of humic acid substances led to enhancement of the ATZ degradation. The notable decrease of ATZ removal efficiency observed in the presence of radical scavengers and the results of free radical tests indicated thatUOH is the dominant active radical species. The mechanism investigation demonstrated that the enhancement effect could be attributed to the introduction of nZnO,which could promote the utilization of O_3, enhance the formation of superoxide radical, and further accelerate the production of hydrogen peroxide and the generation of OH/O_2^-.

Non-woven cotton fabric based intimately coupling of photocatalysis and biodegradation system for efficient removal of Cu(Ⅱ)complex in water

The efficient remediation of heavy metal complexes in water has become a difficult and challenging task owing to their high stability and strong mobility.In this study,a novel strategy was employed for highly efficient removal of Cu-citrate by using intimately coupled photocatalysis and biodegradation(ICPB)system with non-woven cotton fabric as a carrier.Experimental results showed that the ICPB system caused94%Cu removal,which was higher than those of single photocatalysis.After 5 cycles,Cu removal efficiency could still reach 78%within 5 h.The existence of 0–40 mg/L citrate had negligible influence,whereas the presence of 60–100 mg/L citrate exhibited a limited adverse effect on Cu removal(~70%).The decomplexation of Cu-citrate was realized via the function of free radicals and microorganisms.Two main processes,such as bio-adsorption of Cu^(2+) by microorganisms,deposition of Cu^(0) on the surface of material,played important role in Cu removal from aqueous solution.The dominant microorganisms in the system were Proteobacteria,Actinobacteria,Bacteroidetes,Chloroflexi,Chlorophyta,Planctomycetes,and Verrucomicrobia.Furthermore,the performance of ICPB system was also validated through treatment of other heavy metal complexes.This study provided a feasible strategy for the decontamination of heavy metal complexes in wastewater.

Band gap tuning of g-C3N4via decoration with AgCl to expedite the photocatalytic degradation and mineralization of oxalic acid

A series of functional organic-metal AgCl-decorated graphitic carbon nitride(AgCl-CNx)composites were synthesized and applied for the degradation of oxalic acid(OA)under visible light.The highest photocatalytic activity was achieved with AgCl decoration ratio of1.0(denoted as AgCl-CN1.0).The pseudo-first-order constant for OA degradation was 0.0722min-1 with the mineralization efficiency of 90.80%after 60 min reaction in the photocatalytic process with AgCl-CN1.0.A variety of characterization techniques including BrunauerEmmett-Teller,X-ray diffraction,scanning electron microscope,transmission electron microscopy,X-ray photoelectron spectroscopy,Fourier transform infrared spectra,ultraviolet-visible diffuse reflectance spectra,photoluminescence,and Mott-Schottky were utilized to elucidate the physicochemical,microstructure,and optical properties contributing to the improvement of the photocatalytic performance.The results showed that AgClCN1.0had an oblate flaky erythrocyte-like structure with a moderate band gap energy of^3.00 eV.In addition,the effects of the key parameters(i.e.,AgCl-CN1.0 dosage,initial OA concentration,solution pH,and presence of natural organic matter)on OA degradation were systematically investigated.Radical scavenger experiments indicated that photogenerated holes,electrons,superoxide anion radicals,and hydroxyl radicals were the dominant reactive species.Moreover,AgCl-CN1.0 exhibited excellent stability and reusability for OA degradation without detectable Ag+release in the solution over multiple reaction cycles.The efficient OA mineralization could be mainly ascribed to the moderate specific surface area,increased numbers of active sites,and effective interfacial charge transfer of AgCl-CN1.0.Overall,the AgCl-CN1.0 composite was demonstrated to be a highly efficient,stable,and recoverable photocatalyst.

Efficient removal of tetracycline in water by a novel chemical and biological coupled system with non-woven cotton fabric as carrier

As a novel wastewater treatment strategy,the intimate coupling of photocatalysis and biodegradation(ICPB)has been attracted attention,which is ascribed to its combination of the advantages of photocatalytic reactions and biological treatment.The selection of carriers is important since it affects the stability of the system and the removal efficiency of pollutants.In this study,a novel ICPB system was successfully constructed by loading photocatalytic materials(i.e.,TiO_(2),N-TiO_(2),and Ag-TiO_(2))and microbes onto non-woven cotton fabric.The photocatalysts were characterized by scanning electron microscope-energy dispersive spectrometer(SEM-EDS),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).This system exhibited good performance in degrading tetracycline(TC)in water.The results showed that Ag-TiO_(2)-ICPB had the maximum removal efficiency of tetracycline(94.7%)in 5 h,which was 16.5%higher than the photocatalysis alone.After five cycles,82.9%of tetracycline could be still degraded through Ag-TiO_(2)-ICPB.SEM spectrum showed microbes on the material changed little before and after the reactions.This result implied the materials were stable,and then beneficial for degrading of pollutants continuously.The intermediates were detected through ultraperformance liquid chromatography-mass spectrometer(UPLC-MS)and the plausible degradation pathways were proposed.Electron paramagnetic resonance(EPR)analysis showed·OH and O_(2)·-were the main reactive oxygen species for TC degradation.In conclusion,the ICPB system with non-woven cotton fabric as a carrier has certain application prospects for antibiotic-containing wastewater.