应用g-C_(3)N_(4)基复合光催化剂处理水体各类型污染物的研究进展

光催化氧化技术具有效率快、操作简单、能耗低等优点。由于单独的g-C_(3)N_(4)具有电子空穴复合率较高、对可见光的吸收范围较窄的缺点,构建复合物是提高g-C_(3)N_(4)光催化活性的有效方法之一。本文介绍了利用g-C_(3)N_(4)基复合物处理水体各类型污染物的效果,简单阐述了g-C_(3)N_(4)基复合物降解污染物的反应机理,同时介绍了目前g-C_(3)N_(4)基复合物作为光催剂所需解决的问题。

臭氧降解水中氯霉素影响因素及机制研究

抗生素在水环境中具有高毒性和难生物降解性的特点,污水处理厂普通的处理工艺很难将其降解,抗生素通过生物富集等方式在生物体内累积,给生物健康及生态平衡带来严重威胁。文章利用臭氧技术对水体中氯霉素(chloramphenicol,CAP)降解效果评估。考察CAP的初始质量浓度、臭氧质量浓度、初始pH值以及自由基清除剂对CAP的降解影响。通入臭氧的流量为0.6104 mg/min,处理20 min后,溶液中CAP可被完全去除,此时溶液的总有机碳(total organic carbon,TOC)去除率为35.1%,说明降解过程中产生了中间产物。利用液质联用技术分析降解过程中产生的物质,提出CAP可能的降解路径。急性毒性实验结果表明产生的中间产物的毒性逐渐降低,在30 min时含有CAP的废水对V.fischeri的抑制率降低了34.98%。

介质阻挡放电等离子体降解红霉素影响因素研究

抗生素属于难降解物质,普通的物理化学方法不能有效去除。利用介质阻挡放电等离子体(DBD)降解红霉素(ETM),考察ETM初始质量浓度、放电功率、液体流速、空气流量对降解率的影响以及降解过程中TOC的变化。结果表明:放电功率为80 W、初始p H为8、液体流速为50 L/h,空气流量为60 L/h时,处理0.5 mg/L ETM溶液60 min后COD去除率为63.99%,60 min后TOC变化趋于平稳。

气液相等离子体对水中四环素去除及机制研究

本研究采用气液相等离子体处理四环素废水。利用示波器分析放电过程中电流和电压的变化;采用发光光谱测定等离子体在不同放电气体组分下产生的活性物质,其中氩气放电产生的羟基自由基和活性氢的强度明显比其他气体组分强;考察了放电功率、溶液pH、放电气体组分、溶液电导率对四环素去除效果的影响;利用分光光度计测定了长寿命活性物质变化情况,在放电过程中产生的长寿命活性物质包括臭氧、过氧化氢等物质对四环素的降解起到重要作用,且这些物质的浓度随着放电时间的延长逐渐增大。在放电功率为19.7 W,四环素的质量浓度为20 mg/L,pH为6.5,工作气体为空气的条件下,处理20 min时,四环素的去除效率可以达到82.2%。结合紫外-可见光谱分析存在的降解机制,四环素的特征吸收峰强度随着处理时间的延长逐渐降低,其原因可能是苯环上的羟基、酰胺基与芳香环上的烯醇被氧化。

Degradation of tetracycline in water by gas-liquid plasma in conjunction with rGO-TiO_(2) nanocomposite

Tetracycline(TC)is an antibiotic mainly used in livestock production and respiratory infection.Traditional methods are not effective in removing TC from solution.In this study,TC was degraded by gas–liquid plasma in the presence of rGO-TiO_(2)in solution.The rGO-TiO_(2)was prepared by modified hummers and hydrothermal method.The electrical and optical properties of the gas–liquid discharge plasma were studied and the produced long-lived reactive species were analyzed by spectrophotometer.The degradation efficiency of TC was improved by 41.4%after plasma treatment for 12 min in presence of 30 mg l-1 r GO-TiO_(2)compared to that with plasma alone.The degradation efficiency increased with increasing discharge power,but as the initial concentration was increased from 20 to 80 mg l-1,the degradation efficiency of TC decreased.The initial p H had no significant effect on the degradation of TC.The intermediate products were determined by UV–vis spectrophotometry and ESI(+)–MS,and the degradation mechanism was analyzed.The reactive species,including O_(3),·OH,and H_(2)O_(2),etc.,produced in the plasma/catalyst system attracted electron-rich functional groups(amino group,aromatic ring,and double bond).Therefore,the gas–liquid plasma/catalyst system could be an effective and promising method for pharmaceutical wastewater treatment in future.

Degradation and mineralization of ciprofloxacin by gas–liquid discharge non-thermal plasma

A typical quinolones antibiotic ciprofloxacin(CIP) in aqueous solution was degraded by a gas–liquid discharge non-thermal plasma system. The discharge plasma power and the emission intensity of the excited reactive species(RS) generated in the gas phase were detected by the oscilloscope and the optical emission spectroscopy. The effects of various parameters on CIP degradation, i.e. input powers, initial concentrations addition of radical scavengers and p H values were investigated. With the increase of discharge power, the degradation efficiency increased but the energy efficiency significantly reduced. The degradation efficiency also reduced under high concentration of initial CIP conditions due to the competitive reactions between the plasma-induced RS with the degradation intermediates of CIP. Different radical scavengers(isopropanol and CCl_4) on ·OH and H· were added into the reaction system and the oxidation effects of ·OH radicals have been proved with high degradation capacity on CIP.Moreover, the long-term degradation effect on CIP in the plasma-treated aqueous solution proved that the long-lived RS(H_2O_2 and O_3, etc) might play key roles on the stay effect through multiple aqueous reactions leading to production of ·OH. The degradation intermediates were determined by the method of electrospray ionization(+)-mass spectroscopy, and the possible degradation mechanism were presented.

Control of multidrug-resistant planktonic Acinetobacter baumannii:biocidal efficacy study by atmospheric-pressure air plasma

In this research,an atmospheric-pressure air plasma is used to inactivate the multidrug-resistant Acinetobacter baumannii in liquid.The efficacy of the air plasma on bacterial deactivation and the cytobiological variations after the plasma treatment are investigated.According to colony forming units,nearly all the bacteria（6-log） are inactivated after 10 min of air plasma treatment.However,7% of the bacteria enter a viable but non-culturable state detected by the resazurin based assay during the same period of plasma exposure.Meanwhile,86% of the bacteria lose their membrane integrity in the light of SYTO 9/PI staining assay.The morphological changes in the cells are examined by scanning electron microscopy and bacteria with morphological changes are rare after plasma exposure in the liquid.The concentrations of the long-living RS,such as H2O2,NO3^- and O3,in liquid induced by plasma treatment are measured,and they increase with plasma treatment time.The changes of the intracellular ROS may be related to cell death,which may be attributed to oxidative stress and other damage effects induced by RS plasma generated in liquid.The rapid and effective bacteria inactivation may stem from the RS in the liquid generated by plasma and air plasmas may become a valuable therapy in the treatment of infected wounds.