Multi-function adsorbent-photocatalyst MXene-TiO2 composites for removal of enrofloxacin antibiotic from water

MXenes, a new family of two-dimensional transition metal carbides or nitrides, have attracted tremendous attention for various applications due to their unique properties such as good electrical conductivity, hydrophilicity, and ion intercalability. In this work, Ti₃C₂ MXene, or MX, is converted to MX-TiO₂ composites using a simple and rapid microwave hydrothermal treatment in HCl/NaCl mixture solution that induces formation of fine TiO₂ particles on the MX parent structure and imparts photocatalytic activity to the resulting MX-TiO₂ composites. The composites were used for enrofloxacin (ENR), a frequently found contaminating antibiotic, removal from water. The relative amount of the MX and TiO₂ can be controlled by controlling the hydrothermal temperature resulting in composites with tunable adsorption/photocatalytic properties. NaCl addition was found to play important role as composites synthesized without NaCl could not adsorb enrofloxacin well. Adding NaCl into the hydrothermal treatment causes sodium ions to be simultaneously intercalated into the composite structure, improving ENR adsorption greatly from 1 to 6 mg ENR/g composite. It also slows down the MX to TiO₂ conversion leading to a smaller and more uniform distribution of TiO₂ particles on the structure. MX-TiO₂/NaCl composites, which have sodium intercalated in their structures, showed both higher ENR adsorption and photocatalytic activity than composites without NaCl despite the latter having higher TiO₂ content. Adsorbed ENR on the composites can be efficiently degraded by free radicals generated from the photoexcited TiO₂ particles, leading to high photocatalytic degradation efficiency. This demonstrates the synergetic effect between adsorption and photocatalytic degradation of the synthesized compounds.     

氯乙酰胺类除草剂微生物降解研究进展

主要介绍了几种氯乙酰胺类除草剂的微生物降解机制和相关降解酶．目前没有一种纯菌培养物或混合菌群能完全矿化异丙甲草胺和甲草胺，它们只能被细菌和真菌共代谢．毒草胺能被纯菌或混合菌群完全矿化，且有几种不同的矿化途径．乙草胺是我国生产量和使用量最多的三大除草剂之一，然而关于其微生物降解方面的研究在国内外报道的非常少，因此关于乙草胺被微生物降解和矿化的研究工作还有待于进一步加强．参45     

脂肪腈化物的微生物降解

从长期被腈化物污染的土壤中，筛选到３株对腈化物化物降解能力很强的细菌，分别为霍夫曼棒杆菌（Ｃｏｒｙｎｅｂａｃｔｅｒｉｕｍ ｈｏｆｆｍａｎｉｉ Ｂ－２１）、微黄色节杆菌（Ａｒｔｈｒｏｂａｃｔｅｒ ｆｌａｖｅｓｃｅｎｓ Ｂ－２２）和克雷伯氏杆菌（Ｋｌｅｂｓｉｅｌｌａ ｓｐ．Ｐ－２１）。该菌可将乙腈（Ａｃｅｔｏｎｉｔｒｉｌｅ）、丙腈（Ｐｒｏｐｉｏｎｉｔｒｉｌｅ）、丁腈（Ｂｕｔｙｒｏｎｉｔｒｉｌｅ）和丙烯     

中国土地荒漠化／土地退化的防治与环境保护

荒漠化是当今全球最严重的环境问题之一。结合中国国情来看，荒漠化不仅发生于干旱、半干旱地区；也发生于湿润、半湿润地区。中国已存在的荒漠化土地面积１１１．７万ｋｍ￣２，占国土面积的１１．６％；其中风力作用、水蚀作用和物理及化学作用下的荒漠化土地约各占１／３。另外中国还有易受风力和水力作用影响的潜在荒漠化土地５３．５万ｋｍ￣２和８７．５万ｋｍ￣２，潜在盐渍化土地１７．３万ｋｍ￣２。中国土地荒漠化是在脆弱生态条件下，人口过快增长，人为不合理的经营活动如水资源利用不当、过度开垦、过度放牧、过度樵采，以及工矿建设造成的土地与植被破坏、环境污染等所致，对它的防治实质上就是对退化环境的整治。中国荒漠化土地经过近几十年来的治理，个别地区有所好转，但总体上仍在发展中，因而它是环境保护与持续发展中的重要问题，必须引起重视。在总结中国防治荒漠化经验的基础上，提出了防治荒漠化的基本对策。     

好氧颗粒污泥处理高浓度氨氮废水的研究

在不同接种源污泥颗粒化过程中污泥理化性状对比研究的基础上,采用成熟好氧颗粒污泥处理高浓度氨氮废水,对其脱氮行为以及不同C/N条件下好氧颗粒污泥微生物的比耗氧速率、好氧颗粒污泥对氨氮的比降解速率随时间的变化等进行了研究.实验结果表明,在进水氨氮质量浓度较高(480 mg/L)、温度30℃左右的条件下,稳定运行15 d,氨氮的去除率维持在85%左右;进水氨氮的浓度越高,随着微生物对环境的逐渐适应,硝化菌的活性也逐步增加;随着进水氨氮浓度的提高,好氧颗粒污泥对氨氮的比降解速率也逐渐上升.     

Phytoremediation of petroleum hydrocarbons in tropical coastal soils II. microbial response to plant roots and contaminant

GOAL, SCOPE AND BACKGROUND: The goal of this study was to understand the interaction between plants and microorganisms during petroleum-hydrocarbon bioremediation in Pacific Islands coastal soils. Total bacteria and hydrocarbon-degrading microorganisms population dyanamics were examined in the rhizospheres of tropical trees and shrubs, which were evaluated for their phytoremediation potential in a greenhouse experiment. The respective and combined effects of plant roots and diesel contaminant on the microbial populations were determined in relation to diesel fuel depletion. An increase in the grading populations size of the hydrocarbon-degrading populations of microbes, elicited by rhizodeposition, is generally regarded as conducive to an enhanced degradation of petroleum hydrocarbon pollutants in vegetated soil. METHODS: The soil was a coastal sandy loam (pH 7.8) which was artificially contaminated with 10 g of No. 2 diesel fuel/kg soil or left uncontaminated. The pots were irrigated with fertilizer and 1% NaCl. The enumerations were carried out in the contaminated and uncontaminated rhizospheres of three trees, kiawe (Prosopis pallida), milo (Thespesia populnea), and kou (Cordia subcordata) and three shrubs, beach naupaka (Scaevola sericea), false sandalwood (Myoporum sandwicense), and oleander (Nerium oleander). Unplanted control soils were included in the experiment. Total bacteria and phenanthrene-degrading bacteria were enumerated on plates. Diesel- and pristane-degrading microorganisms were enumerated by the most-probable-number technique in tissue-culture plates. RESULTS AND DISCUSSION: All four types of microorganisms responded to the rhizosphere of the 6 plants in uncontaminated soil and to the diesel contaminant in unplanted soil. In contaminated rhizospheres, no effect of the plant on the hydrocarbon-degrader numbers was visible. Total bacteria responded more to the plant roots than to the contaminant. The phenanthrene-degrading bacteria and pristane-degrading microorganisms were more influenced by the contaminant than by the plants. The diesel-degrading microorganisms were equally stimulated by the plants and the contaminant. The numbers of hydrocarbon degraders were similar in the contaminated rhizospheres of the three effective plants (kiawe, kou, and milo) and in those of the three ineffective shrubs. CONCLUSION: The results suggest the quality of the rhizodeposition is plant-dependent and governs the type of diesel-degrader populations that will be enhanced by a given plant. RECOMMENDATIONS AND OUTLOOK: In the proposed phytoremediation-benefit model plant roots maintain high levels of hydrocaron degraders in uncontaminated soil. When the root enters a contaminated zone of soil, those hydrocarbon degraders that prefer the contaminant would switch to the contaminant as a carbon source, effectively removing the hydrocarbons. If the root exudates and the contaminant are equally attractive to the hydrocarbon degraders, the contaminant degradaton would be less effective.     

水葫芦对萘的降解作用研究

分别在静态和动态两种条件下 ,以水葫芦为对象 ,对水生植物净化塘处理萘污水进行研究。结果表明 ,在静态试验中 ,水葫芦净化塘对浓度为 2 5、6 5和 16 1mg L萘污水的 7d净化率分别为 97 1%、93 7%和 90 4 %。动态试验中 ,相同浓度萘污水 7d后的出水净化效率分别为 99 2 %— 99 9%、97 3%— 98 6 %和 94 6 %— 96 7%。进水浓度分别为1 2mg L和 6 5mg L萘污水在水葫芦净化塘中的最佳停留时间分别为 5d和 7d ,水葫芦净化塘动态过程的净化效率高于静态过程     

Anaerobic digestion of livestock and poultry manures spiked with tetracycline antibiotics

Abstract

We investigated the anaerobic degradation of tetracycline antibiotics (tetracycline [TC], oxytetracycline [OTC] and chlortetracycline [CTC]) in swine, cattle, and poultry manures. The manures were anaerobically digested inside polyvinyl chloride batch reactors for 64?days at room temperature. The degradation rate constants and half-lives of the parent tetracyclines were determined following first-order kinetics. For CTC the fastest degradation rate was observed in swine manure (k?=?0.016?±?0.001 d^?1; half-life = 42.8?days), while the slowest degradation rate was observed in poultry litter (k?=?0.0043?±?0.001 d^?1; half-life = 161?days). The half-lives of OTC ranged between 88.9 (cattle manure) and 99.0?days (poultry litter), while TC persisted the longest of the tetracycline antibiotics studied with half-lives ranging from 92.4?days (cattle manure) to 330?days (swine manure). In general, the tetracyclines were found to degrade faster in cattle manure, which had the lowest concentrations of organic matter and metals as compared to swine and poultry manures. Our results demonstrate that tetracycline antibiotics persist in the animal manure after anaerobic digestion, which can potentially lead to emergence and persistence of antibiotic resistant bacteria in the environment when anaerobic digestion byproducts are land applied for crop production.     

TiO2/GeO2复合膜光催化氧化降解农药废水的研究

提出了一种新的TiO₂/GeO₂复合膜圆形光催化氧化反应器，研究了该反应器对经物化处理后的农药废水进行降解的过程。研究表明，光催化氧化的最佳条件是锌片镀TiO₂/GeO₂复合膜、pH=6.7、过氧化氢（H₂O₂）浓度为400 mg/L。并对其他氧化剂对该过程的影响进行了探讨。有机废水通过该反应器处理后，其COD值降为57mg/L。能使有机污染物全部降解为小分子无机物，废水达到国家一级排放标准。     

电化学催化降解水中有机污染物的研究进展

电化学法催化降解废水中的有机污染物已引起广泛兴趣。在电极的作用下 ,电化学反应和化学催化作用结合 ,可导致有机分子的电催化降解。选用合适的电极材料可以加速电化学反应速率 ,有助于有机物的电化学转化。本文讨论了提高电催化降解速率的方法 ,指出了在该领域的研究中存在的问题和发展方向