Photocatalytic degradation efficiency and mechanism of microcystin-RR by mesoporous Bi₂WO₆ under near ultraviolet light

Microcystin-RR (MC-RR) is one of the most common cyanotoxin microcystins in fresh water and is of great concern due to its potential hepatotoxicity. In the present study, Bi(2)WO(6) was synthesized with a hydrothermal method by varying the pH of the reaction solution in the range of 1-11. The surface area of the catalysts decreased, but the crystallinity and crystal size increased with the pH. The adsorption and degradation capacities of the catalysts decreased with increasing the preparation solution pH. The Bi(2)WO(6) prepared at pH 1 (Bi(2)WO(6)-pH1) displayed the highest adsorption and degradation capacity to MC-RR even though it consisted of randomly aggregated particles. Nearly 100% of MC-RR at 10 mg L(-1) was removed after 30 min of irradiation of near-ultraviolet light (300-400 nm) in a solution with Bi(2)WO(6) concentration of 0.2 g L(-1). The photodegradation efficiency of Bi(2)WO(6)-pH1 was greater in acid medium than in basic solutions. Several intermediate products were observed and identified by liquid chromatography/mass spectrometry/mass spectrometry, and a unique photodegradation pathway was proposed. It was assumed that a photo-Kolbe process happened at the site carboxyl acid group of the d-Glu residue by the photogenerated holes, producing a hydroperoxyl product at m/z 513.8. This intermediate could be further decomposed to an alcohol product at m/z 505.8 and a ketone product at m/z 504.8. The aromatic ring and diene bond of the Adda chain could also be attacked by the holes and form phenol and diol products.     

Untreated coffee husk ashes used as flux in ceramic tiles

The agro-industrial activities are responsible for the production of large amounts of solid wastes, which, so far, have found scarce reuse alternatives. Among the former, coffee bean beneficiation generates an equal amount of coffee husks whose highest reuse potential is as fuel. The resulting ashes are frequently an object of illegal covert disposal and a serious source of environmental impact. However, coffee husk ashes (CHA) are particularly rich in alkaline and alkaline-earth metals, and might be adequate to replace the traditional feldspars, which are used in high content as fluxes in clay-based ceramic formulations but are becoming scarce and costly. In this work, the fluxing effect of CHA additions to an industrial clay-based mixture was evaluated. Based on the characterization results and the mullite–silica–leucite phase diagram, additions of 5 to 20 wt.% CHA were made to the clay-based mixture and the resulting compositions were evaluated after sintering at temperatures between 1100 and 1200 °C (60 min soaking time). The results obtained show that firing temperatures near 1180 °C and ~ 10 wt.% CHA addition lead to linear shrinkage, water absorption and flexural strength values that fall within the range specified by floor tile standards (NBR 13817, EN 176 and ISO 13006), requiring no significant changes in processing parameters. Coffee husk ashes can thus advantageously replace feldspars in the role of fluxing material, with the potential to reduce not only natural ceramic raw material consumption, but also production and landfill costs as well as waste disposal area requirements.     

高级氧化组合工艺协同净化微污染水的示范生产实验

为考察催化氧化-UV/H_2O_2-生物活性炭(BAC)高级氧化组合联用工艺在实际生产中对微污染水源水的的处理效能,在淮南某水厂示范工程对微污染淮河水进行了生产实验.结果表明,催化臭氧氧化-BAC组合联用工艺对水中的UV_(254)、DOC、氨氮、CODMn及THMFP均有较好的去除效果,且不会带来溴酸盐的问题.催化臭氧氧化工艺对UV_(254)、DOC、CODMn的平均去除率分别为21.8%、8.1%、10.8%.BAC对氨氮有很好的去除效果,最高去除率可达61%;对DOC和COD_(Mn)的平均去除率分别为10.4%和15.3%.催化臭氧氧化接触池对THMFP的平均去除率为34.9%,最高去除率可达53.2%.UV/H_2O_2在示范性生产实验中,对进一步提高有机物的去除能力有限;在实际生产设计中,考虑UV分解剩余臭氧的效用建议采用:催化臭氧氧化-UV-BAC-砂滤是确保饮用水出水安全可靠的高级氧化工艺必要的组合工艺模式.研究结果可为各自来水厂处理低温低浊水、提高出厂水水质以及自来水厂整体工艺的提升改造提供借鉴和参考.     

三种人工湿地填料对磷的吸附特性研究

采用等温吸附和吸附动力学实验,研究了三种人工湿地填料页岩、陶粒和砾石对磷的吸附特性。结果表明:Freundlich和Langmuir模型均能较好地拟合各填料对磷的吸附特征,各填料对磷的理论饱和吸附量大小依次为页岩(527.992 mg/kg)>陶粒(328.165 mg/kg)>砾石(129.729 mg/kg);各填料对磷的吸附过程分为快、中、慢3个阶段,三种填料对磷的吸附速率依次为页岩>陶粒>砾石;准二级动力学方程、双常数方程和Elovich方程均能较好地描述人工湿地填料对磷的吸附动力学特征,但从相关系数来看,准二级动力学方程的描述更为准确。     

Effect of addition of talc on the sintering characteristics of fly ash based ceramic tiles

The sintering characteristics of fly ash–talc mixtures having 0–100% talc (w/w) in the presence of 10% (w/w) sodium hexa meta phosphate (SHMP) have been studied. In the fly ash rich mixtures, the presence of needle shaped mullite and rhombohedral aluminum phosphate phases is responsible for providing impact strength to sintered tile bodies. On gradual addition of talc, the decrease in the concentration of sillimanite and increase in the concentration of sodium magnesium phosphate crystals is responsible for the observed improvement in the impact strength of tiles. With increase in talc content, initially the % water absorption decreases to reach a minimum for a fly ash–talc mix containing 60% (w/w talc) where after it again starts increasing. The apparent density of the tile samples increases with increasing talc content in the raw mix due to densification as well as higher density of talc as compared to fly ash.     

天津滨海新区湿地植物群落特征及植被演替过程

为了研究滨海新区湿地植物的特征和生态效益,更好的了解湿地植物群落的价值,研究了湿地植物的种类及区系组成、植物多样性及其分布、湿地植被的演替规律,研究得出本区湿地植物种类较多,共232种,科属种分布广泛,植物丰富度较高,均匀度一般,湿地植物受水盐程度影响较大,演替过程主要由水盐程度主导;水分多时向湿生水生植物演替如碱菀、芦苇等,水分少盐度高时多发生向中生盐生植物的演替如獐毛等。