Efficient adsorption of Mn(Ⅱ) by layered double hydroxides intercalated with diethylenetriaminepentaacetic acid and the mechanistic study

In this study, greatly enhanced Mn(II) adsorption was achieved by as-synthesized diethylenetriaminepentaacetate acid intercalated Mg/Al layered double hydroxides(LDHsDTPA). The adsorption capacity of LDHs-DTPA was 83.5 mg/g, which is much higher than that of LDHs-EDTA(44.4 mg/g), LDHs-Oxalate(21.6 mg/g) and LDHs(28.8 mg/g). The adsorption data of aqueous Mn(II) using LDHs-DTPA could be well described by the pseudosecond order kinetics and Langmuir isotherm model. Thermodynamics study results also showed that the adsorption process of Mn(II) by LDHs-DTPA was exothermic as indicated by the negative ΔH value. Furthermore, based on the structural, morphological and thermostable features, as well as FT-IR and XPS characterizations of LDHs-DTPA and the pristine LDHs, the adsorption mechanism of Mn(II) was proposed. The carboxyl groups of DTPA were proposed to be the main binding sites for Mn(II), and the hydroxyl groups of LDHs also played a minor role in the adsorption process. Among the three common regeneration reagents, 0.1 mol/L Na_2CO_3 was the best for reusing LDHs-DTPA in Mn(II)adsorption. Besides, the Mn(II) adsorption performance could be hindered in the presence of typical inorganic ions, especially cations. Further specific modifications of LDHs-DTPA are suggested to get more selective adsorption of Mn(II) in practical applications.     

武汉东湖部分原生动物种类污染值的建立

利用对武汉东湖进行的为期１ 年的原生动物采集及鉴定结果以及同时进行的水质化学测试结果,对所建立的原生动物生物指数进行了验证,表明所得ＣＰＶ与化学综合污染指数呈显著的相关,说明建立的生物指数对淡水水系有广泛的实用性．对汉江中没有观察到的某些原生动物建立了其种类污染值     

Hydroxyl, hydroperoxyl free radicals determination methods in atmosphere and troposphere

The hydroxyl radical (?OH) has a crucial function in the oxidation and removal of many atmospheric compounds that are harmful to health. Nevertheless, high reactivity, low atmospheric abundance, determination of hydroxyl, and hydroperoxyl radical's quantity is very difficult. In the atmosphere and troposphere, hydroperoxyl radicals (HO₂) are closely demanded in the chemical oxidation of the troposphere. But advances in technology have allowed researchers to improve the determination methods on the research of free radicals through some spectroscopic techniques. So far, several methods such as laser-induced fluorescence (LIF), high-performance liquid chromatography (HPLC), and chemical ionization mass spectroscopy have been identified and mostly used in determining the quantity of hydroxyl and hydroperoxyl radicals. In this systematic review, we have advised the use of scavenger as an advance for further researchers to circumvent some of these problems caused by free radicals. The primary goal of this review is to deepen our understanding of the functions of the most critical free radical (?OH, HO₂) and also understand the currently used methods to quantify them in the atmosphere and troposphere.     

机物料中溶解性有机质对土壤吸附除草剂的抑制作用

溶解性有机质(DOM)是陆地及水生生态系统中十分活跃的组分,对有机污染物质的环境行为 (如毒性、迁移转化及生物可降解性等)有着重要的影响,而施用有机物料会释放大量的DOM.采用批量平衡法研究了水稻秸秆腐解产生的溶解性有机质对苄嘧磺隆(BSM)在土壤中吸附行为的抑制作用.结果表明,线性方程能很好地描述BSM在土壤中的吸附行为;添加DOM降低了BSM在土壤中的分配系数即logKd值,其logKd值与对照(不加DOM)间存在极显著差异(P<0.01),秸秆腐解时间越长,logKd值越小;亲水组分和疏水组分在DOM抑制土壤吸附BSM中起着不同的作用;BSM在土壤上的吸附自由能小于40 kJ·mol-1,推测BSM在土壤上主要以物理吸附为主,吸附机理可能有范德华力、疏水键、氢键和偶极键力,不存在化学键吸附作用.     

Characteristics of plankton Hg bioaccumulations based on a global data set and the implications for aquatic systems with aggravating nutrient imbalance

• Hg bioaccumulation by phytoplankton varies among aquatic ecosystems. • Active Hg uptake may exist for the phytoplankton in aquatic ecosystems. • Impacts of nutrient imbalance on food chain Hg transfer should be addressed. The bioaccumulation of mercury (Hg) in aquatic ecosystem poses a potential health risk to human being and aquatic organism. Bioaccumulations by plankton represent a crucial process of Hg transfer from water to aquatic food chain. However, the current understanding of major factors affecting Hg accumulation by plankton is inadequate. In this study, a data set of 89 aquatic ecosystems worldwide, including inland water, nearshore water and open sea, was established. Key factors influencing plankton Hg bioaccumulation (i.e., plankton species, cell sizes and biomasses) were discussed. The results indicated that total Hg (THg) and methylmercury (MeHg) concentrations in plankton in inland waters were significantly higher than those in nearshore waters and open seas. Bioaccumulation factors for the logarithm of THg and MeHg of phytoplankton were 2.4–6.0 and 2.6–6.7 L/kg, respectively, in all aquatic ecosystems. They could be further biomagnified by a factor of 2.1–15.1 and 5.3–28.2 from phytoplankton to zooplankton. Higher MeHg concentrations were observed with the increases of cell size for both phyto- and zooplankton. A contrasting trend was observed between the plankton biomasses and BAF_MeHg, with a positive relationship for zooplankton and a negative relationship for phytoplankton. Plankton physiologic traits impose constraints on the rates of nutrients and contaminants obtaining process from water. Nowadays, many aquatic ecosystems are facing rapid shifts in nutrient compositions. We suggested that these potential influences on the growth and composition of plankton should be incorporated in future aquatic Hg modeling and ecological risk assessments.     

固定化解脂耶氏酵母处理油脂废水研究

利用海藻酸钙包埋固定的解脂耶氏酵母(Yarrowia lipolytica)分别降解以色拉油为惟一碳源和以葡萄糖为惟一碳源的污水,结果表明,在最佳处理条件下,固定化细胞在50 h内,能较好地降解废水中浓度为2 000 mg/L的色拉油和浓度为2 000 mg/L 的COD,降解率都在80%以上;固定化细胞对色拉油、COD降解效率随着时间的延长而增加、随着底物浓度的增加而下降;与未固定菌株相比,固定化细胞有着更好的储存稳定性和可重复使用性,结果进一步提示固定化解脂耶氏酵母适于含油废水以及高COD含量的生活污水处理。     

中空纤维微滤膜污染及阻力分析

选用0．1μm的PVDF中空纤维内压式微滤膜组件，在死端微滤工况下，研究了酵母（平均粒径5．3μm）和高岭土（平均粒径0．7μm）体系在浓度和压力变化时的污染机理及过滤阻力、膜渗透通量的变化规律性。通过恒压堵塞定律积分式的具体形式与实验数据的拟合及根据堵塞过滤定律计算的结果都表明：死端微滤时，酵母体系和高岭土体系均符合滤饼过滤机理。     

船舶柴油机选择性催化还原积碳臭氧直接氧化再生

为解决船舶柴油机SCR催化剂积碳再生问题,提出了臭氧直接氧化再生的方法。实验用玻璃纤维无胶滤筒采集PM,然后在管式炉中用臭氧氧化滤筒中的PM,研究了温度和臭氧浓度对PM氧化的影响。实验表明,臭氧的最佳氧化温度窗口为200~240℃,PM氧化速度随臭氧浓度提高明显加快,PM氧化率可以达到92%以上。根据实验结果,提出了船舶柴油机SCR积碳O3低温再生技术方案。     

响应曲面法优化絮凝处理木薯淀粉废水

采用中心复合实验设计和响应面分析法研究复合絮凝剂聚合氯化铝锌(PAZC)和聚合氯化铝(PAC)混凝处理木薯淀粉废水,进行设计和分析,以溶液pH值和絮凝剂用量为考察因素,分别以COD、浊度去除率为考察指标,选用最佳优化数学模型描述考察指标和考察因素之间的数学关系,并以设定PAZC和PAC对COD去除率(65%),浊度去除率(90%)和SS去除率(90%)的目标值,通过等高线叠加图预测最优实验条件,得到PAZC投量为6.5 mg/L,pH为7.7时,COD去除率和浊度去除率分别达到最大为76.6%和99.9%;PAC投量为19.2 mg/L,pH为7.8时,COD去除率和浊度去除率最大值分别为64.4%和97.1%。经对最优条件进行验证,预测值与验证实验平均值接近。