Bioaccumulation of cadmium bound to humic acid by the bivalve Meretrix meretirx Linnaeus from solute and particulate pathways

Humic acid is an important pool of heavy metals in sediments.Generally,the presence of refractory humic matter in aquatic systems would decrease the bioavailability of Cd and hence control the bioaccumulation of Cd in benthic animals.In the present work,we applied a suspending system to determine the relative importance of particulate and dissolved fractions of humic acid as Cd sources for the bivalve Meretrix meretrix and to investigate the difference of bioaccumulation characteristics of Cd adsorbed on di...     

Selective removal of 2,4-dichlorophenoxyacetic acid from water by molecularly-imprinted amino-functionalized silica gel sorbent

A molecularly-imprinted amino-functionalized sorbent for selective removal of 2,4-dichlorophenoxyacetic acid(2,4-D) was prepared by a surface imprinting technique in combination with a sol-gel process.The 2,4-D-imprinted amino-functionalized silica sorbent was characterized by FT-IR,nitrogen adsorption and static adsorption experiments.The selectivity of the sorbent was investigated by a batch competitive binding experiment using an aqueous 2,4-D and 2,4-dichlorophenol(2,4-DCP) mixture or using an aqueous 2...     

纳米催化剂Pd/SnO_2的制备及催化还原硝酸盐反应的调控

采用热分解法制备了SnO2载体,并用浸渍法制备了Pd/SnO2催化剂.同时,采用X射线衍射仪(XRD)、透射电镜(TEM)、扫描电镜(SEM)及BET比表面积仪等对所制载体和催化剂材料进行了分析表征.结果表明,热分解法和浸渍法都能够获得纳米材料,SnO2及Pd/SnO2的粒径均在9～10nm左右,比表面积分别达到144.99m·2g-1和147.36m·2g-1.在以甲酸为还原剂的Pd/SnO2催化还原硝酸盐体系中,在Pd与SnO2负载比为2%～7%,反应温度为20～50℃和甲酸投加量4.0～24.0mmol·L-1的条件下,催化活性为0.70～9.48mg·min-·1g-1,且催化活性随着负载比、温度和甲酸投加量的增大而增大,随着pH的升高先升后降,最佳pH为3.反应温度升高及pH降低都能够提高Pd/SnO2的选择性.甲酸-Pd/SnO2催化还原硝酸盐体系中还原反应的调控策略为:反应温度宜控制在40～50℃内,这样可同时获得较高的催化活性和选择性,温度过高对催化活性和选择性影响很小,温度过低则会同时降低催化活性和选择性;控制pH为3时,可以获得最大的催化活性及较好的选择性,pH升高会降低Pd/SnO2的催化活性和选择性,pH降低会导致催化活性迅速降低,但对选择性影响不大;甲酸与硝酸盐的物质的量比宜大于4:1,此时可以有效地抑制pH的上升,同时获得较高的催化活性和选择性,甲酸与硝酸盐的物质的量比小于4:1时,会同时降低Pd/SnO2的催化活性和选择性.     

Degradation of acid fuchsine by a modified electro-Fenton system with magnetic stirring as oxygen supplying

The current modified electro-Fenton system was designed to develop a more convenient and e cient undivided system for practical wastewater treatment. The system adopted a cathode portion that employed magnetic stirring instead of common oxygen gas di usion or gas sparging to supply oxygen gas for the electrolyte solution. Key factors influencing the cathode fabrication and activity were investigated. The degradation of acid fuchsine with a self-made graphite-polytetrafluorethylene cathode was studied using a spectrophotometer. It was found that the cathode generated hydrogen peroxide with high current e ciency and the hydrogen peroxide yield of the cathode did not decay after 10 times reuse. With the Pt anode at a ferrous ion concentration of 0.5 mmol/L, a pH of 3, and using magnetic stirring, dye decolorization could be rapidly accomplished but the destruction of benzene rings and intermediates was fairly di cult. With a Fe anode, dye degradation was more complete.     

Catalytic performance of Fe3O4-CoO/Al2O3 catalyst in ozonation of 2-(2,4-dichlorophenoxy)propionic acid, nitrobenzene and oxalic acid in water

Fe3O4-CoO/Al2O3 catalyst was prepared by incipient wetness impregnation using Fe(NO3) 3·9H2O and Co(NO3) 2·6H2O as the precursors,and its catalytic performance was investigated in ozonation of 2-(2,4-dichlorophenoxy) propionic acid(2,4-DP) ,nitrobenzene and oxalic acid.The experimental results indicated that Fe3O4-CoO/Al2O3 catalyst enabled an interesting improvement of ozonation eciency during the degradation of each organic pollutant,and the Fe3O4-CoO/Al2O3 catalytic ozonation system followed a radical-type mechanism.The kinetics of ozonation alone and Fe3O4-CoO/Al2O3 catalytic ozonation of three organic pollutants in aqueous solution were discussed under the mere consideration of direct ozone reaction and OH radical reaction to well investigate its performance.In the catalytic ozonation of 2,4-DP,the apparent reaction rate constants(k) were determined to be 1.456×10-2 min-1 for ozonation alone and 4.740×10-2 min-1 for O3/Fe3O4-CoO/Al2O3.And O3/Fe3O4-CoO/Al2O3 had a larger Rct(6.614×10-9) calculated by the relative method than O3 did(1.800×10-9) ,showing O3/Fe3O4-CoO/Al2O3 generated more hydroxyl radical.Similar results were also obtained in the catalytic ozonation of nitrobenzene and oxalic acid.The above results demonstrated that the catalytic performance of Fe3O4-CoO/Al2O3 in ozonation of studied organic substance was universal to a certain degree.     

Removal of humic acid from aqueous solution by cetylpyridinium bromide modified zeolite

Natural zeolite was modified by loading cetylpyridinium bromide (CPB) to create more e cient sites for humic acid (HA) adsorption. The natural and CPB modified zeolites were characterized with X-ray di raction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and elemental analysis. The e ects of various experimental parameters such as contact time, initial HA concentration, solution pH and coexistent Ca2+, upon HA adsorption onto CPB modified zeolites were evaluated. The results showed that natural zeolite had negligible a nity for HA in aqueous solutions, but CPB modified zeolites exhibited high adsorption e ciency for HA. A higher CPB loading on natural zeolites exhibited a larger HA adsorption capacity. Acidic pH and coexistent Ca2+ were proved to be favorable for HA adsorption onto CPB modified zeolite. The kinetic process was well described by pseudo second-order model. The experimental isotherm data fitted well to Langmuir and Sips models. The maximum monolayer adsorption capacity of CPB modified zeolite with surfactant bilayer coverage was found to be 92.0 mg/g.     

Effect of lime application on microbial community in acidic tea orchard soils in comparison with those in wasteland and forest soils

Lime application is a conventional technology to control acidification in tea orchard soils. We investigated the e ect of lime application on soil microbial community diversity in the soils of three tea orchards, wasteland and forest. The BIOLOG data showed that both the average well color development of all carbon sources and the functional diversity index increased with the liming rate in the tea orchards and the forest, but decreased in the wasteland. The phospholipid fatty acid (PLFA) analysis showed that the structural diversity index of soil microbial community increased with the liming rate in all the tea orchards, the wasteland and the forest. Lime application also increased the soil-bacterial PLFA content in all the soils. Soil fungal and actinomycete PLFAs in the tea orchards showed an increasing trend from 0 to 3.2 g CaCO3/kg application and then a decreasing trend from 3.2 to 6.4 g CaCO3/kg application. The principal component analysis of BIOLOG and PLFA data suggested that lime application had a significant e ect on soil microbial community structure, and land use had a greater e ect on soil microbial community structure compared to lime application.     

氯对模拟管壁生物膜的氧化特性研究

以载片上培养的大肠杆菌生物膜为对象,研究了氯对模拟管壁生物膜中大肠杆菌的灭活效果,同时考察氯氧化生物膜后水中生物可同化有机碳(AOC)、生物可利用磷(MAP)和细菌生长潜能(BRP)的变化情况.结果表明,氯可以有效灭活悬浮态的大肠杆菌,而对生物膜中的大肠杆菌的灭活效率远低于悬浮菌;在相同CT值下,较高浓度的氯对悬浮态和生物膜中大肠杆菌的灭活效果要高于低浓度的氯.氯对生物膜的氧化作用会使生物膜中物质溶出,增加了水中AOC和MAP浓度,如当氯的浓度为1.0 mg/Ｌ(CT值为100 mg·min/L)时,水中AOC由20.78 μg/L增加到120.17 μg/L,MAP含量由0.11 μg/L增加到0.17 μg/L;氯的氧化作用会增加水的细菌生长潜能（BRP）,BRP随着CT值的增加而增加,如当氯投量为1.0 mg/Ｌ(CT值为100　mg·min/L)时,BRP可达到1.10×10⁷ CFU/mL.     

CSTR系统发酵产氢细菌群落动态与产氢能力关系解析

将CSTR系统内pH由4.2一次性提高至6.0左右,启动发酵类型的转化,研究了转化过程系统内的产氢动态和细菌群落.结果表明,在有机负荷维持在（33±1）kg/(m³·d)的情况下,发酵类型10 d内未发生改变,产氢量8 d内未降低,15 d后系统内种群由乙醇型转化为丁酸型,进水碱度由250 mg/L增至2 450　mg/L.研究中利用荧光原位杂交技术（FISH）对反应系统内3类微生物群进行监测发现,在转化过程中Clostridium cluster XI数量增加,Clostridium cluster Ⅰ 和Ⅱ数量减少,而Enterobacteriaceae始终存在,变化不明显.种群的消长同反应系统产氢能力的高低存在密切关联,以Clostridium cluster Ⅰ和Ⅱ占优势的乙醇型发酵具有更佳的产氢能力,平均比产氢速率为23.6 mol/(kg·d).     

碳源类型对A~2O系统脱氮除磷的影响

采用52.5 L的A2O反应器,以乙酸和丙酸分别作为进水唯一碳源,系统研究了进水碳源类型对脱氮除磷和代谢过程的影响.结果表明,在进水COD为250 mg/L左右,NH+4-N为52 mg/L左右的条件下,原水碳源类型对TN的去除影响不大,系统TN去除率均在65%左右.进水碳源类型对TP的去除及相应污泥中PHA的类型、含量和代谢及糖原的变化影响较大.乙酸为唯一碳源时,厌氧区放磷浓度较高,污泥中PHA的成分主要为PHB和PHV,两者在厌氧区的合成量差别不大,PHB在随后的反应过程中变化较大,对除磷代谢过程起主要作用,而PHV的变化较小.丙酸作为进水唯一碳源时,厌氧区的放磷浓度偏低,主要合成PHV,几乎不含PHB,PHV在随后吸磷过程中浓度变化较大,对除磷代谢起主要作用,而且出水TP浓度偏低.碳源类型对污泥中糖原的代谢也有影响,乙酸为碳源时糖原的含量高,变化范围也较大,丙酸为碳源时糖原的变化幅度较小.在同步脱氮除磷系统中,与乙酸相比,丙酸是一种更合适的碳源.