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.     

Modelling sulphate-enhanced cadmium uptake by Zea mays from nutrient solution under conditions of constant free Cd2+ ion activity

A controlled hydroponic experiment was undertaken to investigate Cd uptake in relation to the activity of Cd species in solution other than the free ion (Cd²⁺) by maintaining a constant Cd²⁺ activity under variable SO₄₂⁻ and Cl⁻ concentrations exposed to maize (Zea mays var. Cameron) plants. The objectives of these experiments were: (1) to distinguish and quantify the different uptake rates of free and inorganic-complexed Cd from nutrient solution, and (2) to model the uptake of Cd by maize with a Biotic Ligand Model (BLM) in a system which facilitates the close examination of root characteristics. Results of the current experiments suggest that, in addition to the free ion, CdSO₄⁰ complexes are important factors in determining Cd uptake in nutrient solution by maize plants. Higher nominal SO₄²⁻ concentrations in solution generally resulted in a greater Cd accumulation by maize plants than predicted by the Cd²⁺ activity. A better integration of the complete dataset for the 3 harvest times (6, 9 and 11 days after treatment) was achieved by including consideration of both the duration of Cd exposure and especially the root surface area to express Cd uptake. Similarly, the fit of the BLM was also improved when taking into account exposure time and expressing uptake in terms of root morphological parameters.     

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.     

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.     

以FA与FNA为控制因子的短程硝化启动与维持

为了实现污泥消化液旁侧脱氮,降低主处理区进水氮负荷,试验采用A/O工艺研究消化污泥脱水液短程硝化启动与维持,在常温、长SRT、较高DO条件下,逐步提高进水ALR(以N计)从0.23 kg/(m³·d)到0.78　kg/(m³·d),强化FA对NOB的抑制作用,成功启动了短程硝化.针对废水碱度不足的水质特征,利用FA与FNA的联合抑制使短程硝化得到稳定维持,在稳定运行的30　d内NO^-₂-N积累率一直保持在90%以上.在此期间反应器平均DO浓度一直保持在2 mg/L以上,即使平均DO浓度提高到4.8 mg/L左右,也未出现NO^-₂-N积累率降低,说明利用上述手段维持的短程硝化具有抵抗高DO冲击能力.通过降低进水ALR,导致反应器后段FNA浓度增加,强化了FNA的抑制作用,虽然FA的抑制作用降低,短程硝化仍然连续运行达2个月,当反应器后段FNA的抑制作用撤除后,短程硝化在3　d后被彻底破坏,充分证明了FNA对NOB抑制作用及其对维持本系统短程硝化所起的重要作用.     

不同水分管理方式下水稻生长季N2O排放量估算：模型验证和输入参数检验

利用2005～2007年我国稻田N₂O排放通量的田间原位测定资料和国际上其它地区稻田N₂O报道结果,对作者建立的不同水分管理方式下水稻生长季N₂O排放估算模型进行了验证. 结果表明,持续淹水稻田N₂O排放的拟合结果与其他地区淹水稻田N₂O通量值相一致. 淹水-烤田-淹水的水分管理方式下,稻田N₂O排放的拟合值接近于国际上同类研究结果. 淹水-烤田-淹水-湿润灌溉的水分管理方式下,稻田N₂O排放的估算模型对田间原位测定资料有很好的适切性. 为了检验模型输入参数的可信度,将本研究建立的有关我国水稻生产的相关资料数据库与以往研究报道结果进行了比较,结果表明,两者具有高度的一致性. 数据库资料表明,在20世纪50～70年代间,持续淹水稻田占20%～25%,大约75%～80%的稻田采用淹水-烤田-淹水的水分管理方式. 在20世纪80～90年代间,采用持续淹水,淹水-烤田-淹水和淹水-烤田-淹水-湿润灌溉水分管理方式的稻田分别约占12%～16%、 77%和7%～12%. 20世纪50年代水稻生长季平均每季总施氮量为87.49 kg·hm^-2,而90年代平均为224.64 kg·hm^-2. 其中,化学氮肥的施用量从20世纪50年代的37.4 kg·hm^-2增加到了90年代的198.8 kg·hm^-2,分别占水稻生长季氮输入总量的43%和88%. 在20世纪50～70年代间有机氮的输入量相对比较稳定,平均变幅在45.2～48.2 kg·hm^-2之间,随后逐步降低,有机肥料氮占氮输入总量的比例从20世纪50年代的52%降低到了90年代的9%. 作物残体N输入量从20世纪50年代的4.9 kg·hm^-2增加到了80年代的6.3 kg·hm^-2. 20世纪50～70年代水稻生长季氮肥施用量具明显的空间变异性,而80～90年代间其空间变异较小. 模型验证和输入参数检验的结果表明,该模型能较好地模拟我国不同水分管理方式下的稻田N₂O直接排放量.     

质粒pJP4水平转移介导生物膜系统强化降解2,4-D效应

以携带质粒pJP4[其上含编码2,4-二氯苯氧基乙酸(2,4-dichlorophenoxyacetic acid,2,4-D)降解功能的基因簇(tfd)]的基因工程菌Pseudomonas putida SM1443::gfp2x(pJP4::dsRed)为供体菌,以生物膜系统为对象,通过半连续流实验研究了质粒pJP4水平转移介导基因强化降解2,4-D效应,考察了目标基因在系统中存在状况及基因强化对系统菌群结构的影响.结果表明,以2,4-D(初始浓度为170 mg/L±10 mg/L)为唯一碳源,向生物膜系统加入携pJP4质粒的基因工程菌对2,4-D的降解具有促进作用,运行初期,促进作用较弱,随着半连续流反应的进行,促进作用显著增强,基因强化系统较对照系统对2,4-D的平均降解速率之差达13.3 mg/(L.h).通过对基因强化系统功能基因片段tfdB基因及报告基因gfp的跟踪检测,证实了在pJP4质粒介导下生物膜系统基因水平转移的发生.PCR-DGGE结果表明基因强化的生物膜系统较对照系统在受到2,4-D冲击条件下保持了相对更加稳定的菌群结构.     

壳聚糖吸附酸性大红及Cu2+对吸附的增强作用

采用壳聚糖去除水中酸性大红,对壳聚糖吸附酸性大红的动力学、热力学以及溶液pH、盐浓度、外来Cu2+对吸附的影响进行了研究.准二级吸附动力模型、Langmuir、Freundlich及Dubinin-Radushkevich (D-R)方程分别用来对吸附动力学和等温线进行分析.结果表明,酸性大红在壳聚糖上的吸附是一个化学吸附控制的准二级动力学过程.Langmuir、Freundlich和D-R方程都能较好地描述吸附等温线.溶液pH和温度对吸附有较大影响,而氯化钠浓度对吸附的影响较小.对吸附热力函数的计算结果显示ΔH0<0,表明吸附是一个放热过程.由D-R方程计算的吸附自由能E为9.5~10.7 kJ.mol-1,表明吸附过程为离子交换化学吸附.Cu2+对吸附的影响结果显示Cu2+能显著提高壳聚糖对酸性大红的吸附容量,另外建立了Cu2+浓度与吸附量增加之间的数学模型.     

高分子重金属絮凝剂MAPEI处理含汞废水

以聚乙烯亚胺、巯基乙酸为原料,通过酰胺化反应合成了一种新型高分子重金属絮凝剂--巯基乙酰聚乙烯亚胺(MAPEI),研究其处理含汞废水的性能,并对几个影响因素进行了考察.实验结果表明:①该絮凝剂对Hg2+有很好的捕集功能,其中2万分子量的MAPEI去除率最高;②pH值会影响Hg2+的去除;③碱金属和碱土金属离子对Hg2+的去除有促进作用;④C1-、NO3-可促进对Hg2+的去除,而SO2/4-对Hg2+的去除有抑制作用;⑤Hg2+和致浊物质共存时,会相互促进彼此的去除;⑥Hg2+和致浊物质共存时,MAPEI对Hg2+的去除率比TGA的去除率高.