Kinetics and mechanism of hexavalent chromium removal by basic oxygen furnace slag

Basic oxygen furnace slag(BOFS) has the potential to remove hexavalent chromium(Cr(VI))from wastewater by a redox process due to the presence of minerals containing Fe2+. The effects of the solution p H, initial Cr(VI) concentration, BOFS dosage, BOFS particle size, and temperature on the removal of Cr(VI) was investigated in detail through batch tests. The chemical and mineral compositions of fresh and reacted BOFS were characterized using scanning electron microscope(SEM) equipped with an energy dispersive spectrometer(EDS)system and X-ray diffractometer(XRD). The results show that Cr(VI) in wastewater can be efficiently removed by Fe2+released from BOFS under appropriate acidic conditions. The removal of Cr(VI) by BOFS significantly depended on the parameters mentioned above. The reaction of Cr(VI) with BOFS followed the pseudo-second-order kinetic model. Fe2+responsible for Cr(VI) removal was primarily derived from the dissolution of Fe O and Fe3O4 in BOFS. When H2SO4 was used to adjust the solution acidity, gypsum(Ca SO4·2H2O)could be formed and become an armoring precipitate layer on the BOFS surface, hindering the release of Fe2+and the removal of Cr(VI). Finally, the main mechanism of Cr(VI) removal by BOFS was described using several consecutive reaction steps.     

Mechanism of Methylene Blue adsorption on hybrid laponite-multi-walled carbon nanotube particles

The kinetics of adsorption and parameters of equilibrium adsorption of Methylene Blue(MB)on hybrid laponite-multi-walled carbon nanotube(NT)particles in aqueous suspensions were determined.The laponite platelets were used in order to facilitate disaggregation of NTs in aqueous suspensions and enhance the adsorption capacity of hybrid particles for MB.Experiments were performed at room temperature(298 K),and the laponite/NT ratio(X_l)was varied in the range of 0–0.5.For elucidation of the mechanism of MB adsorption on hybrid particles,the electrical conductivity of the system as well as the electrokinetic potential of laponite-NT hybrid particles were measured.Three different stages in the kinetics of adsorption of MB on the surface of NTs or hybrid laponite-NT particles were discovered to be a fast initial stage Ⅰ(adsorption time t=0–10 min),a slower intermediate stage Ⅱ(up to t=120 min)and a long-lasting final stage Ⅲ(up to t=24 hr).The presence of these stages was explained accounting for different types of interactions between MB and adsorbent particles,as well as for the changes in the structure of aggregates of NT particles and the long-range processes of restructuring of laponite platelets on the surface of NTs.The analysis of experimental data on specific surface area versus the value of X_l evidenced in favor of the model with linear contacts between rigid laponite platelets and NTs.It was also concluded that electrostatic interactions control the first stage of adsorption at low MB concentrations.     

城市土壤吸附重金属动力学特征及其与土壤理化性质的关系

以长春市土壤为对象,既研究了长春市土壤理化性质特征,又采用间歇法研究了城市土壤吸附重金属Pb、Cd和Cu动力学特征及其两者之间的关系。结果表明：长春市土壤pH接近于中性或者偏碱性;土壤碳酸钙、有机质含量升高;土壤砂粒化;土壤CEC和Eh具有逐渐降低的趋势。土壤吸附重金属动力学过程包括快速阶段和慢速阶段,不同重金属在不同吸附阶段吸附速率明显不同。双常数速率方程和Elovich方程基本上可以描述土壤对Pb、CA和Cu吸附的动力学过程。pH、碳酸钙和砂粒含量是影响Pb吸附速率的主要因子;碳酸钙含量是影响CA吸附速率的主要因子。     

反硝化生物滤池的挂膜与启动

研究了反硝化生物滤池的挂膜与启动过程,为反硝化生物滤池的挂膜过程提供理论依据。在滤速1．2ngh（HRT=20min）时,当反硝化生物滤池运行到第25天时,进水硝态氮质量浓度由50mg／L左右下降到25mg／L左右时,硝态氮去除负荷由1．18kg／（m^3·d）下降到1．10kg／（m^3·d）,负荷变化很小,说明挂膜成功。在反硝化生物滤池中,氨氮主要由反硝化细菌的合成作用去除,去除率不高。在碳源和硝态氮浓度都充足的情况下,反硝化反应遵循零级反应动力学规律,反硝化速率与污染物浓度无关,只与反硝化菌的数量有关。     

专性好氧菌降解苯胺废水的动力学研究

研究了苯胺在专性好氧菌Ｏｃｈｒｏｂａｃｔｒｕｍａｎｔｈｒｏｐｉ(人苍白杆菌)作用下的降解规律,讨论苯胺初始浓度及菌种接种量对苯胺降解速率的影响,当初始浓度低于８００ｍｇ／Ｌ时降解速率随浓度增加而加快,高于１０００ｍｇ／Ｌ时则表现出抑制作用;在可降解浓度范围内,该专性好氧菌能将苯胺完全降解而消除其污染;此外,通过对解降过程动力学实验数据的分析计算,得出苯胺的降解反应在不同浓度范围内分别表现为零级或一级关系      

高浓度酚水的湿式氧化研究

在1L高压釜中进行了高浓度苯酚水溶液的间歇湿式氧化实验研究。原水COD_cr为7804～87002mg／L,反应温度150～250℃,氧分压0．7～5．0MPa。结果表明湿式氧化对进水浓度的适应性强,有机物分解快。经30min氧化,COD_cr降低52．9％～90％,苯酚分解86％～99％。表观动力学分析表明反应速度与COD_cr和氧分压分别呈0．873和0．244次方关系,反应活化能为29．43kJ／mol。      

活性污泥生物反应动力学模型研究

介绍了在进行活性污泥法过程模型化研究中,通过对国内外现有成果改进和强化,所建立的结构化生物反应动力学模型。文中提出了建模的系统化方法;采用概念模型图示和矩阵表达法简明清晰地表述了模型化的思路和全部定性定量信息;并简要地介绍了模型参数估值的试验方法及估值结果。      

水溶液中甲基橙的超声化学降解动力学研究

研究了水溶液中甲基橙的超声化学降解动力学。结果表明 ,水溶液中甲基橙可通过超声化学方法降解 ,降解动力学为一级反应 ,降解速率常数为 -2 .2 5× 10 - 3m in- 1。甲基橙降解速率随初始浓度的升高而降低 ,随介质温度的下降而升高 ,随介质酸度的变化而变化。 H2 O2 、F e2 +和 I- 等自由基促进剂可有效加速甲基橙的降解     

含氨基酸的润滑油生物降解性及降解速率方程模拟

在HVI 350矿物润滑油中加入少量月桂酰基甘氨酸,对比研究了加入月桂酰基甘氨酸前后矿物润滑油在土壤中的生物降解特性,并采用指数速率模型对润滑油生物降解动力学进行了模拟.结果表明,月桂酰基甘氨酸可促进HVI 350矿物润滑油生物降解,试验条件下HVI 350矿物润滑油生物降解速率方程为S_t=50.4e~(-0.0155t),半衰期为44.72 d;含月桂酰基甘氨酸的HVI 350矿物润滑油生物降解速率方程为S_t=51.6e~(-0.0224t),半衰期为30.94d.     

Zinc kinetics in the ant Myrmica rubra originating from a metal pollution gradient

Ants are efficient trace metal accumulators, but metal kinetics in ants has not been described. Workers of Myrmica rubra collected in seven meadows along a metal pollution gradient were exposed to dietary Zn (1000 mg kg⁻¹) for a 80 day uptake period followed by 30 days of clean food. Zn concentrations in the ants from all study sites were found to have been maintained on a stable level, indicating very efficient Zn regulation. No proof of adaptation in terms of enhanced elimination or restricted accumulation of Zn was found. Nevertheless, the results illustrate the general kinetics of Zn in M. rubra, irrespective of the differences between sites.