Modelling the biphasic sorption of simazine,imidacloprid, and boscalid in water/soil systems

The sorption kinetics of simazine (6-chloro-N,N′-diethyl-1,3,5-triazine-2,4-diamine), imidacloprid (1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine), and boscalid (2-chloro-N-(4′-chlorobiphenyl-2-yl)nicotinamide), three pesticides of wide use in agriculture, was determined in five different water/soil systems over a time interval from the initial few seconds to about 1 month. In all the experiments, sorption kinetics showed a biphasic pattern characterized by an initial, relatively short phase with a high sorption rate and a later phase with much a lower sorption rate. Initial sorption capacity increased with soil organic carbon content and with sorbate hydrophobicity. We postulate that the first phase of the process involves a fast second-order sorption reaction on superficial sites of soil particles, whereas the second phase depends on diffusion-controlled migration to internal binding sites. A kinetic equation based on this hybrid model accurately fitted all data sets. Less satisfactory results were obtained employing the pseudo-first order, pseudo-second order, Elovich, two site non-equilibrium, or Weber-Morris equation. The superior performance of the hybrid model for describing boscalid sorption probably reflects the high hydrophobic character and consequent low diffusion rates of this compound. The accuracy of modelling was in any case strongly dependent on the time interval considered.     

呼吸计量法对甲醇和葡萄糖为基质的ASM1参数测定

污水水质和污泥特性不同,活性污泥1号模型(ASM 1)参数的测定结果也不相同。研究以甲醇和葡萄糖为基质,对分别经过甲醇和葡萄糖驯化的活性污泥,通过呼吸计量法测定高食微比、中食微比和零食微比下的氧利用速率(OUR)随时间变化的曲线。确定了异养菌产率系数(YH)、异养菌最大比增长速率(μ^H)和衰减系数(bH),并根据YH、μ^H和bH的测定结果和对中食微比下OUR曲线的数值拟合确定了异养菌半饱和常数(ks)、最大比水解速率(kh)和慢速可生物降解底物水解的半饱和常数(KX)。研究结果表明,在20℃下,采用甲醇和葡萄糖为基质测得的YH、bH、μ^H、ks、KX和kh分别为0.53、0.48、5.75、0.9、0.03、3.0和0.87、1.03、2.27、4.45、0.01、7.0。YH、bH、μ^H和ks的值与ASM1中城市污水的推荐值0.67、0.62、6.0、20.0不同,反映了不同基质对参数测定结果的影响。对于慢速可生物降解有机物(Xs)含量低的水质来说,KX和kh对生化反应过程影响不大,可采用ASM1模型的推荐值。     

Mg/Fe水滑石吸附水中磷的动力学及热力学研究

以MgCl2和FeCl3为原料通过共沉淀法制备了Mg/Fe水滑石,并对其进行焙烧得到了焙烧态Mg/Fe水滑石。采用X射线衍射(XRD)和傅里叶红外光谱(FTIR)对所得产物进行了结构表征。利用焙烧前后的水滑石作吸附剂吸附处理含磷废水,比较了两者对磷的吸附能力,并在不同温度和pH条件下进行了吸附动力学实验。结果表明,焙烧前后的水滑石对磷都具有很好的吸附能力,但300℃焙烧后水滑石的吸附能力提高了约5%。动力学实验表明,水滑石对磷的吸附可很好地用准二级动力学方程进行描述,其线性相关系数达0.999以上。在15~35℃下进行了等温吸附实验,结果发现水滑石对磷的吸附更符合Langmuir方程。经热力学研究发现,标准吸附焓变(ΔH0)0J/mol、标准吸附自由能(ΔG0)0J/mol和标准吸附熵变(ΔS0)0J/(mol·K),说明水滑石对磷的吸附反应是自发的吸热反应,且是一个熵增加的过程。     

4种高级氧化法处理高浓度正丙醇废水的动力学比较

研究了1%和10%(V/V)模拟正丙醇废水在UV/TiO2体系、UV/H2O2体系、Fe2+/H2O2体系和UV/TiO2/Fe2+/H2O2体系等4种工艺条件下的降解动力学过程,对比了降解动力学特点及工艺参数对动力学常数的影响,优化工艺参数。结果表明,UV/TiO2体系和Fe2+/H2O2体系的降解过程可分为零级反应阶段和一级反应阶段,转折点分别在反应开始后2 h和氧化剂浓度为6.7 g/L,UV/H2O2体系和UV/TiO2/Fe2+/H2O2体系分别符合零级反应和一级反应规律;相同工艺参数条件下,6 h反应后,组合工艺UV/TiO2/Fe2+/H2O2体系在处理效率达85%,比前3个体系分别高52.0%、8.3%和32.0%,与UV/TiO2体系和Fe2+/H2O2体系的处理效率之和持平,其协同效应提高了速率常数,在目标物浓度降低时依然可维持较高降解速率。而目标物浓度提高10倍后,UV能量利用率提高35.5倍,氧化剂用量是Fe2+/H2O2体系的1/7.1。     

颗粒污泥沉降动力学模型研究

通过分析颗粒污泥沉降过程的特点,采用颗粒物质干涉沉降规律对颗粒污泥沉降过程进行描述·结合Allen阻力公式,建立了颗粒污泥沉降动力学模型,并用实验和文献数据对模型的可靠性进行了验证,模型预测值误差不超过土8%.应用模型对好氧颗粒污泥沉降速度的模拟实验表明,一般好氧颗粒污泥沉降速度在5～120 m/h,沉降速度随好氧颗粒污泥粒径和密度的增大而增加,沉降过程雷诺数(Re)在1～100,处于Allen阻力区.     

Effective rates of heavy metal release from alkaline wastes--quantified by column outflow experiments and inverse simulations

Column outflow experiments operated at steady state flow conditions do not allow the identification of rate limited release processes. This requires an alternative experimental methodology. In this study, the aim was to apply such a methodology in order to identify and quantify effective release rates of heavy metals from granular wastes. Column experiments were conducted with demolition waste and municipal waste incineration (MSWI) bottom ash using different flow velocities and multiple flow interruptions. The effluent was analyzed for heavy metals, DOC, electrical conductivity and pH. The breakthrough-curves were inversely modeled with a numerical code based on the advection–dispersion equation with first order mass-transfer and nonlinear interaction terms. Chromium, Copper, Nickel and Arsenic are usually released under non-equilibrium conditions. DOC might play a role as carrier for those trace metals. By inverse simulations, generally good model fits are derived. Although some parameters are correlated and some model deficiencies can be revealed, we are able to deduce physically reasonable release-mass-transfer time scales. Applying forward simulations, the parameter space with equifinal parameter sets was delineated. The results demonstrate that the presented experimental design is capable of identifying and quantifying non-equilibrium conditions. They show also that the possibility of rate limited release must not be neglected in release and transport studies involving inorganic contaminants.     

高速动能弹撞击装甲结构引起的螺栓连接失效及部件过载损伤研究

目的 验证和揭示高速动能弹对装甲结构的损伤机理。方法 聚焦高速动能弹打击装甲目标时,弹道冲击造成的靶标结构连接失效及部件过载损伤这2种损伤效应,以典型螺栓连接为研究对象,采用高速球形弹丸撞击螺栓连接结构的小尺寸试验对数值模拟方法和材料模型参数进行校验。在此基础上,采用数值模拟和冲击响应谱分析方法对高速动能弹打击全尺寸坦克进行模拟分析,获得撞击过程螺栓连接失效特征、主要影响因素及坦克典型位置部件的冲击加速度曲线和冲击响应谱曲线。结果 在小尺寸试验中,动能输入为0.042MJ时,螺栓连接未发生失效;但25.6MJ动能输入全尺寸坦克时,螺栓发生断裂而使连接失效。数值模拟结果揭示了螺栓发生断裂的主要原因。结论 输入动能大小、连接螺栓直径、模拟设备部件质量和撞击位置为螺栓是否断裂的主要影响因素。坦克某些位置的冲击响应谱曲线高于军用标准给出的临界曲线的下限甚至上限,表明这些位置的部件因高过载损伤导致失效的概率较高。     

高效纤维质降解菌处理木薯酒精废液及其厌氧发酵动力学分析

为提高木薯酒精废液中固形物的降解效率,优化木薯酒精废液的厌氧发酵特性,采用高效纤维质降解菌群作为CSTR（continuous stirred tank reactor,连续搅拌反应器）接种污泥,通过逐级提高进料负荷,研究不同容积负荷下的厌氧消化性能及相应的酶活性变化,建立了厌氧发酵过程动力学模型.结果表明,在高温（55℃）条件下经长时间稳定运行,容积负荷为14 kg/（m3·d）（以COD_Cr计）时,反应器出水ρ（TCOD）（TCOD为总化学需氧量,以COD_Cr计）和ρ（SCOD）（SCOD为溶解性化学需氧量,以COD_Cr计）分别为15 367.6、10 982.8 mg/L,TCOD去除率达到70%~75%;φ（CH₄）在48%左右,沼气产率为0.22 L/g（以每g TCOD计）;此外,木聚糖酶活性、纤维素酶活性在该条件下达到最大值,分别为42.1、30.2 U.脱氢酶活性在容积负荷为12 kg/（m3·d）时达到最大值80.1 TFμg/（h·mL）.动力学模型研究表明,最大原料产气率（y_m）为0.335 L/g（以每g TCOD计）,一级反应常数（k）为0.743 d-1,产气率为0.3 L/g,通过该模型可以得到最佳HRT（hydraulic retention time,水力停留时间）为11.5 d,最佳容积负荷为4.6 kg/（m3·d）.研究显示,在高温高容积负荷条件下,CSTR能够稳定的处理木薯酒精废液,并且能够获得较高的纤维素和半纤维素酶活性.      

组合压气机中尾迹与势流同频/异频干涉的叠加特性

为揭示多级压气机中上下游叶轮对中间叶片叠加气动影响特性,阐述不同叠加干涉情况下下游叶轮进气角度变化,采用数值方法模拟了一级轴流和一级离心组成的组合压气机非定常流场。详细讨论了上游动叶尾迹和下游动叶势流对中间导流叶栅段气流非定常流动的异频和同频叠加干涉特性,依据计算结果,直观地展示了静叶通道中两种干涉间相互激励和抑制作用的位置和时间,与数学公式的推导结果相互印证。研究结果表明:当上下游动叶对中间静叶段异频干涉时,干涉的激励、抑制区域的轴向位置随时间发生变化;当上下游动叶对中间静叶干涉频率相同时,干涉的相互激励、抑制区域的轴向位置不随时间发生变化,但干涉的激励、抑制区域的轴向位置受时序位置影响。另外,上游动叶尾迹与下游离心叶轮势流的不同叠加情况,决定着下游离心叶轮进口相对气流角的大小及波动幅值。 