渗透是一种利用渗透原理的新兴膜技术,近年来在国内外受到了广泛的关注。解析该过程中溶剂水的传递和驱动溶质的反向传递对其发展和应用至为关键。首先开展了两种膜的取向下,正渗透过程中的水通量和溶质反向摩尔通量的实验研究。当驱动溶液在膜分离层侧时,水通量更高,而溶质反向摩尔通量更低,表明水的传递对溶质的反向传递有限制作用。而后分别考察了不同的单一溶质和二元混合溶质作为驱动溶质时,水和溶质的传递现象。当单一中性溶质或电解质作为驱动溶质时,水通量和溶质反向摩尔通量均随驱动溶液浓度的升高而增大;在相同操作条件下,驱动溶质的扩散系数越小,溶质反向摩尔通量越小;中性溶质与电解质混合溶液为驱动溶液时,溶质分子之间存在耦合传递效应。

As a novel technology using the principle of osmosis, forward osmosis has drawn worldwide attentions in recent years. Understanding the simultaneous water transport and solute reverse transport in the forward osmosis processes is essential to the development and application of this emerging technology. In this study, the effects of two membrane orientations on solute reverse molar flux and water flux were investigated. The water flux in the mode of active layer facing draw solution was higher than that in the mode of active layer facing feed solution, whereas solute reverse molar flux presented a contrary result, which indicated that transport of water would restrict the reverse transport of solute. The effects of different types of solute, including one single solute and two-component mixed solutes, on solute flux and water flux were also investigated. Water flux and solute reverse molar flux increased with increasing draw solution concentration when using single neutral solute or ele

为探索土壤环境中尺度效应对溶质运移的影响,建立了瞬时输入条件下考虑尺度效应的溶质运移模型。通过Laplace变换和复变函数理论得到了模型的解析解,并利用解析解分析了弥散尺度效应对溶质运移过程的影响。结果表明:随着土壤弥散尺度效应的增强,土壤中溶质浓度分布范围越广,浓度峰运移的距离越大,但浓度峰值越小;随着入口弥散系数(D0)的增加,溶质运移的范围更大,溶质浓度峰值越小,但浓度峰运移的距离几乎没有变化;随着入口孔隙水流速度(v0)的增加,溶质浓度峰运移的距离越大,溶质的运移锋面越远,而溶质浓度峰值及溶质浓度分布范围几乎没有变化。用一维8 m长土柱中的溶质运移试验资料对所推解析解进行验证,模拟结果与试验结果吻合较好,决定系数可达0.95以上。结果表明所推得的解析解可用来模拟预测较大尺度上溶质运移过程,为土壤环境治理等实际工程提供理论依据。

Solute transport in soil and groundwater is important for water resources management, crop production, and groundwater quality control. Accurate prediction of the transport of solutes is crucial to the effective management of these processes. Traditionally, transport is described with the convection-dispersion equation (CDE) with constant coefficients, but practical problems generally involve non-uniform velocity fields and variable diffusion coefficients due to the complex nature of medium heterogeneity on different scales. Therefore, this study investigated the solute transport behavior along an unsteady flow domain through heterogeneous porous media, and presented a one-dimensional scale-dependent solute transport model, considering linear equilibrium sorption with an instantaneous source in a semi-infinite porous media in order to get a better understanding of the solute transport in soil. The proposed model was analytically solved by using the Laplace transformation technique, wit

旨在建立冷冻浓缩过程冰晶生长的数理模型,用以微观上分析冰晶夹带造成液态食品中溶质损失的问题。探讨结晶时间对冰晶形貌的影响。采用国内外描述相变微观结构的相场模型,将液态食品体系视为水和溶质二元结构,模拟冰晶生长的演变过程。研究等温结晶情况下,计算时间对冰晶生长形貌的影响及其对冰晶内部溶质浓度分布的影响。模拟结果表明,随着时间的延长,冰晶形貌逐渐变大,主干变细,二次分枝乃至三次分枝更加发达;同时,冰晶所包含的溶质浓度越大,各区域的溶质浓度分布也随之改变。由于溶质再分配,冰晶溶质分布曲线存在着波峰与波谷,波峰对应着来不及扩散溶质的冰晶尖端,波谷对应着冰晶固相。结果启示,在等温情况适当控制结晶时间将有效控制冷冻浓缩过程冰晶的形貌演化,降低液态食品冷冻浓缩过程的溶质损失。为进一步研究各种因素对冰晶生长的影响提供理论依据,从而为改进冷冻浓缩工艺、推进其工业化提供技术支持。

The quality of products produced through freeze concentration is better than that produced through evaporation concentration and has lower energy consumed. But freeze concentration has been limited for industrial production because of the loss of soluble solids caused by ice crystal entrainment. Reducing the ice crystal entrainment and losses is critical for industrial production of freeze concentration. The breakthrough is to control ice crystal growth behavior. In order to develop a freeze concentration process mathematical model for simulating the evolution of ice crystal growth from the microscopic structure, through regarding liquid food as water and solute in binary system, the phase-field model theory was applied, liquid food system was treated as water and solute in binary system. The effects of ice crystal growth and solute concentration distribution over crystallized time were studied. Results showed that the crystallized time could affect the growth of lateral branch. Ice cr

总结了周期表元素与Pd的相互作用,按富Pd合金的相图特征,采用经典合金化理论和米德玛键参数分析了固溶度的规律性。建立了周期表元素在Pd中的溶解度方程:ln Cmax=4.6052–k(|△nws1/3|–nR),溶质在Pd溶剂中的极限固溶度(ln Cmax)是Pd溶剂与溶质之间的电子密度差|△nws1/3|的减函数。当Pd溶剂与溶质之间的电子密度差|△nws1/3|相同时,简单金属溶质在Pd中的固溶度大于过渡金属溶质,简单金属和过渡金属溶质在Pd溶剂中具有不同的固溶机制。分析了以各贵金属元素作为溶剂对周期表元素的溶解能力指数与溶质元素电子密度nws1/3的关系,Pd作为溶剂对周期表元素具有最大溶解能力。

Some regularities of interactions of palladium with periodic table elements were summarized, and the solid solubilities of periodic table elements in palladium were analyzed by the classical solid solubility theory and Miedema’s bond parameters. A solubility equation, lnCmax=4.6052–k (|?nws1/3|–nR), was established, the limit solid solubility (lnCmax), of solutes in palladium increases with the electron density difference,|?nws1/3|, between them. The solid solubilities of the simple metal solutes in palladium are larger than those of transition metal solutes with same?nws1/3 based on different solubility mechanisms. The relationship of solvability ability indexes of precious metals as solvents with their electron density nws1/3 were analyzed by their electron density parameters nws1/3, and the palladium solvent has the largest solubility ability index for periodic table elements as solutes.

针对重金属铬(Cr)污染严重的现象，基于简单的二层非完全混合模型，将降雨时农田土壤与积水整个系统分为混合区及混合区以下两个部分，根据水量平衡原理和溶质质量守恒定律，研究土壤在非线性Langmuir吸附条件下，吸附性溶质 Cr(VI)的径流流失规律。试验模拟的田间地表径流是由降雨引起的，根据降雨期间土壤与雨水相互作用情况，将降雨过程分为4个阶段分别求解进行研究。利用室内模拟降雨-径流试验所得数据进行模拟计算，并通过敏感性分析和模型参数对径流流失量的影响分析，阐明模型参数对土壤中吸附性溶质径流流失规律的影响。研究结果表明：此二层非完全混合模型能预测土壤在非线性Langmuir吸附条件下，吸附性溶质Cr(VI)的径流流失规律。该模型对入渗水溶质与土壤混合层溶质之间的非完全混合系数γ非常敏感，对土壤混合层溶质与地表积水-径流水溶质之间的非完全混合系数α不敏感，对Langmuir吸附方程中的参数B、C也不敏感。其中γ和α对模拟径流流失过程的影响主要作用于降雨前期，而Langmuir吸附方程中的参数B对模拟过程的影响作用于降雨前期，C也主要作用于降雨前期，但对后期的影响比其他参数更大。试验数据显示地表径流中溶质含量很低，说明该次试验中混合层溶质进入地表积水-径流层量很少，而模拟α值很小，与实际情况吻合，同时也说明，土壤中流失的污染物重金属Cr(VI)大多存在于地下排水中。

Farmland has become less and less in China, but the heavy metal pollution is very serious recently. So, the study on the loss of adsorptive solute of six-valence chromium, i.e. Cr(VI) from soil to surface runoff becomes very important, which is of great significance to understand the expansion of heavy metal pollution in the field. The problem of chromium pollution has been a very serious and worldwide concern recently. In this paper, based on the water balance and solute mass conservation, a simple two-layer incomplete mixing model is used to study adsorptive solute of Cr(VI) loss from soil into surface runoff with nonlinear Langmuir adsorption. Based on the water infiltration, the rainfall process is divided into four stages. Experimental data under the condition of laboratory simulated rainfall-runoff is used to verify the model with nonlinear Langmuir isotherm adsorption equation. Influences of model parameters on the soil solute loss to surface runoff and model sensitivi