恒电荷土壤与可变电荷土壤K+的吸附特性

对我国 3种典型可变电荷土壤和 4种恒电荷土壤在不同 K 浓度和 p H下 K 的吸附特性进行了研究。结果表明 ,两类土壤 K 吸附量均随平衡 K 浓度增加而增加 ,在低浓度 (添加K 0 .1～ 1.0 mmol/ L )时两者符合线性 ,在高浓度 (添加 K 0 .5～ 5 .0 mmol/ L )下两者符合Langmuir方程。L angmuir方程的参数 K两类土壤间差异不大 ,但以可变电荷土壤 >恒电荷土壤 ,说明前类土壤 K吸附结合能较大 ,吸附 K 不易解吸 ,K 有效性较低。p H降低使土壤 K 吸附量减少 ,但恒电荷土壤与可变电荷土壤减少的机理不同 ,前者主要是由于 H 与 K 的竟争吸附 ,而后者主要是由于表面负电荷减少而引起的电性引力的改变。     

Contribution of Iron and Aluminum Oxides to Electrokinetic Characteristics of Variable Charge Soils in Relation to Surface Charge

The contribution of iron and aluminum oxides to electrokinetic characteristics of variable charge soils was studied through determination of electrophoretic mobilities of the red soils treated with either removal of iron oxides or coating of aluminum oxides,and of those deferrated under natural conditions.After removal of the iron oxides,zeta potentials of the latosol and the red earth decreased obviously with a shift of IEP to a lower pH,from 6.4 to 5.3 and 4.1 to 2.4 for the former and the latter,respectively,and the electrokinetic change for the latosol was greater than for the red earth.Zeta potentials of the kaolinite sample increased markedly after coated with iron oxides.The striking effect of iron oxides on electrokinetix properties of the soils was also demonstrated by the electrokinetic differences between the samples from the red and white zones of a plinthitic horizon formed naturally,and between the samples from the gley and bottom horizons of a paddy soil derived from a red earth.The coatings of aluminum oxides on the latosol and the yellow earth made their zeta potentials rise pronouncedly and their IEFs move toward higher pHs,from 6.2 to 6.8 and 4.3 to 5.3 for the former and the latter,respectively.The samples with different particle sizes also exhibited some electrokinetic variation.The experiment showed that the effects of iron and aluminum oxides were closely related to the pH and type of the soils.     

离子强度对可变电荷表面吸附性铜离子解吸的影响:可变电荷土壤

为进一步了解离子强度对可变电荷表面吸附性铜离子连续性解吸的影响,研究两种可变电荷土壤在去离子水和0.1 mol·L~(-1)NaNO_3溶液中吸附铜离子后,依次在去离子水和浓度由低到高的NaNO_3溶液中连续解吸时,离子强度变化对不同pH段铜离子解吸的影响。结果表明,解吸过程中离子强度变化方向对解吸分值随pH升高的变化趋势的影响完全不同,当离子强度由大变小时,解吸分值曲线的总体趋势是随着pH的升高而降低,反之,曲线呈现为钟形,且当去离子水第一次解吸在0.1mol·L~(-1)NaNO_3溶液中吸附的铜离子时,两种可变电荷土壤的第一次去离子水解吸均可出现重吸附现象,但铁质砖红壤解吸分值绝对值要小于红壤。整个解吸过程中,两种可变电荷土壤的铜离子吸附性铜离子的解吸特征与高岭石基本相似,但可变电荷土壤与高岭石以及两种可变电荷土壤之间,解吸分值的变化规律均存在一定的差异性,可变电荷土壤中的氧化铁含量多少被认为是导致这些差异的主要原因。     

Adsorption of Phosphate on Variable Charge Soils

The study about the adsorption of phosphate on four variable charge soils and some minerals revealed that two stage adsorption appeared in the adsorption isotherms of phosphate on 4 soils and there was a maximum adsorption on Al-oxide-typed surfaces between pH 3.5 to pH 5.5 as suspension pH changed from 2 to 9, but the adsorption amount of phosphate decreased continually as pH rose on Fe-oxide typed surfaces. The adsorption amount of phosphate and the maximum phosphate adsorption pH decreased in the order of yellow-red soil > lateritic red soil > red soil > paddy soil, which was coincided with the content order of amorphous Al oxide. The removement of organic matter and Fe oxide made the maximum phosphate adsorption pH rise from 4.0 to 5.0 and 4.5, respectively. The desorption curves with pH of four soils showed that phosphate desorbed least at pH 5. Generally the desorption was contrary to the adsorption with pH changing.     

Proton Dissociation from Surfaces of Variable Charge Soil andMnierals

Experiments on proton dissociation from the surfaces of goethite, amorphous Al oxide, kaolinite and latosol were carried out, showing amphoteric behavior with reactions of proton dissociation-association on the surfaces and buffering capacity in such a sequence as amorphous Al oxide>latosol>kaolinite>goethite. Dissociation constants of surface proton, pKsa, are significantly correlated with surface charge density, which has been proved with an electrochemical model. The intrinsic constants of proton dissociation, Ksa(int), gained by extrapolation to zero charge conditions of plots of pKsa against ao, could be used to estimate the acidity strength of variable charge surfaces. The value of pKse(int) is 8.08 for goethite, 1.2 for morphous Al oxide, 6.62 for kaolinite and 5.32 for latosol.     

中性紫色土和砖红壤表面电荷性质的比较研究

采用恒流置换法测定了中性紫色土、砖红壤表面电荷总量、表面电位、表面电荷密度及表面电场强度,并讨论了电解质浓度、类型、pH以及环境温度对两种土壤电性参数影响的差异。结果表明:(1)在2:1型电解质体系(Mg(NO3)2)中,中性紫色土和砖红壤的表面电位分别约为-0.18V和-0.10 V。中性紫色和砖红壤表面电荷密度分别为-0.55 C m-2和-0.038C m-2;表面电场强度分别为-4.41E+08J m-1 C-1和-5.40E+07J m-1 C-1。紫色土的表面电荷密度、表面电场强度的值都比砖红壤高出约一个数量级。(2)两种土壤表面电荷密度随电解质浓度增加呈增加趋势,砖红壤的增加幅度要远大于中性紫色土;而表面电位随电解质浓度的增加有所降低,同样砖红壤的减小幅度要远大于中性紫色土。(3)pH对中性紫色土表面电荷性质的改变不是特别明显,而对砖红壤的表面电位和表面电荷密度都有很大程度的增加。     

Ion Transport Dynamics in Acid Variable Charge Subsoils

This is a mini-review of the research work conducted by the authors with the objective of studying ion transport in variable charge subsoils collected from different areas around the world. An attempt is made in these studies to relate the unique behavior manifested during ionic transport in these subsoils with their mineralogical, physical and chemical properties, which are markedly different from those in soils from temperate regions. The variable charge subsoils have a relatively high salt sorption capacity and anion exchange capacity (AEC) that retards anions downward movement. The AEC correlates closely with the anion retardation coefficients. Ca²⁺ applied with gypsum in topsoil may be transported to the subsoil and may improve the subsoil chemical properties. These results may help in developing appropriate management strategies under a range of mineralogical, physical, and chemical conditions.     

Ion Transport Dynamics in Acid Variable Charge Subsoils

This is a mini-review of the research work conducted by the authors with the objective of studying ion transport in variable charge subsoils collected from different areas around the world. An attempt is made in these studies to relate the unique behavior manifested during ionic transport in these subsoils with their mineralogical, physical and chemical properties, which are markedly different from those in soils from temperate regions. The variable charge subsoils have a relatively high salt sorption capacity and anion exchange capacity (AEC) that retards anions downward movement. The AEC correlates closely with the anion retardation coefficients. Ca²⁺ applied with gypsum in topsoil may be transported to the subsoil and may improve the subsoil chemical properties. These results may help in developing appropriate management strategies under a range of mineralogical, physical, and chemical conditions.     

Effect of Electrolytes on Surface Charge Characteristics of Red Soils

The zero point of charge (ZPC) and the remaining charge σp at ZPC are two important parameters characterizing surface charge of red soils.Fourteen red soil samples of different soil type and parent material were treated with dithionite-citrate-dicarbonate (DCB) and Na2CO3 respectively.ZPC and σp of the samples in three indifferent electrolytes (NaCl,Na2SO4,and NaH2PO4) were determined.Kaolinite was used as reference.The results showed that ZPC of red soils was affected by the composition of parent materials and clay minerals and in significantly positive correlation with the content of total iron oxide (Fet),free iron oxide (Fed),amorphous iron oxide (Feo),aluminum oxide (Alo) and clay,but it was negatively correlated with the content of total silica (Sit).The σp of red soils was also markedly influenced by mineral components.Organic components were also contributing factor to the value of σp.The surface charges of red soils were evidently affected by the constitution of the electrolytes.Specific adsorption of anions in the electrolytes tended to make the ZPC of red soils shift to a higher pH value and to increase positive surface charges of the soils,thus leading to change of the σp value and decrease of the remaining net negative charges,even to the soils becoming net positive charge carriers.The effect of phosphate anion was greater than that of sulfate ion.     

土壤表面电荷特征与重金属吸附解吸的相互关系

土壤对重金属的吸附 解吸与土壤性质特别是土壤表面电荷性质密切相关。本文概述了恒电荷土壤与可变电荷土壤表面电荷特征与重金属吸附 解吸的相互关系及研究进展。     

Adsorption of Potassium and Sodium Ions by Variable Charge Soils

Adsorption of potassium and sodium ions by four typical variable charge soils of South China was studied.The results indicated that the variable charge soils saturated with H and Al showed a much higher preference for potassium ions relative to sodium ions,and this tendence could not be changed by such factors as the pH,the concentration of the cations,the dielectric constant of solvent,the accompanying anions and the iron oxide content etc.,suggesting that this difference in affinity is caused by the difference in the nature of the two cations.It was observed that a negative adsorption of sodium ions by latosol and lateritic red soil in a mixed system containing equal amount of potassium and sodium ions at low pH,which is caused by a competitive adsorption of potassium and sodium ions and repulsion of positive charge on the surfaces of soil particles for cations.The adsorption of potassium and sodium ions increased with the decreases in the dielectric constant of solvent and the iron oxide content.Sulfate affected the adsorption of potassium and sodium ions through changing the surface properties of the soils.     

Charge Properties and Clay Mineral Composition of Tianbao Mountains Soils

The clay mineral association,oxides of clay fraction and surface charge properties of 7 soils,which are developed from granite,located at different altitudesof the Tianbao Mountains were studied.Results indicate that with the increase in altitude,1) the weathering process and desilicification of soil clay minerals became weaker,whereas the leaching depotassication and the formation process of hydroxy-aluminum interlayer got stronger;2)the contents of amorphous and complex aluminum and iron,and the activity of aluminum and iron oxides for soil clay fraction increased;and 3) the amount of variable negarive charge,anion exchange capacity and the values of PZC and PZNC also increased.The activity of aluminum and iron oxides,the accumulation of aluminum,and surface charge characteristics and their relation to clay oxides of the vertical zone soils were observed and recorded.     

Adsorption of Potassium and Calcium Ions by Variable Charge Soils

Interactions of potassium and calcium ions with four typical variable charge soils in South China were examined by measuring pK-0.5pCa value with a potassium ion-selective electrode and a calcium ion-selective electrode,and pK value with a potassium ion-selective electrode.The results showed that adsorption of potassium and calcium ions increased with soil suspension pH,and the tendency of the pK-0.5pCa value changing with pH differed with respect to pH range and potassium to calcium ratio.Adsorption of equal amount of calcium and potassium ions led to release of an identical number of protons,suggesting similar adsorption characteristics of these two ions when adsorbed by variable charge soils.Compared with red soil,latosol and lateritic red soil had higher adsorption selectivities for calcium ion.The red soil had a greater affinity for potassium ion than that for calcium ion at low concentration,which seems to result from its possession of 2:1 type minerals,such as vermiculite and mica with a high affinity for potassium ion.The results indicated that adsorption of potassium and calcium ions by the variable charge soils was chiefly caused by the electrostatic attraction between the cations and the soil surfaces.Moreover,it was found that sulfate could affect the adsorption by changing soil surface properties and by forming ion-pair.     

动力换档离合器充/放油特性仿真研究

为研究动力换档离合器换档过程中的充油和放油特性，基于动力换档离合器的工作原理，建立了动力换档离合器充油和放油两个过程的动态特性数学模型。应用动态仿真软件，将充/放油过程的动态特性以统一的仿真模型描述。通过仿真得到了对动力换档离合器充/放油过程的动态特性影响最大的离合器结构参数是充油油道直径。摩擦片间隙（离合器活塞行程）主要影响充/放油时间，而卸压孔直径的影响程度随着其值的增加而加大。在进行离合器设计、液压系统设计以及电控系统设计时，必须充分考虑油液温度的影响。试验结果验证了仿真方法及仿真模型的正确性和有效性。     

Charge modifications to improve the emulsifying properties of whey protein isolate

Whey protein isolate was modified by ethylene diamine in order to shift its isoelectric point to an alkaline pH. The extent of the modification was studied using SDS-PAGE and MALDI-TOF mass spectrometry. The modified whey proteins were used as an emulsifier to stabilize oil-in-water emulsions at acidic and neutral pH ranges, and their emulsifying properties were compared with that of the unmodified whey proteins and with the previously studied ethylene diamine modified sodium caseinate. The emulsifying activity of the modified whey proteins was similar to that of the unmodified ones, but the stability of an emulsion at pH 5 was significantly improved after the modification. Charge and coverage of droplet surface and the displacement of the interfacial proteins by surfactant Tween 20 were further studied as a function of pH. As compared with the unmodified whey proteins, the modified ones were proven to cover the interface more efficiently with extensive surface charge at pH 5, although the interfacial layer was less resistant to the surfactant displacement.     

Adsorption of Chloride, Nitrate and Perchlorate by Variable Charge Soils

Two cells consisting of a chloride-selective electrode and a nitrate-selective electrode or of a chloride-selective electrode and a perchlorate-selective electrode were directly put in the soil suspension to determine the concentration ratios Cl-/ NO3- or Cl-/ ClO4- for studying the adsorption of the three anions by variable charge soils. It was found that all the concentration ratios CCl- / CNO3- and CCl- / CClO4- in suspension were smaller than unity when soil samples were in equilibrium with mixed KCl and KNO3 or KCl and KClO4 solutions of equal concentration. The order of the amount of chloride, nitrate and perchlorate adsorbed by variable charge soils was Cl-> NO3-> ClO4- when the soils adsorbed these anions from the solution containing equal concentrations of Cl-, NO3- and ClO4-. Such factors as the pH of the suspension, the iron oxide content of the soil etc. could affect the amounts and the ratios of anions adsorbed.     

Charge properties of mixtures of minerals with variable and constant surface charge

Surface charge of mixtures of lepidocrocite and illite determined by adsorption of potential-determining and electrolyte ions is studied as a function of pH and NaCl concentration. Deviations between results obtained by both methods were a function of the illite content of the mixtures, and can be mainly attributed to coatings of hydroxyaluminium complexes on the constant charge surfaces of the clay mineral, which can react with H⁺ ions or release exchange sites by precipitation of well-formed hydroxides. These coatings of aluminium complexes can cause H⁺ consumptions similar to those due to lepidocrocite. Some ideas are put forward for modelling charge properties of mixed systems.     

Zero Point of Charge Determination of Monoionic Montmorillonites by Transport Number Method

The zero points of charge (ZPC) of a natural bentonite and those of its homoionic forms (Na, Ca and Al) were determined by the transport number method. The influence of the interlayer cation was observed in the different pH values of the ZPC obtained. No influence of the water contains was observed.     

表面电荷性质对紫色土粘粒悬浮液稳定性影响研究

表面电荷性质对于水体中粘性泥沙颗粒的稳定和聚沉起重要作用，因此本试验测定3种紫色土胶体的表面电荷性质，并讨论其随环境条件改变而变化对紫色土粘粒悬浮液稳定性的影响。结果表明：（1）3种紫色土胶体在2：1型电解质中的表面电位分别约-0．14～-0．192 V．1：1型电解质中约为其2倍，在2种离子体系中的絮凝值分别为0．72～1．12mol／m^3和11．7～17．8mol／m^3，胶体稳定性随其表面电位增加而增强；（2）1：1型电解质中粘粒悬浮液完全沉降时间分别达到40．6～47．0h，比在2：1型电解质中长12．4～14．6h，电解质浓度增加，粘粒悬浮液完全沉降时间下降．稳定性减弱。pH对完全沉降时间影响强烈，当pH=5时，2种电解质体系中的粘粒悬浮液完全沉降时间减少近1／2；pH=3时，60min左右悬浮液已经沉降完全。3种紫色土悬浮液稳定性是酸性紫色土〈中性紫色土〈石灰性紫色土。     

Zn Adsorption by Variable Charge Soils in Relation to pH

Zn adsorption by pure oxides or in the presence of a high concentration of inner electrolyte has been extensively studied.But,in studies on Zn adsorption in the complicated soil system,especially in variable charge soils,profound knowledge about the absorption mechanism still lacks.In this paper,taking Zn ion adsorption by two typical variable charge soils as the object of the study,author discusses the relation between Zn adsorption and pH and possible adsorption mechanisms.The results showed that in the low pH range where the amount of Zn adsorbed did not exceed 50% of Zn added,the specific adsorption was the diminant mechanism.The species of Zn specifically adsorbed was free Zn^2 ion.In the middle and high pH ranges,the mechanisms of specific and electrostatic adsorptions co-existed,accounting for about 70% and 30%,respectively.Noteworthily,in the high pH range,the hydroxyl Zn ion (ZnOH^ ) from Zn^2 hydrolysis probably was a preferable species for specific absorption.