低分子量有机酸对两种可变电荷土壤吸附铜的影响

采用室内实验方法,研究了3种低分子有机酸对两种可变电荷土壤吸附铜的影响。结果表明,有机酸对铜吸附的影响与有机酸的种类和土壤类型有关,柠檬酸和苹果酸能显著增加可变电荷土壤对铜的吸附,而草酸在低浓度下对铜吸附有一定的增加作用,随着草酸加入量的增加其主要表现为对铜吸附的抑制作用。有机酸主要通过与铜形成表面三元络合物来增加铜的吸附量,以这一机制吸附的铜不能为中性盐NaNO3交换而解吸,因此可以降低铜的活动性和生物有效性。

Effect of Heavy Metals on Phosphorus Retention by Typic Udic Ferrisols: Equilibrium and Kinetics

A study was conducted to examine the effect of heavy metals (Cu,Pb, Zn and Cd in combination or alone) on the equilibrium andkinetics of phosphorus (P) retention in typic udic ferrisols by usingboth equilibrium and flow techniques. Fourteen soil samples withvarying artificial contamination of Cu, Pb, Zn and Cd were prepared.Heavy metal pollution led to increases in retention capacity andmaximum buffering capacity (MBC) of soil P. The rate of P retentionwas also increased and the time to reach equilibrium was advanced byheavy metals addition.

Effects of Sorbed Phosphate on Kinetics of Cn^（2＋） Sec－ondary Adsorption in Soils

The effects of sorbed phosphate on the kinetics of Cu￣2+ secondary adsorption on three major types ofsoils in southern and Central China were studied using the batch method and flow (or miscible displacement)techniques. Both of the methods showed that diffusions were the ratedetermining steps in the Cu￣2+ adsorp-tion by the soils. By the flow method, the course of Cu￣2+ adsorption kinetics consisted of two steps-sn initialrapid process and a later slow process of Cu￣2+ adsorption; while by the batch method, the 90% of Cu￣2+adsorption reaction was found to finish within first 1 minute. The results obtained using the flow method alsoindicated that for red soil and yellow-brown soil, Cu￣2+ adsorptions during the initial reaction periods wererestrained when the soils sorbed phosphate, whereas the adsorption reactions were stimulated at the finaltime. For grey Chao soil, sorbed phosphate retarded the Cu￣2+ adsorption in the whole reaction period. Theresults obtained using the batch method and flow techniques all implied that the different effects of sorbedphosphate would be attributed to its effects on Cu￣2+ ion diffusion in soil solution.

Adsorption Kineties of Pb￣(2+) and Cu￣(2+) on Variable Charge Soils andMinerals V .Effects of Temperature and Ionic Strength￣*1

The study results of the effects of temperature and ionic strength on the adsorption kineties of Pb￣2+ and Cu￣2+ bylatosol, red soil and kaolinte coated with Mn oxide showed that Pb￣2+ and Cu￣2+ adsorption by all samples, as awhole, increased with missing temperature. Temperature also increased both values of X_m (the amount of ionadsorbed at equilibrium) and k (kinetica constant) of Pb￣2+ and Cu￣2+. The activation energies of Pb￣2+ adsorption werekaolin-Mn >red soil>goethite and those of Cu￣2+ were latosol> red soil > kaolin-Mn >goethite. For a given singlesample the activation energy of Cu￣2+ was greater than that of Pb￣2+. Raising ionic strength decreased the adsorptionof Pb￣2+ and Cu￣2+ by latosol, red soil and kaolinite coated with Mn oxide but increased Pb￣2+ and Cu￣2+ adsorption bygoethite. The contrary results could be explained by the different changes in ion forms of Pb￣2+ or Cu￣2+ and in surfacecbarge characteristics of latosol, red soil, kaolin-Mn and goethite. Increasing supporting electrolyte concentration in-creased X_m and k in goethite systems but decreased X_m and k in kaolin-Mn systems. All the time-dependent data fit-ted the surface second-order equation very well.

Adsorption Kinetics of Pb^(2+) and Cu^(2+) on Variable Charge Soils and Minerals:Ⅰ.Technique

A new technique for studying the adsorption kinetics of heavy metals,Pb^2+ and Cu^2+,on variable charge surfaces was established with two selective electrodes and microcomputer control system.Feasibility of the technique,including interference of other ions (mainly Fe^3+ and Al^3+),response time of electrodes,and the pH range of testing,was studied.Comparision with the most widely used miscible displacement technique,which was considered insufficient in studying 30-minute rapid reactions,at present time showed that the new technique was more advantageous in testing in situ,easy to operate,and economic.

Infrared Study of Cu^(2+) Adsorption by Surface of Goethite

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The Kinetic Study of Adsorption of Copper Metal Ion in Selected Contaminated Red Soil Samples in Palestine

Heavy metals are persistent pollutants in the environment. Problems associated with the cleanup of sites contaminated by metals have demonstrated the need to develop remediation technologies that are feasible, quick, and effective in a wide range of physical settings. In this study we have investigated the adsorption of Cu（lI）, onto red soil in single and multi-element systems as a function of soil and heavy metal concentrations. Before contamination, soils were characterized to determine particle size, pH, organic matter content and heavy metal contents. The results of experimental sorption data fitted very well the Freundlich isotherm model with n = 1.4 and k = 1.25 and first order kinetics model. The best pH for adsorption of Cu^2＋ on red soil was found to be 4.0. Adsorption of metals on soil increased in the order Cu 〉 Pb 〉 Zn ≈ Cd. This trend might be related to the increase in the electronegativity of the metal ion.

Retention and Mobility of Copper and Lead in Soils as Influenced by Soil Horizon Properties

The mobility and bioavailability of heavy metals in soils is largely governed by sorption and desorption phenomena.Cu2+ and Pb2+ are among the most potentially toxic heavy metals and they are present,often concomitantly,in many polluting spills and in agrochemicals.The objective was to assess and compare the competitive sorption and desorption capacities and sorption hysteresis of Cu2+ and Pb2+,as well as their migration through the profiles of four natural soils:a Humic Umbrisol,an Umbric Cambisol,an Endoleptic Luvisol and a Humic Cambisol.In all horizons Pb2+ was invariably sorbed and retained to a greater extent than Cu2+.The sorption and retention of Cu2+ were most in?uenced by pH,e?ective cation exchange capacity(CECe) and Mn oxide content.On the other hand,the fixation capacity of Pb2+ was most in?uenced by pH,CECe,and Mn oxide and organic matter contents.pH and CECe were the individual soil properties most markedly in?uencing Cu2+ and Pb2+ sorption and retention.In all the horizons Pb2+ exhibited greater hysteresis than Cu2+.In each soil the hysteresis in the A horizon was greater than that in the B horizon,except in the Bt horizon of the Endoleptic Luvisol,due to its high pH and vermiculite content.Based on migration indices,Pb2+ was less mobile than Cu2+ in the studied soils.

Kinetics of Specific and Non-Specific Copper Sorption on Aggregates of an Acidic Paddy Soil from the Taihu Lake Region in East China

The Taihu Lake region in East China has become prone to soil acidification, which changes heavy metals such as copper(Cu) in soil into water-soluble species and increases the mobility and contamination risks of heavy metals in the biological environment. In this study, the kinetics of Cu2+sorption by the bulk soil and the aggregate size fractions of an acidic paddy soil collected from the Taihu Lake region, the effects of temperature on Cu2+sorption, and the p H changes of the solution were investigated by static sorption and magnetic stirring. The aggregate size fractions were prepared by low-energy ultrasonic dispersing and freeze-drying. The total sorption amounts of the bulk soil and the aggregate size fractions for Cu2+followed a descending order of clay > coarse sand > bulk soil > silt> sand, corresponding to those of organic matter content, free iron oxide content, free aluminum oxide content, and cation exchange capacity. The kinetic sorption curves of Cu2+by the bulk soil and the aggregates, which were divided into two stages(rapid and slow sequentially), were well fitted by the first-order equation, the diffusion equation, and the Elovich equation, showing significant correlations(P < 0.05). Specific and non-specific sorption dominated in the fast and slow stages, respectively, and the former was predominant throughout the sorption process. The specific sorption accelerated and the non-specific sorption decelerated with rising temperature. The p H of the solution decreased significantly during the specific sorption and remained unchanged or increased slightly during the non-specific sorption. When the specific sorption terminated, the p H of the solution was minimized nearly simultaneously.The sorption progress of Cu2+by the bulk soil significantly preceded that by the aggregates. Therefore, heavy metal contamination may be another factor reducing soil p H and metal sorption forms should be taken into consideration in studies of mitigating soil heavy metal pollution or determining environmental capacity of heavy metal in soil.