On The Reaction Of Humic Acids On Some Heavy Metal Ions And The Affecting Factors

Humic acids, the most widely distributed natural organic matter in the biological environment, are distributed almost everywhere in our environment such as the soil, water and deposit. Owing to their great variety of function groups, such as carbonyle group, alcohol hydroxyl group, phenol alcohol group, keto acid, aldehyde, ketone, and ether, et al, they have great activation in reaction, and can react on such matters as metal ions, oxide, hydroxide, minerals, organic matters and toxic pollutants. These reactions can produce endless variety of soluble and insoluble substances of physical and chemical stability,and they are greatly significant in controlling and adjusting the maintenance of soil nutrients, the formation of good soil structure,the soil acidity and basicity, thewater and soil conservation, the decrease or removal of toxic substances in soil and water, the balanceof plant element nutrient, the structure and function of the overall soil and aquatic biological system.Although the study on humus focused on soil fertility has been going on for over 100 years, it is not until the recent 10 years that the great significance of humus to the biological environment has been realized.Both the function of humus in maintaining soil fertility and in controlling and adjusting the shifting, transformation and circulation of substances are based on its special physical and chemical qualities and its great activation. In spite of the different focuses, different studies have generalities, in which the reaction of humic acid on different kinds of metal ions are of great significance in two aspects. The study on the characteristic parameter and mechanism in the reaction of humic acids on heavy metal ions is the basis to understand the way humic acids control and adjust the organic effectness of metalions or toxicity control, and to measure the shape and distribution of metal ions in the environment Although in simple chemical system there has been thorough understanding of the reaction of metal ions on organic matters, yet because of the complexity of humic acids, the reaction will become rather complicated when humic acids are involved.On the one hand, there have been manystudies worldwide on single elemnt, and most of them lay particular stress on imitating experimentaldata by means of different mathematical models, but ignore the actual existing form of humic acids solution. On the other hand, presently, there have been only some studies on such elements as Cu, Zn and Hg, and they only focus on the determination of complexing constant.But metal elements are in fact of various kinds and forms, and the heavy metal pollution in the nature is mainly satellite phemnenon and syndrome. For example, Cd and Zn have the same geochemical and environmental characteristics, and in zinc mining there is often emitting into the environment. And humus often differs in its structure and qualities because of the difference in refining method, area, climate and plantation.This experiment aims at these problems and focuses on studying the characteristics of theadsorption and desorption of Cu. Pb and Cd on huic acids, the pH of the solution, temperature, the effect of ion strength, the kinetic and thermological characteristics of reactions, and the complexing stability and cooridination number of Cd and Zn to humic acid, both respectively and put together. Such methods as improved potentialtitration, ion selective electrode, and ion-exchange equilibrium method are used in the experiment. The following procedure is followed in the experiment: Firstly, determine the basic components and the function groups of the humic acids on trial; calibrate the chosen electrode with standard solution; probe into the characteristics of the system of reaction of proton on humic acids; set up a "stable index"; use this "stable index" to get the potential titration of humic acids and determine the disosociation constant and the study the adsorption pattern of humic acids to Cu, Pb and Cd by using electrode under constant conditions and thus de...