| Humum acids , the most widely distributed natural organic matter in the biological environmenare 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, phencalcohol 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, the water and soil conservation, the decrease or removal of toxic substances in soil and water, the balance of 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 humlic 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 efectness 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 ionson 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 many studies worldwideon single element, and most of them lay particular stress on imitating experimental data by means of different mathematical models, but ignore the actual existing form of humic acids solution. On the otherhand, presently, there have been only some studies on such metals elements as Cu, Cd, Zn, Hg, Pb and some thulium such as La, Pu and Nd, which can be studied used simple ion elect electrode ,and they only focus on the determination ofcomplexing constant.But because of the lack of good veracity ion elect electrodes,there have been rare report about Fe, Al, Mn ions research recently.fortnermore anciently research seldom consider the redox activity of humus and some possess redox activity metals such as Fe, Mn. In fact, Fe, Al, Mn metal ions have very impoetant function in envirment.Al and Fe are the most content two elements in lithosphere and soil. Al contents are 8.05% and 4.65% of lithosphere and soil.Fe contents are 7.13% and 3.80% of lithosphere and soil. Althought Mn content in soil far less than those of Al and Fe, it is the same as Al and Fe,they have important effects on earth chemistry circle of elements.on soil form and upgrowth.on soil mineral air slake and grown soil action,on soil nutrient circle and on the validity.toxicity etc.Thus, despite the means of study is complex, it is very necessary of the study on mechanism of humus acids and Fe, Al, Mn metal ions.lt has very important guidance meaning on illuminating commonly rule of humus acids and metal ions,developping and updating science knowledge in this aspect.accmodating and cortroling the transferring,transforming and toxicity of metal ions.As a result, this experiment key aims at these problems and focuses on studying the characteristics of the adsorption and desorption of Fe, Al ions on humic acids, the effect of the pH, temperature and ion strength of the solution, the kinetic and themological characteristics of reactions, the complex coordination number and complexing stability and the mechanism of humus acids adsorption by Fe2O3, MnO2 or Al2O3 solid sorbent. Furthermore this experiment also studied the dynamics characteristics of oxidation-reduction of Fe3+ reacting with humus acids, and the isothermal adsorb Cu2+ ion characteristics of HA- amorphous Fe2Os complex colloid. The main achievement result in the study is as fellows:The character of humic acid adsorb and desorption Fe3+ ion and Al3* ion at different acidity, ion strength and temperature were studied, first used sulphopropyl Sephadex C-25 chromatography method. Humic acid (HA) and fulvic acid were extracted evergreen broad leaved forest surface layer soilof Jingyun Mountain in China. The results showed that the max adsorption Smaxwere increased with the increased pH when pH less than 6.0,but the Smax were decreased with the increased pH when more than 6.0. The adsorption equilibrium constants k were increased with the increased pH, while the thermodynamic standard free energy change AGj were all decreased, at the same ion strength and temperature. At the same pH and temperature, the max adsorption Smax and adsorption equilibrium constants k were increased while the thermodynamic standard free energy changes AGm0 were all decreased when ion strength changed from zero to 0.10 mol L"\ but the changes of these character constants were in reverse when ion strength continually rose to 0.15 mol I/'.When temperature was increased, the max adsorption quantities, adsorption equilibrium constants k, and the AGme were all greatly decreased, which indicated that hoisted temperature was disadvantage to adsorption reaction. The thermodynamic standard enthalpy change AHjsaiA entropy change ASm8 of adsorption reaction were all less than zero, which suggested that adsorption reaction was exothermic reaction and proceeded towards more sequence. At the same condition, the bigger pH, the bigger absolute value of AHmeand ASme, which suggested the bigger pH were advantage to the process of adsorption reaction. The reduce percents of Fe3+ ion were decreased with increased pH, which can used power function equation to describing, whose correlative coefficient reached notability correlative. The desorption percents of HA-Fe3+ increased when pH decreased, and the curve of desorption percents was linear equation, whose correlative coefficient also reachednotability correlative, which indicated the adsorption reaction was a including humic acid interior and exterior "two-phases" reaction. The Smax and k were increased while the thermodynamicstandard free energy change AGm8 were all decreased with the increased pH.at the same ion strength and temperature.The results of effect of temperature on humic acid adsorb and desorption Al3+ ion was similar to those of Fe3+,but the 5max , k and the AGme of A\'+ all less than those of Fe3+,which suggested that the absorption degree and intension of Al3+ all less than those of Fe3+,and the chemistry band absorption in HA-A13+ less than that of HA-Fe +.The stability and thermodynamic character of humic acid coordinate Fe3+ ion and Mn2+ ion at different acidity, ion strength and temperature were studied, used ion-exchange equilibrium method. The results showed that at the same ion strength and temperature, the condition stability constant and coordination number of complexation compound HA-Fe3+ were increased with the rise in pH, which suggested that high pH be advantage to the process of coordination reaction. At the same pH and temperature, the condition stability constant and coordination number of HA-Fe3+ were increased when ion strength changed from zero to 0.10 mol-L"1, but the changes of these character constants were in reverse when ion strength continually rose to 0.15 mol-L"1. The thermodynamic standard free energy change AGj and the thermodynamic standard enthalpy change Ahrml'and entropy change Asj of coordinate reaction of HA-Fe3+were all negative when temperature were 298.2 and 308.2K, which suggested that coordinate reaction was spontaneous and exothermic reaction, and indicated the low temperature be advantage to the process of reaction. The condition stability constant of HA-Mn2+ complexation compound was increased with the rise in pH which was similar to that of HA-Fe3+, but the coordination number of HA-Mn2+was different,it was increased with the rise in pH when pH between 3.0 and 5.0,while it was decreased with the rise in pH when pH between 5.0 and 7.0. The condition stability constant of HA-Fe3+ was increased with the rise in ion strength. The coordination number was increased when ion strength changed from zero to 0.10 mol-L'1, but the coordination number was decreased when ion strength continually rose to 0.15 mol-L"1.; The change rule of AGme,AHmeand ASme of HA-Mn2+ was similar to that of HA-Fe3+ when temperature were 298.2 and 308.2K, which suggested that HA-Mn2+ coordinate reaction was spontaneous and exothermic reaction, and indicated the low temperature be advantage to the process of reaction.However the absolute values of AGm8,AHmeand ASm0 of HA-Mn2+far less than those HA-Fe3+ The condition stability and the coordination number of HA-Mn2+ were all less than those of HA-Fe3+. HA and Mn2+ ion only form quite feeble complexation compound.The dynamics of oxidation-reduction of Fe3+ reacting with different concentrations HA and FA were studied used bathophenanthroline colorimetry. The results showed that different curve equations of dynamics were used. The results were that two rank reaction equations were relatively satisfaction. The velocity constants of Fe3+ reacting with HA and FA were decreased while the half time were increased when concentrations of Fe3+ increased. The velocity constants of Fe3+ reacting with HA were more than those of FA, the half time of the former were less than the latter. The reduction ability and oxidation-reduction capacity of HA reacting with Fe3+ was larger than the latter. The mechanism of humic acid react with Fe3\ Al \Mn + metal ions was studied used infrared spectroscopy. The infrared spectroscopy of the coordination complex which formed by HA and Fe3+,Al3+,Mn2+ ions were basically same as HA, showed there be no qualitative changes taken place about the main organic functional groups, but there were some changes taken place about the... |
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