Environmental Behaviors Of Heavy Metal Lead On Goethite As Influenced By Humic Acids

The rapid industrial and agricultural development brought increasingly serious environment problems.Currently there are many reports look at researches of behaviors of soil and the soil's effects on the heavy metal environments.Most of those researches focus on soil's degradation and adsorption effects on the heavy metal as well as soil components' effects on heavy metal which would affect heavy metal's effectiveness.Humic acid(HA) is a major component in soil.It is the most active multinomial substance in soil.Goethite is a natural substance which widely exists in soil.The substance has a strong obligate adsorptivity.The increasing amount of 'three waste',exhausted gases of automobiles,sewages,chemical fertilizers and solid wastes are resulting increasing content of Lead in soil.The issues of the lead pollution in soil-plant-environment become more serious.Therefore the safety of the agricultural products is threatened.Up to date,there are already many researches on how humic acid(HA) and goethite affect the lead environment,however,the researches on the combined action of humic acid and goethite on lead environment are less.The aim of this dissertation is to look at the characteristic of the adsorption and desorption of humic acid and multiple goethite colloid on heavy metal.This dissertation is carried out through isothermal adsorption and desorption practices and will discuss the factors that affect the lead adsorption.Also the dissertation will compare the combined effect of humic acid and goethite with the effect of humic acid or goethite alone to study the characteristic of goethite act on lead under the effects of humic acid.In the end, the dissertation will discuss how multiple colloid removes polluted substance in the refused seepage.The thermal research showed that both goethite and multiple colloid have high adsorption rate that is over 68%.Unlike these two substance,the adsorption rate of humic acid changes irregularly.However,along the increasing balance density of lead,the adsorptions of these three substances are increasing.Freundiclich and Langmuir models are appropriate to describe the isothermal adsorption of lead of three substances.The max adsorbance of multiple colloid is 883.48mg/g,which has the strongest adsorptivity.Goethite with 842.75mg/g is in the second place. Humic acid with 453.79mg/g is the weakest adsorptive agent.However,the adsorption ability of these three substances is different.Set sort by the ability:multiple colloid＞HA＞goethite.Set sort by the desorption rate of lead:HA＞goethite＞multiple colloid.Multiple colloid's adsorption rate is less than 1%.Due to the contractual difference of those substances,they exert the different characteristic of adsorption/desorption of lead.Their abilities of adsorption/desorption is resulted by multiple factors that work together.Results showed that the adsorption amounts of lead on goethite,HA and Multiple colloid were effect by multiple factors such as pH,temperature,ionic strength and coexist ion cadmium and so on.The research showed that the adsorption amounts of lead on these three colloids were similar.When pH was increased,the adsorption amount was increasing irregularly.In the research, the adsorption amount in high pH was more than in low pH.When pH was 7.0,the balance adsorption amount on goethite,HA and mulriple colloid were 116.61mg/g,114.84mg/g, 132.4mg/g respectively.But when pH was 4.0,the balance adsorption amount on goethite,HA and multiple colloid just were 107.9mg/g,105.9mg/g,108.9mg/g.But the adsorption rates had changed differently.Both goethite and humic acid have high adsorption rate with increasing pH. Unlike these two substances,the adsorption rate of multiple colloid decreased a little.With the increasing of temperature,the adsorption abilities of lead on goethite and multiple colloid increased as well as adsorption amount.In this experiment,adsorption amount of lead in 25℃was higher than in 15℃,which also showed the adsorption of lead on goethite and multiple colloid were endothermic reactions.But with the decreasing of temperature,the adsorption of lead on HA was increasing,which was a exothermic reaction.The adsorption amount also increased with the increasing ionic strength.In one word,the ionic strength could affect the adsorption process directly.When there was another ion cadmium,and the concentration of cadmium was fixed,the adsorption of lead on goethite,HA and multiple colloid preferential adsorb lead.The competition adsorption of lead was higher than cadmium.The adsorption isotherms in binary-component systems showed that there were competition among lead and cadmium by goethite and multiple colloid.Adsorption of lead was depressed by the presence of cadmium in the adsorption solution. But the adsorption amount of lead on HA by the presence of cadmium was almost as the same as the adsorption amount when there was only one lead metal ion.The adsorption rate and desorption rate of lead were both correlated to the sort of colloids. For HA,the adsorption amount could be up to 90%of the equilibrium adsorption amount within 256 min,and the Multiple colloid within 500 min,the goethite within 1000 min.Compared with the adsorption process,desorption processes of lead realized less slowly.For HA,the desorption amount could also be up to 90%of the equilibrium desorption amount within 256 min,but the goethite within 1500 min and the multiple colloid within 1000 min.The multiple colloid had a good effect on main contaminations of refused seepage.The optimal amount was 5 mg/g.among these main contaminations,the best adsorption on the multiple colloid were P and COD,next were potassium,lead and cadmium,the worse was Nitrogen.The adsorption rate were COD84.77%,P 86.49%,N 35.11%,K⁺ 47.69%,Pb²⁺ 58.21%,Cd²⁺ 37.14%.The mulriple colloids adsorb these contaminations more and more with increasing of temperature.When the temperature is 35 and the amount of colloid is 5 mg/g,the adsorption amounts of all these contaminations were Pb²⁺0.084mg/g,Cd²⁺0.0088mg/g,K⁺189.67 mg/g,COD 1153.8 mg/g,N 106.64 mg/g,P 23.27 mg/g,adsorption rates were COD87.82%,P90.45%,N39.99%,K⁺48.8%,pb²⁺62.69%,Cd²⁺41.9%。...