Electrokinetic Remediation Of Cadmium And Lead Contaminated Brunisolic Soil Of Jiaodong

Soil is one of the main natural resources which mankind's survival and development depend on, is also an important component of the human ecological environment. But in recent years the problem of soil contaminated by heavy-metal is increasingly serious. In many parts of China, especially in some economically developed areas, agricultural products are polluted by heavy metal seriously which affect the development of the agricultural economy and the people's health. Acute poisoning may occur in humans or other living organisms due to a high intake of cadmium and lead which hold a distinct position among the heavy metal contaminants. When the contaminants contained cadmium and lead enter the soil, the soil may be polluted persistently. Even if the pollution way is stopped, cadmium and lead are also absorbed by plant. And pollution sources of cadmium and lead are many, so their polluted scope is broad, and their potential harm is great.Electrokinetic remediation technology (EK) is one of new technologies in recent decades, it may be effectively applied in the remediation of inorganic matter, organic matter and radioactive substance in soil. Electric effect generated by this technology is impacted weakly by the hydraulic permeability in soil. So it is applicable for treating multiaxial and dense soil. At the same time it has many merits such as less reagent consumption, easy installation, simple operation and so on, so it has more irreplaceable advantages than other technologies. Domestic and foreign scholars have done a great deal of research on the electrokinetic mechanism and practical application. But different soil properties effect its application much, so it needs be studied specifically.In this study, electrokinetic treatability of brunisolic soil which widely distributes in the Jiaodong peninsula polluted with cadmium and lead is investigated. We try to solve the precipitation of heavy metals and cost of treatment in order to settle the problem of soil contaminated by heavy metal ion. Main work is as follows:(1) Firstly, some physico-chemical properties and acid/base bufer capacity of the experimental soil is mensurated.Then do some sorption and desorption tests including: cadmium and lead sorpted by soil under different pH, desorption capability when acetic acid and citric acid are added.(2) Treating the soil polluted by cadmium and lead alone with EK. There are four methods: that not controlling any more; ammonium acetate-acetic acid; acetic acid- acetic acid; citric acid-acetic acid. Their removal rates are contrasted, then the shape of the heavy metal is analysed with Tessier, energy consumption is also accounted.(3) Anode approaching method is researched in order to reduce the treating cost. The paper summarizes the acid principle of this technology. Then treating the soil contaminated by cadmium and lead with it. At the same time,other two tests are designed to be compared.Based on the analysis and comparison of the test data, we can get the conclusion, the result shows:(1) The acid/base bufer capacity of this brunisolic soil is more powerful. So it is not easy to be acided, this makes the use of acid increase during the EK, thus the cost of treatment is raising.(2) Electroosmotic flow is disappeared when the pH near the anode is much lower. If we can adjust the pH properly, the electroosmotic flow is appeared again.(3) The removal rate of cadmium in the EK that not controlling any more is low, 2.55%. Lead is 19.51% near the anode. The treatment cost of this method is low, 0.05-0.06 yuan/kg soil. The removal rates of cadmium and lead are 32.21% and 29.05% controlling by ammonium acetate-acetic acid, but it still exists enrichment, the reason is that the pH of soil is still high. The removal rate of cadmium and lead are increased to 63.73%, 46.93%, the treatment cost is 1.03 yuan/kg soil. In the test that controlled by citric acid-acetic acid the removal rate of cadmium and lead become lower, 61.45% and 45.74%.But the most heavy metal is enriched near the cathode, the treatment cost is 1.02 yuan/kg soil.(4) In this soil residual-Cd and organic bound-Cd are little. The main shape of cadmium changes from exchangeable-Cd to carbonates-bound-Cd and Fe-Mn oxides-bound-Cd. Lead has all five shapes in this soil, but it changes between exchangeable-Pb , carbonates-bound-Pb, Fe-Mn oxides-bound-Pb and organic bound-Pb.(5) The anode approaching method can enrich most of cadmium and lead near the cathode gradually. It can make the acidification zone change largely. The theory is mathematically described as .And its cost of treatment is low, if it is supplemented by other treatment methods, its practicality is stronger.