Research On The Control Action Of Colloid TiO₂ To The Water And Soil Environment Heavy Metals Pollution

The colloid TiO2 was prepared with Titanium chloride (or titanium sulfate) as source matter, which can precipitate and chemical immobilization of heavy metals of the simulation contaminated water. It was speculated that colloid TiO₂ had the similar process in the soil solution. Therefore, it proposed for the first time the issue of the situ immobilization of soil heavy metals by colloid TiO2, and then discussed the feasibility of the issue. In this paper, removal efficiency of the wastewater heavy metals by colloid TiO2 was evaluated for the first time; the effects of colloid TiO2 on the accumulation of heavy metals in wheat and the speciation distribution of heavy metals were mainly studied.1. The removal characteristics of lead and cadmium from simulate wastewater by collide Titanium were investigated under various conditions of pH, initial metal concentration and titanium dioxide dose. The results indicated lead and cadmium reached their maximum removal efficiency 82.75% and 51.50% at the initial concentration were 800mg/L and 400mg/L, respectively. At the beginning the removal efficiency increased with the increase dose of the titanium dioxide, when the dose reached 200mL/L, the change of the removal efficiency was small. The pH had a significant effect on the removal efficiency, at pH≤1, the removal efficiency was lowest, and the removal efficiency increased in a progressive manner from pH 2 to pH 6;At pH 9, the removal efficiency of lead and cadmium reached 99.90% and 82.75%, respectively. The XPS result showed that there are existed chemical sorption between lead and titanium dioxide, but cadmium has no such sorption characteristics.2. Using ICP-MS, the available Pb, Cu and Zn contents in soils and the total Pb,Cu and Zn contents in root and shoot of wheat were quantitatively analyzed. The result showed that after the colloid Titanium dioxide treatment , compared the control ,the available Pb, Cu and Zn contents in soils were reduced 47.31%, 33.64% and 40.50%, respectively, the total Pb,Cu and Zn contents in shoot of wheat were reduced 55.39%, 54.40% and 70.56%, respectively. However, the total Pb,Cu and Zn contents in root of wheat were increased 57.30%, 85.67% and 13.81%, respectively. So it was concluded that the colloid Titanium dioxide effectively decreased the available Pb, Cu and Zn contents in soils, so the total Pb,Cu and Zn contents in shoot of wheat were decreased , too. Although, the total Pb,Cu and Zn contents in root of wheat increased evidently , the different of the height and weight of the wheat were not significant compared the control.3. BCR sequential chemical extraction procedure was used to determine the heavy metal morphology (acetic acid exchangeable morphology, iron-manganese oxides, organic matter morphology and residue morphology of Cu, Zn and Pb) in soil treated with colloid TiO2 and humic acid. It showed that the morphologies contents of Cu were not obvious differences between the treatment groups and the control; however the morphologies contents of Zn and Pb have obvious changes, in the control groups, the iron-manganese oxides of the Zn and Pb were at a rather high level, which in 57.45% and 55.20% respectively; while in the treatment groups, most of Zn was found in the residue morphology in 74.08%, 74.95% and 73.90% respectively in three treatments, and most of Pb was found in residue morphology in 86.64%, 88.60% and 81.11% respectively.