Study On Dissolution Behavior Of Harmful Elements In Pantries

In recent years, the tailings filling, an efficient, safe mining method has been applied in many mines. In order to study the condition of underground environment polluted by bleeding after the phosphate tailings are filled in mined-out area. The phosphate tailings of a certain mine in Guizhou were used as filling aggregate to make backfill, and the dissolution tests of harmful elements were conducted.Referring to the analysis results of properties for phosphate tailings, fly ash and cement, the total hardness, sulphate, fluoride, total phosphorus and Fe were selected as the indexes of dissolution test. Through the static immersion test of phosphate tailings and backfill, the dissolving rules of various elements in the both were similar,the concrete conclusions are as follows:(1) With time increasing, temperature rising and liquid- solid ratio decreasing,the dissolved concentration of total hardness, sulphate, phosphorus and fluoride gradually rised. The dissolved concentration rised rapidly in the first ten days of soaking, then the increasing rate was slower, then changed to be steady at thirtieth day.(2) Under the conditions of low pH in soaking, the dissolved concentration of total hardness, sulphate, total phosphorus presented the rising trend, which was obvious especially when pH value was less than 3. The dissolved concentration of fluoride increased with the increase of pH value.(3) Under the conditions of changing soaking time, liquid-solid ratio and temperature, the dissolving rules of Fe was not obvious. When the pH of soaking was at 2, the dissolution concentration of Fe increased a lot, which shows it’s much easier to dissolve out Fe in lower pH.(4) By contrasting the dissolution test data from phosphorus and phosphorus tailings backfill tailings, the results show that under the same experimental conditions,the dissolution concentrations of total phosphorus and fluoride in backfill were less than that in phosphate tailings, and the dissolution concentration of sulfate in backfill was higher than that in phosphate tailings.In order to investigate the influence rate of soaking temperature, liquid-solid ratio, pH and time on filling body total hardness, sulphate, total phosphorus and dissolution concentration of fluoride, an orthogonal experiment including four factorsand five levels was designed. Nemerow index was chosen as an experinment index,the results showed that the liquid-solid ratio was the most influential factor of dissolved concentration, followly pH, time and temperature.The fuzzy comprehensive evaluation method was used to evaluate nine factors of backfill bleeding according to the groundwater quality standard of China. The analysis results indicated the pollution level of the bleeding belong to V, the pollution degree was serious, the main pollution factors were the total hardness and sulphate.The dissolution test data of backfill were used as training samples. By using the toolbox of compensation fuzzy neural networks, four prediction models of dissolution concentration on total hardness, sulphate, total phosphorus and fluoride were built.The established models were inspected, and the results showed the models based on compensation fuzzy neural networks can provide reliable prediction data, it’s prediction accuracy was high and can have certain feasibility.