Experimental Study On Stabilization/Solidification Of Non-Ferrous Tailings

Due to the differences of ore properties,beneficiation technology and beneficiation equipment in different mines,the particle size of tailings produced by beneficiation plants is different.In order to clarify the leaching and retention mechanism of heavy metals in coarse and fine particle tailings induced by stabilization/solidification,this study selects Dushan and Qinglong antimony deposit in Guizhou province and Shenxiandong lead-zinc deposit in Yunnan province as the study areas,and carries out an experimental study on the stabilization of heavy metals in coarse particle antimony tailings and solidification of fine particle lead-zinc tailings.The stabilization performance of tailings and the feasibility of consolidation prevention and control are systematically analyzed,and the leaching toxicity and morphological transformation characteristics of heavy metals arsenic（As）,antimony（Sb）,lead（Pb）,zinc（Zn）and cadmium（Cd）as well as the compressive strength of solidified specimens are expounded.The formation of hydration products and stabilization/consolidation mechanism of leaching behavior of heavy metals under different influence conditions are analyzed combined with the microstructure.The stabilization test results show that the application of red mud and fly ash is conducive to the increase of p H of tailings,and the dry sludge and rice husk ash increase the content of organic matter in tailings.Under neutral condition,the leaching concentration of As and Sb is the minimum,that is,the stability effect is the best when As and Sb are in 5%red mud,10%fly ash,5%dried sludge,1%rice husk ash,1%Fe SO₄.After treatment,the leaching concentration of As in the tailings of Dushan and Qinglong antimony deposit not exceed 0.01mg/L and 0.05mg/L respectively according to GB/T 14848-2017 groundwater standard.The weak acid extraction state content of As and Sb decrease,which reduces the bioavailability of As and Sb.The crystal structure of calcium silicate hydrate and calcium carbonate appear in the stabilized products after treatment,which promotes the close bonding between the tailings sand particles and the stabilizer,reduces the metal leaching amount.The solidifying and cementing test results show that the application of cement is conducive to the increase of p H of tailings curing system,and the leaching concentration and compressive strength of Pb,Zn and Cd are affected by different cement content,water-solid ratio and slurry concentration.After curing,the leaching concentrations of Pb,Zn and Cd not exceed 0.01,1 and 0.005 mg/L of GB/T 14848-2017 groundwater Class III standard,which reduces the risk of metal release in tailings.The density of solidified body reaches maximum(2.18 g/cm³*10^-6)when cement is added with 40%cement,water-solid ratio of 0.25 and slurry concentration of 80%,and the compressive strength of the specimen reaches maximum（13 MPa）.This indicates that in the same compaction process of solidified body,the samples with lower cement content tend to have more gaps,which affects the compressive strength and density of the specimen.The microscopic analysis results show that the interlacing of C-S-H,ettringite and calcite crystals makes the connection between pore particles in the specimen more compact,and increases the compressive strength of the solidified specimen,at the same time,the effect of hydration products on metal leaching and specimen strength determines the solidified cementation performance of tailings.The results of stress-strain characteristics of the specimen show that the water-solid ratio affects the plasticity of the solidified body,and the cement content still has a good bearing capacity and residual strength.