Research On The Production Of Tailings-based Geopolymers And The Solidification Of Heavy Metal Ions

Tailings,as the main solid waste discharged during mineral processing,is an important challenge for the sustainable development of the world.At present,with the continuous tightening of national environmental protection policies,the rational disposal of mine tailings and how to reduce,harmless and recycle tailings have become important problems faced by various mining enterprises.Geopolymer is a new type of inorganic non-metallic material,which has the advantages of simple preparation process and low energy consumption.Therefore,the use of tailing as a raw material for the production of geopolymers can realize the resource utilization of tailings,which is beneficial to mining enterprises to reduce the amount of tailings and obtain economic benefits.The research work took the cyanide heap leaching tailings of the Haihua Gold Mine in Mangshi,Dehong Prefecture,Yunnan Province as the research object,and explored the feasibility of using the tailing to make geopolymer.And through a series of conditional tests and optimization tests,the process of using the tailing to prepare geopolymer gel material was systematically studied,and the preparation scheme of tailing-based geopolymer was obtained.At the same time,the experiment investigated the ability of tailing-based geopolymers to solidify heavy metal ions,which were produced under different conditions.During the test,the tailings were pretreated by fine grinding and calcination.After the pretreatment,the dolomite in the tailings was decomposed into calcium carbonate and calcium oxide.Based on this,the influence of the addition amount of water glass and the modulus of water glass on the 3d and 28d compressive strength of tailings-based geopolymers was studied using single-factor condition tests.The test results showed that when the addition of water glass was 6%and the water glass modulus was 1.4,the tailing-based geopolymer could achieve higher compressive strength.In addition,the response surface optimization experiments were used to study the effects of metakaolin addition,liquid-solid ratio and curing temperature on the 3d and 28d compressive strength of tailing-based geopolymers.And the optimization test results showed that the best conditions for the production of geopolymers are:water glass modulus 1.4,water glass addition 6%,metakaolin content 34.50%,liquid-solid ratio 0.37,curing temperature 67.00?.The compressive strength of the tailing-based geopolymer produced under this condition could reach a high value.The 3d and 28d compressive strengths were 27.45 MPa and 45.17 MPa,respectively,and their strengths meet the national requirement for 45R grade ordinary Portland cement.The heavy metal ion leaching test was carried out by TCLP?Toxicity Characteristic Leaching Procedure?.In the experiment,Zn SO₄,Cu SO₄,Pb?NO₃?₂,and Cd?NO₃?₂ were used as heavy metal additives.The effects of metakaolin addition,curing age and heavy metal ion dosage on the ability of tailing-based geopolymers to solidify heavy metal ions were studied.The test results showed that under the influence of the addition amount of metakaolin,age and the heavy metal ions dosage,the leaching amount of Zn²⁺,Cu²⁺,Pb²⁺,Cd²⁺and the efficiency of solidifying heavy metal ions are basically consistent.When the content of metakaolin and the age of curing increased,the content of each heavy metal ion in the tailing-based geopolymer leaching solution was showing a downward trend,and the curing efficiency was improved.When the content of heavy metal ions in the tailing-based geopolymer increased,the content of heavy metal ions in the leaching solution increased slowly first,and then sharply increased.During the test,except that the leaching amount of heavy metals of individual samples exceeded the national standard,the leaching amount of heavy metal ions of most samples was far lower than the national standard.It showed that the tailings-based geopolymer had a good curing effect on heavy metal ions.The results showed that using tailings and other solid wastes as raw materials could successfully produce tailings-based geopolymer materials with good mechanical properties.At the same time,its three-dimensional network structure was also effective for curing heavy metal ions.Studying tailings-based geopolymers is of great significance for tailings recycling and solidification of heavy metal ions.