Study On Preparation And Properties Of Copper Tailings/Metakaolin Geopolymer

Geopolymer is a new type of gel material that has been newly developed in recent years.It is composed of inorganic[Al O₄]and[Si O₄]tetrahedrons and has a three-dimensional network structure.The geopolymer has low energy consumption during preparation,simple preparation process,less CO₂ emission,and good mechanical properties,solidification effect of heavy metals and durability.After analyzing the utilization methods of various copper tailings resources and the performance characteristics of geopolymers,this study uses copper tailings as the main raw material to prepare geopolymers by adding metakaolin and alkaline activators,and then strengthens copper Tailings to explore the effects of different chemical activators,chemical activator additions and calcination temperature on the properties of activated geopolymers,and finally to discuss the high temperature resistance and chemical resistance of copper tailings geopolymers prepared under optimal conditions performance.Through experiments on the preparation of geopolymers from copper tailings,the study found that the most important factor affecting the performance of geopolymers is the water-cement ratio,followed by the amount of metakaolin,and finally the modulus of the alkali activator.The optimal ratio of the ratio is 0.3,the content of metakaolin is 20%,the modulus of the alkali activator is 1.4,and the 3d and 28d compressive strengths of the geopolymer samples prepared under the optimal conditions are respectively 79.8MPa,88.8MPa,and at the same time the curing efficiency of geopolymer on Cu²⁺reached more than 99%.Microscopic analysis revealed that C-S-H amorphous gel material was formed inside the geopolymer.These gel materials filled the gaps between the copper tailings and metakaolin particles,and were tightly cemented with the mineral structure in the copper tailings,form dense gel structure.In the copper tailings preparation geopolymer strengthening and resistance experiment,it is found that Na OH and Na₂CO₃ can destroy the Al-O and Si-O in the copper tailings due to their alkalinity,making the active Si and Al easier to dissolve.The performance of prepared geopolymer is stronger,and because Na OH is more alkaline than Na₂CO₃,the best chemical activator is Na OH.A suitable temperature is needed to activate copper tailings by calcining copper tailings.When the temperature is too low,it is not enough to destroy Al-O and Si-O.When the temperature is too high,the mineral structure that serves as the skeleton structure in the copper tailings will be destroyed.The performance of the prepared geopolymer is reduced.It is found through experiments that the optimal temperature is 600°C.Similarly,the optimal addition amount of chemical activator is 6%through experiments.The compressive strength of the 3d geopolymer sample prepared at a calcination temperature of 600°C,the addition of Na OH activator at 6%is 82.5MPa and the Cu²⁺leaching concentration in the geopolymer is 281ug·kg^-1,the curing efficiency of the activated geopolymer to Cu²⁺is 99.8%,and the activated geopolymer has good properties.The microscopic analysis found that the mineral components such as dolomite and silica in the activated geopolymer were reduced relative to the unactivated geopolymer,which indicated that by strengthening the copper tailings,the active Si and Al in the copper tailings were further dissolved,and The absorption peak of Si-O or Al-O has shifted,which also shows that the Si-O and Al-O in the copper tailings are destroyed,and the active Si and Al in the copper tailings are easier to dissolve and generate more dense gel material finally further improves the performance of the geopolymer.The resistance test of the copper tailings geopolymer prepared under the optimal conditions showed that the compressive strength loss rate of the geopolymer sample was 70.4%and the Cu²⁺leaching concentration was 42.1 mg·kg^-1,at a temperature of800?.The compressive strength loss rate after soaking in H₂SO₄ solution and HCl solution is 66.1%and 61.5%.Compared with ordinary Portland cement,copper tailings geopolymer has good high temperature resistance and chemical resistance.