Study On Key Technology And Mechanism Of Preparing Magnesium Based Building Materials From Magnesite Tailings

In recent years,with the large-scale mining of magnesite in China,the tailings are piled up and occupy a lot of land resources.In order to utilize the magnesium resources in the tailings while consuming and treating magnesite tailings,improve its added value and reduce the cost of tailings treatment.In this paper,magnesite tailings in Liaoning Province are used as raw materials to study their thermal decomposition,acid leaching and preparing MOS and MKPC.While consuming tailings,industrial waste acid is also treated,and the discarded magnesium resources in tailings are extracted,so as to improve their added value.The thermal decomposition kinetics of magnesite tailings is studied.The results show that the main thermal decomposition range of magnesite tailings is 550℃～650℃,the decomposition rate is the largest at about648.9℃,and the maximum weight loss rate is 43.77%.When the heating rate is 10℃/min,the thermal decomposition kinetic equation of magnesite tailings is dα/d T=（8.97×10⁸/β）·e^-147991/RT（1-α）^2/3,activation energy E=147.99 k J/mol,pre exponential factor A=8.97×10⁸.The reaction mechanism function is f（?）=（1-（?））2/3,and the reaction order n=2/3,which belongs to the three-dimensional phase boundary reaction model.The activity of magnesia is related to the calcination conditions of magnesite tailings.There is a range of calcination temperature and calcination time,which makes the activity of magnesia the highest.Increasing the calcination temperature or prolonging the calcination time can reduce the activity of magnesia.When calcined at900℃-120 min,the activity of magnesium oxide is highest;At about1200℃-180 min,magnesium oxide is basically inactivated and becomes dead burned magnesium oxide.Study on acid leaching technology of magnesite tailings.The results show that the leaching rate of magnesium can reach 71.87% when the acid concentration is 20%,the acid leaching time is 2.9 h and the liquid-solid ratio is 11.6.Although the leaching rate is low,the calcination process is omitted and the energy consumption is reduced.The leaching rates of boron mud and asbestos tailings were 95%and 70%respectively.This process condition can be used to extract magnesium resources from magnesite tailings.The full solid waste-MOS was prepared by using the acid leaching mixture and magnesite tailings obtained.The results show that the 28-days compressive strength of full solid waste-MOS can reach 47.7 MPa.Study on MKPC is prepared by using dead burned magnesia obtained from calcining magnesite tailings.The results show that the initial setting time is controlled above 20 min,and the strength can reach 52.64 MPa in 3-days.Through the comparative study with commercial calcined magnesia,it is found that the dead burned magnesia prepared by calcining magnesite tailings prolongs the initial setting time of potassium magnesium phosphate cement by 48.53%,but the strength decreases slightly.