Study On Comprehensive Utilization Technology And Mechanism Of Boron Mud Based On Magnesium Cementitious Material

Boron mud is the solid waste left over from the production of boron chemical products from boron ore.This project will take boron mud from an abandoned yard in Yingkou,Liaoning Province as raw material,and combine boron mud with magnesium-based cementitious materials to prepare magnesium oxychloride cement and magnesium oxysulfide cement respectively,which provides simple and convenient operation for boron mud treatment.It is a large-scale application technology that is easy to promote;at the same time,in the process of resource utilization,the magnesium resources in the boron mud are fully utilized,and the high value-added utilization of the boron mud is realized.The main conclusions of this study are as follows:The magnesium oxychloride cement was prepared by using boron mud,and the influence of the molar ratio,the content of magnesium oxide,the content of fly ash,and the molding method on its mechanical properties was studied respectively,and the optimal experimental conditions of the magnesium oxychloride cement were determined:the molar ratio Mg O:Mg Cl₂=5（the molar ratio is calculated according to the mass of activated magnesium oxide）,the content of magnesium oxide is 22%,the content of fly ash is 20%,the content of modifier A is 2%,and the final flexural strength of magnesium oxychloride cement is 6.70MPa,compressive strength 45.26MPa.Boron mud was acid leaching to obtain boron mud mixture to substitute industrial magnesium sulfate to prepare magnesium thioxide cement.The optimal acid leaching conditions:solid-liquid ratio=1:2,reaction time more than 16h,under this condition,the content of magnesium sulfate in the mixture of boron mud reaches 16%,the utilization rate of sulfuric acid remains above 70%,meet the experimental requirements.The optimum experimental conditions for the preparation of magnesium thioxide cement are as follows:molar ratio Mg O:Mg SO₄=7,magnesium oxide content 16%,fly ash content 25%,The content of modifier B is 11.25%,Under this condition,the flexural strength of magnesium oxysulfide cement obtained is8.00MPa,and the compressive strength is 36.50MPa.And using the above ratio to conduct field experiments,the pavement laid after long-term maintenance is in good condition.Magnesium oxide is prepared by calcining boron mud,and a solid waste magnesium oxysulfide cement is prepared by combining the boron mud mixture.Through the study of the thermal decomposition kinetics of boron mud,the results show that the decomposition rate of boron mud is the largest at 550℃,and the decomposition is complete at about 650℃.The optimum calcination range is determined by calcination experiments:calcination temperature is 600℃-650℃,calcination time is 2h-2.5h,under this condition,the activity of magnesia is 16.7%,and the inactive boron mud is used as aggregate.Based on the molar ratio of Mg O:Mg SO₄=7,the compressive strength of the prepared magnesium oxysulfide cement is37.00MPa,which confirms that the magnesium oxide calcined by boron mud is enough to replace the purchased light-burned magnesium oxide powder to prepare building materials.