Removal Of Nitrate From Brine Water By Biochar-supported Nano Zero Valent Iron Composites And Their Modified Composites

With the rapid development of industry and agriculture in our country,the pollution of nitrate nitrogen has become a problem that cannot be ignored and urgently needs to be solved.As a product of ion exchange membrane treatment in waterworks,the pollution problem of high concentration of nitrate nitrogen contained in brine is becoming more and more serious.As a new type of treatment technology,the use of nano-zero-valent iron and its composite materials for the treatment of nitrate nitrogen has become a hot spot for studies in the environmental field in recent years.In this study,different proportions of nano zero-valent iron/biochar composites and Cu reinforced modified composites were prepared by wet method under anaerobic conditions,and then a series of sequencing batch experiments were carried out to explore the removal effect of nitrate nitrogen under different conditions.On this basis,the treatment of actual ion exchange concentrated water was simulated through continuous flow experiment,which provided a scientific reference for the treatment of actual concentrated water.The main results of this paper are as follows:（1）The mass ratio of BC-nZVI material affects the removal rate of nitrate nitrogen,and the removal rate of nitrate nitrogen by BC1-nZVI2 reaches the highest 99.10%.When the initial concentration of nitrate nitrogen is 150 mg L^-1,the maximum removal amount of nitrate nitrogen by BC1-nZVI2 is 495.2 mg g^-1.The optimal dosage of BC1-nZVI2 is 10 g L^-1,and the initial pH value has a greater influence on the removal of nitrate nitrogen by BC1-nZVI2.Neutral conditions are beneficial to the transformation to nitrogen gas,while acid or alkali is conducive to the transformation to ammonia nitrogen.The longer the aging time of BC1-nZVI2,the lower the removal rate of nitrate nitrogen.（2）BC1-nZVI2-Cu10 was the optimal iron-copper ratio material,and its removal rate of nitrate nitrogen was 99.03%.After the reaction,the content of ammonia nitrogen in the product BC1-nZVI2 decreased,and the reaction rate increased.The optimum dosage of BC1-nZVI2-Cu10 was 6.6 g L^-1.The effect of initial pH value on the removal of nitrate by BC1-nZVI2-Cu10 was less than that by BC1-nZVI2.At pH 11,the removal rate of nitrate by BC1-nZVI2-Cu10 was 90.72%.SO₄^2-in the solution had little effect on the removal of nitrate nitrogen by BC1-nZVI2-Cu10.When PO₄^3-existed in the solution,the lowest removal rate of nitrate nitrogen by BC1-nZVI2-Cu10 was 46.50%.（3）In the continuous flow experiment,when BC1-nZVI2-Cu10 was used as filler material,the highest nitrate nitrogen removal rate was 81.40%.The penetration time(t_0.8)corresponding to BC1-nZVI2 and BC1-nZVI2-Cu10 was the fifth day and the seventh day,respectively.The higher the filling layer height is,the longer the corresponding penetration time(t_0.8)is.The greater the flow rate,the shorter the penetration time,and the lower the removal rate of nitrate nitrogen.