Phosphogypsum stabilization of bauxite residue:Conversion of its alkaline characteristics

作     者：Shengguo Xue Meng Li Jun Jiang Graeme J.Millar Chuxuan Li Xiangfeng Kong 

作者机构：School of Metallurgy and Environment Central South University Institute for Future Environments Science and Engineering Faculty Queensland University of Technology 

出 版 物：《Journal of Environmental Sciences》 (环境科学学报（英文版）)

年 卷 期：2019年第31卷第3期

页      面：1-10页

核心收录：

学科分类：083002[工学-环境工程] 0830[工学-环境科学与工程（可授工学、理学、农学学位）] 08[工学] 

基　　金：supported by the National Natural Science Foundation of China(Nos.41701587 and 41371475) the Environmental Protection's Special Scientific Research for Chinese Public Welfare Industry(No.201509048) 

主　　题：Bauxite residue Phosphogypsum Alkaline ions Alkaline transformation Soil formation 

摘      要：Reduction of the high alkalinity of bauxite residue is a key problem to solve to make it suitable for plant growth and comprehensive utilization. In this study, phosphogypsum, a waste product from the phosphate fertilizer industry, was used to drive the alkaline transformation of the bauxite residue. Under optimal water washing conditions(liquid/solid ratio of 2 mL/g, 30°C, 24 hr), the impact of quantity added, reaction time and reaction mechanism during phosphogypsum application were investigated. Phosphogypsum addition effectively lowered p H levels and reduced the soluble alkalinity by 92.2%. It was found that the concentration of soluble Na and Ca ions in the supernatant increased gradually, whilst the exchangeable Na+and Ca^(2+)in solid phase changed 112 mg/kg and 259 mg/kg, respectively. Ca^(2+)became the dominant element in the solid phase(phosphogypsum addition of 2%, liquid/solid ratio of 2 mL/g, 30°C, 12 hr). X-ray diffraction data indicated that cancrinite and hydrogarnet were the primary alkaline minerals. SEM images suggested that phosphogypsum could promote the formation of stable macroaggregates, whilst the content of Ca^(2+)increased from 5.6% to 18.2% and Na reduced from 6.8% to 2.4%. Treatment with phosphogypsum could significantly promote the transformation of alkalinity cations by neutralization, precipitation and replacement reactions.This research provided a feasible method to promote soil formation of bauxite residue by phosphogypsum amendment.