Variation of alkaline characteristics in bauxite residue under phosphogypsum amendment
Yi-wei Li , Xing-hua Luo , Chu-xuan Li , Graeme J. Millar , Jun Jiang , Sheng-guo Xue
Journal of Central South University ›› 2019, Vol. 26 ›› Issue (2) : 361 -372.
Variation of alkaline characteristics in bauxite residue under phosphogypsum amendment
Aiming at alkaline problem of bauxite residue, this work focused variation of alkaline characteristics in bauxite residue through phosphogypsum treatment. The results demonstrated that the pH of bauxite residue reduced from initial 10.83 to 8.70 when 1.50 wt% phosphogypsum was added for 91 d. The removal rates of free alkali and exchangeable sodium were 97.94% and 75.87%, respectively. Meanwhile, significant positive correlations (P<0.05) existed between pH and free alkali, exchangeable sodium. The effect of free alkali composition was CO32–>OH–> AlO2–>HCO3–. In addition, alkaline phase decreased from 52.81% to 48.58% and gypsum stably presented in bauxite residue which continuously provided Ca2+ to inhibit dissolution of combined alkali. Furthermore, phosphogypsum promoted formation of macroaggregate structure, increased Ca2+, decreased Na+ and Al3+ on the surface of bauxite residue significantly, ultimately promoting soil formation in bauxite residue.
bauxite residue / alkaline regulation / free alkali / phosphogypsum amendment / soil formation in bauxite residue
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