Variation of alkaline characteristics in bauxite residue under phosphogypsum amendment

磷石膏改良作用下赤泥的碱性变化（英文）

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 CO3^2–>OH^–>AlO2^–>HCO3^–.In addition,alkaline phase decreased from 52.81%to 48.58%and gypsum stably presented in bauxite residue which continuously provided Ca^2+to inhibit dissolution of combined alkali.Furthermore,phosphogypsum promoted formation of macroaggregate structure,increased Ca^2+,decreased Na+and Al^3+on the surface of bauxite residue significantly,ultimately promoting soil formation in bauxite residue.

赤泥碱性转化是氧化铝工业处置固体废物面临的世界性难题。本文开展工业废弃物对赤泥碱性改良研究,结果表明:磷石膏最优添加量为1.50 wt%,处理91天后,赤泥pH由10.83降至8.70;自由碱去除率为97.94%,可交换性钠去除率为75.87%,自由碱、可交换性钠和赤泥pH存在显著正相关关系(P<0.05);自由碱的作用效果为CO_3^(2–)>OH–>AlO_2~–>HCO_3~–;化学结合碱含量从52.81%降至48.58%,固相中稳定性强的石膏为液相体系持续提供Ca^(2+),抑制结合碱的溶解;磷石膏促进团聚体形成,表面Ca^(2+)含量增加, Na^+、Al^(3+)含量降低,有利于加快赤泥土壤化进程。