School of Metallurgy and Environment, Central South University, Changsha 410083, China.
School of Metallurgy and Environment, Central South University, Changsha 410083, China.
J Environ Sci (China). 2019 Mar;77:1-10. doi: 10.1016/j.jes.2018.05.016. Epub 2018 May 25.
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 pH 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 in solid phase changed 112 mg/kg and 259 mg/kg, respectively. Ca 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 macro-aggregates, whilst the content of Ca 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.
降低赤泥的高碱度是使其适合植物生长和综合利用的关键问题。在本研究中，磷石膏作为磷肥工业的一种废物，被用于驱动赤泥的碱性转化。在最优的水洗条件下（液固比为 2mL/g，30°C，24 小时），考察了磷石膏添加量、反应时间和反应机制的影响。磷石膏的添加有效地降低了 pH 值，并将可溶性碱度降低了 92.2%。研究发现，上清液中可溶性 Na 和 Ca 离子的浓度逐渐增加，而固相中可交换的 Na 和 Ca 分别变化了 112mg/kg 和 259mg/kg。Ca 成为固相中的主要元素（磷石膏添加量为 2%，液固比为 2mL/g，30°C，12 小时）。X 射线衍射数据表明，钙霞石和水钙铝榴石是主要的碱性矿物。SEM 图像表明，磷石膏可以促进稳定的大团聚体的形成，同时 Ca 的含量从 5.6%增加到 18.2%，Na 的含量从 6.8%降低到 2.4%。用磷石膏处理可以通过中和、沉淀和取代反应显著促进碱度阳离子的转化。这项研究为用磷石膏改良促进赤泥成土提供了一种可行的方法。
