赤泥土壤化过程中盐分对团聚体形成的影响研究

Bauxite residue, an alkaline, saline bauxite processing waste, is generated by the Bayer process when alumina is extracted from bauxite ores. Due to its high alkalinity and salinity, little evidence exists to effectively exploit bauxite residue as an industrial by-product for other applications. Large volumes of bauxite residue are disposing on the disposal areas, which may cause a series of environmental and ecological pollution issues. Revegetation of the residue converts it to a soil-like medium which has been regarded as a promising approach for large-scale remediation in disposal areas. However, poor physical structure of the residues deters plant growth which limits vegetation establishment. According to ecological investigation of typical bauxite residue disposal areas and natural succession phenomenon, the project investigates distribution characteristics and evolution rule of residue salt ions on the disposal areas following natural weathering processes. Based on optimization leaching rate, dissolution equilibrium and leaching kinetics of ions in bauxite residue during water leaching, the critical salt ions are screened to investigate their effects on aggregate formation of the residues according to aggregate size distribution and dynamic variation rules of electrochemical property on residue aggregates. Furthermore, mechanism of aggregate formation by critical ions and the improvement of physical structure of bauxite residue have been analyzed to investigate the effects of salt transformation on aggregate formation in bauxite residue following substrate amelioration. The findings of this project may provide a theoretical basis for understanding the effects of salt transformation on aggregate formation in bauxite residue, and offers a scientific basis for improving soil genesis and vegetation reconstruction on the disposal areas.

赤泥是氧化铝企业生产过程中排放的高碱性固体废弃物，因其碱性强，盐分含量高，综合利用难度大，大量赤泥堆存在赤泥堆场。赤泥土壤化和堆场植被重建是实现赤泥规模化、生态化处置最具前景、且行之有效的方法，然而赤泥较差的物理结构限制植物的生长，影响赤泥堆场的生态重建。通过开展氧化铝企业赤泥堆场生态调查，针对赤泥堆场土壤发生现象，研究自然风化过程中赤泥堆场盐分分布特征及迁移转化规律，结合赤泥盐分离子溶解转化行为，筛选赤泥关键盐分离子。分析关键盐分离子作用下赤泥团聚体粒径分布特征、表面电化学性质动态变化规律，探究关键盐分离子对赤泥团聚体形成的影响。通过赤泥基质改良实验，分析关键盐分离子在赤泥团聚体中的作用机制及赤泥团聚结构变化特征，揭示赤泥土壤化过程中盐分转化对团聚体形成的影响。研究结果能够丰富赤泥土壤化过程中盐分转化及其对土壤形成的认识，为赤泥土壤化及堆场植被重建提供实践指导和科学依据。

赤泥是氧化铝企业生产过程中排放的高碱性固体废弃物，因其碱性强，盐分含量高，综合利用难度大，大量赤泥堆存在赤泥堆场。赤泥土壤化和堆场植被重建是实现赤泥规模化、生态化处置最具前景、且行之有效的方法，然而赤泥较差的物理结构限制植物的生长，影响赤泥堆场的生态重建。本项目以河南某氧化铝企业赤泥堆场为研究对象，系统研究了赤泥土壤化过程中盐分对团聚体形成的影响。自然成土过程中，赤泥盐碱性逐渐降低，赤泥主要阳离子为Ca2+和Na+，主要阴离子为CO32-、HCO3-、Al(OH)4-和OH-。水浸过程中，赤泥盐碱性离子最佳浸出条件为L/S为 2、温度30℃、浸出时间24h。Ca2+/Na+作用下赤泥微团聚体崩解行为差异显著，微团聚体的表面电势和电场强度随着电解质浓度的增加而逐渐降低，Ca2+浓度增加有助于赤泥颗粒的絮凝团聚。结合土柱淋溶实验，含钙物质添加改变了赤泥渗透性能，有利于赤泥渗滤液中Na+、K+、CO32-的迁移，进而影响赤泥盐碱性。相比于天然高分子有机物和人工合成共聚物，天然-人工合成共聚物能够有效促进赤泥大团聚体的形成，并改善赤泥团聚体孔隙结构，但对赤泥盐碱性影响较小。结合不同改良剂对赤泥团聚体粒径分布、团聚体稳定性、团聚体三维结构、孔隙特征等的影响，研选基于含钙废物-有机物联合的赤泥成土过程团聚体稳定性调控材料组合，为赤泥土壤化及堆场植被重建提供实践指导和科学依据。