Abstract:

Red mud is the biggest environmental pollution problem in alumina industry, and alkalinity regulation is the key to red mud disposal. The simulated solution of the CaCl₂ generated from the resource recycling process of red mud was selected as the agent to study the alkalinity regulation of red mud. Factors that may affect the alkalinity regulation were investigated. Column leaching experiments were conducted to simulate the leaching process in the actual red mud storage process, and pot experiments were carried out to evaluate the soil formation potential of dealkalized red mud. The results show that the pH of the leachate decreased to 8.39 and the concentration of Ca and Na ions reached 7.74g/L and 1.22g/L under the optimal conditions of solid-to-liquid ratio of 500g/L, Ca²⁺ concentration of 10g/L, reaction temperature of 85℃ and reaction time of 2h, respectively. In addition, the dealkalization equilibrium can be reached in one dealkalization process. The Na/Ca ratio of the column leaching effluent reached 107.8, which was much higher than that of seawater (25.8), suggesting that it could be used as raw materials for chlor-alkali industry. The pH of red mud decreased from 11.14 to 8.05 after dealkalization. The seven-day germination rate of ryegrass in the mixed matrix of dealkalized red mud and sawdust reached 92%, which was higher than that in fresh soil (84%), suggesting that dealkalized red mud is suitable for plant growth. In summary, the use of recycled CaCl₂ for red mud alkalinity regulation can provide a low-cost, green and environmentally friendly method for red mud disposal.

Key words: red mud, alkalinity regulation, recycled CaCl₂, column leaching, soil formation

摘要：

赤泥是氧化铝行业最大的环境污染问题，碱性调控是处置赤泥的关键。本文以赤泥资源化过程中产出的CaCl₂溶液的模拟液作为脱碱剂对赤泥进行碱性调控研究，考察了可能影响碱性调控过程的因素，并进行了柱淋洗实验以模拟实际赤泥堆存过程中的淋洗过程，进行盆栽试验来评估脱碱赤泥的土壤化潜力。结果表明：在固液比为500g/L、脱碱液Ca²⁺浓度为10g/L、反应温度为85℃、反应时间为2h的条件下，浸出液中Ca、Na浓度分别为7.74g/L和1.22g/L，pH可降低至8.39，并且一次脱碱过程即可达到脱碱平衡。柱淋洗流出液Na/Ca比高达107.8，远高于海水Na/Ca比（25.8），可用作氯碱工业原料；脱碱后赤泥pH由11.14降至8.05。黑麦草在脱碱赤泥与锯末的混合基质中的七天发芽率达到92%，高于新鲜土壤中黑麦草发芽率（84%），表明脱碱后赤泥适合植物生长。利用CaCl₂回收液进行赤泥碱性调控可为赤泥处置提供一种成本低廉、绿色环保的方法。

关键词: 赤泥, 碱性调控, CaCl₂回收液, 柱淋洗, 土壤化