The strong alkalinity of red mud is a key reason that threatens the environment and restricts the secondary use of red mud. Freeze-thaw (FT)-acid washing (AW) is proposed to remove alkali to improve the dealkalization efficiency of red mud. FT-AW tests were performed using red mud with oxalic acid (OA) and citric acid (CA) to examine the effect of FT cycles and eluent concentration on the dealkalization efficiency. Results showed that the FT-AW method significantly increased the dealkalization efficiency under the synergy of FT and AW. After 5 times of FT-AW, the alkali removal efficiencies of red mud with OA and CA as eluents reached 97.5% and 95.5%, which were 27.3% and 18.9% higher than those of the control group, respectively. The effect of OA on dealkalization was more sensitive than that of CA. The results of SEM-EDS and XRD showed that FT cycles destroyed the crystal structure of red mud and released part of the bonded alkali. The FT-AW method provides a novel idea for future large-scale red mud dealkalization by using FT alternation in seasonally frozen soil areas.

赤泥的强碱性是威胁环境、限制赤泥二次利用的关键原因。提出冻融（FT）-酸洗（AW）脱碱以提高赤泥的脱碱效率。使用含有草酸（OA）和柠檬酸（CA）的赤泥进行 FT-AW 测试，以检查 FT 循环和洗脱液浓度对脱碱效率的影响。结果表明，在FT和AW的协同作用下，FT-AW方法显着提高了脱碱效率。经过5次FT-AW后，以OA和CA为淋洗液的赤泥脱碱效率分别达到97.5%和95.5%，分别比对照组提高了27.3%和18.9%。OA对脱碱作用的影响比CA更敏感。SEM-EDS和XRD结果表明FT循环破坏了赤泥的晶体结构并释放了部分结合碱。FT-AW方法为未来在季节性冻土地区利用FT交替进行大规模赤泥脱碱提供了新的思路。