赤泥冻融-淋洗脱碱试验研究

Experimental study on dealkalization of red mud by freeze-thaw and washing

强碱性限制了赤泥在诸多领域的综合利用。以河南某拜耳法氧化铝厂提供的赤泥为研究对象,提出冻融协同化学淋洗的脱碱方案,即利用反复冻融土颗粒原有结构的同时,破坏结合碱晶体结构,使赤泥中包裹的结构碱进一步释放,能够增加接触面积的原理,进行冻融-淋洗脱碱试验。考察冻融作用对赤泥结构的影响以及草酸浓度、冻融次数对赤泥脱碱率的影响,同时通过XRD物相分析、粒度分析和电子显微镜扫描,从微观层面分析冻融-淋洗脱碱的机理。结果表明,冻融作用可破坏赤泥颗粒中含有结合碱物质的晶体结构,有助于淋洗液与结合碱接触反应,从而提高脱碱率;在草酸浓度为0.5 mol/L,2次冻融淋洗的条件下,赤泥的脱碱率可达94.96%,较常温条件下提高14.26%。该研究为今后季节冻土区冻融交替现象赤泥脱碱提供了新思路。

The comprehensive utilization of red mud in many fields is limited because of its strong alkalinity.Taking the red mud provided by a Bayer alumina plant in Henan Province as the research object,this paper put forward the dealkalization scheme of freeze-thaw combined with chemical washing.That is,the original structure of soil particles was repeatedly frozen and thawed,and the combined alkali crystal structure was destroyed to further release the structural alkali wrapped in the red mud,which can increase the contact area.Freeze-thaw and washing experiment was carried out and the effects of freeze-thaw on the structure of red mud and the effects of oxalic acid concentration and freeze-thaw times on the dealkalization rate of red mud were investigated.At the same time,the mechanism of freeze-thaw and washing dealkalization was analyzed from the micro level by XRD phase analysis,particle size analysis and electron microscope scanning.The results showed that freeze-thaw could destroy the crystal structure of bound alkali in red mud particles,which was conducive to the contact reaction between leaching solution and bound alkali,so as to improve the dealkalization rate.Under the condition of oxalic acid concentration of 0.5 mol/L and twice freeze-thaw and washing,the dealkalization rate of red mud could reach 94.96%,which was 14.26%higher than that under normal temperature.This study provided a new idea for the dealkalization of red mud in the alternating phenomenon of freezing and thawing in seasonal frozen soil area in the future.