摘要
赤泥是氧化铝生产过程中产生的工业废渣,其强碱性使得赤泥存在环境污染风险高、资源化利用困难等问题.因此,急需寻求赤泥脱碱的有效方法和新途径.微生物脱碱法因其经济有效、无二次污染的特点而备受关注.本文利用巨大芽孢杆菌菌液对赤泥脱碱,通过高效液相色谱(HPLC)、XRD、SEM-EDS和FT-IR分别对细菌代谢产物、脱碱前后矿物的物相组成、微观形貌和官能团结构进行分析,研究了巨大芽孢杆菌对赤泥脱碱的作用机制.结果表明:在菌量为5.67×1013 CFU/mL、液固比为25(mL/g)和温度为35℃的条件下可将脱碱样品的pH值降低至8.55,10 d的单次脱碱率达到30.4%,比无菌添加时的pH值降低了1.48,脱碱率提高22.6%;脱碱后赤泥中方钠石、钙霞石等碱性矿物的衍射峰强度减弱,方解石的衍射峰强度增强,赤泥表面有菌株附着,并出现明显的溶蚀形貌,一些碱性矿物的铝硅酸盐结构被溶解;巨大芽孢杆菌主要利用代谢产生的两种含量较高的有机酸(苹果酸和丙酸)与赤泥中的碱性物质发生酸碱中和,实现对赤泥的脱碱.
Abstract
Red mud is an industrial waste generated in the process of alumina production.Its strong alkalinity makes the red mud have problems,such as high risk of environmental pollution and difficulty in resource utilization.Therefore,there is an urgent need to seek effective methods and new ways for dealkalizing red mud.Microbial dealkalization has attracted much attention due to its cost-effective and non-secondary pollution characteristics.In this paper,we used Bacillus megaterium bacterial solution to dealkalize red mud.Then we analyzed the bacterial metabolites,the physical composition of minerals before and after dealkalization,the microscopic morphology and the structure of functional groups by high-performance liquid chromatography(HPLC),XRD,SEM-EDS and FT-IR,respectively,and investigated the mechanism of the role of Bacillus megaterium in the dealkalization of red mud.The results show that the pH of the dealkalized sample can be reduced to 8.55 under the conditions of bacteria concentration of 5.67×1013 CFU/mL,liquid-solid ratio of 25,and temperature of 35℃and the single dealkalization rate of 10 d reaches 30.4%,which is 22.6%higher than that of the sterile addition with reduction of pH by 1.48.After the dealkalization,the diffraction peaks of alkaline minerals,such as siderite and chalcocite in the red mud are weakened,but the diffraction peaks of calcite are strengthened.The surface of the red mud is attached with strains of bacteria,displaying obvious dissolution morphologies,and the aluminosilicate structure of some alkaline minerals is dissolved.Bacillus megaterium primarily utilizes two types of organic acids(malic acid and propionic acid)with high content produced by its metabolism,which can neutralize with the alkalinity in the red mud and achieve the dealkalization of the red mud.
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