微波造孔活化粒状赤泥并应用于废水深度净化的基础研究

Red mud, which is produced from alumina industry, nowadays has been the largest nonferrous residue pilled up around the global.Recently, using red mud as adsorbent to purify waste water containing heavy metal ions or organics become one of the heated research direction. But because of some difficulty in activation, separation, circulation and indistinction of principle, the process is still can not be applicated in large-scale.This research prefered to adopt microwave pore-making and activation process (MPA) to produce new type adsorbent with red mud. The principle of MPA process lies in that microwave energy can selectively and quickly act with water, organics and the high-microwave-adsoption solids existing in wet granular red mud(GRM), which can explosively make tiny pore and chanel generated because of water vaporation and organics volatilization. Thus the process can activate the adsorption characteristics and increase the intensity of the GRM, and it can become a porous adsorbent with high strength, and be used in purifying the waste water containing pollutants of heavy metal ions and/or organics deeply.The research contents include: the process and foundation research of granulating red mud containing high alkali and water directly, MPA, and adsorption and desorption of purefying waste water. The key research content lies in the internal relations of activation, pore-making and strengthening of GRM with microwave energy. This study will supply the basic theories as well as new process for producing GRM with high strength, high activity and recyclable absorbent for purifying waste water deeply.

近来，将氧化铝生产的废渣赤泥应用于吸附净化处理含重金属离子和有机物的废水已经成为赤泥综合利用的热点研究方向之一。但由于存在活化难、分离难、循环使用难和机理不清等关键问题，无法实现规模化应用。本研究拟采用微波造孔活化技术,即利用微波选择性、快速作用于经直接制粒的湿式粒状赤泥内的水、有机物和强吸波固体物相，在不添加造孔剂的情况下，使其内部急剧产生水蒸气、有机物挥发而爆发形成微孔和通道，实现造孔活化和强化，从而把赤泥粒制成高强度多孔吸附剂，应用于重金属和有机废水的深度吸附净化。研究内容主要包括高碱性、高含水赤泥直接制粒、微波造孔活化、处理有机或重金属废水的吸/脱附方法及机理研究等。拟通过系统实验、建模和模拟优化等，重点研究微波能量内部驱动下的赤泥颗粒活化、造孔和强度提高的机理以及它们之间的内在联系。本研究将为把赤泥制备成高强度、高活性和可循环使用的废水深度处理吸附剂提供可靠的基础理论和工艺指导。

以高含水、高碱性的拜耳法赤泥为研究对象，利用微波选择性、快速作用于经直接制粒的湿式粒状赤泥并形成微孔和通道，实现造孔活化和硬度强化。通过小型实验和扩大型实验发现，与常规加热相比，微波加热对粒状赤泥（GRM）的活化造孔效果更好，其表面积从14.07 m2/g增加到31.02 m2/g，粉化率从9.79%降到4.68%。在微波加热条件下，不同粘结剂制备GRM的活化效果的顺序为：淀粉>硅酸钠>水泥。确定微波活化造孔GRM扩大型实验的最佳条件为：6%淀粉作为粘合剂，微波加热温度为500℃，微波功率为2.6 kW，保温时间为30 min。此时，GRM吸附剂的BET表面积，孔体积和粉化率分别为15.58m2/g，0.0337cm3/g和9.6%。此外，提出微波能量内部驱动下赤泥颗粒活化、造孔和强度提高的机理。从热力学和动力学方面，分别研究GRM处理含Cd2+废水和含亚甲基蓝废水的吸附实验。结果表明，GRM是一种具有吸附效果好、速率快，再生效果好的廉价吸附材料。微波活化后GRM的MB极限吸附量qmax可高达17.6 mg/g，远远大于未活化GRM的9.9 mg/g。与未活化的GRM相比，微波活化后的GRM吸附速率很快，10 min内就达到穿透点。此外，还比较了连续脱附和分段脱附，硝酸脱附和微波脱附的效果。