高岭土铝活化法制备改性粘土及其除藻机制

以焙烧高岭土为原料,通过酸-碱组合活化、原料复配、控温熟化等连续处理步骤活化高岭土中的铝制备改性粘土(MC)。采用正交试验设计对该方法进行优化,考察了制备条件对获得改性粘土除藻效果的影响规律,探讨了不同制备条件下获得改性粘土除藻效率差异的机制。结果表明,酸-碱组合活化pH值对改性粘土的除藻效率具有显著影响(P<0.05),控制碱中和后的pH£3.6获得改性粘土的除藻效率可达90%以上。通过分析改性粘土的理化特征及絮凝除藻时的絮凝体特征发现,在最佳制备条件下,高岭土矿晶中铝大量被活化,合成改性粘土的片层致密且卷曲、微表面粗糙,分散到海水中时活化单体铝(Al_a)、多羟基铝(Al_b)含量更高,粘土表面电性由负转为正,絮凝卷扫藻细胞的作用增强,因而合成改性粘土具有更高消除赤潮生物的能力。

Modified clay preparation via kaolin aluminum activation and its algae removal mechanism

This study analyzed modified clay (MC) prepared from calcined kaolin using a new method for activation of aluminum, which includes acid pickling, base neutralizing, supplementation of uncalcined kaolin clay, and aging. The algae removal efficiency (ARE) of MC was evaluated as a way to optimize various treatment conditions of the new method. Results showed that the acid pickling-base neutralization step had a significant impact on the ARE (P<0.05), achieving 90% of ARE when pH of the treated slurry calibrated to no more than 3.6 by base neutralization. Analysis of physicochemical properties of the MC and the examination of floc revealed that MC prepared with the optimized conditions had a compact curled sheet structure and a rough micro-surface, which exuded a large amount of activated aluminum from the mineral crystals, with higher contents of both the monomer aluminum (Al_a) and the polyhydroxy aluminum (Al_b) when MC was dispersed in seawater, suggesting that the activated aluminum was easily transformed into Al_a and Al_b. Meanwhile, the zeta potential of the suspended MC particles changed from negativity to positivity. As a consequence, the activated aluminum and the improved clay surface thus ensured that the MC has a higher capability to eliminate red tide algae.