腐殖酸作用下酸性多孔介质中纳米TiO2的迁移与滞留机制

探讨了富里酸（FA）和胡敏酸（HA）存在条件下饱和石英砂填充柱中纳米二氧化钛（nTiO₂）的迁移和滞留机制.结果表明，pH 4.0条件下，不存在FA和HA时，nTiO₂不发生迁移；FA和HA吸附到nTiO₂表面，改变nTiO₂电动性质，促进其在饱和多孔介质柱中迁移.随着FA和HA浓度由1mg/L升高至10mg/L，nTiO₂的流出率（填充柱流出液与进液中nTiO₂总量的比值）分别由0.01和0.88升高至0.91和0.94；相同条件下，HA在nTiO₂表面的吸附量比FA大，对nTiO₂迁移性的促进作用也更大.离子抑制nTiO₂的迁移，且CaCl₂影响大于NaCl.相同NaCl浓度，与FA相比，HA作用下nTiO₂的迁移性更强，并且7%~56%的nTiO₂沉降在第二极小势能区，高于FA作用下的4%~17%，更易被重新释放.nTiO₂与石英砂之间的高势垒促进nTiO₂的迁移，而低势垒、第二最小势能、阻塞作用、扩散和重力沉降是nTiO₂滞留的主要原因.

Mechanisms of mobility and retention of nano-TiO2 in acidic porous media in the presence of humus acids

The mechanisms of mobility and retention of titanium dioxide nanoparticles (nTiO₂) in well-defined porous media composed of clean quartz sand in the presence of fulvic acid (FA) and humic acid (HA) were studied under acidic conditions. nTiO₂ were immobile in the porous media in the absence of FA and HA at pH 4.0. FA and HA could be adsorbed onto the surface of nTiO₂, change the electrokinetic properties of nTiO₂, and facilitate the transport of nTiO₂. The elution of nTiO₂ increased from 0.01 and 0.88 to 0.91 and 0.94 with the increase of FA and HA from 1mg/L to 10mg/L respectively. Compared to FA, more HA was adsorbed onto nTiO₂, and thus the facilitated effect of HA on transport of nTiO₂ was stronger. Ions inhibited the mobility of nTiO₂, and the effect of CaCl₂ was greater than that of NaCl in same concentration. The mobility of nTiO₂ was better in the presence of HA than FA. In addition, 7%~56% nTiO₂ was deposited in the secondary energy minimum well in the presence of HA, higher than 4%~17% in the presence of FA, which could be easily released when the environmental conditions changed. High energy barriers between nTiO₂ and quartz promoted the mobility of nTiO₂, while a combination of the secondary minimum energy, straining, diffusion and gravitational deposition were involved in the retention of nTiO₂.