全氟辛烷磺酸盐(PFOS)在藻渣/小球藻上的吸附行为及机理

为了开发新型廉价生物吸附剂,以高效吸附去除水体中全氟辛烷磺酸盐(PFOS),对小球藻提取生物柴油后的藻渣吸附酸性水体中的PFOS进行了吸附行为及机理的研究。小球藻提取生物质柴油后,比表面积、孔容、孔径几乎没有变化;等电点由3.3降低至2.7;蛋白质含量由51.45%提高到57.35%。在酸性条件下(pH≤3),小球藻和藻渣对PFOS的吸附率均达到99%以上;随着pH值增加至7,二者的吸附去除率迅速降低,但仍保持在22%~26%。小球藻和藻渣对PFOS的最大吸附容量分别为353.69 mg/g和444.83 mg/g。Freundlich模型能较好地拟合二者对PFOS的吸附数据,表明为多层吸附,即小球藻以静电吸引的形式吸附PFOS阴离子,并疏水分配至所含蛋白质中;而藻渣中含量较高的蛋白质对PFOS的疏水性分配作用是导致藻渣吸附量增高的主要原因。

Sorption behavior and mechanism of perfluorooctanesulfonate(PFOS) on Chlorella and Chlorella residues

A novel sorbent from the Chlorella residues after extraction of bio-oils was used to remove perfluorooctanesulfonate (PFOS) from water, and the sorption behavior and mechanism were studied. There was no obvious change of the specific surface area (BET), pore volume and pore sizes before and after extracting lipids of Chlorella, which had slight effect on sorption behavior. But the pH at point of zero charge (pH_pzc) of Chlorella and Chlorella residues was 3.3 and 2.7, respectively. The percent of protein content increased from 51.45% (Chlorella) to 57.35% (Chlorella residues). The increase of protein led to an improvement of the maximum sorption capacities of PFOS on the two sorbents from 353.69 mg/g to 444.83 mg/g. The sorption efficiency of PFOS reached 99% on both Chlorella and Chlorella residues when the solution pH was below 3.0. However, it rapidly decreased to 22%~26% with the pH increasing to 7. Freundlich model well fitted the sorption isotherm of PFOS, which suggested that multilayer sorption was occurred. The electrostatic attraction between PFOS and Chlorella was the main driving force, and then PFOS was partitioned into the Chlorella protein with hydrophobic interaction. For Chlorella residues, hydrophobic interaction contributed in the sorption process.