ABSTRACT

This paper reports on the removal of linear alkylbenzene sulfonate (LAS) by conventional and cetyltrimethylammonium bromide (CTAB)-aided coagulation-filtration processes. The addition of CTAB led to the formation of CTAB-LAS aggregates, whose surface charge was negative at a CTAB-LAS molar ratio < 1 and positive at a molar ratio > 1. The efficacy of the coagulation-filtration process strongly depended on the electrostatic interactions between hydroxide floc and both free LAS and CTAB-LAS aggregate. Since free LAS is anionic, its adsorption onto the hydroxide floc was enhanced when the floc was positively charged. Ferric hydroxide floc (pH < 6.0) and aluminum hydroxide floc (pH < 7.4) showed positive surface charges and were thereby effective in removing free LAS. The optimal coagulation pH for removing the CTAB-LAS aggregate depended on the CTAB/LAS molar ratio. A higher coagulation pH was effective in removing LAS under the CTAB/LAS molar ratio > 1. However, in this case, excessive free CTAB remained after coagulation-filtration. Therefore, the lower coagulation pH with a CTAB/LAS molar ratio < 1, with the hydroxide floc and CTAB-LAS aggregate being positively and negatively charged, respectively, was recommended for LAS removal. In chemical industry wastewater, the optimal CTAB dose was higher than that in synthetic wastewater due to coexistent chemicals scavenging CTAB. Consequently, coagulation-filtration using a ferric chloride coagulant under the CTAB/LAS molar ratio of 0.7–2.0 and pH 4.5 was recommended for LAS removal from chemical industry wastewater, where the observed LAS removal efficiency reached 91 ± 3% without any deterioration of COD removal.

摘要

本文报道了通过常规和十六烷基三甲基溴化铵 (CTAB) 辅助混凝过滤工艺去除直链烷基苯磺酸盐 (LAS)。CTAB 的加入导致 CTAB-LAS 聚集体的形成，其表面电荷在 CTAB-LAS 摩尔比 < 1 时为负，在摩尔比 > 1 时为正。混凝过滤过程的功效很大程度上取决于静电氢氧化物絮凝物与游离 LAS 和 CTAB-LAS 聚集体之间的相互作用。由于游离 LAS 是阴离子的，因此当絮凝物带正电时，它对氢氧化物絮凝物的吸附会增强。氢氧化铁絮凝物 (pH < 6.0) 和氢氧化铝絮凝物 (pH < 7.4) 显示出正表面电荷，因此可有效去除游离 LAS。去除 CTAB-LAS 聚集体的最佳混凝 pH 值取决于 CTAB/LAS 摩尔比。在 CTAB/LAS 摩尔比 > 1 的情况下，较高的混凝 pH 可有效去除 LAS。然而，在这种情况下，在混凝过滤后会残留过多的游离 CTAB。因此，建议使用 CTAB/LAS 摩尔比 < 1 的较低混凝 pH 值，氢氧化物絮凝物和 CTAB-LAS 聚集体分别带正电和负电，用于 LAS 去除。在化学工业废水中，由于共存的化学物质清除 CTAB，CTAB 的最佳剂量高于合成废水。因此，建议使用 CTAB/LAS 摩尔比为 0.7-2.0 和 pH 4.5 的氯化铁混凝剂进行混凝过滤，以去除化学工业废水中的 LAS，