不同添加剂对阴离子表面活性剂与多价阳离子沉淀行为的影响

用透光率法研究了不同添加剂对阴离子表面活性剂(SDBS)与多价阳离子(Ca2+)在不同条件下沉淀行为的影响,研究结果表明,在溶液中加入NaCl增大其盐度,加入NaOH、NaHCO3提高其pH值,加入多价金属离子螯合剂(EDTA)或表面活性剂复配,均对SDBS与Ca2+的沉淀有抑制作用,但SDBS与Ca2+的沉淀行为随着体系条件的不同而不同。比较几种方法抑制沉淀的效果,认为加入EDTA的方法比增加体系盐度或增大体系pH值要好,而表面活性剂(阴离子表面活性剂SDBS与非离子表面活性剂TX-100)复配后,混合体系抗Ca2+的能力更强,即使混合表面活性剂中非离子表面活性剂含量很少(实验中阴离子、非离子表面活性剂摩尔比例为10:1)。溶液中就几乎没有沉淀生成,表明非离子表面活性剂对阴离子表面活性剂钙盐沉淀的抑制作用比NaCl、NaOH、NaHCO3和EDTA强,且这种抗Ca2+的能力随着混合表面活性剂中非离子表面活性剂含量的增加而增强。图5参8

Effect of different additives on the precipitating behavior of anionic surfactant and multivalent cation

The precipitating behaviors of anionic surfactant and mul- tivalent canon at different conditions were studied by means of light transmission measurement. The results show that by adding different additives, anionic surfactant and multivalent canon displayed differ-ent precipitating behaviors. When the concentration of Ca2+ was 1.0×10-3 mol/L, less amount of precipitate formed as the increase of NaCl concentration, and when the NaCI concentration was O.lmol/L, no precipitate existed. The precipitating behaviors of anionic sur- factant and multivalent ion also changed with the change of pH. If EDTA was added, less surfactant precipitate was formed because of the chelation between EDTA and Ca2+. When the EDTA concentra- lion was O.Olmol/L, no precipitate existed, suggesting that adding nonionic surfactant TX-100 could inhibit the formation of surfactant precipitate. When the molar content of nonionic surfactant was 10%, there was almost no precipitate.