硫酸根对钙基层状双金属氢氧化物去除SDS的影响

Study on the effect of sulphate on removal of SDS by calcium base-like bimetallic hydroxide

利用铝酸三钙(C 3A)水化合成钙基层状双金属氢氧化物(CaAl-LDH-Cl)。通过静态吸附实验考察不同十二烷基硫酸钠(sodium dodecyl sulphate,简称SDS)初始浓度下,CaAl-LDH-Cl在SDS体系、SDS-SO ^(2-)_(4)共存体系中对SDS的吸附效果,并结合XRD、FTIR、SEM和TG等测试手段探究硫酸根对CaAl-LDH-Cl去除SDS的影响机制。结果表明:SDS-SO ^(2-)_(4)共存体系中CaAl-LDH-Cl对SDS的吸附量(4.65 mmol·g^(-1))明显高于SDS体系吸附量(3.42 mmol·g^(-1));两种体系中CaAl-LDH-Cl吸附SDS的行为均符合Langmuir模型,属于单分子层吸附;硫酸根促进CaAl-LDH-Cl去除SDS的机理:(1)CaAl-LDH-Cl自溶解产生的Ca ^(2+)与SDS生成Ca-SDS沉淀,以及SO ^(2-)_(4)通过离子交换作用生成的CaAl-LDH-SO 4,均增加了产物的层间距,提高CaAl-LDH-Cl对SDS的吸附量;(2)SO ^(2-)_(4)的存在有利于SDS胶束形成,促进了CaAl-LDH-Cl对SDS的吸附。

The calcium based layered double hydroxide(CaAl-LDH-Cl)was synthesized by hydrating tricalcium aluminate(C3A).A static adsorption experiment was conducted to investigate the adsorption effect of sulfate on removal of SDS by CaAl-LDH-Cl in SDS system and SDS-SO ^(2-)_(4) coexistence system under different initial sodium dodecyl sulphate(SDS)concentrations;also,combined with XRD,FTIR,SEM and TG,the influence of sulfate on the removal of SDS by CaAl-LDH-Cl was explored.The results showed that the adsorption capacity of CaAl-LDH-Cl on SDS(4.52 mmol·g^(-1))was significantly higher than that on SDS(3.68 mmol·g^(-1)).The adsorption behavior of CaAl-LDH-Cl on SDS in the two systems conformed to the Langmuir model and belonged to monolayer adsorption.The mechanism of how sulfate promote the removal of SDS by CaAl-LDH-Cl was as follows:1)CaAl-LDH-Cl and SDS have self-dissolution reaction to generate Ca-SDS precipitation;SO ^(2-)_(4) occupies part of the position of Cl-in CaAl-LDH-Cl to generate CaAl-LDH-SO 4,both of which increase the layer space of product;2)The presence of ^(2-)_(4) is beneficial to the formation of SDS micelles,which promotes the adsorption of SDS by CaAl-LDH-Cl.