表面活性剂改性Fe_(3)O_(4)对As(Ⅴ)和As(Ⅲ)的吸附

Adsorption of As(Ⅴ)and As(Ⅲ)by surfactant-modified Fe_(3)O_(4)

利用3种构型的阳离子表面活性剂[十六烷基三甲基溴化铵(CTAB)、二亚甲基-1,2-二(N-十二烷基-N,N-二甲基溴化铵)(Gemini12-2-12)和癸烷-1,10-双(三甲基溴化铵)(Bola)]分别修饰Fe_(3)O_(4)纳米颗粒,制得Fe_(3)O_(4)@CTAB、Fe_(3)O_(4)@Gemini和Fe_(3)O_(4)@Bola纳米颗粒(三者统称Fe_(3)O_(4)@surfactants),将其用于水中As(Ⅴ)和As(Ⅲ)的处理。通过XRD、TEM、FTIR和磁性测量系统(VSM)对其进行了表征,同时对As(Ⅴ)和As(Ⅲ)的吸附进行吸附动力学、吸附等温模型拟合和吸附行为的研究,并考察了Fe_(3)O_(4)@surfactants的吸附-解吸再生循环性能及结构稳定性。结果表明,Fe_(3)O_(4)@surfactants对As(Ⅴ)的吸附效果均高于As(Ⅲ),吸附符合准二级动力学模型和Langmuir吸附等温模型,且Gemini 12-2-12表面活性剂所修饰的Fe_(3)O_(4)纳米颗粒的吸附容量最大。该吸附过程的吸附驱动力主要来自阳离子表面活性剂分子在固液界面的排列行为、表面活性剂头基与阴离子的静电作用以及尾链与As(Ⅴ)、As(Ⅲ)之间的配位作用。以去除效率较高的As(Ⅴ)进行循环实验,经过5次吸附-解吸循环实验后,Fe_(3)O_(4)@surfactants对As(Ⅴ)的吸附率依然维持在85%左右,且纳米颗粒回收率均在90%以上。

Fe_(3)O_(4)@CTAB,Fe_(3)O_(4)@Gemini and Fe_(3)O_(4)@Bola(the three collectively referred to Fe_(3)O_(4)@surfactants)were synthesized via Fe_(3)O_(4) nanoparticle modification with three configurations of cationic surfactants[cetyltrimethylammonium bromide(CTAB),dimethylene-1,2-bis(N-dodecyl-N,N-dimethylammonium bromide)(Gemini 12-2-12)and decamethonium bromide(Bola)]respectively,and then used for As(Ⅴ)and As(Ⅲ)removal in water treatment.The Fe_(3)O_(4)@surfactants obtained were characterized by XRD,TEM,FTIR and magnetic measurement system(VSM).Meanwhile,The adsorption kinetics,adsorption isotherm models fitting and adsorption behavior for As(Ⅴ)and As(Ⅲ)as well as the adsorption-desorption regeneration cycle performance and structural stability of Fe_(3)O_(4)@surfactants were investigated.The results demonstrated that Fe_(3)O_(4)@surfactants displayed higher adsorption capacity for As(Ⅴ)than As(Ⅲ)with adsorption process fitting to the quasi-secondary kinetic model and the Langmuir adsorption isotherm model,and Fe_(3)O_(4)@Gemini exhibited largest adsorption capacity among the three Fe_(3)O_(4)@surfactants.The driving force of this adsorption process was mainly contributed by the arrangement behavior of cationic surfactant molecules at the solid-liquid interface,the electrostatic interaction between the surfactant head group and the anion,and the coordination between the tail chain and As(Ⅴ)and As(Ⅲ).The cycle experiments were carried out with As(Ⅴ)with high removal efficiency,after five adsorption-desorption cycles,the adsorption rate of As(Ⅴ)by Fe_(3)O_(4)@surfactants was still maintained at about 85%,and the recovery of nanoparticles were all above 90%.