两种天然矿物改性材料对模拟废水中Cd^(2+)的吸附特性

Adsorption Characteristics of Cadmium(Ⅱ) Simulated Wastewater by Two Organic Modified Mineral Materials

为了提升天然非金属矿物对Cd^(2+)的吸附性能,采用MT(蒙脱石)和HP(海泡石)为前驱材料,依次通过酸纯化和SDS(十二烷基磺酸钠)改性后合成了有机非金属矿物材料,利用扫描电镜(SEM)、傅里叶变换红外光谱(FT-IR)、X射线荧光光谱分析(XRF)等手段对2种改性材料[SDS-MT(十二烷基磺酸钠改性蒙脱石)和SDS-HP(十二烷基磺酸钠改性海泡石)]吸附Cd^(2+)的机制进行探究,并对吸附过程分别进行了动力学拟合和等温吸附方程拟合.结果表明:(1)SDS-MT和SDS-HP吸附模拟废水中Cd^(2+)的效果分别比未改性的MT和HP平均提升约40%和19.5%.(2)改性过程没有改变2种前驱材料的基本结构,但引起其元素质量分数、阳离子交换量和比表面积的改变.(3)SDS-MT、SDS-HP对模拟废水中Cd^(2+)的吸附量受溶液的p H影响较大,最大吸附量分别达16.54、9.24 mg/g,2种改性材料对模拟废水中Cd^(2+)的吸附过程能较好地满足准二级动力学方程,并且其平衡传质时间较短.(4)SDS-MT对模拟废水Cd^(2+)的吸附模型较满足于Freundlich吸附等温模型,推测SDS-MT是一种有限吸附位点的吸附剂,吸附过程为单分子层吸附,而SDS-HP则较好的满足Langmuir吸附等温模型.研究显示,对2种天然非金属矿物材料的有机改性能够有效提升材料对Cd^(2+)的吸附容量,发挥材料的实际运用价值.

In order to enhance the removal of Cd from wastewater by natural non-metallic minerals, Montmorillonite (MT) and Sepiolite (HP) were used as precursors and were modified by acid purification and Sodium dodecyl sulphater (SDS). The mechanism of Cd ^2+ adsorption by the two modified materials was analyzed by SEM, FT-IR and XRF. The adsorption properties of the two modified materials were fully characterized by adsorption kinetics and adsorption isotherms. The results showed that:(1) The percentages of Cd adsorption by Sodium dodecyl sulfate modified montmorillonite (SDS-MT) and Sodium dodecyl sulfate modified sepiolite (SDS-HP) were about 40% and 19.5%, which are higher than those of the untreated minerals.(2) During the modification process, the basic structures of the two precursors were not changed, while elemental mass fraction, cation exchange capacity, and specific surface area of both modified materials were changed.(3) The sorption of Cd ^2+ by SDS-MT SDS-HP was strongly pH dependent and the maximum adsorption capacities were 16.54 and 9.24 mg/g. The kinetic process of Cd ^2+ adsorption on the SDS-MT SDS-HP was well fitted by the pseudo-second-order kinetic model and the adsorption equilibrium time of the two materials was shorter. The Cd ^2+ adsorption on the SDS-MT could be better described by the Freundlich model, suggesting SDS-MT is a monolayer adsorption process with limited adsorption sites, whereas the sorption on SDS-HP could be better described with the Langmuir model. Therefore, the organic modification of two natural mineral montmorillonite and sepiolite can effectively improve the adsorption capacity of Cd ^2+ and exert the maximum use value of the materials.