氧化石墨烯/海藻酸钠复合膜对Pb(Ⅱ)的吸附性能和机制

Adsorption properties and mechanism of Pb(Ⅱ) adsorbed by graphene oxide/sodium alginate composite membrane

海藻酸钠(SA)基的过滤膜是处理含Pb(Ⅱ)废水的理想膜分离材料,将氧化石墨烯(GO)和尿素添加进SA中,以CaCl2溶液交联,制备出GO/SA复合膜,并考察了其对水溶液中Pb(Ⅱ)的吸附性能。通过静态吸附实验,探讨了Pb(Ⅱ)初始浓度、GO质量分数、初始pH值和吸附时间、吸附-解吸次数等对GO/SA复合膜吸附Pb(Ⅱ)效果的影响;对吸附过程进行了吸附动力学和吸附热力学分析,利用FTIR-ATR、XPS等对GO/SA复合膜吸附Pb(Ⅱ)的机制进行了解析。结果表明,GO/SA复合膜对Pb(Ⅱ)的吸附量与Pb(Ⅱ)初始浓度正相关,在pH=5时吸附效果最优,GO质量分数为0.3wt%时为最优配比;吸附过程符合伪二级动力学模型;热力学等温吸附过程符合Langmuir等温吸附模型,温度为318 K时,Langmuir模型拟合得到的GO/SA复合膜吸附量达到320.51 mg·g-1。GO/SA复合膜对Pb(Ⅱ)的吸附机制主要为物理吸附。

The sodium alginate(SA)-based filtration membrane is an ideal membrane separation material for wastewater containing Pb(Ⅱ).It is very valuable but lacking to study the effect of adsorption behavior on membrane filtration.The graphene oxide(GO)and urea were added into SA and crosslinked with CaCl2 solution to prepare GO/SA composite membrane to investigate its adsorption performance for Pb(Ⅱ)in aqueous solution.The effects of Pb(Ⅱ)initial concentration,GO mass fraction,initial pH value,adsorption time,adsorption-desorption times and other conditions on the adsorption effect were investigated by static adsorption experiments.The adsorption kinetics and adsorption thermodynamics analysis were also carried out on the adsorption process.The adsorption mechanism of Pb(Ⅱ)on GO/SA composite membrane was analyzed by FTIR-ATR and XPS.The experimental results show that the adsorption amount of Pb(Ⅱ)is positively correlated with the initial concentration of Pb(Ⅱ),the adsorption effect is optimal at pH=5,and GO mass fraction of 0.3 wt%is the optimal ratio;the adsorption process conforms to the pseudo second-order kinetic model;The thermodynamic isotherm adsorption process accords with the Langmuir isotherm adsorption model.At temperature of 318 K,the adsorption capacity of GO/SA composite membrane obtained by the Langmuir model is 320.51 mg·g-1.The adsorption mechanism of GO/SA alginate composite membrane on Pb(Ⅱ)is mainly physical adsorption.