麦秸秆负载纳米水合氧化铁去除水中Cu^(2+)的特性研究

Study on characteristics of wheat straw loaded with nano-hydrated iron oxide for removing Cu^(2+)from water

将秸秆资源化利用与废水处理相结合,通过温和简便的浸渍法将水合氧化铁(HFO)纳米颗粒稳定地负载在麦秸秆表面制得二维片状纳米复合吸附剂(记为WS-HFO)用于去除水中的重金属Cu^(2+),并探究了WS-HFO对Cu^(2+)的吸附性能及机理。扫描电镜(SEM)观测到麦秸秆微观形貌有明显变化,负载的HFO纳米颗粒直径为50~80 nm,通过氮气吸附/脱附曲线确定了材料的比表面积和孔径分布。投加量实验中0.07 g的WS-HFO对50 mL 16 mg/L Cu^(2+)的去除率接近100%。溶液pH对WS-HFO吸附Cu^(2+)有较大影响,pH为5.9时吸附量最大;竞争吸附实验证明共存阳离子Na^(+)、Mg^(2+)、Ca^(2+)浓度高时不利于Cu^(2+)的吸附。WS-HFO对Cu^(2+)的吸附动力学符合准二级动力学方程,吸附等温线符合Langmuir模型,WS-HFO对低浓度Cu^(2+)有很强的吸附亲和力。固定床柱吸附/脱附运行结果表明,1.8 g的WS-HFO能有效处理1980 mL模拟废水,使得出水平均Cu^(2+)低于0.05 mg/L。以4 mol/L NaCl为脱附剂,7次循环重复利用试验Cu^(2+)去除率能保持在89%~100%。

In this study,nanocomposite materials were developed combining straw resource utilization with wastewater treatment.The two-dimensional sheet nanocomposite adsorbent WS-HFO was prepared by stable loading of hydrated iron oxide(HFO)nanoparticles on the surface of wheat straw through a mild and simple impregnation method for the removal of heavy metal Cu^(2+)in water.The adsorption performance and mechanism of WS-HFO for Cu^(2+)were also explored.SEM characterization revealed significant changes in the microstructure of wheat straw,and the diameter of loaded HFO nanoparticles was 50-80 nm.Specific surface area and pore size distribution of the materials were determined by N_(2) adsorption/desorption curves.In the dosing experiments,removal rate of 50 mL 16 mg/L Cu^(2+)by 0.07 g WS-HFO was almost 100%.Solution pH had a great influence on the Cu^(2+)adsorption onto WS-HFO,and the adsorption capacity was maximum at pH 5.9.Competitive adsorption experiments proved that high concentrations of coexisting cations Na+,Mg^(2+)and Ca^(2+)were not conducive to the adsorption of low concentration Cu^(2+).The adsorption kinetics of WS-HFO for Cu^(2+)followed pseudo-second dynamics equation,the adsorption isotherm conformed to Langmuir model.WS-HFO had strong adsorption affinity for Cu^(2+).The fixed-bed column adsorption/desorption running showed that 1.8 g WS-HFO could effectively treat 1980 mL simulated wastewater with the average effluent Cu^(2+)concentration below 0.05 mg/L.When 4 mol/L NaCl was used as desorption agent,the removal rate of Cu^(2+)could remain at 89%-100%in the 7 recycling tests.