复合煤矸石颗粒材料对Cr(Ⅵ)的吸附特性及机制

Adsorption Characteristics and Mechanisms of Cr(Ⅵ)on Coal Gangue-Chitosan Particulate Composite Material

文章以煤矸石为原料,采用单因素实验并结合响应面方法,优化改性煤矸石制备条件,通过负载壳聚糖制备新型复合颗粒吸附材料。采用动力学模型、等温吸附平衡曲线和热力学模型拟合原煤矸石、改性煤矸石和复合煤矸石3种材料对Cr(Ⅵ)的吸附特性,并结合XRF、TG-DSC、XRD及SEM分析表征手段探讨了其吸附机制。结果表明,缺氧条件下,煅烧温度698℃、煅烧时间28 min、煤矸石/ZnCl_(2)质量比为20∶13时制得的改性煤矸石对Cr(Ⅵ)的去除率最大;当壳聚糖/改性煤矸石质量比为0.09时,Cr(Ⅵ)的去除率达到97.57%。3种煤矸石材料吸附Cr(Ⅵ)均符合准二级动力学方程。复合煤矸石吸附Cr(Ⅵ)更符合Freundlich模型,吸附量随温度增加而减小,是放热反应。3种材料对Cr(Ⅵ)的最大吸附量依次为改性煤矸石(9.56 mg/g)>复合煤矸石(7.38 mg/g)>原煤矸石(4.88 mg/g)。复合煤矸石颗粒材料克服了原煤矸石和改性煤矸石处理废水时固液分离困难的缺点,是一种新型环保重金属离子吸附剂。

According to single factor experiments and response surface methods,modified coal gangue(CG)was prepared at 698℃under oxygen-limited atmosphere for 28 minutes,and the CG-ZnCl_(2)with feeding ratio of 20∶13.Newly developed particulate composite material which was prepared with chitosan-modified CG mass ratio of 0.09,accomplished a significantly higher Cr(Ⅵ)removal rate(97.57%),more than 86.40%of modified CG.Adsorption kinetics,isothermal adsorption equilibrium,and adsorption themodynamics were used to investigate the adsorption mechanism of composite material,and the adsorption characteristics was analyzed by XRF,TG-DSC,XRD and SEM.The results indicated that adsorption kinetics of Cr(Ⅵ)on three kinds of CG agreed with the quasi-second-order kinetics equation.The adsorption process of Cr(Ⅵ)onto composite is more consistent with the Freundlich model,which is spontaneous exothermic reaction.The adsorption mechanism of Cr(Ⅵ)onto composite material mainly includes intermolecular coordination reaction and pore filling.Above all,CG-Chitosan particulate composite is a new type of environment-friendly adsorbent for heavy metal ions,with high dispersion degree,solving the problems of solid-liquid separation in the wastewater treatment.