烟秸杆生物碳对铬(Ⅵ)废水的吸附动力学和热力学

Kinetics and thermodynamics of adsorption of Cr(Ⅵ)onto tobacco straw derived-biochar

以农业废弃物烟秸杆为原料,以KH2PO4为活化剂,制备了烟秸杆生物碳(简称TSC500),通过静态吸附实验研究了TSC500对含Cr(Ⅵ)废水的吸附性能。采用比表面积分析仪对TSC500进行了测试,实验考察了p H值、吸附剂用量、吸附时间、Cr(Ⅵ)初始浓度和温度对Cr(Ⅵ)吸附的影响,深入研究了TSC500对Cr(Ⅵ)的吸附行为。结果表明,在p H=3、温度313 K条件下,0.2 g TSC500吸附100 mg/L Cr(Ⅵ),去除率和吸附容量分别达到91.32%和45.66 mg/g,Langmuir和Freundlich比Temkin等温模型更好地拟合吸附实验数据;准一级和准二级动力学模型均能较好地描述该吸附行为,相关系数高达0.99;计算得到热力学参数ΔGθ、ΔHθ和ΔSθ值表明该吸附过程为自发吸热过程。

The preparation of derived-biochar（ TSC500） by monopotassium from agricultural wastes,tobacco straw,was studied to adsorb Cr（ Ⅵ） from aqueous solution. TSC500 was characterized by Brunauer-Emmett-Teller（ BET） analysis. Batch experiments were conducted to investigate the effects of p H,adsorbent dose,contact time,initial Cr（ Ⅵ） concentration and temperature on Cr（ Ⅵ） adsorption onto TSC500. The results showed that the removal efficiencies and adsorption capacity were 91. 32% and 45. 66 mg / g under the following conditions：p H of 3. 0,adsorbent dose of 0. 2 g,initial Cr（ Ⅵ） concentration of 100 mg / L and temperatures of 313 K,respectively. The adsorption isotherms data fit the Langmuir and Freundlich model better than Temkin model. Adsorption of Cr（ Ⅵ） followed the First-order and Second-order kinetics with a correlation coefficient R2 higher than0. 99. The obtained thermodynamic parameters（ ΔGθ）,ΔHθand ΔSθ） showed that the adsorption of Cr（ Ⅵ）onto TSC500 was an endothermic and spontaneous process.