水热炭吸附Cr(Ⅵ)热-动力学行为及水热裂解时间的影响

Thermodynamic and Kinetic Adsorption of Cr(Ⅵ) on Hydrochars and the Effect of Hydrothermal Time

以花生壳为原材料,通过水热炭化法在200℃下以不同的水热裂解时间(1 h、5 h、10 h)制备出水热炭,开展去除水中Cr(Ⅵ)的实验研究。通过水热炭样品红外光谱FTIR表征、元素含量分析、扫描电镜SEM表征等对比分析,表明水热炭化法可以制备出多孔的碳材料,且随着水热裂解时间的增加,水热炭的产率逐渐降低、芳香性逐渐增强、极性官能团逐渐减少,这些性质的改变会影响其吸附能力。通过批实验进行水热炭对水中Cr(Ⅵ)的吸附研究,结果表明准二级动力学模型适用于该吸附过程,热力学Freundlich模型可以更好地描述吸附等温线。由热力学参数计算可知,水热炭吸附Cr(Ⅵ)属于优惠吸附(容易进行)和自发性、物理吸附,且为吸热过程。实验结果表明随着花生壳水热裂解时间的增加,水热炭吸附Cr(Ⅵ)的能力逐渐增强。因此,水热炭可以作为经济型吸附剂应用于水污染修复,相关成果对于综合利用农业废弃物具有重要实践价值。

The agricultural wastes of peanut shells were used as carbonaceous material precursors,which were heated under the hydrothermal temperature of 200 ℃ and kept for the desired time duration of 1 h,5 h or 10 h to prepare the hydrochars for the removal of Cr（Ⅵ） from aqueous solution.According to FT-IR spectrum,elemental analysis and SEM characterization of hydrochar samples,the results showed that hydrothermal carbonization method is feasible for porous carbon-based hydrochars,and the aromaticity increases with hydrothermal time,while the yield and the polar functional groups decrease.These properties would affect the adsorption performance of hydrochars.The batch experiments showed that the adsorption kinetics of Cr（Ⅵ） on hydrochars followed the pseudo-second-order model and the Freundlich model well fitted the isothermal adsorption.According to thermodynamic study,such sorption behavior belongs to a preferential easy process,which is also a spontaneous,endothermic and physical adsorption.The adsorption capacity of Cr（Ⅵ） on hydrochars were enhanced with the hydrothermal time on biomass of peanut shells.Therefore,hydrochars could be applied as an economic adsorbent in water remediation.The present study could also provide an important practical value for the com-prehensive utilization of agricultural wastes.