浸提−汽爆改性对澳洲坚果壳生物吸附铅的影响

采用单因素实验和响应面法相结合的方法，系统地研究了预浸剂种类与浓度、蒸压力与保压时间以及后浸提等汽爆工艺因素对澳洲坚果壳吸附水中Pb（II）能力的影响，优化改性工艺，并通过扫描电镜、红外光谱法分析改性对吸附剂理化性质的影响。结果表明：预浸剂种类与浓度、蒸汽压力与保压时间以及后浸提等汽爆改性工艺参数对澳洲坚果壳吸附水中Pb（II）的能力均有显著影响。适宜的预浸剂和后浸提剂分别为HCl溶液和NaOH溶液，优化后的改性工艺为预浸剂HCl浓度为0.49 mol/L，蒸汽压力2.29 MPa，保压时间8.4 min。汽爆改性使澳洲坚果壳表面变得粗糙多孔，比表面积增加，为Pb（II）的吸附提供更大的物理空间；木质素与糖类之间的化学键被破坏，在后浸提中部分木质素被去除，一些羟基与Na⁺发生结合，吸附过程中Pb²⁺与Na⁺间又发生离子交换。按优化工艺改性的澳洲坚果壳对Pb（II）的吸附量是不改性澳洲坚果壳的4.6倍，合适的预浸—汽爆—后浸提工艺可以极大地提高农林废弃物的生物吸附性能。

Effect of Extracting-steam Explosion Modification on Lead Biosorption of Macadamia Nutshells

In this study, the effects of types and concentrations of presoaking agents, steam pressure, retention time, and post-extraction on the Pb(II) adsorption onto steam-exploded macadamia nutshells were systematically studied by a single-factor experiment combined with response surface methodology. The modification process was optimized, and the changes in the physical and chemical properties of the modified shells were characterized by scanning electron microscopy and infrared spectroscopy. The result proved that process parameters of steam explosion modification such as types and concentrations of presoaking agents, steam pressure, retention time and post-extraction had significant effects on the adsorption of macadamia nutshell for Pb(II) in water. HCl and NaOH solutions were optimized as the presoaking agent and the post-extractant, respectively. The optimum modification process was the HCl concentration of 0.49 mol/L, steam pressure of 2.29 MPa, and retention time of 8.4 min. The modification makes the surface of macadamia nutshells rough and porous, increased the specific surface area and the physical space for Pb(II) adsorption. The chemical bonds between lignin and carbohydrates were destroyed by the modification. The lignin was partly removed during the post-extraction. Some hydroxyl groups were combined with Na+, and ion exchange occurred between Pb2+ and Na+ during the adsorption process. The Pb(II) adsorption capacity of the modified macadamia nutshells was 4.6 times much as that of unmodified ones. A suitable SE process can greatly improve the biosorption performance of agricultural waste.