不同处理方式对生物炭吸附Sr(Ⅱ)的影响机制

Effect of Different Treatments on Sr(Ⅱ) Adsorption on Biochar

生物炭是一种常见的优质吸附剂,但生物炭中的灰分会遮盖其表面的官能团及填充孔道,从而影响生物炭的吸附性能。为了探明生物炭中灰分对Sr(Ⅱ)吸附性能的影响,以玉米秸秆为原料,在绝氧条件下、不同裂解温度下制备生物炭样品,并选用水、氢氟酸及王水对生物炭样品进行处理,然后测试各样品对Sr(Ⅱ)的吸附量。最后,采用X射线衍射分析(XRD)、元素分析、比表面积及孔径分布(BET)、傅里叶变换红外光谱(FTIR)、扫描电子显微镜(SEM)等分析技术,对生物炭及改性生物炭的性质进行表征分析,解析生物炭中灰分组分对Sr(Ⅱ)吸附的影响机制。结果表明:在500℃下制备的生物炭对Sr(Ⅱ)的吸附能力较强,且经HF改性处理后其吸附能力提升约15%;各改性样品对Sr(Ⅱ)的吸附均符合准二级动力学模型,且均符合Langmuir模型。分析测试结果表明:HF可大幅度降低生物炭表面的水溶性阳离子与Si元素含量,降低了水溶性阳离子与Sr(Ⅱ)的竞争吸附且暴露更多的吸附位点,提升了生物炭对Sr(Ⅱ)的吸附能力。

Biochar is the common adsorbent with high quality, however the ash component in biochar could cover the functional groups on the surface and fill the pores, affecting the adsorption capacity on biochar. In order to investigate the effect of ash component in biochar on the adsorption capacity to Sr(Ⅱ), the biochar was obtained via the anaerobic pyrolysis method under different temperatures using the corn straw as the raw material. Then the biochar samples were treated with water, hydrofluoric acid and aqua reginis, and the Sr(Ⅱ) adsorption amounts on each sample were tested. Finally, the interaction mechanism of ash component on Sr(Ⅱ) adsorption to biochar was discussed via pH, elemental analysis, XRD, FTIR, SEM, etc. As shown in the results, the biochar sample obtained at 500 ℃ exhibits the perfect adsorption capacity. The adsorption capacity of biochar modified with HF increases by 15%. According to the results of adsorption kinetics experiments, all of the biochar samples are well described by pseudo-second-order kinetic model. According to the results of adsorption isotherms experiments, the adsorption data match the Langmuir model well. HF can decrease the contents of water-soluble cation and Si element, which can reduce the competitive adsorption with Sr(Ⅱ) and expose more adsorption sites, leading to an increase in the Sr(Ⅱ) adsorption capacity on biochar.