洗脱处理对生物质炭吸附铜离子行为的影响

Influence of Elution of Biochar on Its Adsorption of Cu(Ⅱ)

常用生物质炭制备方法会产生焦油、醋液和无机盐等热解副产物,这些物质附着在生物质炭表面,会影响对其性质和应用的研究。以四种溶剂(水、稀酸溶液、稀碱溶液、无水乙醇)作为洗脱剂,对生物质炭进行浸泡处理,比较洗脱前后的性质;用洗脱后的生物质炭吸附铜离子,探讨不同洗脱处理是否会对生物质炭吸附重金属离子的能力产生影响;分析不同洗脱处理得到上清液的成分,探讨洗脱处理去除的热解副产物组成;比较洗脱前后生物质炭的漫反射傅里叶变换红外光谱,分析洗脱处理对其表面官能团的影响。结果表明,四种洗脱处理均能不同程度地去除生物质炭表面附着的热解副产物,为使洗脱处理对生物质炭性质的影响较小,据此建议以醇-水处理和水洗处理作为生物质炭吸附铜离子研究的前处理方法。

During production, biochars often adsorb pyrolysis by-products such as tar, pyroligneous liquor, and inorganic salts, which may influence the adsorption of the biochars. In this study, freshly prepared biochar was soaked and rinsed using 4 different solvents （ultrapure water, dilute acid, dilute alkali solution and ethanol）. The supernatants obtained from different elution treatments were analyzed using a gas-chromatography mass spectrometer（GC-MS）. The surface properties of biocbar before and after elution were studied by diffuse re- flectance infrared Fourier transform spectroscopy（ DRIFTS ）. The adsorption of Cu^2＋ by the eluted biochar was investigated by batch equilib- rium method. The main components of pyrolysis by-products were organic acids, alcohols, ethers, esters, aldehydes, and ketones. All elution solvents could remove the by-products to certain extents. However, data of both DRIFTS and GC-MS showed that alkali-water and acid- water could react with biochar and pyrolysis by-products or promote the hydrolysis of biochar, thus modifying the surface properties of biochar and in turn its adsorption. Alcohol-water and water had the least influences on biochar properties and could be used to pre-treat biochars.