柚子皮生物炭质用于河水中苯系物的固相微萃取

Solid phase microextraction of benzenes in river water by pomelo peel biochar

苯、甲苯、乙苯和二甲苯(邻二甲苯、间二甲苯、对二甲苯)组成的苯系物(BTEX)是炼油厂和石化厂等工业园区普遍制造和排放的碳氢化合物,具有一定的毒性和致癌作用,对生态环境和人类健康造成极大威胁。研究以低成本、绿色且富含木质素和含氧官能团的柚子皮作为植物原料,在有限氧条件下采用程序升温热解法制备了柚子皮生物炭质吸附剂,通过N吸附-脱附等温线和孔径分布图对不同热解温度下制备的柚子皮生物炭质吸附剂的孔隙结构进行了考察。结果表明:在1 000℃热解温度下制得的柚子皮生物炭质具有更高的比表面积(749.9 m^(2)/g)、更大的孔体积(0.42 cm^(3)/g)、更集中的孔径分布(2~3 nm)。将吸附剂通过溶胶-凝胶法(sol-gel)涂覆在铁丝上制成固相微萃取纤维,与气相色谱-火焰离子化检测器(GC-FID)相结合,对影响萃取和分离BTEX的条件进行优化,建立了用于BTEX检测的高灵敏度分析方法。方法具有检出限低(0.004~0.032μg/L)、线性范围宽(1~100μg/L)、线性关系好、萃取效率高(约为商品化涂层聚二甲基硅氧烷(7μm)的2.9~18.3倍)等优势。此外,应用该方法已成功在河水样本中检测出了乙基苯(4.80μg/L),邻二甲苯(3.00μg/L)和对二甲苯、间二甲苯(2.46μg/L)。最后将该方法应用于河水样本的加标试验中,得到了满意的回收率(75.7%~117.6%)。实验结果表明所建立的分析方法可实现对环境水样(河水)中BTEX的低成本、高灵敏度检测。

Pomelo peel, as a by-product of pomelo consumption, is rich in various fiber and functional compounds. The utilization of the valuable components found in pomelo peel may mitigate environmental concerns. In this study, pomelo peel rich in lignin and oxygen-containing functional groups was used to prepare pomelo peel biochar(PPB) via temperature-programmed pyrolysis at different temperatures(800 ℃ and 1 000 ℃). Their structures were investigated by Nadsorption-desorption isotherms and BJH pore size distribution. The results showed that PPB1000(pomelo peel biochar prepared at 1 000 ℃) had a higher specific surface area(749.9 m^(2)/g), larger pore volume(0.42 cm^(3)/g), more concentrated pore size distribution(2-3 nm), and better adsorption performance than commercial activated carbon. PPB1000 exhibited excellent capability to capture benzenes(BTEX, including benzene(B), toluene(T), ethylbenzene(E), and xylene(X)) through hydrogen bonds, π-π, and electrostatic interactions. Additionally, their honeycomb porous structure could provide additional adsorption sites and material transport paths. PPB1000 was coated on iron wire using the sol-gel method to prepare chemically and mechanically stable solid phase microextraction(SPME) fibers. By combining PPB1000-based SPME analysis with gas chromatography-flame ionization detection(GC-FID), an effective method was developed for the extraction and determination of BTEX. The optimized method had low LODs(0.004-0.032 μg/L), wide linear range(1-100 μg/L), and good linear relationship(determination coefficients, r^(2)≥0.991 9). The RSDs of the intra-batch(n=6) and inter-batch(n=5) precisions were 1.04%-6.56% and 1.03%-12.42%, respectively. The method validation results showed that PPB1000 had good stability. Compared with the commercial reagent polydimethylsiloxane(7 μm), PPB1000 had a higher extraction efficiency. When applied to the analysis of BTEX in natural water samples, trace levels of ethylbenzene(4.80 μg/L), o-xylene(3. 00 μg/L), and m-xylene and p-xylene(2.46 μg/L) were detected. Recovery tests were performed to validate the reliability of the method, and recoveries were between 75.7% and 117.6%. This effective pretreatment process combined with GC-FID could realize the rapid detection of BTEX and is promising for the analysis of BTEX in complex matrixes in the future.