热解温度对棉杆生物炭中水可提取有机物与Cu(Ⅱ)络合特性的影响

Effect of pyrolysis temperature on the binding properties of Cu(Ⅱ) with WEOM extracted from cotton stem biochar

本文以棉杆生物炭中水可提取的有机物(water extracted organic matter,WEOM)为研究对象,采用二阶导数荧光和二维相关光谱分析方法研究低温(300℃)和高温(600℃)热解温度下生物炭WEOM的荧光组分变化及其与Cu(Ⅱ)离子的络合特性.研究结果表明,低温和高温热解生物炭WEOM的含量分别为20172.3 mg·kg^(-1)和5.9 mg·kg^(-1);低温热解生物炭WEOM以类腐殖酸为主,而高温热解生物炭WEOM以类富里酸为主.二维相关光谱(2D-COS)分析结果显示,低温热解生物炭WEOM中类腐殖酸(409 nm)能够优先与Cu(Ⅱ)离子发生络合作用,而高温热解生物炭WEOM中类富里酸组分(372 nm)优先与Cu(Ⅱ)离子结合. 300℃热解生物炭WEOM-Cu(Ⅱ)的lg K值在4.85-5.30之间,类富里酸物质表现出较高的lg K值. 600℃热解棉杆生物炭WEOM与Cu(Ⅱ)的lg K值在4.23-5.19之间,随着波长的增加,lg K值呈现逐级增大的趋势,且具有较高的荧光配位比,研究结果能够为生物炭用于土壤改良和修复提供指导依据.

In this study, water extracted organic matter(WEOM) were extracted from cotton stem biochar at 300 ℃ and 600 ℃ pyrolysis temperatures, whose fluorescent components and binding properties with Cu(Ⅱ) were investigated by using second derivative fluorescence and twodimensional correlation spectroscopy(2D-COS). The results showed that the content of WEOM for biochar was 20172.3 mg·kg^(-1) and 5.9 mg·kg^(-1) at low and high pyrolysis, respectively. Biocharderived WEOM was dominated by humic-like substances at low temperature pyrolysis and fulviclike substances at high temperature pyrolysis, respectively. The result of 2D-COS indicated that humic-like substances at 409 nm combined preferentially with Cu(Ⅱ) at low temperature pyrolysis and fulvic-like substances at 372 nm preferentially complexed with Cr(Ⅲ) at high temperature pyrolysis. The lg K values were in the range of 4.85-5.30 for biochar-derived WEOM-Cu(Ⅱ) at300 ℃, in which fulvic-like obtained a relatively high lg K value. The lg K values ranged from 4.23 to5.19 for biochar-derived WEOM-Cu(Ⅱ) at 600 ℃, and lg K value increased with an increase of wavelength. Meanwhile, the fraction in the initial fluorescence(f) was higher for biochar-derived WEOM-Cu(Ⅱ) at 600 ℃ than these at 300 ℃. The results of WEOM-Cu(Ⅱ) can provide guidance for the application of biochar in soil improvement and remediation.