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    不同解吸剂对土壤介质中萘解吸和氧化降解的影响

    Effects of Different Desorbing Agents on the Desorption and Oxidative Degradation of Naphthalene in Soil Media

    • 摘要: 为研究萘(NAP)污染土壤的高效修复技术,系统探究了NAP在不同土壤介质中的解吸行为,分析NAP对土壤老化的影响,并对比无机盐(CaCl2)、低分子量有机酸(柠檬酸(CA),草酸 (OA),天冬氨酸(ASP))和表面活性剂(吐温-80 (Tween-80),十二烷基硫酸钠 (SDS),烷基糖苷(APG))这3类解吸剂对NAP的解吸作用,以及3类解吸剂对亚铁离子(Fe(II))活化过二硫酸盐(PDS)氧化体系降解NAP的影响。结果表明:土壤黏粒含量越高,老化时间越长,NAP解吸越困难;弱碱性(pH=9.0)有利于NAP解吸,且解吸过程符合拟二级动力学模型。3类解吸剂对NAP的解吸效果存在显著差异:低分子量有机酸解吸效果最优,其中1 mmol/L的CA解吸48 h时,NAP去除率可达到36.1%,显著优于OA和ASP;表面活性剂均能显著提升解吸效果,Tween-80因临界胶束浓度(CMC)低、疏水性适宜,因而表现最佳,且Tween-80浓度越高,解吸效果提升越明显;低浓度(<10 mmol/L) CaCl2可通过竞争吸附位点促进解吸,高浓度(100 mmol/L) CaCl2则因为会导致土壤有机质絮凝沉淀而抑制解吸。在后续氧化降解过程中,表面活性剂与CaCl2因竞争活性氧物种(ROS)而抑制NAP降解,但3种低分子量有机酸对NAP降解均起到正向作用;当PDS/Fe(II)/CA/NAP物质的量之比为15∶5∶1∶1时,120 min内NAP去除率达到97.5%。研究证实,CA兼具高效解吸土壤NAP和强化后续氧化降解的双重功能。本文为CA应用于有机污染场地的绿色高效修复提供了理论依据。

       

      Abstract: To develop efficient remediation technologies for naphthalene (NAP)-contaminated soil, this study systematically investigates the desorption behavior of NAP in various soil media, analyzes the effects of soil aging on NAP retention, and compares the desorption performance of three categories of desorbents toward NAP, including inorganic salt (CaCl2), low-molecular-weight organic acids (Citric acid (CA), Oxalic acid (OA), Aspartic acid (ASP)), and surfactants (Tween-80, sodium dodecyl sulfate (SDS), alkyl polyglycoside (APG)). The influences of the three desorbent categories on NAP degradation in the ferrous ion (Fe(II))-activated persulfate (PDS) oxidation system are also evaluated. The results reveal that NAP desorption becomes more difficult with increasing soil clay content and longer aging duration. Weakly alkaline conditions (pH = 9.0) facilitate NAP desorption, and the desorption process conforms to the pseudo-second-order kinetic model. Significant differences are observed in the NAP desorption efficiency of the three desorbent groups. Low-molecular-weight organic acids exhibit the optimal desorption capacity; specifically, 1 mmol/L CA achieves a NAP removal rate of 36.1% after 48 h of desorption, which is markedly superior to OA and ASP. All tested surfactants substantially improve NAP desorption, among which Tween-80 delivers the best performance owing to its low critical micelle concentration (CMC) and suitable hydrophobicity, with desorption efficiency rising evidently as Tween-80 concentration increases. Low-concentration CaCl2 ( <10 mmol/L) promotes NAP desorption by competing for soil adsorption sites, while high-concentration CaCl2 (100 mmol/L) inhibits desorption by inducing flocculation and precipitation of soil organic matter. In the subsequent oxidative degradation stage, surfactants and CaCl2 suppress NAP degradation via competing for reactive oxygen species (ROS), whereas all three low-molecular-weight organic acids exert positive promotional effects on NAP removal. When the molar ratio of PDS/Fe(II)/CA/NAP is set to 15∶5∶1∶1, the NAP removal rate reaches 97.5% within 120 min. This study verifies that CA possesses dual functions: Efficiently desorbing soil-sorbed NAP and enhancing subsequent oxidative degradation. The present work provides theoretical support for the green and efficient remediation of organic-contaminated sites using CA.

       

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