改性活性炭对电动联合渗透反应屏障法去除污染土中铬的特性研究

Characteristics of modified activated carbon in removing chromium from contaminated soil via EK–PRB method

摘要

为解决传统电动修复方法中易造成污染物在电极区富集的问题，并进一步提升修复效率，采用自行设计的电动联合渗透反应屏障修复装置（EK–PRB）探讨了改性活性炭渗透反应屏障（PRB）材料与电解液协同作用对铬去除效果的影响. 试验结果表明，电解液与 PRB 材料之间的协同效应尤为关键，其中柠檬酸（CA）与盐酸改性活性炭联用时修复效果最优，对铬（Ⅵ）和总铬的去除率分别达到 93.1% 和 77.96%. 此外，EK–PRB 技术还显著降低了土壤中弱酸提取态与可还原态铬的含量，降幅分别超过 91.2% 和 64.12%. 相较于传统电动修复法，EK–PRB 技术优势明显，改性活性炭 PRB 可有效吸附迁移过程中的铬，缓解其在阳极区域的积累，促进土壤中铬的均匀去除.

Abstract

With the rapid acceleration of global industrialization, soil contamination by heavy metals has become a critical environmental challenge, drawing significant attention from the scientific community. Chromium pollution is particularly pervasive, primarily stemming from industrial discharges such as leather processing, textile printing, and electroplating, as well as various agricultural activities. Cr predominantly exists in the trivalent [Cr(III)] and hexavalent [Cr(VI)] oxidation states. Although Cr(III) exhibits low mobility and is readily adsorbed onto soil particles, Cr(VI) is characterized by high solubility, mobility, and acute toxicity. Cr(VI) readily disperses through the vadose zone into the groundwater, posing a severe and persistent threat to ecological safety and human health. Electrokinetic (EK) remediation has emerged as a promising technology for treating low-permeability soils (such as clays) because of its unique electrically driven transport mechanism. However, given the complexity and heterogeneity of actual soil contamination, employing a single remediation technique often fails to achieve the desired pollutant removal efficiency. To overcome this technical bottleneck, an integrated electrokinetic–permeable reactive barrier (EK–PRB) system is designed and optimized in this study. The objective was to achieve in situ interception and removal of migrating pollutants by incorporating a chemically modified activated carbon PRB layer. The synergistic mechanisms between various electrolytes and PRB materials was systematically investigated to optimize the system performance. Specifically, activated carbon was functionalized using hydrochloric acid and cetyltrimethylammonium bromide (a cationic surfactant), to precisely regulate the pore structure and surface charge characteristics of the material. Three electrolytes with distinct driving mechanisms were introduced: citric acid (a complexing agent), potassium chloride (a conductive salt), and sodium dodecylbenzenesulfonate (an anionic surfactant). The remediation efficacy was comprehensively evaluated by monitoring key parameters, including electrical current evolution, soil pH distribution, and spatiotemporal migration patterns of Cr. The experimental results indicate that the remediation efficiency is heavily dependent on the physicochemical compatibility between the electrolyte and the PRB material. The combination of a citric acid (CA) electrolyte with hydrochloric acid-modified activated carbon demonstrated optimal performance, achieving removal rates of 93.10% for Cr(VI) and 77.96% for total Cr. Mechanistically, this superior performance was attributed to the strong chelating action of CA, which effectively prevented precipitation and promoted the desorption of adsorbed Cr from soil particles. Simultaneously, the acid-modified PRB layer provided abundant active sites and favorable surface conditions for the precise interception of migrating chromium-citrate complexes. Comparative analysis confirmed that the anolyte Cr concentration in the EK–PRB remediated group was significantly lower than that in the conventional EK remediated group, verifying the efficacy of the PRB layer in mitigating anode enrichment. Furthermore, BCR (Bureau Communautaire de Référence) sequential extraction analysis revealed that the designed technology substantially altered the chemical speciation of the residual Cr. Post-remediation, the soil exhibited reductions exceeding 91.2% and 64.12% in the bioavailable weak acid extractable and reducible fractions, respectively, which are considered the most environmentally hazardous forms. In summary, compared to conventional EK remediation, the proposed EK–PRB technology not only achieves high-efficiency remediation but also promotes uniform removal and deep stabilization of Cr, offering a robust solution for the remediation of Cr-contaminated sites.

关键词

电动联合渗透反应屏障 / 改性活性炭 / 铬污染土 / 修复 / 电解液

Key words

electrokinetic–permeable reactive barrier / modified activated carbon / chromium-contaminated soil / remediation / electrolyte

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基金资助

浙江省自然科学基金重点资助项目(LZ25E080009)

国家自然科学基金资助项目(52378372)

宁波市青年科技创新领军人才资助项目(2025QL070)

宁波大学研究生科研创新资助项目(IF2025007)