Alkali/Fe-modified biochar for Cd-As contamination in water and soil: Performance and Mechanism

Linwei Zeng, Dinggui Luo, Lirong Liu, Xuexia Huang, Yu Liu, Lezhang Wei, Tangfu Xiao, Qihang Wu
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Abstract

Fabricating low-cost and efficient adsorbents to purify water and soil with Cd-As contaminants remains challenging. Previous studies have demonstrated that alkali-modified and iron-modified biochar promote the adsorption of cationic and anionic pollutants. Herein, alkali/Fe-modified cotton straw-based biochar (FACSB) was fabricated, and its performance and the mechanism for remediation of Cd(II) and As(V) in water and soil were investigated. The initial pH, kinetics, isotherms, and coexisting ions on single and binary-adsorption water systems, whilst the temporal effects of passivation in co-contaminated soils, were systematically examined. The results showed that the maximum adsorption capacity of Cd and As were 42.57 and 30.69 mg/g for single-adsorption system, 41.27 and 34.51 mg/g for binary-adsorption adsorption system, respectively, enhancing adsorption for As when Cd presence. The presence of Mg2+ and Ca2+ competed with Cd, whereas PO43- inhibited As adsorption, and the high ionic strength exerted a detrimental impact on Cd adsorption. The mechanisms for removing Cd and As could mainly involve physisorption and chemisorption, respectively. Continuous soil incubation for half-year revealed a substantial reduction in the bioavailability of Cd and As, decreasing by 79.99% and 34.72%, respectively, at 5% treatment (amendment/soil ratio). The amendment, rising soil pH, and organic matter content (SOM) facilitated to immobilize contaminants. The above results indicate that FACSB is promising for Cd and As pollution remediation applications.
碱/铁改性生物炭对Cd-As在水和土壤中的污染:性能和机理
制造低成本和高效的吸附剂来净化含有Cd-As污染物的水和土壤仍然具有挑战性。以往的研究表明,碱改性和铁改性的生物炭促进了阳离子和阴离子污染物的吸附。在此基础上,制备了碱/铁改性棉秆生物炭(FACSB),并研究了其对水和土壤中Cd(II)和As(V)的修复性能和机理。系统地研究了单吸附和双吸附水系统的初始pH、动力学、等温线和共存离子,以及共污染土壤中钝化的时间效应。结果表明,单吸附体系对Cd和As的最大吸附量分别为42.57和30.69 mg/g,双吸附体系对Cd和As的最大吸附量分别为41.27和34.51 mg/g, Cd存在时对As的吸附能力增强。Mg2+和Ca2+的存在与Cd竞争,而PO43-的存在抑制了As的吸附,并且高离子强度对Cd的吸附产生不利影响。Cd和As的脱除机制主要为物理吸附和化学吸附。土壤连续孵育半年,Cd和As的生物有效性显著降低,5%处理(改良剂/土壤比)分别降低79.99%和34.72%。修正、土壤pH值上升和有机质含量(SOM)有助于固定化污染物。上述结果表明,FACSB在镉、砷污染修复中具有广阔的应用前景。
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