Escuela de Geología, Universidad Industrial de Santander, Bucaramanga 680002, Colombia.
Escuela de Geología, Universidad Industrial de Santander, Bucaramanga 680002, Colombia.
Sci Total Environ. 2021 Mar 15;760:143959. doi: 10.1016/j.scitotenv.2020.143959. Epub 2020 Dec 8.
Biochar is a low-cost and environmentally friendly amendment with strong ability for adsorption of mercury (Hg) from aqueous solutions, contaminated soils, and sediments. In the present study, six biochars were prepared from the pyrolysis of cocoa pod husk, sugarcane bagasse and banana pseudostem at 400 and 600 °C in order to use them as an organic amendment and to evaluate their capacities to reduce the bioavailability, methylation potential, and mobility of Hg present in mine tailings without environmental treatment. To quantify the effects of each variety of biochar, incubation experiments of soil were established by mixing mine tailings with 5% by weight of biochar for 90 days. Once the incubation time concluded, sequential extraction procedures were carried out to determine the fractionation of the Hg species. Speciation analysis results indicated that the remedial effects of biochar depended on the source of organic matter and pyrolysis temperature. The bioavailable and organic Hg fractions decreased respectively by up to 75 and 79%, indicating a methylation potential reduction. Immobile Hg fraction increased to 76% with respect to the control. Adsorption and stabilization to HgS from the soluble forms of Hg reduce the percentage of bioavailable Hg. The organic Hg fraction reduction was correlated with the decrease of the bioavailable Hg fraction and with direct adsorption processes in the biochar structure. Highly porous biochars developed at high temperature, with large contents of superficial polar functional groups (H/C), and high pH, electrical conductivity, ash percentage and cation exchange capacity values favor the stabilization and adsorption of Hg in mine tailings. In summary, the application of biochar could be an effective method for the remediation of Hg-contaminated mine tailings, transforming the Hg species into less toxic, soluble, reactive, and bioavailable forms.
生物炭是一种低成本且环境友好的改良剂，对水溶液、污染土壤和沉积物中的汞（Hg）具有很强的吸附能力。本研究以可可豆荚、甘蔗渣和香蕉假茎为原料，在 400 和 600°C 下热解制备了 6 种生物炭，旨在将其作为一种有机改良剂，评估它们在不进行环境处理的情况下降低矿山尾矿中 Hg 的生物有效性、甲基化潜力和迁移性的能力。为了量化每种生物炭的效果，通过将矿山尾矿与 5%重量的生物炭混合进行了 90 天的土壤孵育实验。孵育时间结束后，采用连续提取程序测定 Hg 形态的分馏情况。形态分析结果表明，生物炭的修复效果取决于有机物的来源和热解温度。生物可利用和有机 Hg 分数分别下降了高达 75%和 79%，表明甲基化潜力降低。与对照相比，不溶 Hg 分数增加到 76%。从可溶性 Hg 形式吸附和稳定到 HgS 减少了生物可利用 Hg 的百分比。有机 Hg 分数的降低与生物可利用 Hg 分数的降低以及生物炭结构中的直接吸附过程有关。在高温下制备的具有高比表面积、丰富的表面极性官能团（H/C）、高 pH 值、电导率、灰分含量和阳离子交换能力的多孔生物炭有利于 Hg 在矿山尾矿中的稳定和吸附。总之，生物炭的应用可能是一种有效修复 Hg 污染矿山尾矿的方法，将 Hg 形态转化为毒性较低、可溶性、反应性和生物可利用的形式。
