School of Civil Engineering and Architecture, Wuhan University of Technology, Wuhan, 430070, PR China.
School of Civil Engineering and Architecture, Wuhan University of Technology, Wuhan, 430070, PR China.
Environ Pollut. 2020 Oct;265(Pt B):115018. doi: 10.1016/j.envpol.2020.115018. Epub 2020 Jun 15.
In this study, sludge-derived biochar was prepared and utilized to support nano-zero-valent iron (NZVI-SDBC) for removing Cr(VI) and Cr(III) from aqueous solution with the aim of investigating their removal and transformation. Under the conditions of initial pH of 4, dosage of 1 g/L, temperature of 25 °C, and rotational speed of 160 rpm, 64.13% Cr species could be removed by NZVI-SDBC from Cr(VI) solution and 28.89% from Cr(III) solution. Coexisting ions experiments showed that Cu(II) and humic acids dramatically affected the removal of Cr(VI) and Cr(III), while the effect of Na(I) and Ca(II) was almost negligible. Based on this, through the coexistence and pre-loaded Cr(III) experiments, the conversion from Cr(VI) to Cr(III) was demonstrated to enhance the further attraction on Cr(VI) and promote the subsequent removal of Cr(VI). The SDBC of NZVI-SDBC could serve as electron shuttle mediator to facilitate the electron transfer between adsorbed Cr(VI) and NZVI for ortho-reduction. The transformation and removal mechanisms were further discussed by various characterizations. The kinetics of Cr(VI) removal suggested that the removal process of Cr(VI) could be divided into three phases dominated by different mechanisms (adsorption, direct/ortho reduction, electrostatic attraction), in which Cr(VI) and Cr(III) showed different behaviors of interaction. The removal of Cr(III) mainly depended on sufficient adsorption sites and the direct complexation with Fe(II). Finally, the reusability of NZVI-SDBC was assessed by adsorption/desorption recycling test. These results provided new insights into the removal and transformation mechanisms of Cr(VI) and Cr(III) by biochar-based nanocomposites.
在这项研究中，制备了污泥衍生生物炭并用于负载纳米零价铁（NZVI-SDBC），以去除水溶液中的 Cr(VI) 和 Cr(III)，并研究它们的去除和转化。在初始 pH 值为 4、用量为 1 g/L、温度为 25°C、转速为 160 rpm 的条件下，NZVI-SDBC 可从 Cr(VI) 溶液中去除 64.13%的铬物种，从 Cr(III) 溶液中去除 28.89%的铬物种。共存离子实验表明，Cu(II) 和腐殖酸显著影响 Cr(VI)和 Cr(III)的去除，而 Na(I) 和 Ca(II)的影响几乎可以忽略不计。基于此，通过共存和预加载 Cr(III)实验，证明了 Cr(VI)向 Cr(III)的转化增强了对 Cr(VI)的进一步吸引力，并促进了随后对 Cr(VI)的去除。NZVI-SDBC 的 SDBC 可作为电子穿梭体介导剂，促进吸附 Cr(VI)和 NZVI 之间的电子转移，实现邻位还原。通过各种表征进一步讨论了转化和去除机制。Cr(VI)去除动力学表明，Cr(VI)的去除过程可分为三个阶段，由不同的机制（吸附、直接/邻位还原、静电吸引）主导，其中 Cr(VI)和 Cr(III)表现出不同的相互作用行为。Cr(III)的去除主要取决于充足的吸附位点和与 Fe(II)的直接络合。最后，通过吸附/解吸循环试验评估了 NZVI-SDBC 的可重复使用性。这些结果为生物炭基纳米复合材料去除和转化 Cr(VI)和 Cr(III)的机制提供了新的见解。
