Department of Soil Science, Luiz de Queiroz College of Agriculture (ESALQ), University of São Paulo (USP), 13418900 Piracicaba, SP, Brazil; Department of Crop and Soil Sciences, North Carolina State University, 27695 Raleigh, NC, USA.
Department of Crop and Soil Sciences, North Carolina State University, 27695 Raleigh, NC, USA.
Sci Total Environ. 2023 Mar 20;865:161286. doi: 10.1016/j.scitotenv.2022.161286. Epub 2022 Dec 30.
Water contamination by arsenic (As) affects millions of people around the world, making techniques to immobilize or remove this contaminant a pressing societal need. Biochar and iron (oxyhydr)oxides [in particular, biogenic iron (oxyhydr)oxides (BIOS)] offer the possibility of stabilizing As in remediation systems. However, little is known about the potential antagonism in As sorption generated by the dissolved organic carbon (DOC) from biochar, or whether DOC affects how As(V) interacts with BIOS. For this reason, our objectives were to evaluate the i) As(V) sorption potential in BIOS when there is presence of DOC from pyrolyzed biochars at different temperatures; and ii) identify whether the presence of DOC alters the surface complexes formed by As(V) sorbed in the BIOS. We conducted As(V) sorption experiments with BIOS at circumneutral pH conditions and in the presence of DOC from sugarcane (Saccharum officinarum) straw biochar at pyrolyzed 350 (BC350) and 750 °C (BC750). The As(V) content was quantified by inductively coupled plasma mass spectrometry, and the BIOS structure and As(V) sorption mechanisms were investigated by X-ray absorption spectroscopy. In addition, the organic moieties comprising the DOC from biochars were investigated by attenuated total reflectance Fourier transform infrared spectroscopy. The addition of DOC did not change the biomineral structure or As(V) oxidation state. The presence of DOC, however, reduced by 25 % the sorption of As(V), with BC350 being responsible for the greatest reduction in As(V) sorption capacity. Structural modeling revealed As(V) predominantly formed binuclear bidentate surface complexes on BIOS. The presence of DOC did not change the binding mechanism of As(V) in BIOS, suggesting that the reduction of As(V) sorption to BIOS was due to site blocking. Our results bring insights into the fate of As(V) in surface waters and provide a basis for understanding the competitive sorption of As(V) in environments with biochar application.
砷（As）污染水影响着全世界数百万人，因此，开发固定或去除这种污染物的技术成为当务之急。生物炭和铁（氢）氧化物（尤其是生物成因的铁（氢）氧化物（BIOS））为稳定修复系统中的砷提供了可能。然而，对于生物炭溶解有机碳（DOC）产生的砷吸附的潜在拮抗作用，以及 DOC 是否影响砷（V）与 BIOS 的相互作用，人们知之甚少。为此，我们的目标是评估：i）在存在不同热解温度的生物炭衍生的 DOC 时，BIOS 对砷（V）的吸附潜力；ii）确定 DOC 的存在是否改变了吸附在 BIOS 上的砷（V）形成的表面络合物。我们在中性 pH 条件下进行了 BIOS 对砷（V）的吸附实验，并在存在热解甘蔗（Saccharum officinarum）秸秆生物炭衍生的 DOC 时（350°C 热解的 BC350 和 750°C 热解的 BC750）进行了实验。采用电感耦合等离子体质谱法（ICP-MS）定量砷（V）含量，采用 X 射线吸收光谱法（XAS）研究 BIOS 结构和砷（V）吸附机制。此外，采用衰减全反射傅里叶变换红外光谱法（ATR-FTIR）研究了生物炭衍生 DOC 中的有机基团。DOC 的存在并没有改变生物矿化结构或砷（V）的氧化态。然而，DOC 的存在使砷（V）的吸附减少了 25%，其中 BC350 对砷（V）吸附容量的降低贡献最大。结构建模表明，砷（V）主要在 BIOS 上形成双核双齿表面络合物。DOC 的存在并没有改变砷（V）在 BIOS 中的结合机制，这表明砷（V）在 BIOS 上的吸附减少是由于位点被占据。我们的研究结果深入了解了地表水砷（V）的归宿，并为理解生物炭应用环境中砷（V）的竞争吸附提供了依据。
