Niazi Nabeel Khan, Bibi Irshad, Shahid Muhammad, Ok Yong Sik, Burton Edward D, Wang Hailong, Shaheen Sabry M, Rinklebe Jörg, Lüttge Andreas
Institute of Soil and Environmental Sciences, University of Agriculture Faisalabad, Faisalabad 38040, Pakistan; MARUM and Department of Geosciences, University of Bremen, Bremen D-28359, Germany; Southern Cross GeoScience, Southern Cross University, Lismore 2480 NSW, Australia.
Institute of Soil and Environmental Sciences, University of Agriculture Faisalabad, Faisalabad 38040, Pakistan; MARUM and Department of Geosciences, University of Bremen, Bremen D-28359, Germany.
Environ Pollut. 2018 Jan;232:31-41. doi: 10.1016/j.envpol.2017.09.051. Epub 2017 Sep 29.
In this study, we examined the removal of arsenite (As(III)) and arsenate (As(V)) by perilla leaf-derived biochars produced at 300 and 700 °C (referred as BC300 and BC700) in aqueous environments. Results revealed that the Langmuir isotherm model provided the best fit for As(III) and As(V) sorption, with the sorption affinity following the order: BC700-As(III) > BC700-As(V) > BC300-As(III) > BC300-As(V) (Q = 3.85-11.01 mg g). In general, As removal decreased (76-60%) with increasing pH from 7 to 10 except for the BC700-As(III) system, where notably higher As removal (88-90%) occurred at pH from 7 to 9. Surface functional moieties contributed to As sequestration by the biochars examined here. However, significantly higher surface area and aromaticity of BC700 favored a greater As removal compared to BC300, suggesting that surface complexation/precipitation dominated As removal by BC700. Arsenic K-edge X-ray absorption near edge structure (XANES) spectroscopy demonstrated that up to 64% of the added As(V) was reduced to As(III) in BC700- and BC300-As(V) sorption experiments, and in As(III) sorption experiments, partial oxidation of As(III) to As(V) occurred (37-39%). However, XANES spectroscopy was limited to precisely quantify As binding with sulfur species as AsS-like phase. Both biochars efficiently removed As from natural As-contaminated groundwater (As: 23-190 μg L; n = 12) despite in the presence of co-occurring anions (e.g., CO, PO, SO) with the highest levels of As removal observed for BC700 (97-100%). Overall, this study highlights that perilla leaf biochars, notably BC700, possessed the greatest ability to remove As from solution and groundwater (drinking water). Significantly, the integrated spectroscopic techniques advanced our understanding to examine complex redox transformation of As(III)/As(V) with biochar, which are crucial to determine fate of As on biochar in aquatic environments.
在本研究中，我们考察了300℃和700℃下制备的紫苏叶生物炭（分别称为BC300和BC700）在水环境中对亚砷酸盐（As(III)）和砷酸盐（As(V)）的去除效果。结果表明，Langmuir等温线模型最能拟合As(III)和As(V)的吸附，吸附亲和力顺序为：BC700-As(III)＞BC700-As(V)＞BC300-As(III)＞BC300-As(V)（Q = 3.85 - 11.01 mg g）。一般来说，除了BC700-As(III)体系外，随着pH从7升高到10，As去除率降低（76% - 60%），在BC700-As(III)体系中，pH为7至9时As去除率显著更高（88% - 90%）。表面官能团有助于此处所研究生物炭对As的螯合。然而，与BC300相比，BC700显著更高的比表面积和芳香性有利于更高的As去除率，这表明表面络合/沉淀主导了BC700对As的去除。砷K边X射线吸收近边结构（XANES）光谱表明，在BC700-和BC300-As(V)吸附实验中，高达64%的添加As(V)被还原为As(III)，而在As(III)吸附实验中，As(III)发生了部分氧化为As(V)（37% - 39%）。然而，XANES光谱在精确量化As与硫物种以类AsS相形式结合方面存在局限性。尽管存在共存阴离子（如CO、PO、SO），两种生物炭都能有效地从天然As污染的地下水中去除As（As含量为23 - 190 μg L；n = 12），其中BC700的As去除率最高（97% - 100%）。总体而言，本研究强调紫苏叶生物炭，尤其是BC700，具有从溶液和地下水中（饮用水）去除As的最大能力。重要的是，综合光谱技术增进了我们对生物炭与As(III)/As(V)复杂氧化还原转化的理解，这对于确定水生环境中As在生物炭上的归宿至关重要。
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