Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Tianjin Engineering Center of Environmental Diagnosis and Contamination Remediation, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China E-mail:
CNPC Research Institute of Safety and Environmental Technology, Beijing 102206, China and State Key Laboratory of Petroleum Pollution Control, Beijing 102206, China.
Water Sci Technol. 2019 May;79(9):1705-1716. doi: 10.2166/wst.2019.170.
Biochars produced from different feedstocks via pyrolytic carbonization and ultraviolet (UV) modification were used as alternative adsorbents for aqueous hexavalent chromium (Cr(VI)) remediation. Structural and morphological analysis showed that UV irradiation increased the surface area of biochar and added a large amount of oxygen-containing functional groups on the biochar's surface, resulting in about 2-5 times increase of Cr(VI) removing capacity (14.39-20.04 mg/g) compared to that of unmodified biochars (3.60-8.43 mg/g). The sorption ability among different feedstocks after modification was as follows: corn stack > sawdust > wheat straw. The adsorption kinetics and adsorption isotherm data agreed well with the pseudo-second-order model and Freundlich model, respectively. Experimental and modeling results suggested that the oxygen-containing functional groups and surface areas of biochars were notably increased after UV irradiation, which was mainly governed by surface complexation. X-ray photoelectron spectroscopy analysis showed that reduction occurred during Cr(VI) adsorption. In addition, UV irradiation significantly increased the concentration of dissolved organic matter (DOM) in biochars. The collected outcomes showed that UV-modified biochar was a good material for the removal of hexavalent chromium from aqueous medium. The excellent adsorption capacity, environmental-friendly and low cost properties made the novel material an auspicious candidate for environmental remediation.
不同原料经热解碳化和紫外（UV）改性得到的生物炭被用作水相中六价铬（Cr(VI)）修复的替代吸附剂。结构和形态分析表明，UV 辐照增加了生物炭的表面积，并在生物炭表面添加了大量含氧官能团，与未改性生物炭（3.60-8.43mg/g）相比，Cr(VI)去除能力（14.39-20.04mg/g）提高了约 2-5 倍。改性后不同原料的吸附能力如下：玉米秸秆＞木屑＞小麦秸秆。吸附动力学和吸附等温线数据分别与准二级模型和 Freundlich 模型吻合较好。实验和模型结果表明，UV 辐照后生物炭的含氧官能团和表面积明显增加，这主要是由表面络合作用决定的。X 射线光电子能谱分析表明，Cr(VI)吸附过程中发生了还原反应。此外，UV 辐照显著增加了生物炭中溶解有机质（DOM）的浓度。综上结果表明，UV 改性生物炭是一种从水介质中去除六价铬的良好材料。其良好的吸附能力、环境友好性和低成本特性使这种新型材料成为环境修复的理想候选材料。
