State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, PR China; School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, PR China.
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, PR China; School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, PR China.
Sci Total Environ. 2020 Jul 10;725:138419. doi: 10.1016/j.scitotenv.2020.138419. Epub 2020 Apr 4.
Biochar and hydrochar have been served as attractive adsorbents for remediation of polluted water and soil, but it is lack of the long-term ageing effects on competitive adsorption of co-existing heavy metals by these carbonized materials. By this, corn stalk was used as carbon precursor to prepare biochar (500 °C) and hydrochar (200 °C). The single-metal and binary-metal Cd(II)/Cu(II) sorption were conducted on biochar and hydrochar before and after ageing using artificial accelerated ageing of 5% HO treatment. The elemental analysis, BET, SEM, FTIR, XRD and Zeta potential were used to characterize the physicochemical properties of carbonized material samples. The results showed that oxidative ageing could increase O content and O-containing functional groups but decrease C content, metal content and aromaticity degree. Ageing hardly affected the SSA and crystallographic structures of biochar and hydrochar. The reduction of metal content in Aged-BC caused a decline of sorption capacity, indicating that cation exchange would be the predominant factor involved in biochar sorption for Cd(II) and Cu(II). As for hydrochar with more O-containing functional groups than biochar, the dominated sorption mechanism would be surface complexation, due to higher sorption capacity of Aged-HC with richer O-containing functional groups. In binary-metal system, the competitive sorption of Cd(II) and Cu(II) on biochar was observed obviously but that on hydrochar was limited. Ageing could increase the sorption capacity of Cd(II) in binary-metal system, resulting in alleviating competitive adsorption. The total sorption amount of Cd(II) and Cu(II) by biochar was markedly greater than that of hydrochar before or after ageing, suggesting that biochar can be still more capable than hydrochar for handling Cd(II) and Cu(II) in single-metal or binary-metal. These findings suggest us to consider the long-term effect on immobilization of co-existing heavy metals and alleviating competitive adsorption of carbonized materials as alternative amendment for contaminated sites.
生物炭和水热炭已被用作修复污染水和土壤的有吸引力的吸附剂，但缺乏这些碳化材料对共存重金属的竞争吸附的长期老化效应。为此，以玉米秸秆为碳前驱体，制备生物炭（500°C）和水热炭（200°C）。采用 5%HO 人工加速老化处理，对生物炭和水热炭老化前后的单金属和双金属 Cd(II)/Cu(II)吸附进行了研究。采用元素分析、BET、SEM、FTIR、XRD 和 Zeta 电位对碳化材料样品的物理化学性质进行了表征。结果表明，氧化老化可以增加 O 含量和含 O 官能团的含量，但降低 C 含量、金属含量和芳构化程度。老化几乎不影响生物炭和水热炭的比表面积和结晶结构。Aged-BC 中金属含量的降低导致吸附容量下降，表明阳离子交换将是生物炭吸附 Cd(II)和 Cu(II)的主要因素。对于含 O 官能团比生物炭多的水热炭，由于含有更多含 O 官能团的 Aged-HC 具有更高的吸附容量，表面络合将是主要的吸附机制。在二元金属体系中，观察到 Cd(II)和 Cu(II)在生物炭上的竞争吸附，但在水热炭上的竞争吸附有限。老化可以增加二元金属体系中 Cd(II)的吸附容量，从而减轻竞争吸附。老化前后生物炭对 Cd(II)和 Cu(II)的总吸附量明显大于水热炭，表明生物炭在单金属或双金属体系中处理 Cd(II)和 Cu(II)的能力仍强于水热炭。这些发现提示我们，要考虑长期老化对共存重金属固定化的影响，以及碳化材料缓解竞争吸附的能力，作为污染场地的替代修复措施。
