Korea Polar Research Institute (KOPRI), Incheon 21990, Republic of Korea.
Department of Environmental Sciences and Biotechnology, Hallym University, Chuncheon, Gangwon-do 24252, Republic of Korea.
Environ Res. 2021 Jun;197:111059. doi: 10.1016/j.envres.2021.111059. Epub 2021 Mar 22.
The concentration of chromium (Cr) in natural water and soil environments has gradually increased in recent decades, owing to intensive use of Cr in industry and its subsequent disposal. In this study, we performed a comparison study on chromate (Cr) reduction by tea waste (green tea, black tea, red tea, and chamomile) in water (25 C) and ice (-20 C) to develop a new strategy for environmental-friendly stabilization of hazardous Cr by freezing. This study shows that the freezing process can enhance the reduction of Cr by tea waste. The residual Cr concentration ratios (C/C, where C is the concentration of Cr after the reaction (5 h) and C is the initial concentration of Cr (20 μM) in the system) by tea wastes in water were in the range of 0.71 (green tea) to 0.92 (chamomile); however, the ratios dramatically decreased under the freezing process (i.e., 0.06 by green tea, 0.13 by black tea, 0.18 by red tea, and 0.08 by chamomile). According to the results obtained from the fluorescent, chromatographic, and spectroscopic analyses, under the freezing process, the enhanced reduction of Cr could be explained by the freeze concentration of Cr, phenolic components in tea extracts, and protons in small liquid pockets in liquid-like layers (LLLs). In addition, the proposed system can efficiently purify the real Cr-containing wastewater (i.e., electroplating wastewater), indicating that the system will be economically feasible in cold regions (i.e., polar regions).
近年来，由于工业上大量使用铬以及随后的处置不当，天然水和土壤环境中的铬浓度逐渐增加。在这项研究中，我们比较了在水（25°C）和冰（-20°C）中，用茶渣（绿茶、红茶、黑茶和洋甘菊）还原铬酸盐（Cr）的情况，以期开发一种通过冷冻实现环境友好型稳定处理危险 Cr 的新策略。研究表明，冷冻过程可以增强茶渣对 Cr 的还原作用。在水体系中，茶渣对 Cr 的残留浓度比（C/C，其中 C 是反应（5 小时）后 Cr 的浓度，C 是体系中 Cr 的初始浓度（20μM））的范围为 0.71（绿茶）至 0.92（洋甘菊）；然而，在冷冻过程中，这些比值急剧下降（即，绿茶为 0.06，红茶为 0.13，黑茶为 0.18，洋甘菊为 0.08）。根据荧光、色谱和光谱分析的结果，在冷冻过程中，Cr 的浓缩、茶提取物中的酚类成分以及小液滴中的质子在类液相层（LLLs）中的冻融作用可以解释 Cr 还原增强的原因。此外，该体系可以有效地净化实际含 Cr 废水（例如电镀废水），表明该体系在寒冷地区（如极地地区）具有经济可行性。
