Faculty of Chemical and Food Engineering, Bahir Dar Institute of Technology, Bahir Dar University, Ethiopia.
Department of Chemical and Biochemical Engineering, University of Western Ontario, London, Ontario, N6A5B9, Canada.
Chemosphere. 2022 Sep;303(Pt 2):135024. doi: 10.1016/j.chemosphere.2022.135024. Epub 2022 May 23.
Cellulose-reactive anionic dyes are one of the dominant colorants used in textile finishing. Unfortunately, they also produce large quantities of wastewater that must be treated before discharge, demanding low-cost and sustainable adsorbents that can easily be implemented, especially for developing countries with thriving cotton-based textile sectors. In this study, a high specific surface area (670 m/g) water hyacinth root powder (WHRP) bioadsorbent that is neither carbonized nor activated was prepared to remove cellulose-reactive anionic blue dye from an aqueous solution. The effect of adsorption pH (pH = 2-8), adsorbent dose (1 g/L-6 g/L), dye concentration (50 mg/L-500 mg/L), adsorbent particle size (50 μm-1000 μm), mixing speed (100 rpm -200 rpm), and adsorption temperatures (22 °C-60 °C) were systematically studied. It was found that the protonation of lignin polyphenols in WHRP at pH = 2 was responsible for the observed high (∼99%) adsorptive removal of reactive blue dye. The maximum equilibrium adsorption capacity was 128.8 mg/g when 1 g/L WHRP and 500 mg/L dye concentration were used. In addition, adsorption isotherms, kinetic models, and adsorption thermodynamics were investigated. Increasing adsorbent dose, decreasing adsorbent particle size, increasing mixing speed, and lowering temperature favored the adsorption of reactive dye to WHRP adsorbent. The batch adsorption data were best fitted with both Langmuir and Temkin models, especially at 22 °C, while the adsorption kinetic behavior was described best using pseudo-second-order kinetics. Adsorption of cellulose-reactive blue dye to WHRP was spontaneous as characterized by the negative Gibbs energy (-11 kJ/mol to -24 kJ/mol) and exothermic with negative enthalpy (-13 kJ/mol to -23 kJ/mol). The overall adsorption process was controlled by more than one mechanism since the intraparticle diffusion was not the only rate-limiting step under our experimental conditions. Taken together, the abundantly available and sustainable WHRP is an efficient adsorbent that could be scaled up for treating cellulose-reactive dye-contaminated water.
纤维素反应性阴离子染料是纺织整理中使用的主要着色剂之一。不幸的是，它们也产生大量的废水，在排放之前必须进行处理，这就需要低成本和可持续的吸附剂，可以很容易地实施，特别是对于蓬勃发展的以棉花为基础的纺织部门的发展中国家。在这项研究中，制备了一种具有高比表面积（670 m/g）的水葫芦根粉末（WHRP）生物吸附剂，该吸附剂既不碳化也不活化，用于从水溶液中去除纤维素反应性阴离子蓝染料。系统研究了吸附 pH（pH=2-8）、吸附剂用量（1 g/L-6 g/L）、染料浓度（50 mg/L-500 mg/L）、吸附剂粒径（50 μm-1000 μm）、混合速度（100 rpm-200 rpm）和吸附温度（22°C-60°C）对吸附的影响。结果表明，WHRP 中木质素多酚的质子化作用在 pH=2 时负责观察到的高（约 99%）反应性蓝染料的吸附去除。当使用 1 g/L WHRP 和 500 mg/L 染料浓度时，最大平衡吸附容量为 128.8 mg/g。此外，还研究了吸附等温线、动力学模型和吸附热力学。增加吸附剂用量、减小吸附剂粒径、提高混合速度和降低温度有利于反应性染料向 WHRP 吸附剂的吸附。批处理吸附数据最适合 Langmuir 和 Temkin 模型，特别是在 22°C 时，而吸附动力学行为最适合使用拟二级动力学模型描述。纤维素反应性蓝染料在 WHRP 上的吸附是自发的，特征是负的吉布斯自由能（-11 kJ/mol 至-24 kJ/mol）和放热的，焓为负（-13 kJ/mol 至-23 kJ/mol）。由于在我们的实验条件下，不是唯一的速率限制步骤，因此整个吸附过程受多种机制控制。总的来说，丰富的、可持续的 WHRP 是一种有效的吸附剂，可以扩大规模用于处理纤维素反应性染料污染的水。
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