The feasibility of using Eucalyptus citriodora leaves (ECL), an abundantly available agricultural waste, for adsorption of an anionic dye, direct red 31 (DR31), adsorption from hydrous solution has been examined in the present research. The batch adsorption trials were performed to analyse the effects of pH, contact time, initial dye concentration, adsorbent dose, temperature and particle size on DR31 removal from its aqueous solution on biochar of ECL. A maximum of 97% removal of DR31 dye was observed at pH and initial adsorbate concentration of 2 and 40 mg/L by the ECL biochar, respectively. Equilibrium data were examined by Langmuir and Freundlich isotherms. Langmuir isotherm appeared as the best fit model with the highest adsorption capacity of 3.2 mg/g. The kinetic results were also examined and found pseudo-second-order to be the best fit which expressed that the adsorption rate was mainly regulated by chemisorption. ECL biochar maintained > 41.56% adsorption capacity of DR31 dye even after five adsorption–desorption consecutive cycles. Phytotoxicity studies on Vigna radiata substantiated the non-toxic nature of the treated DR31 dye-containing water. The present study reveals that the biochar of ECL can be utilized as a cost-effective adsorbent to make the dye-contaminated wastewater reusable.

使用柠檬桉的可行性叶子（ECL），一种大量可用的农业废物，用于吸附阴离子染料，直接红 31（DR31），在本研究中已经研究了从水溶液中的吸附。进行批量吸附试验以分析 pH、接触时间、初始染料浓度、吸附剂剂量、温度和粒径对 ECL 生物炭水溶液中 DR31 去除的影响。ECL 生物炭在 pH 值和初始吸附物浓度分别为 2 和 40 mg/L 时观察到最多 97% 的 DR31 染料去除。通过 Langmuir 和 Freundlich 等温线检查平衡数据。Langmuir 等温线作为最佳拟合模型出现，最高吸附容量为 3.2 mg/g。还检查了动力学结果，发现伪二级是最佳拟合，表明吸附速率主要受化学吸附调节。即使经过五个吸附-解吸连续循环后，ECL biochar 仍保持 > 41.56% 的 DR31 染料吸附容量。植物毒性研究Vigna radiata证实了处理过的含 DR31 染料的水的无毒性质。本研究表明，ECL 生物炭可作为一种经济高效的吸附剂，使受染料污染的废水可重复使用。