A novel adsorbent of modified nanoclay was synthesized by covering of alum on the montmorillonite nanoclay (Al/nanoclay). Al/nanoclay was applied as an efficient superadsorbent to remove Direct Red 23 (DR23) from colored wastewater. The adsorbent was characterized by Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and zeta potential analysis. The effects of various operating parameters, such as contact time, initial dye concentration, adsorbent dose, pH and ionic strength on the performance of adsorption, have been studied. The adsorption experiments showed that pH has an obvious effect on the adsorption efficiency and the highest percentage of DR23 dye removal was observed at pH 2. Zeta potential measurement confirmed that the adsorption mechanism is ascribed to electrostatic interaction between sulfonic groups of the anionic dye and the positive surface charge of the adsorbent. The pseudo-second-order kinetic model and the Langmuir isotherm were found to best describe the DR23 adsorption and the maximum monolayer adsorption capacity at the conditions of pH 2 and the adsorbent dose of 0.05 g/L was 2,500 mg/g. The findings recommend that Al/nanoclay can be successfully used for DR23 dye removal from the colored wastewater.

中文翻译：

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通过改性蒙脱石纳米粘土作为超级吸附剂从水溶液中吸附直接红 23 染料：机理、动力学和等温线研究

通过在蒙脱石纳米粘土（Al/纳米粘土）上覆盖明矾，合成了一种新型改性纳米粘土吸附剂。铝/纳米粘土被用作有效的超级吸附剂，以从有色废水中去除 Direct Red 23 (DR23)。通过傅里叶变换红外光谱、能量色散 X 射线光谱和 zeta 电位分析对吸附剂进行了表征。研究了各种操作参数，如接触时间、初始染料浓度、吸附剂量、pH 值和离子强度对吸附性能的影响。吸附实验表明，pH 对吸附效率有明显影响，在 pH 2 时观察到 DR23 染料去除率最高。Zeta 电位测量证实吸附机制归因于阴离子染料的磺基与吸附剂表面正电荷之间的静电相互作用。发现伪二级动力学模型和朗缪尔等温线最能描述 DR23 吸附，在 pH 2 和 0.05 g/L 吸附剂剂量为 2,500 mg/g 的条件下，最大单层吸附容量。研究结果表明，铝/纳米粘土可以成功地用于从有色废水中去除 DR23 染料。