Abstract

This study describes the synthesis of calix[6]arene hexaester appended Amberlite XAD-4 (resin 2) and its application for the removal of reactive blue-5 (RB-5) and direct black-38 (DB-38) azo dyes from aqueous media. The newly synthesized resin 2 was characterized by using various analytical techniques such as FTIR spectroscopy, elemental analysis, scanning electron microscope, and thermogravimetric analysis. In this approach, adsorption efficiency of resin 2 for azo dyes was explored by optimizing various parameters such as pH, adsorbent dose, role of electrolytes, and contact time. From results it has been observed that percentage adsorption of these azo dyes is highly dependent on pH of the solution. The maximum adsorption of RB-5 and DB-38 was achieved at pH 3 and pH 9, respectively. Isotherm evaluation has judged that adsorption behavior can be better demonstrated by Langmuir and D–R models. The kinetic studies revealed that removal process of selected dyes follow pseudo-second-order kinetic model. The positive and negative values of ΔH and ΔG, respectively, confirm the endothermic and spontaneous nature of this adsorption process. Moreover, results shows that resin 2 has proved highly effective adsorbent for the removal of azo dyes from aqueous environment.

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