Synthesis and characterization of nano-zinc oxide fiber: adsorption of acid blue 92 dye, isotherms, thermodynamics and kinetics

Rapid industrialization, particularly textile/dyeing, causes substantial surface water contamination by various dyes and pigments globally. Bangladesh’s export-oriented textile industry has grown dramatically in recent decades, causing significant pollution of nearby water bodies. In this work, nano-zinc oxide was synthesized by a precipitation method with PEG 400 and characterized using SEM, XRD and FTIR techniques and found to be fiber-like, perfectly wurtzite and pure. The nano-ZnO was applied to remove acid blue 92, an ionic dye, from aqueous solution to investigate it as an adsorbent. The effects of pH, adsorbent dosage, AB92 concentration and contact time on adsorption process were investigated for optimization. According to the correlation coefficients ( R 2 ) and the fitting of Redlich-Peterson model, the adsorption process followed Langmuir isotherm at lower temperature and Freundlich isotherm at higher temperature with Temkin model. The adsorption process was found to be endothermic and spontaneous. For adsorption thermodynamics, ΔH was found to be +20.32 kJmol -1 , and ΔG was varied from -1.86 to -3.84 kJmol -1 as the temperature increased from 291 to 317 K. The adsorption kinetics exhibited pseudo second order. The Temkin isotherm and Elovich kinetic model suggested that the process to be chemisorption. The nano-ZnO showed tremendous re-usability as an adsorbent for the removal of AB92. The results are suggesting for designing nano-ZnO-based methods to remove organic pollutants efficiently from industrial effluents for ecological and sustainable development. The mechanisms of nano-ZnO fiber formation and anionic dye adsorption on nano-ZnO are also discussed.