Counterion Effects on the Adsorption of Acid Orange 8 from Aqueous Solution onto HDTMA-Modiﬁed Nanozeolite from Fly Ash

Denise A Fungaro,Carina P Magdalena

doi:10.13189/eer.2014.020206

Abstract

Surfactant-modified nanozeolites from coal fly ash were used for the removal of Acid Orange 8 (AO8) from water. The zeolitic material was modified by two cationic surfactants i. e., hexadecyltrimethyl ammonium bromide (HDTMA-Br) and hexadecyltrimethyl ammonium chloride (HDTMA-Cl). Both the modified nanozeolites were characterized using various techniques to obtain its physical and chemical constituents. The adsorbents before and after adsorption were characterized by X-ray diffraction (XRD). The dynamical data obtained at different concentrations for the two organozeolites fit well with pseudo-second-order kinetic model. The equilibrium adsorption data were interpreted in terms of the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. The results showed that the adsorption of AO8 was influenced by HDTMA-zeolite counterion. Zeolite modified with HDTMA-Br was most efficient than zeolite modified with HDTMA-Cl for AO8 removal. Negative values of Gibbs free energy change (ΔG o ) for dye adsorption onto HDTMA-modified zeolites indicates that the adsorption process is spontaneous and thermodynamically favorable. As a result, surfactant-modified nanozeolites from coal fly ash could be used as effective adsorbents for AO8 removal from wastewater.

Highlights

Dyestuff industries and textile industries are, respectively, the largest producers and users of dyes, producing tons of residues which are released into the environment causing serious problems
Among the synthetic dyes released in effluents, azo dyes is one of the more detrimental classes because it is highly persistent in the aquatic environment, due to its chemical compositions, involving aromatic rings, azoic linkages and amino groups[1,2]
Zeolites synthesized from Brazilian fly ash have been used as low cost adsorbent for dye removal [5,6,7]

Summary

Introduction

Dyestuff industries and textile industries are, respectively, the largest producers and users of dyes, producing tons of residues which are released into the environment causing serious problems. Dye removal is complicated by the structural diversity of dyes that may be used in a single dyeing operation, and by other wastewater constituents that may attenuate the treatment process. Because the surface of zeolites is negatively charged and hydrophilic in nature, little affinity toward organic pollutants such as anionic dyes is expected. The surfactants that are commonly employed in the previous studies in attaching onto the surface of zeolite are hexadecyltrimethylammonium (HDTMA). These quaternary amines are composed of a hydrophilic and positively charged head group and a hydrophobic tail in their molecule structures [8,9,10]

Objectives

Methods

Results