Removal of Reactofix golden yellow 3 RFN from aqueous solution using wheat husk—An agricultural waste

Abstract

The wheat husk, an agricultural by-product, has been activated and used as an adsorbent for the adsorption of Reactofix golden yellow 3 RFN from aqueous solution. In this work, adsorption of Reactofix golden yellow 3 RFN on wheat husk and charcoal has been studied by using batch studies. The equibrium adsorption level was determined to be a function of the solution pH, adsorbent dosage, dye concentration and contact time. The equilibrium adsorption capacities of wheat husk and charcoal for dye removal were obtained using Freundlich and Langmuir isotherms. Thermodynamic parameters such as the free energies, enthalpies and entropies of adsorption were also evaluated. Adsorption process is considered suitable for removing color, COD from wastewater.

Introduction

The presence of the color in water is unpleasant; moreover, some dyes also toxic to human being and other animals. Many industries are releasing color constituents, i.e. dyes in watsewater which is contaminating our water resources. Azo dyes constitute a major class of environmental pollutants accounting for 60–70% of all dyes and pigments used. These compounds are characterized by aromatic moieties linked together with azo groups (NN). The release of azo dyes into the environment is a concern due to coloration of natural waters, toxicity, mutagenicity and carcinogenicity of these dyes and their bio-transformation products [1]. Therefore, considerable attention has been given to evaluating the fate of azo dyes during wastewater treatment and in the natural environment. A range of conventional treatment technologies for dye removal have been investigated extensively [2], [3], [4], [5], [6], [7], [8], such as activated sludge, chemical coagulation, carbon adsorption, electrochemical treatment, reverse osmosis, hydrogen peroxide catalysis, etc. However, most of the above methods suffer from one or other limitations and none of them were successful in completely removing the color from wastewater [9].

Azo dyes require an effective treatment technique for their complete removal. Therefore, the aim of this work is to evaluate the adsorption treatment of azo dye. Adsorption hold promise in the treatment of wastewater, as it is inexpensive, simply designed, easy to handle and provides sludge-free cleaning operations. Commercially activated carbon has long been used as a standard adsorbent for color removal. In spite of its wide spread use in various cleaning procedures, activated carbon remains expensive; therefore, the development of low-cost alternative adsorbent has been the focus of recent research. About the selection of adsorbents, a literature survey reveals that materials such as commercially available activated carbon [10], [11], [12], [13], [14], zeolites [14] have been used in the past for the treatment of textile effluents. A number of non-conventional sorbent have been tried for the removal of chemical pollutant such as: peat [15], [16], chitin [17], apple promace and wheat straw [18], sulfonated coal [19], organomontmorillonite [20], coir pith [21], slag from the manufacture of steel [22], fly ash [23], [24] have been used for the removal of dyes. Recently Gupta and Ali [25] have reviewed the utility of the low-cost adsorbent for the removal of various pollutants including dyes. In present adsorption studies, wheat husk (agricultural waste) is converted into a cheap adsorbent and used for the removal of dye. Efforts have been made to convert this waste into a potential and low-cost adsorbent. The present work reports the results of adsorption studies (with charcoal and wheat husk) on an azo dye Reactofix golden yellow 3 RFN (Scheme 1), with particular reference to color removal and wastewater treatment. It is an acid dye and the acidic group acts as auxochrome in this dye.