Removal of Reactofix golden yellow 3 RFN from aqueous solution using wheat husk—An agricultural waste
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.
Section snippets
Adsorbent development
Two hundred grams of wheat husk was treated with hydrogen peroxide (30%) at 60 °C for 24 h to oxidize the adhering organic matter. The resulting material washed with double distilled water and filtered and again dried to 100 °C, powdered, grounded and sieved to the desired particle size. Physiochemical characterization of wheat husk has been carried out and the results are being shown in Table 1.
Adsorbate
Reactofix golden yellow 3 RFN was obtained from Aldrich chemical Co., USA. All other reagents were of
Sorption studies
Adsorption isotherms were determined for various dye-adsorbent systems. The distribution of dye between adsorbent and the dye solution at equilibrium is important in establishing the capacity of the adsorbent for the dye. Adsorption studies were carried out taking charcoal and wheat husk (bio-sorbent) as adsorbents. The effect of pH, concentration, adsorbent dose, temperature, and particle size of adsorbents were studied, in order to optimize each parameter for maximum uptake. Isotherms were
Chemical oxygen demand (COD)
COD of initial colored and treated filtrate of charcoal and wheat husk solutions was determined and it was observed that the COD values show (Table 5) a significant decrease from 1416 to 352, 220 and 320 mg/L, respectively, indicating less toxicity of the treated products in comparison to original dye.
Conclusion
Based on the results wheat husk was found to be an effective adsorbent for the removal of Reactofix golden yellow 3 RFN and it has good adsorption capacity which is comparable with the other low-cost adsorbent reported for the removal of similar and other ionic dyes using low-cost adsorbents (Table 6). Wheat husk is cheap and easily available material thus it is a better replacement of activated carbon. Wheat husk is a waste product hence its use as an adsorbent on one hand would solve its
Acknowledgement
The authors are thankful to the Council of Scientific and Industrial Research (CSIR), New Delhi, India for consistent encouragement and financial support.
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