ADSORPTION OF METHYLENE BLUE AND BRILLIANT GREEN DYES UNTO MODIFIED ACTIVATED CARBON PREPARED FROM AGRICULTURAL WASTES

ABSTRACT

This study intends to investigate the analysis of removal of Methylene Blue (MB) and Brilliant Green (BG) dyes from aqueous solutions by adsorption on modified activated carbon prepared by chemical activation of coconut shell, eucalyptus tree, corn cob and flamboyant pod. The maximum percentage methylene blue removal was obtained as 95.0% for coconut shell, 93.2% for eucalyptus tree, 99.9% for corn cob and 99.7% for flamboyant pod with all adsorbent dosage at 5g per 0.003mL. Also, the maximum percentage brilliant green removal was obtained as 97.0% for coconut shell, 98.2% for eucalyptus tree, 99.6% for corn cob and 99.6% for flamboyant pod with all adsorbent dosage at 5g per 0.003mL. The adsorption isotherms of the adsorption process were studied and Freundlich model showed the best fit with equilibrium data. To optimize the operating conditions, the effects of contact time, adsorbent dosage, and pH were investigated by two level factorial experimental design method; adsorbent dosage was found as the most significant factor, lower than 95% confidence level with P = 0.0008 for Methylene Blue and P = 0.0069 for Brilliant Green. The obtained  results are very promising since the utilization of these agricultural wastes activated carbon used in this work played a critical role in the adsorption of dyes.

C HAPTER ONE

1.0  INTRODUCTION

1.1  Background of the study

The release of dyes into wastewaters from textile, cosmetic, paper and coloring industries poses serious environmental problems (El-Qada, Allen and Walker, 2008). Dye presence in wastewater poses problems in a number of ways. Dye availability in water, even if it is just small in quantity is unwanted and highly visible. Color prevents the proper entrance of sunlight into water bodies; it also retards photosynthesis; hinder the growth of aquatic biota and affect the solubility of gas within the water bodies in water bodies. Dyes role in connection with several lung, skin and many other respiratory problems have been reported globally (Jadhav,  Phugare,  Patil  and  Jadhav,  2011).  Direct  release  of  dyes  containing wastewater into municipal environment can cause the production of poisonous carcinogenic products. The highest degrees of toxicity were discovered in diazo direct and raw dyes (Gupta, Mittal, Malviya and Mittal, 2009). Therefore, before wastewater is released into municipal environment, it is very important to reduce dye amount or concentration present in it.

The commonly applied methods of treating wastewater are coagulation and flocculation, electrochemical treatment, liquid–liquid extraction, chemical oxidation and adsorption. Many methods have recently been used to remove both MB and BG from industrial effluents. Among these methods, Adsorption is the most effective way for the removal of organic compounds from solution in term of its low cost of operation, ease of design, sensitivity to poisonous materials and simplicity of operation (El-Qada, et al., 2008). But its use is limited because of high cost and associated problems of regeneration and this problem has initiated a constant and continuous search for cheaper substitutes. Adsorption process make use of carbons. Wide varieties of high carbon content materials such as wood, coal, peat; nutshells, sawdust, bones, husk, petroleum coke and others have been utilized to produce activated carbon of varying efficiencies (Ponnusami, Krithika, Madhuram and Srivastava, 2007). These materials, usually in irregular and bulky shapes, are always adjusted to exhibit the desired final shapes, roughness and hardness.

Generally, the production of activated carbon involves pyrolysis or carbonization and activation as the two main production processes (Bonnamy, 1999). Numerous carbonaceous materials, particularly, those of agricultural base, are being investigated to possess potential as activated carbon. The suitable ones have minimum amount of organic material and a long storage life. Similarly they consist of hard structure to maintain their properties under usage conditions. They can be obtained at a low cost. Some of the materials that meet the above conditions have been used, in past works, to produce activated carbons which were subsequently used for the treatment of wastewater and adsorption of hazardous gases. Agricultural by-products like rice straw, soybean hull, sugarcane bagasse, peanut shell, pecan shell and walnut shells were used  by Ponnusami et al. (2007) to  produce Granulated Activated Carbons (GACs). The choice of a particular material for the production of effective adsorbent (activated carbon) is based on low cost, high carbon and low inorganic content. Agricultural materials have attracted the interest of researchers for the production of adsorbents because of their availability in large amount and at a low cost (Foo and Hameed, 2011). The selected materials employed in this study were coconut shell, corn cob, flamboyant pod and eucalyptus tree. Use of agricultural by-product for the production of activated carbon is primarily for economic and ecological advantages (Foo et al., 2011).

Commercial activated carbon used in surface and wastewater treatment is largely derived from coal. The advantages of coal-based carbons can be seen in their ability to remove toxic organic compounds from industrial and municipal wastewater and potable water as well. Another significant application of coal-based carbons is decolorization. The feedstock for these  carbons,  usually  bituminous  coal,  is  a  non-renewable  resource.  The  long-term availability of coal and its long-term environmental impact coupled with its potentially increasing cost has prompted researchers to consider renewable resources such as agricultural by-products as an alternative. Many efforts have been made to use low cost agro waste materials in substitute for commercial activated carbon (Crini, 2006). Some agro waste materials studied for their capacity to remove dyes from aqueous solutions are coir pith, pine sawdust, tamarind fruit shell, bagasse, rice husk, orange peel, palm kernel shell, cashew nut shell and wall nut shell, (Mittal, Kaur and Mittal, 2008). The present investigation is an attempt  to  remove  Methylene  blue  and  Brilliant  green  from  synthetic  wastewater  by adsorption process using a low cost activated carbon prepared from agricultural wastes as an adsorbent. The coconut shell and corn cob are considered as an agricultural wastes, therefore using them as raw materials for production of activated carbon is more economical than the coal based activated carbon. In this study, the carbon adsorption method will be investigated for its efficiency in colour removal from water bodies.

1.2 Statement of the problem

The presence of organic pollutants compounds such as dye in water causes serious problems due to their toxicity, suspected carcinogenicity and adverse effects on the human nervous system that cause many health disorders. Removing these contaminants from water is a significant challenge because of ever-increasing pollution of drinking water, the shortage of high quality fresh water and frequent release of wastewater by production companies into water body.

1.3  Aim and objectives

The aim of this project is to remove methylene blue and brilliant green dyes from synthetic wastewater using modified carbons made from agricultural wastes. This aim can be achieved through the following objectives:

1.   To  carry  out  characterization  of  adsorbent  by  Raman  Spectroscopy  (RS)  and Brunauer-Emmet-Teller (BET).

2.   To study the interaction of the mixture of methylene blue and brilliant green dyes on the adsorption sites of the activated carbon.

3.   To study the main and interaction effects of the parameters used for the experiments on adsorption process

4.   To study the percentage removal of the adsorbents and compare results by measuring the percentage of color remove.

5.   To  determine  the  isotherm  model  where  equilibrium  data  of  the  adsorption mechanism will be best represented using modified activated carbon.

1.4 Scope of the study

This project investigates the adsorption capacity of four different activated carbons prepared from low cost agricultural wastes on the removal of dyes from aqueous solution. The pH, contact time and carbon dosage effects as well as the interaction nature of the mixture of methylene blue and brilliant green on the adsorption sites of activated carbons will be investigated. Adsorption equilibrium data will be determined. This data will be subjected to Freundlich and Langmuir models to determine isotherm models that will be most appropriate for equilibrium. This work will be experimental, Raman Spectroscopy (RS) will be used for determination of functional groups present in the carbons and Brunauer-Emmet-Teller (BET) will be used to determine the adsorption capacity of the carbons.

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