International Journal of Scientific and Innovative Research 2015; 3(1) : 91-107, P-ISSN 2347-2189, E- ISSN 2347-4971 www.ijsir.co.in 91 STUDIES ON THE BATCH ADSORPTION OF METHYLENE BLUE FROM AQUEOUS SOLUTIONS ONTO RICE HUSK *R. SRIVASTAVA 1 , D.C.RUPAINWAR 2 1 Department of Chemistry, Isabella Thoburn College, Lucknow, India, 2 Department of Applied Chemistry, Indian Institute of Technology, Banaras Hindu University , Varanasi, India *Address for Correspondence : Dr. R. Srivastava, MS-124, Sector- D, Aligang, Lucknow, India, E-mail ID: abhiruchi124@yahoo.com ABSTRACT In this study, adsorption of methylene blue (MB) dye onto clean rice husks (CRH) and acid- modified CRH was investigated with respect to the contact time, MB concentrations, acid concentrations and acid types used in the acid modification processes. The results indicate that the acid modification process reduces the MB sorption efficiency from 98% for CRH to 67% for NRH (nitric acid treated rice husk), 59% for HRH (hydrochloric acid treated rice husk) and 55% for SRH (sulfuric acid treated rice husk). In order to investigate the adsorption mechanisms, four kinetic models, i.e., pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion models were fit to the experimental results. The characteristic parameters and correlation coefficients for each kinetic model were determined. The fits of the kinetic results from the kinetic equations were compared with the experimental data. The results indicate that the acid modification process changes the MB adsorption mechanism. Langmuir, Freundlich, Temkin, Redlich-Peterson (RP), and Langmuir-Freundlich (LF) isotherm models were also employed to analyze the equilibrium data, and the correlations of the experimental data to the isotherms was examined. The LF isotherm was found to best represent the data for MB adsorption onto CRH. The separation factor revealed the favorable nature of the isotherm to the MB-CRH system. Keywords: Methylene Blue , Rice Husks, Waste Water, Isotherm Models, Kinetics INTRODUCTION Many industries, such as the cosmetics, leather, carpet, dye manufacturing and textile finishing industries, use dyes to color their products. They also consume a lot of clean water, which becomes colored wastewater, poured into the environment where trade wastewater measures are not in place [1,2] . The effluents of these industries can cause local environmental problems by significantly affecting photosynthetic activity in aquatic life because of the reduced light penetration. The effluents may also be toxic to some forms of aquatic life because of the presence of metals, chlorides, etc., in them [3,4] In addition, introducing dye compounds into the aquatic environment is aesthetically displeasing. Because of these negative impacts, there is a need to develop de- colorization methods that are effective and suitable for industrial use. Currently, the major methods for dye and color removal involve microbial, physical and/or chemical processes, such as microbial degradation, chemical oxidation, and membrane separation process have been proposed from time to time [5–10] . However, all of the current methods suffer from one limitation or another, and none have been successful in removing color from wastewater completely. Adsorption is probably the simplest process for dye removal. Currently, activated carbon is believed to be the most effective adsorbent and is the most popular. Physicochemical treatment for the removal of dissolved dyes from wastewaters [4] ; however, its manufacturing and regeneration costs are high [11] .In order to reduce the cost of an adsorption system, some attempts have been made to find low cost alternative adsorbents. A wide variety of materials such as Aspergillus niger, biomass, algal biomass, Spirogyra rhizopus biomass, rice husk, bark, wheat shell, citric acid esterifying wheat straw, dehydrated