International Journal of Chemical Engineering and Applications, Vol. 1, No. 4, December 2010 ISSN: 2010-0221 342 Abstract—The removal of methylene blue (a basic dye) from its aqueous solution by adsorption on silica gel has been carried out. It has been noted that low adsorbate concentration, low temperature and basic medium favor the removal of the dye. A 95.2% removal of the methylene blue was achieved at 25 mg/liter dose, 35 O C & at pH 10.The kinetics studies were made using the model suggested by Langergren. The rate constants were found to be 1.22/min for 30 O C and 6.58/min for 35 O C. The equilibrium data fits well in the Langmuir and Freundlich model of adsorption. Effect of temperature was studied. Fixed bed studies were made in a glass column. It was found that at 1.6cm of adsorbent bed height, 97.6% removal was possible. The adsorption capacity of silica gel has been estimated as 195 mg/liter in fixed bed study. Index Terms—basic dye, textile wastewater, adsorption, silica gel, capacity. I. INTRODUCTION The removal of colour from textile wastewater is one of the major environmental problems because of the treatment of such water by conventional methods. Colored waters are also objectionable on aesthetic ground for drinking and other municipal as well as agriculture purpose[1],[2],[3].Many colored effluents are composed of non-biologically oxidisable organic components because of the molecular size and structure of the dyestuffs. The increasingly tighter legislation of effluent discharges in most countries will bring new developments, resulting in considerably smaller amount of effluents [4]. Adsorption is a physico-chemical process which offers great potential for treating effluents containing undesirable components and render them safe and reusable.[5],[6],[7],[8].The feasibility of using silica gel for adsorption of a methylyne blue has been tested in this study. The major advantage of an adsorption system for water pollution control, are low investment in terms of both initial and land cost, simple design easy operation and no effect by toxic harmful substance [9]. Adsorption offers an attractive method of treatment for producing high quality colorless effluents. It is important to study the dependence of initial and final concentration of the adsobate on the contact time with the adsorbent under several operating conditions. Various low cost material such as, bagasse pith [10], Fullers earth [11], Activated carbon [12], Ash cinder [13], Coconut husk [14], Aquatic Plants [15] have been investigated with varying degrees of success. The present investigation reports on the use of silica gel to adsorb the dye-methylene blue from aqueous solution in a batch and column study. II. MATERIALS AND METHODS Stock solution of dye was prepared by dissolving 200mg of dye/liter of double distillated water was taken in a 250 ml beaker and a known quantity of adsorbent i.e. Silica gel was added to it .The pH of the solution was adjusted to a desired value using HCL & NaoH. After pH adjustment the temperature of the solution was also adjusted at the end of reaction time. The solution was filtered through the whatman filter paper No.42 and the filtrate was taken to analyses the dye present in the solution by UV spectrophotometer (systronics-118) at 665 nm. In order to have a clear picture of the effect of different parameters on the adsorption of dye, the experiments were carried out at different initial concentrations, dosages, pH, and different temperatures. During the uptakes of dye from the solution by adsorption process, two factors namely; concentration of dye in the solution and time of contact between adsorbate and adsorbent phases, play an important role. A rapid transport of adsorbate cuts through the equilibrium period. The time taken to attain the equilibrium is important to predict the efficiency and the feasibility of the adsorbent. The experiments were conducted at two different initial concentrations of dye i.e. 25mg/liter & 12.5 mg/liter of solution. The amount of adsorbent is kept fixed at 500 mg & at room temperature i.e.20 O C with a pH 8. Adsorption at Different Adsorbent Doses: -The experiment was carried out to observe the effect of different amount of adsorbent on the adsorption of dye on silica gel. Moreover the experiment was conducted for two concentration of dye solution i.e. 25mg/liter & 12.5 mg/liter to observe comparative study of the two. The experimental procedure was same as described earlier and the total time of experiment was 10 min. The temperature was fixed at 20 O C ( ± 5 O C) & pH 8. Adsorption at Different pH Values: -The aim of the experiment was to find out a suitable pH range for the maximum efficiency of the removal process. The experiment was carried out for two different concentration of the dye i.e. 25 mg/liter and 12 .5 mg/liter of solution for each concentration of solution, the temperature was maintained at 20 O C ( ± 5 O C) . The pH was adjusted by adding 1N HCL or NaoH as desired. Adsorption at Different Temperature: -Temperature has significant effect on the process of adsorption. Physical adsorption is always an exothermic process and hence any increases in temperature do not favor the extent of adsorption. Therefore at higher temperature silica gel proved to be good adsorbent. The decrease in adsorption density is attributed to the weakening of adsorptive forces between the adsobate and adsorbent and also between the adjacent sites of adsorbed phase. Time rate adsorption studies were carried out at a particular initial concentration of dye solution at 25mg/liter and 12.5 mg/liter and at a particular pH value of 8 of the solution; with total time of the experiment 10 minutes at different temperatures 35 o C, 45 o C, 55 o C, 60 o C & 65 o C. Kinetic Study: - Kinetic studies have been carried out by using Freundlich, Langmuir and Langergren equations. Sorption Studies of Methylene Blue on Silica Gel R.W.Gaikwad and S.A.Misal