REMOVAL OF METHYLENE BLUE FROM AQUEOUS SOLUTION USING GHASSOUL, A LOW-COST ADSORBENT

The present study examined the use of ghassoul, natural clay available in large quantities under the Atlas Mountains in Morocco, for the removal of the basic dye, methylene blue, from aqueous solutions. The effect of initial dye concentrations, agitation time, pH and temperature on adsorption capacities of methylene blue was investigated. The initial pH of the aqueous solution and the change of temperature (25-55 °C) were found to have little effect on the adsorption process. The adsorption was a rapid with 90-99% of the dye removed within the first 10-20 min. The adsorption kinetics are described successfully using a pseudo-second order rate equation and the rate constant decreases with increasing the initial concentration of MB. Experimental and calculated kinetic data for equilibrium are well expressed by Langmuir isotherm. The equilibrium adsorption capacity of ghassoul was determined with the Langmuir equation as well as the pseudo-second-order rate equation and found to be >290 mg dye per gram of the adsorbent. The results indicate that ghassoul could be employed as a low cost alternative to commercial activated carbon in wastewater treatment for the removal of colour and dyes.