Adsorption kinetics of methylene blue removal from aqueous solutions using potassium hydroxide (KOH) modified apricot kernel shells

In this study, the adsorption kinetics of methylene blue (MB) with potassium hydroxide (KOH) modified apricot kernel shells were investigated. It was observed that the surface acidity decreased the result of the oxidation carboxylic groups after basic treatment. According to obtained values from kinetic studies, the required time to reach equilibrium is about 240 minutes. The rate-limiting step was found as chemisorption and the pore diffusion is not only rate-limiting step on the adsorption process. The adsorption process was best described by the Langmuir isotherm model and obtained q(m) value is 33.67 mg/g at 25 degrees C temperature. The adsorption took place as endothermic (Delta H = 27.92 kj/mol). Adsorption capacity increased considerably depending on increasing pH. Optimum agitation speed was determined as 250 rpm.