Optimisation of preparation of hazelnut shell activated carbon for adsorption of Cr (III)

Abstract

The aim of this study was the optimization of the activated carbon production process by dehydration-carbonization using concentrated H₂SO₄ from the hazelnut shells found as locally and readily available agricultural waste and the adsorption of Cr(III) on the activated carbon produced by this method. Adsorption experiment was carried out at conditions of 25°C and initial concentration of 30 mg Cr(III)/L. Optimum process conditions to ensure maximum adsorption capacity was investigated by means of statistically designed experiments and steepest ascent experiments. The optimum values were found as impregnation ratio of 4.5 ml H₂SO₄/g hazelnut shell, oven temperature of 50°C, and holding time in the oven of 19.8 hours respectively and maximum adsorption capacity as 14.76 mg Cr(III)/g HSAC. The surface properties HSAC were investigated by scanning electron microscopy and FTIR and agreed with outcomes. The adsorption mechanism can be rapid ion exchange and slow chemisorption or/and an outer-sphere complexation at pH 3.5-6.0 during process.