Preparation and Characterisation of Biochar from Hazelnut Shell and Its Adsorption Properties for Methylene Blue Dye

Abstract

One of the major pollutants in water resources are organic dyes that are widely used by different industries. Methylene blue (MB) is one of them which is quite harmful for aquatic life. This pollutant must be removed with proper methods. Adsorption is one of the most popular methods because of its high purification yield and known as a cost effective process if the sorbent is inexpensive. In this study, biochar which is used as an adsorbent has been produced from hazelnut shells used as the raw material. Chemical, thermal and surface characteristics of raw hazelnut shell were investigated by FT-IR, TG/DTG, SEM and elemental analysis. Biochar characteristics were determined by FT-IR, BET and SEM analysis. The effect of different adsorption parameters such as pH, initial dye concentration, contact time, adsorbent dosage and temperature on the adsorption of MB onto hazelnut shell char were examined in batch experiments. The equilibrium of adsorption was modeled using Langmuir and Freundlich isotherm models. The maximum adsorption yield of MB was found to be 83% at pH 4.0, adsorbent dosage of 4 g/L, contact time of 300 min., initial dye concentration of 15 mg/L and temperature of 45 o C. In addition, the Freundlich isotherm was found to be the best fitting isotherm model for the adsorption process. The pseudo-first-order and pseudo-second-order kinetic models were applied to the experimental data and thermodynamic parameters such as Gibbs free energy, enthalpy and entropy were determined.