Production of activated carbons from hazelnut shell and its characterization

Activated carbon is one of the most common adsorbents used in the removal of micropollutants from aqueous media by adsorption. Although activated carbons were commercially produced from wood, antrasit, lignite and bitumnious coal, some agricultural by-products such as almond, apricot, hazelnut and coconut shells, olive and grape stones and sugar cane bagasse have also been used in the studies related to the production of activated carbons. As activation procedure can be done by passing water vapour and carbon dioxside on the starting materials carbonized, it can be also carried out by a carbonization process followed by the activation of starting materials by means of activating agents.In the study, the production of activated carbon was aimed from hazelnut shells as starting material. The activation procedure was carried out by contacting 50 g of hazelnut shells with 200 mL of phosphoric acid solutions with different concentrations at differemt contact times. After the activation, the hazelnut shells were carbonized by passing N2 gas at a constan rate in an owen for times ranging from 1 to 4 hours at different temperatures (350-650 °C).The yield of the activated carbons is, to a large extent, dependent upon the temperature and time of carbonization. The higher the temperature and time of carbonization, the less amount of the activated carbon produced is. The ash content of the activated carbons was changed in the range of 5.32 % to 39.00 %. Carbon contents of activated carbons produced by carbonization carried out at lower temperatures for shorter period of carbonization time were higher. However, the carbon content of activated carbons decreased with increase in the temperature and the time of carbonization. The amounts of acid insoluble inorganic matter of activated carbons are varies depending upon the carbonization conditions. The amount of acid insoluble inorganic matter of sample obtained by carbonization at 650 °C for 2 hours was calculated as 51.65 %. This is the highest value determined. Iodine adsorption capacities of the activated carbons are quite high. Iodine number (IN) of the activated carbon obtained by carbonising hazelnut shells at 650 °C for 2 hours is determined as 397.7 mg I2/g. Surface areas of the activated carbons were determined by BET method. The surface area of activated carbon sample prepared from hazelnut shells activated with % 30 phosphoric acid for 72 hours by carbonising at 600 °C for 2 hours was calucaulated as 362.83 m2/g. This value was determined as 397.63 m2/g from BET surface area analyser. This is the highest value determined at this study.