In another study carried out by Nowicki et al. NO2 removalwas examined using activated carbon prepared from walnut shell.The produced activated carbon had high surface area of 2305 m2/gand pore volume of 1.15 cm3/g . Comparison of various activation methods revealed that chemical activation with KOHcontribute to microporosity development more than physical activation with CO2. Using walnut shell activated carbon in dry condition, NO2adsorption capacity of 66 mg NO2/g was achieved.The data proved the differences in the effectiveness of activation by KOH and CO2, illustrating the influence of the activation method.The adsorption capacities of KOH and CO2 activation are 66.3 mg NO2/g and 58.1 mg NO2/g respectively. The heating rate is lower, so a longer time is needed to increase the temperature. Using this method, well developed porous structure of activated carbon can be achieved. The activated carbon prepared at high temperature
(800 8C) had a five time greater surface area and larger total porevolume compared to the sample prepared at lower temperature (400 8C). The optimum data showed that 97–98% of total pore volume was micropores. In subsequent research, Nowicki et al. employed chemical activation using KOH to prepare activated carbon from plum stone. Highly microporous activated carbon with a surface area of