Comparison of the Effect of Pyrolysis Temperatures and Activating Materials on Properties of Modified Biochar

Agricultural wastes are appropriate precursors for producing modified biochar due to their availability and cheapness. To investigate the effect of activating material type, activation temperature and biochar type on the properties of modified biochar, a factorial experiment was conducted in a completely randomized design with three replications. Experimental factors included four types of activating agents (CaCl2, ZnCl2, H3PO4 20%, and H3PO4 50%), three types of biochar produced from organic wastes (wheat straw, almond, and walnut hull) and two activation temperatures (300 and 500°C). Also, the control treatment included non-treated biochar with activating material and heated at 300°C and 500°C. The results showed that the highest CEC content was related to modified biochar by H3PO4 20% and 50% as an activating material at both 300 and 500°C activation temperatures. The maximum pH and EC values were related to the modified biochar by CaCl2 at both activation temperatures of 300 and 500°C. The highest yield was obtained for modified biochar produced at an activation temperature of 300°C. The highest amount of organic carbon (OC) and nitrogen were obtained from the modified biochar produced at activation temperature of 300°C from H3PO4 (20% and 50%) and ZnCl2 as an activating material, respectively. The maximum C/N content was related to the modified biochar activated with H3PO4 20% and 50% at activation temperature of 300°C. According to the results, the best treatment for producing modified biochar in order to store carbon in the soil and to adsorb pollutants from the soil is the H3PO4 (20% and 50%) as an activating material and 300°C as an activation temperature.