Abstract: A series of biochars were obtained under the limited oxygen cracking condition at different carbonization temperatures of 200, 300, 400, 500, 600, 700 ℃, respectively, with cow dung as raw material. The structures and properities of these biochars, i.e. surface morphology, element contents, specific surface area, pore size, surface functional groups and adsorption properties, were examined via scanning electronic microscopy, elemental analyzer, specific surface area and pore size distribution analyzer, and by means of Boehm titration, iodine adsorption and methylene blue adsorption. It was shown that the yields and volatile matter content decreased, while the contents of ash and fixed carbon and pH increased with the increasing carbonization temperature. Besides, the morphological features of biochars became more regular and the pores were denser. When the carbonization temperature was raised appropriately, it was beneficial to form pore and increase the number of micropores pore, the specific surface area and pore volume were increased, yet the pore size was decreased. With the increased carbonization temperature, the C contents of biochars increased, while the H and O contents decreased, and the N contents increased at first and then decreased, and the values of H/C,(O+H)/C and O/C were reduced, indicating that the aromatic properties and structural stability of biochars were enhanced, yet the polarity and hydrophilicity were both weakened. With the increasing carbonization temperatures, the carboxyl contents of surface functional groups were firstly increased and then decreased, the contents of carbonyl groups continuously increased, yet the contents of lactone and phenolic hydroxyl groups, the total contents of acid and oxygen-containing functional groups were gradually decreased. The adsorption value of iodine and methylene blue increased at first and then decreased with the increasing carbonization temperatures, andy both reached the highest value under 600 ℃.

Key words: waste, resourcezation, carbonization temperature, cow dung biochars