Abstract:

The effects of anhydrous calcium chloride on the physicochemical properties of cotton straw based porous biochar were studied with cotton straw as raw material under different temperature. The morphology and structure were characterized by simultaneous thermal analysis(TG-DSC), X-ray diffraction(XRD), Raman spectroscopy(Raman), scanning electron microscopy(SEM), transmission electron microscopy(TEM) and N₂ adsorption-desorption analysis. The TG results showed when the pyrolysis temperature reached 500 ℃, the weight loss of the samples was less, so 550-750 ℃ was selected as the pyrolysis temperature range. The experimental results showed that the samples prepared by the two pyrolysis methods(direct pyrolysis and CaCl₂ activation) were amorphous carbon structure. During 550-750 ℃, for direct pyrolysis, the I_D/I_G values of Roman analysis were about 0.93, the maximum specific surface area was 2.09 m²/g and the average pore size was 7.21 nm; for CaCl₂ activation, the I_D/I_G values were about 0.85, the maximum specific surface area was 487.68 m²/g and the average pore size was 5.97 nm. And the samples prepared by the activation method are better than the samples prepared by the direct pyrolysis method in the degree of graphitization, specific surface area and pore size, while the samples prepared by the direct pyrolysis method had larger pore size, high degree of disorder and good stability.

Key words: cotton straw carbon, direct pyrolysis, activation pyrolysis