The Effects of Pre-treatments and Low-temperature Pyrolysis on Surface Properties of Biochar from Sunflower Straw as Adsorption Material

Carbon adsorbent materials that were prepared from sunflower straw by a combination of pre-treatment and low-temperature pyrolysis showed better adsorption compared with untreated carbon. Four different pretreatment agents ( steam, alkali ( KOH), phosphoric ( H3PO4), and salt ( ZnCl2)) were analyzed with respect to their effects on the maximum surface area and the micropore area. Samples were measured by thermogravimetric analysis ( TGA), X-ray powder diffraction ( XRD), scanning electron microscopy ( SEM), surface area analysis, and pore size analysis. The surface area, pore volume, and N-2-adsorption capacity of the samples were closely correlated with the pre-treating agent. A biochar with a maximum surface area of 877.6 m(2)/g and a micropore area of 792.8 m(2)/g was prepared with phosphoric acid ( H3PO4) as the pre-treatment agent at a temperature of 400 degrees C. The main result of the one-stage pre-treatment procedure was the number of micropores. The two-stage, low-temperature pyrolysis procedure focused on the volume of the pores. Carbonized sunflower straw, with pretreated and low-temperature pyrolysis procedures, was judged to be a highly effective and economic method to prepare carbon adsorbents.