Preparation Of Sludge-stalk Based Activated Carbon Applied To H₂S Adsorption

Activated carbon is a solid adsorbent material with well-developed pore structure and unique surface chemistry and has been widely used for H2 S removal. Municipal sludge and crop straw are two kinds of waste from urban life and agricultural production, preparing activated carbon material which has industrial application value with them is of great significance to the resource utilization and environmental pollution control. In this paper, municipal sludge and corn stalk were used to prepare sludge-stalk based activated carbon by pyrolysis with KOH. The adsorbent prepared was applied to the H2 S removal, the activating reaction process of activated carbon was systematically studied and the desulfurization mechanism was preliminarily discussed. The main contents and conclusions are as follows:(1) When the mixture/KOH ratio was certain, with the increase of the stalk proportion in feedstock, the yield of activated carbon was decreased, the specific surface area, total pore volume, micropore volume and Vmicro/Vtotal rate were increased, the breakthrough and saturation time of H2 S were extended, and the corresponding sulfur capacities were increased. The suitable quality ratio(dry basis) of sludge and stalk was 3:7.(2) The pores in the activated carbons were mainly mesopores and the micropores were less. Moderate KOH was conducive to the pore development in activated carbon while excess KOH made part of the micropores expand to mesopores and even macropores. The activated carbon(C372) whose mixture/KOH ratio was 10:2 had the highest Vmicro/Vtotal rate and the best desulfurization efficiency.(3) From the research on KOH activation process and mechanism, it was discovered that adding suitable amount of KOH not only brought the decomposition of the easily degradable substance forward, but also promoted the pyrolysis of the hardly degradable substance. The activation product was mainly K2CO3.(4) The bigger the Vmicro/Vtotal rate of activated carbon, the higher the desulfurization activity. The Vmicro/Vtotal rates of C372 and C374 were maximum, 0.590 and 0.587 respectively, and the corresponding saturation sulfur capacity were also the largest, 7.00 and 6.59 mg H2S/g catalyst, respectively. Therefore, the sulfur capacity of activated carbon was determined by micropore volume and total pore volume synergistically.(5) The products of H2 S oxidation over the activated carbon were mainly elemental sulfur and a little sulfuric acid. The main reason for activated carbon inactivation was that all the micropores were filled with the desulfurization products or all the ostioles were blocked.