Extraction and quantitation of various potassium salts in straw ash

Biomass ash contains various potassium salts, which have high potential as crop fertilizers. In this study, a method of extracting and quantifying various potassium salts from straw ash was proposed and investigated. Straw ash was prepared in a muffle furnace at 500°C and then successively and repeatedly treated through leaching, filtration, concentration, and crystallization. The extracted products were analyzed by X-ray diffraction and X-ray fluorescence. Results show that the elemental potassium content and potassium salt content in the recovered products reached 43.1 and 78.1%, respectively. The potassium salts mainly existed as K2SO4, KCl, and K2CO3 at a molar mass ratio of 1:2.33:1.73. The extraction ratio of the products increased with increasing extraction time. The initial extraction ratio was 35.71%. This ratio increased to 50.15 and 69.43% when the extraction process was repeated for the second and sixth times, respectively. This work provides an efficient method of recovering and extracting potassium salts from biomass ash for use as potash fertilizers.