Chemical Conversion of Paper Sludge Ash into Cation Exchanger Via Acid Leaching

Abstract

Alkali conversion of paper sludge ash into cation exchanger via acid leaching was examined. The extraction behaviors of major elements (Si, Al, Ca and Mg) from the ash into hydrochloric acid (1 mol/L HCl) and sulfuric acid (0.5 mol/L H₂SO₄) aqueous solutions were almost same except Ca due to the formation of gypsum in the H₂SO₄ solution. The ashes leached with 1 mol/L HCl and 0.5 mol/L H₂SO₄ aqueous solutions were converted into zeolite-P and tobermorite, respectively, while the raw ash was converted into hydroxysodalite. The cation exchange capacities of the converted products from the ashes leached with HCl and H₂SO₄ were 1.30 and 0.75 mmol/g, respectively, which were higher than that of the product from the raw ash (0.60 mmol/g). These results indicated that paper sludge ash could be converted into different types of cation exchanger via acid leaching.