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 H 2 SO 4 ) aqueous solutions were almost same except Ca due to the formation of gypsum in the H 2 SO 4 solution. The ashes leached with 1 mol/L HCl and 0.5 mol/L H 2 SO 4 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 H 2 SO 4 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.

Calcium Silicate Hydrate Cation-Exchanger from Paper Recycling Ash and Waste Container Glass

“…Previous studies have demonstrated that paper recycling ash [25,29,30,36,37,56] and post-consumer container glass [18][19][20][21] are suitable feedstocks for the hydrothermal synthesis of 11 Å tobermorite. PRA contains potentially reactive calcium (alumino)silicate phases (e.g., åkermanite, β-dicalcium silicate, anorthite, and gehlenite) that can be exploited in the hydrothermal synthesis of tobermorite, although its molar composition, 0.74 < [Ca]/[Si+Al] < 0.92 and 0.27 < [Al]/[Si+Al] < 0.44, also promotes the formation of katoite [29,36,37,56].…”

“…Previous studies have demonstrated that paper recycling ash [25,29,30,36,37,56] and post-consumer container glass [18][19][20][21] are suitable feedstocks for the hydrothermal synthesis of 11 Å tobermorite. PRA contains potentially reactive calcium (alumino)silicate phases (e.g., åkermanite, β-dicalcium silicate, anorthite, and gehlenite) that can be exploited in the hydrothermal synthesis of tobermorite, although its molar composition, 0.74 < [Ca]/[Si+Al] < 0.92 and 0.27 < [Al]/[Si+Al] < 0.44, also promotes the formation of katoite [29,36,37,56]. Accordingly, stoichiometric additions of silicate-bearing reagents such as sodium metasilicate or silica have been shown improve the tobermorite yield by appropriately tailoring the constituent ratios to 0.80 < [Ca]/[Si+Al] < 0.85 and 0.0 < [Al]/[Si+Al] < 0.18 [25,36,37].…”

“…Previous studies have considered the hydrothermal synthesis of tobermorites from a wide range of commercial and industrial waste materials under relatively mild conditions (i.e., 80-125 • C in water or 0.5-4 M NaOH (aq) ) in order to appraise the reactivity of the feedstock components and to understand the relationship between the structure and properties of the product [16][17][18][19][20]25,29,30,35,36,39,56,73]. Accordingly, the present study investigated the hydrothermal synthesis of Al-substituted tobermorite from a mixture of paper recycling ash (PRA), waste container glass (WCG), and lime at 100 • C in 4 M NaOH (aq) .…”

“…Sludges generated from the de-inking and reprocessing of waste paper are commonly incinerated for the purposes of volume-reduction and energyrecovery [55]. The resulting paper recycling ash (PRA) contains potentially reactive calcium (alumino)silicate phases that can be exploited in the hydrothermal synthesis of tobermorite when stoichiometrically adjusted with additional silicate-bearing reagents [25,29,30,56].…”

“…While it is technically possible to recycle up to 90% of waste soda-lime-silica container glass (WCG), in practice, this target is undermined by various geographical, infrastructural, and economic factors [57][58][59]. Accordingly, approximately 200 Mt of post-consumer container glass is currently landfilled per annum [56]. Many studies have been carried out to upcycle this WCG into value-added products such as sorbents, ion-exchangers, catalysts, ceramics, geopolymers, and construction materials [57,[59][60][61][62][63][64][65].…”