Effects of Step-Wise Acid Leaching with HCl on Synthesis of Zeolitic Materials from Paper Sludge Ash

Abstract

Incinerated ash with a relatively high Ca content, paper sludge ash, was converted to zeolitic materials with high cation-exchange capacities (CECs) by aging at 80 °C in NaOH solution via step-wise acid leaching with HCl to reduce the ash Ca content. The extraction of Ca, Mg, Si, and Al from the ash into the acid solutions during leaching and the products obtained from the leached ash by reaction with an alkali were examined. The contents of Ca and Mg in the ash were more easily extracted from the ash than those of Si and Al in the initial leaching. The leachant pH decreased with increasing numbers of leaching steps, and the amounts of Si, Al, and Ca extracted from the ash increased as a result of the dissolution of gehlenite (Ca2Al2SiO7), one of the main minerals in the ash. Zeolites A and P were synthesized from the leached ashes, and hydroxysodalite was synthesized from the raw ash. With increasing numbers of leaching steps of the ash, the obtained product contained lower released Ca, whereas the product contained higher released Na and has higher CEC, depending on the zeolite phases in the product. The product with the highest CEC was synthesized from third-leached ash, and its CEC was 1.5 mmol/g, which is about four times higher than that of the raw ash (0.4 mmol/g).

Research on High-Pressure Hydrochloric Acid Leaching of Scandium, Aluminium and Other Valuable Components from the Non-Magnetic Residues Obtained from Red Mud after Iron Removal

“…The WAT sample contains four aluminum phases, namely, Ca2Al2SiO7, Ca3Al2Si3O12, Mg3Al2Si3O12, and MgAl2O4 (Figure 1), but the solid residues obtained by HPAL of the WAT sample using 10 and 20% HCl contains no gehlenite, which fully dissolves at low leaching temperatures. These results correlate with the data of other researchers [54], where gehlenite passed into the solution in 1M HCl after 3-stage leaching during 2 hours at room temperature. Aluminum in the solid residues is in Ca3Al2Si3O12, Mg3Al2Si3O12, and MgAl2O4 phases that were incompletely dissolved at the experimental conditions.…”

Research on High-Pressure Hydrochloric Acid Leaching of Scandium, Aluminum and Other Valuable Components from the Non-Magnetic Tailings Obtained from Red Mud after Iron Removal

“…The WAT sample contains four aluminum phases, namely, Ca2Al2SiO7, Ca3Al2Si3O12, Mg3Al2Si3O12, and MgAl2O4 (Figure 1), but the solid residues obtained by HPAL of the WAT sample using 10 and 20% HCl contains no gehlenite, which fully dissolves at low leaching temperatures. These results correlate with the data of other researchers [59], where gehlenite passed into the solution in 1 M HCl after three-stage leaching during 2 h at room temperature. Aluminum in the solid residues is in the Ca3Al2Si3O12, Mg3Al2Si3O12, and MgAl2O4 phases that were incompletely dissolved at the experimental conditions.…”

“…Two samples of non-magnetic tailings were derived by reduction roasting-a magnetic separation process of red mud (RM) from the Bogoslovsky Aluminium Plant (Russian Federation, Krasnoturyinsk, 59.84 • N, 60.19 • E) at optimal conditions according to our previous work [53]. The first sample codenamed as without addition tailings (WAT) was obtained by the reduction roasting of RM at 1300 • C for 1 h. The second sample codenamed as sodium sulfate addition tailings (SSAT) was obtained by reduction roasting of the mixture of 84.6 wt.% RM and 15.4 wt.% Na 2 SO 4 at 1150 • C for 3 h. Both the roasted samples were ground, screened through a 300-mesh sieve, and magnetically separated using a wet method by the Davis tube XCGS-50 (Shaoxing Weibang Mining Machinery Manufacturing Co., Ltd., Zhejiang, China) at magnetic field intensity of 0.1 T. Table 1 demonstrates the chemical compositions including iron content of the RM, WAT, and SSAT samples.…”

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

“…The leaching conditions were decided by conferring previous papers [19][20][21][22] . Ash of 25 g was stirred in the 100 mL aqueous 28 J. ION EXCHANGE solution of 1 mol/L HCl or 0.5 mol/L H 2 SO 4 for 24 h with a magnetic stirrer at room temperature.…”