Hydrothermal Synthesis of Sodalite-Type N-A-S-H from Fly Ash to Remove Ammonium and Phosphorus from Water

Abstract

In this study, the hydrated sodium aluminosilicate material was synthesized by one-step hydrothermal alkaline desilication using fly ash (FA) as raw material. The synthesized materials were characterized by XRD, XRF, FT-IR and SEM. The characterization results showed that the alkali-soluble desilication successfully had synthesized the sodium aluminosilicate crystalline (N-A-S-H) phase of sodalite-type (SOD), and the modified material had good ionic affinity and adsorption capacity. In order to figure out the suitability of SOD as an adsorbent for the removal of ammonium and phosphorus from wastewater, the effects of material dosing, contact time, ambient pH and initial solute concentration on the simultaneous removal of ammonium and phosphorus are investigated by intermittent adsorption tests. Under the optimal adsorption conditions, the removal rate of ammonium was 73.3%, the removal rate of phosphate was 85.8% and the unit adsorption capacity reached 9.15 mg/L and 2.14 mg/L, respectively. Adsorption kinetic studies showed that the adsorption of ammonium and phosphorus by SOD was consistent with a quasi-secondary kinetic model. The adsorption isotherm analysis showed that the equilibrium data were in good agreement with the Langmuir and Freundlich model. According to thermodynamic calculations, the adsorption of ammonium and phosphorus was found to be a heat-absorbing and spontaneous process. Therefore, the preparation of SOD by modified FA has good adsorption properties as adsorbent and has excellent potential for application in the removal of contaminants from wastewater.

Ammonium recovery from municipal wastewater by ion exchange: Development and application of a procedure for sorbent selection

“…) is in good agreement with the estimates reported in previous studies conducted with natural zeolites, that vary in the 34-41 mg N g dry resin − 1 range for Chabazite [18,19], 12-52 mg N g dry resin − 1 for Clinoptilolite [19,23] and 16-25 mg N g dry resin − 1 for zeolites synthetized from fly ash [25]- [27]. Similarly, the operating capacity assessed for Chabazite/Phillipsite in BT tests conducted with different WWTP effluents at the 4 mg N L − 1 BP is similar to the values previously reported for natural zeolites, that vary in the 3-8 mg N g dry resin − 1 range in studies conducted with WWTP effluents [45], synthetic wastewater [50] and groundwater [47].…”

“…Although chemical synthesis obtains more uniform and pure materials than natural zeolites in terms of reticular structures, pore size and channels, natural zeolites have greater mechanical strength. Langwaldt [19] studied the behavior of Chabazite and 7 different Clinoptilolites by means of adsorption isotherms and continuous tests conducted with synthetic ammonium solutions, reporting a 36 mg N g dry resin − 1 CEC for a Chabazite, and 12-19 mg N g dry resin − 1 for 7 Clinoptilolites; Leyva-Ramos [18] obtained CECs in the 34-41 mg N g dry resin − 1 range for a Chabazite tested in different cationic forms, in batch conditions and synthetic ammonium solution; Guida [23] estimated 52 mg N g dry resin − 1 for a natural Clinoptilolite and 60 mg N g dry resin − 1 for an engineered Zeolite-N. Zhao reported in batch conditions a CEC of 16 mg N g dry resin − 1 for a synthetic zeolite obtained from coal fly ash [25]; Liu obtained a CEC of 25 mg N g dry resin − 1 for a zeolite P1 synthetized from fly ash [26]; Lv reported 17 mg N g dry resin − 1 for a Sodalite-type N-A-S-H synthetized from fly ash [27]. However, most of the previous works were conducted by batch tests and using synthetic ammonium solutions.…”