کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5745954 | 1618788 | 2017 | 10 صفحه PDF | دانلود رایگان |
- PO43â adsorption and precipitation were separated according to experimental factor.
- PO43â precipitation can be anticipated by saturation index of Ca-P precipitate.
- Result of PO43â removal percentage change indicates PO43â precipitation.
- CD-MUSIC model calculation shows occurrence of PO43â precipitation.
Phosphate (PO43â) removal on calcite often entails two processes: adsorption and precipitation. Separating these two processes is of great importance for assessment of PO43â stability after removal. Thus, this study was aimed at finding a critical range of conditions for separating these two processes in calco-carbonic equilibrium, by adjusting PO43â concentration, reaction time and pH. PO43â removal kinetic results showed that: (I) At pH7.7, PO43â removal was mainly by adsorption at initial PO43â concentration â¤2.2 mg Lâ1 and reaction time â¤24 h, with dominant precipitation occurring at initial PO43â concentration â¥3 mg Lâ1 after 24 h reaction; (II) At pH8.3, adsorption was the key removal process at initial PO43â concentration â¤7.5 mg Lâ1 and reaction time â¤24 h, whereas precipitation was observed at initial PO43â concentration of 10 mg Lâ1 after 24 h reaction, (III) At pH 9.1 and 10.1, PO43â removal mechanism was mainly by adsorption at initial PO43â concentration â¤10 mg Lâ1 within 24 h reaction. Based on the kinetic results, it is suggested that PO43â precipitation will occur after 24 h reaction when saturation index of amorphous calcium phosphate is between 1.97 and 2.19. Besides, increasing PO43â concentration does not cause a continuous decline of PO43â removal percentage. Moreover, experimental removal data deviated largely from the theoretical adsorption value by CD-MUSIC model. These indicate occurrence of precipitation which is in agreement with the kinetic result. Therefore our study will provide fundamental reference information for better understanding of phosphorous stabilization after removal by calcite.
Journal: Chemosphere - Volume 183, September 2017, Pages 419-428