Sajad Mazloomi1,2, Mahmood Yousefi3, Heshmatollah Nourmoradi1,2, Mahmoud Shams4,5. 1. 1Department of Environmental Health Engineering, School of Public Health, Ilam University of Medical Sciences, Ilam, Iran. 2. 2Biotechnology and Medicinal Plants Research Center, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, Iran. 3. 3Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. 4. 4Social Determinants of Health Research Center, Mashhad University of Medical Sciences, Khorasan Razavi Province, Iran, P.O. Box: 91735-951, Mashhad, IR Iran. 5. 5Department of Environmental Health Engineering, School of Health, Mashhad University of Medical Sciences, Mashhad, Iran.
Abstract
BACKGROUND: Phosphate (PO4 3-) is the main etiological factor of eutrophication in surface waters. Metal organic frameworks (MOFs) are novel hybrid materials with amazing structural properties that make them a prominent material for adsorption. METHODS: Zeolitic imidazolate framework 67 (ZIF-67), a water stable member of MOFs, with a truncated rhombic dodecahedron crystalline structure was synthesized in aqueous environment at room temperature and then characterized using XRD and SEM. PO4 3- adsorption from synthetic solutions using ZIF-67 in batch mode were evaluated and a polynomial model (R2: 0.99, R2 adj: 0.98, LOF: 0.1433) developed using response surface methodology (RSM). RESULTS: The highest PO4 3- removal (99.2%) after model optimization obtained when ZIF-67 dose, pH and mixing time adjusted to 6.82, 832.4 mg/L and 39.95 min, respectively. The optimum PO4 3- concentration in which highest PO4 3- removal and lowest adsorbent utilization occurs, observed at 30 mg/L. PO4 3- removal eclipsed significantly in the presence of carbonate. The equilibrium and kinetic models showed that PO4 3- adsorbed in monolayer (qmax: 92.43 mg/g) and the sorption process controlled in the sorption stage. Adsorption was also more favorable at higher PO4 3- concentration, according to the separation factor (KR) graph. Thermodynamic parameters (minus signs of ∆G°, ∆H° of 0.179 KJ/mol and ∆S° of 44.91 KJ/mol.K) demonstrate the spontaneous, endothermic and physisorption nature of the process. CONCLUSION: High adsorption capacity and adsorption rates, make ZIF-67 a promising adsorbent for PO4 3- removal from aqueous environment.
BACKGROUND: Phosphate (PO4 3-) is the main etiological factor of eutrophication in surface waters. Metal organic frameworks (MOFs) are novel hybrid materials with amazing structural properties that make them a prominent material for adsorption. METHODS: Zeolitic imidazolate framework 67 (ZIF-67), a water stable member of MOFs, with a truncated rhombic dodecahedron crystalline structure was synthesized in aqueous environment at room temperature and then characterized using XRD and SEM. PO4 3- adsorption from synthetic solutions using ZIF-67 in batch mode were evaluated and a polynomial model (R2: 0.99, R2 adj: 0.98, LOF: 0.1433) developed using response surface methodology (RSM). RESULTS: The highest PO4 3- removal (99.2%) after model optimization obtained when ZIF-67 dose, pH and mixing time adjusted to 6.82, 832.4 mg/L and 39.95 min, respectively. The optimum PO4 3- concentration in which highest PO4 3- removal and lowest adsorbent utilization occurs, observed at 30 mg/L. PO4 3- removal eclipsed significantly in the presence of carbonate. The equilibrium and kinetic models showed that PO4 3- adsorbed in monolayer (qmax: 92.43 mg/g) and the sorption process controlled in the sorption stage. Adsorption was also more favorable at higher PO4 3- concentration, according to the separation factor (KR) graph. Thermodynamic parameters (minus signs of ∆G°, ∆H° of 0.179 KJ/mol and ∆S° of 44.91 KJ/mol.K) demonstrate the spontaneous, endothermic and physisorption nature of the process. CONCLUSION: High adsorption capacity and adsorption rates, make ZIF-67 a promising adsorbent for PO4 3- removal from aqueous environment.
Entities:
Keywords:
Adsorption; Metal organic frameworks (MOFs); Phosphate; RSM; Thermodynamic; ZIF-67