evaluation of phosphate removal from aqueous solution using metal organic framework; isotherm, kinetic and thermodynamic study

Phosphate (po43−) 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. 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. po43− adsorption from synthetic solutions using zif-67 in batch mode were evaluated and a polynomial model (r2: 0.99, r2adj: 0.98, lof: 0.1433) developed using response surface methodology (rsm). the highest po43− 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 po43− concentration in which highest po43− removal and lowest adsorbent utilization occurs, observed at 30 mg/l. po43− removal eclipsed significantly in the presence of carbonate. the equilibrium and kinetic models showed that po43− adsorbed in monolayer (qmax: 92.43 mg/g) and the sorption process controlled in the sorption stage. adsorption was also more favorable at higher po43− 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. high adsorption capacity and adsorption rates, make zif-67 a promising adsorbent for po43− removal from aqueous environment.