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

Abstract

Background Phosphate (PO 4 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. PO 4 3− adsorption from synthetic solutions using ZIF-67 in batch mode were evaluated and a polynomial model (R 2 : 0.99, R 2 adj : 0.98, LOF: 0.1433) developed using response surface methodology (RSM). Results The highest PO 4 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 PO 4 3− concentration in which highest PO 4 3− removal and lowest adsorbent utilization occurs, observed at 30 mg/L. PO 4 3− removal eclipsed significantly in the presence of carbonate. The equilibrium and kinetic models showed that PO 4 3− adsorbed in monolayer (q max : 92.43 mg/g) and the sorption process controlled in the sorption stage. Adsorption was also more favorable at higher PO 4 3− concentration, according to the separation factor (K R) graph. Thermodynamic parameters (minus signs of ΔG°, ΔH°of 0.179 KJ/mol and ΔS°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 PO 4 3− removal from aqueous environment.

Performance of metal–organic frameworks for the adsorptive removal of potentially toxic elements in a water system: a critical review

“…Monolayer maximum phosphate adsorption was observed as 92.43 mg g À1 where the thermodynamic parameters demonstrate the spontaneous, endothermic and physisorption nature of the process. 158 Modied MOFs were then used in phosphate adsorption provided enhanced removal capacity as expected. Polyethyleneimine impregnated MOF UiO-66 of 9.45% PEI loadings resulted a maximum removal capacity of 73.15 mg P g À1 at room temperature, and the removal was successful over a wide pH range from 2-7 with reaching the equilibrium in 50 min.…”

“…157 Zeolitic imidazolate framework 67 (ZIF-67) was developed as a waterstable member of MOFs and observed as an efficient material in phosphate removal. 158 Model optimization reported the highest removal of PO 4 3À which is 99.2% with ZIF-67 dose of 832.4 mg L À1 , at pH 6.82 and mixing time of 39.95 min. Monolayer maximum phosphate adsorption was observed as 92.43 mg g À1 where the thermodynamic parameters demonstrate the spontaneous, endothermic and physisorption nature of the process.…”

Removal of phosphate from aqueous solutions using granular ferric hydroxide process optimization by response surface methodology

“…Most countries in the world use phosphate as an essential material in their industrial processes [2]. Mineral phosphate salts are widely used in the pharmaceutical industry, detergents, chemical fertilizers, textiles, semiconductor components, foodstuffs, fire extinguishers and water refinery [3][4][5]. Urban wastewater is one of the main sources of phosphorus entry into receiving waters.…”

“…To create the phenomenon of eutrophication, a concentration of 0.005-0.05 mg L -1 of phosphate is required in terms of phosphorus [9]. The standard of phosphate in drinking water is 0.2 mg L -1 and the standard for discharge of effluent to surface water is 6 mg L -1 [3,10]. The excessive biological proliferation will age the lake and reduce its quality as a result of the excessive growth of algae and plants, and the entry of toxic compounds that produces flavours and odours, reduces oxygen and changes the ecological system of the streams and rivers [11][12][13].…”

“…While biological phosphorus removal methods may include disadvantages such as high sludge production, design complexity, and the need for exploitation skills, microorganism sensitivity to environmental factors and the need for a carbon source and high cost of investment and exploitation and sequestration methods has the disadvantages of high cost of chemicals and the high sludge volume and non-specificity of the process, adsorption by advanced adsorbents can be a very promising process for controlling nutrients in aquatic resources, by eliminating these limitations [20,21]. The adsorption process is a suitable method for removing phosphate from aqueous media, which increases the adsorption capacity of the materials by activating the surface [3,21]. Nowadays, the use of chelating resins is increasing and because of their high adsorption capacity, stability and selectivity, they are used in the removal of elements [22].…”