title: Kinetics of the reversible reaction of struvite crystallisation.
abstract: The crystallisation of struvite could be a sustainable and economical alternative for recovering phosphorus from wastewater streams with high phosphate concentrations. Knowledge regarding the kinetics and thermodynamics that are involved in the crystallisation of struvite is the key to determine the optimal conditions for obtaining an efficient process. This study was conducted in a continuous stirred batch reactor. Different sets of experiments were performed in which struvite was either dissolved (undersaturated) or precipitated (oversaturated). These experiments were conducted at different temperatures (25, 30 and 35 °C) and pH values (8.2, 8.5 and 8.8) to determine the kinetics of struvite precipitation and dissolution. Struvite crystallisation was modelled as a reversible reaction. The kinetic rate parameters of struvite precipitation were 1.03·10(-4), 1.25·10(-4) and 1.54·10(-4) mol m(-2) min(-1) at 25, 30 and 35 °C, respectively. Similar kinetic rate parameters were determined for struvite dissolution. Struvite heterogeneous crystallisation can be represented by a first-order kinetic model that fitted well the experimental data.
authors.affiliation: Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain. Electronic address: dafne.crutchik@gmail.com.
authors.forename: D
authors.initials: D
authors.lastname: Crutchik
authors.affiliation: Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Garrido
mesh_terms: D003460:Crystallization; D007700:Kinetics; D010710:Phosphates / Q000302:isolation & purification*; D000069877:Struvite / Q000737:chemistry*; D013816:Thermodynamics; D014865:Waste Disposal, Fluid / Q000295:instrumentation / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*
chemical_list: D010710:Phosphates; D014874:Water Pollutants, Chemical; D000069877:Struvite
keywords: Heterogeneous crystallisation; Phosphorus recovery; Solubility product; Struvite; Supersaturation; Wastewater