The effect of sodium alginate on struvite crystallization in aqueous solution: A kinetics study

As a representative of extracellular polymeric substances (EPS), the effect of sodium alginate (SA) crystallization kinetics of struvite, was investigated by constant composition technique under the conditions of 25 °C, pH 8.5, ion strength 0.1 mol L−1 NaCl. The results indicated that SA reduced the crystal growth rate of struvite significantly, attributed to the adsorption of SA and subsequently blocking of active growth sites onto the surface of struvite forming. Moreover, the adsorption followed Langmuir adsorption isotherm model, from which the affinity constant was calculated to be 63.6 × 104 L mol−1. Furthermore, SA in supersaturated solution affects the crystallization kinetics of struvite without changing its crystal growth mechanism. Additionally, SA can make the surface charge of struvite more negative, thus obviously reduce the settleability of struvite.