Effect of Reaction Time on Phosphate Mineralization from Microalgae Hydrolysate

Abstract

The development of algal biorefineries is strongly associated with the nutrient management, particularly phosphorus, which is a limited mineral resource. Flash hydrolysis (FH) has been widely applied to a variety of algae species to fractionate its constituents. This chemical-free, subcritical water technique was used to extract more than 80 wt % of phosphorus available in the Scenedesmus sp. as water-soluble phosphates in the aqueous phase (hydrolysate). The phosphate-rich hydrolysate was subjected to the hydrothermal mineralization (HTM) process at 280 °C and 5–90 min of residence time to mineralize phosphates as allotropes of calcium phosphate such as hydroxyapatite (HAp) and whitlockite (WH). In the current study, the effect of reaction time on phosphate mineralization from the hydrolysate as well as the composition, structure and the morphology of the precipitates were studied. Calcium hydroxide and commercial HAp were used as the mineralizer and seeding material, respectively. More than 97 wt % of p...