New approach for enhancing Chlorella vulgaris biomass recovery using ZnAl-layered double hydroxide nanosheets

The lack of cost-effective techniques for harvesting microalgae is a major challenge for microalgal application in wastewater treatment plants as well as large-scale production of microalgae. Here, a novel approach for the recovery of Chlorella vulgaris biomass using zinc aluminum-layered double hydroxide (ZnAl-LDH) nanosheets is introduced. ZnAl-LDHs are a green eco-friendly and efficient flocculent with capacity up to 0.521 g g(-1). The adsorption and agglomeration of microalgal cells onto LDH layers were elucidated and confirmed. Different factors affecting flocculation efficiency including LDH concentration, algae concentration, pH, temperature, and time were studied and statistically optimized using the Plackett-Burman design. The best flocculation efficiency (96%) was obtained at the following conditions: pH 6, 35 A degrees C temperature, and microalgae concentration range from 4.8 to 8.7 mg L-1 based on chlorophyll a content, 1 g L-1 LDH dosage and sedimentation time of 1 min. LDH concentrations higher than 1 g L-1 had no positive effect on the efficiency of the flocculation process.