Heavy metal adsorption capacity of powdered Chlorella vulgaris biosorbent: effect of chemical modification and growth media

This study investigates the effect of chemical modification and growth medium on the surface characteristics and heavy metal adsorption capacities of Chlorella vulgaris biosorbents, which are prepared in a powder form for the ease of their transport and application. NaOH treatment partially lyses surface cells on cell aggregates, producing rough microscale structures on the biosorbent surface, which enhances the specific surface area by 19-fold and the heavy metal adsorption capacity by factors of 2.4–4.1. Autotrophic C. vulgaris incubation using nitrogen- and phosphorus-rich medium is even a more effective strategy for enhancing the adsorption capacity, showing factors of 1.6–9.4 increase compared to the use of a minimal medium. High phosphorus content of cell residues on the biosorbent surface obtained by luxury phosphorus uptake is responsible for the substantial enhancement. This study suggests a potential of utilizing nitrogen- and phosphorus-rich waste streams to produce a highly efficient microalgal biosorbent for heavy metal adsorption.