Effects of nitrogen depletion on the biosorption capacities of Neochloris minuta and Neochloris alveolaris for five heavy metals

Abstract

Neochloris minuta and Neochloris alveolaris grown in nitrogen-rich (+ N) and nitrogen-depleted (-N) media were tested for their heavy metal maximum biosorption capacities (qmax) and adsorption percent efficiencies (R%). By removing nitrogen from the growth media, both algal species showed an increase in their lipid content and a decrease in their protein content. Langmuir and Freundlich adsorption isotherms were used to determine the qmax and adsorption efficiencies of the + N and −N algae in the recovery of Pb2+, Cd2+, Zn2+, Cu2+, and Ni2+. When comparing the two types of algae, N. alveolaris showed the highest adsorption capacities for all five metals either in + N or -N media. The maximum adsorption efficiency percentage of the lowest concentration metal ions for N. alveolaris was 87.10% for Pb2+, 64.98% for Cd2+, 59.50% for Zn2+, 60.08% for Cu2+, and 50.61% for Ni2+. In both algae, nitrogen depletion (-N) caused an increase in the qmax values for Zn2+ and Cu2+. Additionally, the qmax of N. minuta for Cd2+, Zn2+, Cu2+ and Ni2+ increased by the nitrogen depletion demonstrating that the treatment can be applied to improve the biosorption capacity of a particular alga for multiple heavy metals. The biosorption capacity for these algae for heavy metals was also discussed in terms of their biomass compositions and the type of hard or soft metal acid based on the Pearson theory of Hard and Soft, Acid and Bases (HSAB).

Microalgal Phycoremediation: A Glimpse into a Sustainable Environment

“…The exposed functional groups have a significant impact on the cell surface attraction for HMM species. The biosorption capabilities of cadmium(II), lead(II), nickel(II), zink(II), and copper(II) in Neochloris minuta and N. alveolaris have been evaluated based on biomass, composition, and type of hard or soft metal acid [107]. Biosorption can be controlled by changing the type and quantity of functional groups on the cell surface.…”

Phycoremediation mechanisms of heavy metals using living green microalgae: physicochemical and molecular approaches for enhancing selectivity and removal capacity

“…According to Pearson acid-base concept, the affinity of the cell surface towards species of HMs considerably depends on the functional groups. For instance, the biosorption capacity of Pb(II), Cd(II), Zn(II), Cu(II), and Ni(II) into Neochloris minuta and N. alveolaris was related to the HSAB theory in terms of their biomass compositions and the type of hard or soft metal acid based ( Giarikos et al., 2021 ). Indeed, changing the nature and density of functional groups at the cell surface, regulated the affinity and sorption behavior for specific metal species.…”

Biosorption of Zn by dried biomass of Euglena gracilis from aqueous solutions

“…2019). In the scientific literature, we can find several papers that point out the possibility of algae-derived biosorbents using in the removal of Zn from model solutions (Areco et al 2018;Giarikos et al 2021;Gu and Lan 2021). Only a limited number of papers have addressed the application of Euglena biomass in heavy metal removal.…”