Bio-sorption of toxic metals from industrial wastewater by algae strains Spirulina platensis and Chlorella vulgaris: Application of isotherm, kinetic models and process optimization

The present study evaluates the effect of an acidic treatment on the improvement of the percentage removal of toxic metal (%TMrem) from wastewater by algae strains (Spirulina platensis (SP) and Chlorella vulgar (CV)) under different adsorbent dosages (0.2-2.5 g), a pH of (4-8) and contact time (5-100 min). The acidic treatment (Ac-T) altered the functional groups on the surface of algae promoting more electronegative groups and improved the %TMrem of Al, Ni and Cu. Treated SP removed up to 95.0 +/- 0.3% (Std. Dev = 0.24), 87.0 +/- 0.2% (Std. Dev = 0.34)%, and 63.0 +/- 0.3% (Std. Dev = 0.14) of Al, Ni, and Cu at the optimum pH of 5.5, 6.0, and, 7.0 and an adsorbent dosage of = 2.5 +/- 0.1 g/L (Std. Dev = 0.14) g/L, respectively. Lower %TMrem of 87.0% +/- 0.2 (Std. Dev = 0.09), 79.1 +/- 0.4% (Std. Dev = 0.08), and 80.0 +/- 0.2% (Std. Dev = 0.04) were achieved with treated CV, respectively. The optimum operational conditions for maximum %TMrem were determined at (C-algae = 4.8 +/- 0.2 g(MNPs).L-1, C-t = 88 +/- 1, and pH = 6) using the response surface methodology (RSM). The adsorption of TMs on algae is endothermic, spontaneous, and follows Langmuir and second-order kinetics. Zeta potential measurements indicated that the adsorption mechanism between the toxic metal (TM) and algal strains is controlled by electrostatic interaction. As such, bio-sorption is a sustainable and efficient technology for the removal of TM from wastewater. (C) 2020 The Authors. Published by Elsevier B.V.

Automated summary

The acidic treatment improved the percentage removal of toxic metals by algae strains, especially Al, Ni, and Cu. Optimum operational conditions were determined for maximum removal efficiency, with SP showing better performance under specific pH and adsorbent dosage.