Chromium(III) removal by Spirulina platensis biomass

Dried and 48 h re-hydrated biomass of Spirulina platensis was employed as a biosorbent in tests of chromium(III) removal from water. Various concentrations of biomass (from 1 to 3 g l−1) and metal (from 25 to 200 mg l−1) were tested. Increasing and re-hydrating biomass allowed removing almost entirely up to Cr0 = 100 mg l−1 of Cr3+ (95% of removal with X0 = 3 g l−1 of re-hydrated biomass), whereas, lower percentages were obtained at higher concentrations of pollutant (56% of removal at Cr0 = 200 mg l−1). Kinetics of the biosorption was generally better at low Cr(III) concentrations (kads = 1.41 and 1.44 h−1 at Cr0 = 35 mg l−1 and X0 = 1 g l−1 of dry and re-hydrated biomass, respectively). The kinetics of the process and the adsorption capacity of biomass were finally put into relationship, highlighting that, at low concentrations of pollutant (Cr0 = 25, 35 and 50 mg l−1), re-hydrated biomass did not lead to noticeable improvement, whereas, as the concentration of Cr(III) was increased from 75 to 200 mg l−1, re-hydratated biomass ensured remarkably higher removal.