Oxyanion Recovery from Wastewater with Special Reference to Selenium Uptake by Marine Macroalgae

This study investigates the capacity of green and brown algae to sustainably remove oxyanions from contaminated waters, highlighting their cost-effectiveness. Often considered biomass waste and contributors to organic contamination, these algae can be used as effective biosorbents, aligning with circular economy principles and sustainable waste management. Various pre-treatments were tested to enhance adsorption capacity, with mixed results regarding their effectiveness. The focus then shifted to the use of Cladophora sericea algae for the uptake and removal of selenium species, specifically selenite (Se(IV)) and selenate (Se(VI)). The effects of different operational parameters on oxyanion uptake by algae were studied in batch mode. The assessments were conducted on a single-component and a multi-component synthetic matrix. The results indicate that pH significantly impacts biosorption, with equilibrium achieved in 90 min. Both pseudo-first-order and pseudo-second-order models provided a good fit to the experimental data. The algae’s retention capacity for selenium remained largely unaffected by the presence of other anions, a key advantage for application in complex real effluent matrices. Kinetic studies performed under different values of initial pollutant concentration and biosorbent mass indicate a biosorbed amount at an equilibrium of 570 µg g−1.