Biogenic manganese oxides generated by green algae Desmodesmus sp. WR1 to improve bisphenol A removal

Biogenic manganese oxides (BioMnOx) have attracted considerable attention as active oxidants, adsorbents, and catalysts. This study investigated the characteristics of algae-generated BioMnOx and determined its oxidative activity towards bisphenol A (BPA), an endocrine disrupter. Amorphous nanoparticles with a primary Mn valency of +3 were found in BioMnOx produced by Desmodesmus sp. WR1. The mechanism might be that algal growth created conditions favorable to Mn oxidation through increasing DO and pH. Initial Mn²⁺ concentrations of 6, 30, and 50mgL^-1 produced a maximum of 5, 13, and 11mgL^-1 of BioMnOx, respectively. Mn²⁺-enriched cultures exhibited the highest BPA removal efficiency (∼78%), while controls only reached about 27%. BioMnOx may significantly promote BPA oxidation in algae culture, enhancing the accumulation of substrates for glycosylation. Moreover, continuous BioMnOx increase and Mn²⁺ decrease during BPA oxidation confirmed Mn oxide regeneration. In conclusion, Mn oxide formation by microalgae has the potential to be used for environmental remediation.