Reducing the impact of antibiotics in wastewaters: Increased removal of mitoxantrone from wastewater by biosynthesized manganese nanoparticles

Abstract

In recent years, the efflux of antibiotics into the environment has increased due to increased pharmaceutical usage worldwide. This has led to an urgent need for novel methods to sustainably treat wastewaters. In this study, mitoxantrone (MTX) was selected as representative contaminant antibiotic and a green tea extract was used to cleanly synthesize manganese nanoparticles (Mn NPs) for the subsequent removal of MTX from wastewaters with a maximum removal efficiency of 97.4% (97.40 mg g−1) in laboratory trials and a removal efficiency of 77.3% in real wastewaters. SEM analysis showed that MTX was uniformly adsorbed onto the negatively charged Mn NPs surface whereas FTIR analysis revealed that chemical attachment of MTX on the surface of Mn NPs was via N–H groups within the MTX molecules. Isothermal adsorption and kinetic studies further confirm that the adsorption of MTX was via a Langmuir and pseudo-second-order model, suggesting that chemisorption was occurring. A mechanism for the Mn NPs based MTX adsorption was proposed, involving a combination of valence bond adsorption, hydrogen bonding, electrostatic interaction and pore-filling. Overall, biosynthesized Mn NPs has significant potential for practical applications in removing MTX from contaminated wastewater due to low material costs and a high MTX adsorption capacity. In addition, the synthetic method used was both environmentally friendly and sustainable involving no use of harsh surfactants or solvents common in more traditional synthetic routes.