Onion (Allium Cepa) Processing Waste as a Sorption Material for Removing Pollutants from Aqueous Media

Abstract

The paper summarizes the literature data on the use of onion (Allium cepa) processing waste as sorption materials to remove various pollutants (metal ions, dyes, antibiotics) from aqueous media. It provides brief literature data on the structure, volume of cultivation, and chemical composition of some components of onion biomass. It was found that onions contain many amino acids, vitamins, polyphenolic compounds, and other biologically active compounds that have various functional groups in their composition. This contributes to the removal of various metal ions (Ca2+, Cd2+, Cr(VI), Cu2+, Hg2+, Mg2+, Ni2+, Pb2+, Zn2+) from aqueous media with native and modified onion processing waste (onion skin). The work shows the possibility of increasing the sorption characteristics of pollutants by treating the Allium cepa biomass with various chemical reagents. It was found that the pollutant adsorption isotherms on onion skin are most often more accurately described by the Langmuir and Freundlich models, less often by other models. The kinetics of the process predominantly corresponds to the pseudo-second-order model. It was shown that the use of onion skin extracts modified with various chemical compounds is promising for removing heavy metal ions. The work also shows the possibility of using onion skin modified by plasma and microwave radiation to remove the Methylene blue dye from simulated solutions.