Textile Wastewater Treatment Using Activated Graphene-Like Biochar Derived from Onion Peel Biomass

Allium cepa L., popularly known as onion, has many benefits aside from being used as a vegetable. This study explored onion peel biomass by converting it to biochar (BC) followed by activation with KOH under optimal temperature and mix ratio. Various characterizations such as Raman, SEM, XRD and BET were performed to examine the surface and morphological properties of the activated biochar. The developed BC was utilized to treat textile wastewater composing methyl orange (MO) dye. The KOH-activated onion peel biochar showed a surface area of 1725.6 m 2 /g, resulting in a maximum dye adsorption capacity of 454.54 mg/g. Raman spectroscopy further revealed the existence of graphene-like structures of the biochar. The adsorption kinetics show that BC follows the pseudo-second-order model with an R 2 of 0.9988. The isotherm experiments also conformed to the Langmuir model with an R 2 of 0.9958. The influence of pH was studied, and results showed higher removal efficiencies at a pH of 2. Finally, the regeneration and recyclability of the prepared adsorbent was run for three successive cycles, after which it maintained appreciable adsorption capacity and removal efficiencies. Overall, the BC derived from onion peel demonstrated that it could be a promising alternative and high-performance adsorbent for treating textile wastewater.