Experimental analysis of citrus fruit waste-derived biochar-based Fe–Mn doped ZnO composite for photocatalytic degradation of Rhodamine B dye

In the era of global water scarcity, textile industries pose a significant environmental threat by consuming huge quantities of freshwater and later releasing it with dye contamination. The present study aims to synthesize a novel Fe-Mn doped ZnO/Biochar composite from citrus fruit waste biomass (92% yield) to photocatalytically degrade Rhodamine B (RhB) dye under UV light and simultaneously adsorb on its surface. X-Ray Diffractogram revealed that the composite is crystalline (34.99 nm) in nature. Scanning Electron Microscopy revealed its heterogeneously rough and porous morphology (∼0.4 µm). The carbonyl peak (C O) was previously observed at 1631 cm −1 got shifted slightly to 1620 cm −1 , indicating very strong absorption from the composite surface functional groups to the RhB dye molecules. In addition, a small shift (544–470 cm −1 ) was also seen in the ZnO stretching peak as per the Fourier Transform Infrared spectra. The moderate percentage removal efficiency was found out to be 60.02% at pH= 3 with 10 ppm as the initial concentration of RhB dye. Efficient separation of charges is achieved through a Type II heterojunction system where photogenerated electrons and holes migrate across the ZnO/biochar surface. The adsorption behavior was favored by Langmuir isotherm (K L =0.25 L mg −1 , q max =6.12 mg g −1 , R 2 =0.97) showing mono-layer formation and rate kinetics was governed by pseudo-first order kinetics (K 1 =0.06 min −1 , q max =5.83 mg g −1 , R 2 =0.99) exhibiting physisorption behavior. Therefore, a novel as-synthesized environmentally benign waste biomass derived composite was effective in removing the RhB dye molecules from contaminated water.