Green synthesis of Fe₂O₃ from seedless lemon peel extract for anionic dye adsorption

In this study, the Fe₂O₃ material was synthesized by green chemistry using seedless lemon peel extract. The structural characteristics of Fe₂O₃ were analyzed through SEM, FTIR, XRD and BET analytical methods. Factors affecting the adsorption of anionic dyes (Congo Red, Methyl Red, Methyl Orange) were also evaluated, such as temperature, pH, time, Fe₂O₃ dosage and dyes' concentration.

It was shown that the material has a heterogeneous cubic shape with iron and oxygen elements at the ratio of 43% and 12%. The crystal faces (120), (220), (400), (018), the material was identified as γ- Fe₂O₃ with a characteristic spinel structure with tetrahedral and octahedral shapes. The free functional groups on the surface are OH, Fe-O, with 635.58 cm^-1 was attributed to the octahedral and tetrahedral sites of the Fe-O band. Temperature is the least influential factor and value was 30 °C. It can be seen that γ-Fe₂O₃ is the good adsorbent in the pH4-pH6 range, for 60 to 90 min, at dosage of 0.5 to 2 g/L and a dyes' concentration of 200-300 mg/L. The maximum adsorption capacities of MO, CR, and MR were recorded 31.349 mg/g, 49.071 mg/g, and 119.705 mg/g, respectively. The adsorption mechanism has also been predicted and shown to depend on the type of dye with different interaction and adsorption capabilities. This helps the adsorption capacity of Fe₂O₃ material from lemon peel extract to be more diverse and applied more widely.