Adsorption of Methyl Orange onto Calcium Ferrite for Environmental Sustainability ^†

Wastewater poses public and environmental problems when discharged into aquatic systems due to industrial, agricultural, or domestic activities. Water pollutants commonly found in effluents include dyes, surfactants, phenolics, chlorides, heavy metals, etc., which are detrimental to plants, animals, and human lives. These effects are noticeable in the slow photosynthetic activity of aquatic plants, which also serve as a breeding ground for bacteria, viruses, and vectors, leading to waterborne diseases. Herein, the potential of calcium ferrite (CaFe₂O₄) as an adsorbent for the removal of methyl orange (MO) dye from wastewater was evaluated by studying the adsorption kinetics. Batch adsorption experiments were carried out after reacting calcium chloride (CaCl₂) with ferric nitrate (Fe(NO₃)₂), and the mixture was heated continuously at 90 °C for two hours to form the CaFe₂O₄ precipitate, which was then calcined for four hours at 600 °C in a furnace. The synthesized CaFe₂O₄ was found to have high adsorption capacity for MO, as evidenced by its ability to remove 80.02% of MO dye from wastewater within one hour. Furthermore, the adsorption capacity at equilibrium (q_e) and at variable time (q_t) for the kinetic model with a linear regression coefficient (R²) value of 0.9979 signifies that the adsorption process is best described by pseudo-second-order kinetic models. Thus, CaFe₂O₄ can be effectively used for the removal of dyes such as MO from wastewater to ensure sustainability.