Removal of phenol from aqueous solution using montmorillonite-Fe3O4-humic acid (MFH) nanocomposite

Abstract Phenol is a highly toxic pollutant commonly found in industrial wastewater. Its removal is crucial to protect the environment and human health. Various methods are available for phenol removal, but adsorption is the most widely used and effective approach. Fe 3 O 4 nanoparticles (NP) have emerged as a promising adsorbent due to their cost-effectiveness, high surface area, and exceptional adsorption capabilities. However, its small size can lead to issues such as oxidation, aggregation, and difficulty in separation. This study introduces a new approach for phenol removal using a montmorillonite-Fe 3 O 4 -humic acid (MFH) nanocomposite. The synthesis of the MFH nanocomposite involved dispersing Fe 3 O 4 nanoparticles onto montmorillonite clay and coating the surface with humic acid to enhance stability and adsorption efficiency. The prepared MFH nanocomposite was thoroughly characterized to find the morphology, composition and functional group. FTIR spectroscopy revealed the presence of Fe-O, O-Si and C=O vibrations which confirmed the successful formation of the nanocomposite. The average crystal size of the synthesized nanoparticles is obtained from XRD analysis as 10.99 nm. The Fe 3 O 4 : montmorillonite ratio was found to influence the adsorption performance, with a Fe 3 O 4 :montmorillonite ratio of 1:4 exhibiting the highest removal efficiency. Batch experiments were performed to assess the phenol removal effectiveness of the MFH nanocomposite. At optimum operating conditions of pH 4 and contact time 150 minutes, the phenol removal efficiency was found to decrease from 98% to 87% when the concentration of phenol in influent increased from 10 to 100 mg/L. The adsorption kinetics of phenol on MFH followed the pseudo-second-order kinetic model, indicating a chemisorption process with strong correlation and agreement between experimental and predicted results. The Langmuir and Freundlich isotherm models both provided suitable descriptions of the adsorption behaviour. The maximum adsorption capacity (q m ) was determined to be 11.14 mg/g. The presence of carbonyl groups(C=O), Hydroxyl groups (-OH) and silanol groups (Si-O) in MFH offers a significant advantage for enhancing the removal efficiency of phenol. The phenol sorption capacity of MFH nanocomposites was found to be significantly greater compared to that of magnetite. The results showed that the developed MFH nanocomposite offers a promising solution for the efficient removal of phenol from wastewater.