Green Synthesis of Tea Tree Oil-Mediated Iron Oxide Nanoparticles for Efficient Arsenate [As(V)] Removal: Synthesis, Characterization and Adsorption Mechanism

This study describes how iron oxide nanoparticles were made using tea tree oil and tested for their ability to remove arsenate [As(V)] from water. The nanoparticles were examined with several techniques, including FESEM, TEM, XRD, FTIR,

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potential analysis, and GC-MS, to understand their shape, structure, and surface features. Experiments were conducted to determine how factors such as pH (2 to 7), contact time (0 to 240 minutes), adsorbent amount (0.5 g per liter), and initial As(V) concentration (10 to 100 mg per liter) at 25 °C affected arsenate removal. The best adsorption happened at pH 5. Most of the arsenate was removed in the first 60 minutes, and the process reached a balance at about 240 minutes. The results showed that the pseudo-second-order kinetic model best fit the data (R

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~ 0.998), indicating that chemisorption is the main process. The Langmuir and the Freundlich isotherm models were used to analyze the equilibrium data. The Langmuir model fit better (R2 ~ 0.998) than the Freundlich model (R2 ~ 0.987), suggesting that adsorption mostly happens in a single layer on similar active sites. The Langmuir model predicted a maximum adsorption capacity of 216.9 mg/g. The mechanism suggests that As(V) is mainly removed via inner-sphere surface complexation, in which arsenate exchanges with surface =Fe-OH groups, aided by positive electrostatic interactions in mildly acidic conditions. Overall, iron oxide nanoparticles prepared with tea tree oil exhibit strong adsorption capacity for arsenate, making them promising for sustainable arsenic removal.