Exploring zero-valent iron nanoparticles (nZVI) for Bisphenol A removal: experimental investigations and Monte-Carlo simulation insights

Numerous personal care products contain Bisphenol-A (BPA), a hormone disruptor that ultimately finds its way into waterways. A combination of experimental investigations and Monte-Carlo simulations (MCS) were used to explore zerovalent iron nanoparticles (nZVI) for their removal. The nZVI exhibited an absorption peak (λmax) at 373 nm with a mesoporous structure (pore size 2.138 nm), 159.419 m2 g−1 surface area, and crystalline peaks. The adsorption processes were positively influenced by batch parameters. BPA adsorption on nZVI varied with temperature as predicted by Freundlich and Langmuir isotherms, achieving a maximum adsorption capacity (qmax) of 982.13 mgg−1 at 308 K and pH 2. The adsorption process at 303 and 308 K was physisorption, whereas, at 313 K, it was chemisorption suitably described by pseudo-second-order kinetics. The exothermic and spontaneous nature of the adsorption processes were demonstrated by the negative values of enthalpy (−ΔH°) and free energy (−ΔG°) that decreased with increasing temperatures (308–328 K). The density function theory and MCS studies showed that BPA's phenyl ring, isopropyl, and hydroxyl groups interacted electrostatically with nZVI, specifically crystal plane 121 with the most negative adsorption energy (ΔEads), enhancing BPA removal. Through optimized adsorption mechanisms, nZVI can effectively remove BPA from wastewater.