Kaolinite-supported nanoscale zero-valent iron for removal of Pb²⁺ from aqueous solution: Reactivity, characterization and mechanism

The use of nanoscale zero-valent iron (nZVI) to remediate contaminated groundwater is limited due to its lack of durability and mechanical strength. To address this issue, 20% (w/w) nZVI was loaded onto kaolinite as a support material (K-nZVI). More than 96% of Pb²⁺ was removed from aqueous solution using K-nZVI at an initial condition of 500 mg/L Pb²⁺ within 30 min under the conditions of 10 g/L of K-nZVI, pH 5.10 and a temperature of 30 °C. To understand the mechanism of removal of Pb²⁺, various techniques were implemented to characterize K-nZVI. Scanning electron microscopy (SEM) indicated that K-nZVI had a suitable dispersive state with a lower aggregation, where the mean specific surface area and average particle size as determined by the BET-N₂ method and X-ray diffraction (XRD), were 26.11 m²/g and 44.3 nm, respectively. The results obtained from XRD, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) indicated that a small number of iron oxides formed on the surface of K-nZVI, suggesting that free Pb²⁺ was adsorbed onto K-nZVI and subsequently reduced to Pb⁰.