Performance of high-gravity chemical precipitation process in continuous fabrication of nano-sized α-FeOOH

Nano-sized α-FeOOH (Higee-FeOOH) was continuously fabricated using the high-gravity chemical precipitation process. The fabrication temperature was 25 °C; the aqueous FeCl₃ (0.15 mol/L) flowed at 0.5 L/min; the aqueous NaOH (0.45 mol/L) flowed at 0.5 L/min, and the rotating speed was 1800 rpm. Based on an EDS analysis, Higee-FeOOH thus fabricated comprised 35.6 % Fe and 64.4 % O. The high-gravity chemical precipitation process continuously fabricated Higee-FeOOH at 9.4 kg/day. Higee-FeOOH had a needle-like structure with an average grain size of 43.7 nm, as determined by XRD, and a mean size of 579.6 nm, as determined by SEM. The average pore size, BET specific surface area, and Langmuir specific surface area of Higee-FeOOH were 12.4 nm, 48.3 m²/g, and 63.4 m²/g, respectively. As determined using a Langmuir model, the maximum Pb²⁺ adsorption capacity of Higee-FeOOH was 166.9 mg/g. However, the commercial nano-sized α-FeOOH that was obtained from Sigma-Aldrich had a much lower maximum Pb²⁺ adsorption capacity of 25.9 mg/g. Therefore, Higee-FeOOH can be used to adsorb Pb²⁺ from water.