β-FeOOH/C nanocomposite for elemental mercury removal as a new approach to environmental and natural gas processes

Abstract

β-FeOOH/C nanocomposite was successfully prepared by self-assembled method of iron oxyhydroxide on carbonized sample from date stone. The phases, morphology and structure of the prepared β-FeOOH/C sample were characterized by XRD, FT-IR, BET and TEM, then compared to both parent amorphous carbon and FeOOH. The three samples are tested for their adsorptive properties toward elemental mercury removal in fixed-bed adsorption at different temperatures (25, 40, 55 and 70 °C). The data indicate high dispersion of β-FeOOH nanorods, of ≈ 5-25 nm in length and ≈ 1-2 nm in diameter, within the porous carbon structure. The maximum adsorption capacity was 1405.1 μg/g for β-FeOOH/C at a flow rate 250 mL/min, temperature 25 °C and 50 μg/Nm3 as Hg° initial concentration. The operating life of FeOOH/C is detrimined from breakthrough curve. The breakthrough time (tb) at Cout/Cin=0.05‒0.1 and equilibrium time (te) at Cout/Cin = 0.9‒1.0 were found to be 11 hours and 27 days, respectively. The adsorption mechanisms follow pseudo‒first‒order kinetics. Yoon‒ Nelson and Thomas models good described the experimental Hg° breakthrough curve model. The findings reveal the feasibility of FeOOH/C composite to be used as a potential and low-cost adsorbent for removing Hg° from natural gas, by not only reducing the environmental problems associated with gaseous mercury emissions but also by making the process more economical and simple.