Immobilization of β-FeOOH nanomaterials on the basalt fiber as a novel porous composite to effectively remove phosphate from aqueous solution

Abstract A novel porous basalt fiber (BF) loaded with β-FeOOH adsorbent (FeOOH/BF) was successfully fabricated and used to effective removal of phosphate in the aqueous solution. The FeOOH/BF composite was thoroughly characterized by X-ray diffraction, Fourier transform infrared spectrometer, Scanning electron microscopy-energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The results demonstrated that dense β-FeOOH nanomaterials with 17.2 nm were immobilized on the surface of BF. The BET surface area of composite was 105.79 m2/g with a pore volume of 0.163 cm3/g and average pore diameter of 6.177 nm. The best phosphate removal efficiency was achieved in the pH range of 5~10. Adsorption kinetics and isothermal adsorption studies showed that the pseudo-second-order model and the Freundlich isotherm fitted the experimental data better, indicating that the phosphate adsorption onto FeOOH/BF tend to multi-molecular layer and chemical adsorption, and the maximum phosphate adsorption capacity of 39.08 mg/g was calculated. The coexisting anions (e.g., Cl-, SO42- and NO3-) had slight effects on phosphate adsorption compared with the obvious disturbance of CO32-. Ligand exchange, inner-sphere complexation and electrostatic attraction were the main mechanisms of FeOOH/BF for removal of phosphate. The used FeOOH/BF could be effectively regenerated by 0.3 mol/L NaOH and the adsorption efficiencies still maintaining 80% of initial adsorption capacity after three cycles. The proposed FeOOH/BF might be acted as a promising adsorbent for efficient and preferable phosphate removal from contaminated water.