BACKGROUND
Adsorption plays a significant role in phosphate removal and recovery. Metal (hydro)oxides are the most popular adsorbents for phosphate adsorption, but their performances differ greatly, with different adsorption mechanisms under different conditions. A comparative study of phosphate adsorption onto iron hydroxide and iron oxide doped activated carbon fiber (ACF‐FeOH and ACF‐FeO) was performed.
RESULTS
The phosphate adsorption performance of ACF‐FeOH and ACF‐FeO with different initial pH, ion strength and competing ions was investigated. The contrasting results showed that the amount adsorbed by ACF‐FeOH is higher than that by ACF‐FeO, and phosphate adsorption on ACF‐FeOH is more dependent on pH and ion strength than on ACF‐FeO. The adsorption mechanisms were studied by zeta potential measurements, X‐ray photoelectron spectroscopy (XPS) analysis and batch desorption tests. The significantly higher isoelectric point (IEP) of ACF‐FeOH with respect to that of ACF‐FeO resulted in a greater phosphate adsorption by ACF‐FeOH than by ACF‐FeO. XPS analysis showed that the concentration of surface hydroxyl groups on ACF‐FeOH is also higher than that on ACF‐FeO.
CONCLUSION
ACF‐FeOH performs better than ACF‐FeO with higher adsorption capacity. Electrostatic interaction and ion exchange are the two main adsorption mechanisms both for ACF‐FeOH and for ACF‐FeO. This study should provide some guidance on the preparation and application of iron‐based sorbents in phosphorus removal and recovery. © 2015 Society of Chemical Industry