Adsorption of phosphate from aqueous using iron hydroxides prepared by various methods

In this study, various iron hydroxides were prepared by different methods and their physical properties and P adsorption performance were investigated. The iron hydroxides prepared by five different methods (open-heating hydrolysis (Fe(H-A)), closed-heating hydrolysis (Fe(H-S)), urea (Fe(U)) addition, NaOH (Fe(S)) addition and NH3/NH4Cl buffer (Fe(A)) addition) were either akageneite or amorphous in nature. The specific surface area was larger for the amorphous precipitates, Fe(S) and Fe(A). Fe(A) showed the highest P adsorption performance among the adsorbents. Furthermore, there was a positive correlation between the specific surface area of the adsorbents and the maximum amount of adsorption. Fourier transform infrared spectroscopy (FT-IR) and N-2 adsorption analyses revealed that in iron hydroxides after P adsorption, the proportion of OH-OH hydrogen bonds and specific surface area decreased. Therefore, it was suggested that the specific surface area and OH species were important for analyzing the adsorption performance of the prepared iron hydroxide. On the other hand, the adsorption performance of Fe(A) decreased with increasing treatment temperature and pH. Fe(A) with 1 M NaOH solution after adsorption allowed almost complete desorption of the adsorbed P, which was confirmed by FT-IR, and the high specific surface area of the adsorbent was maintained. Therefore, it was concluded that Fe (A) can be a recyclable, high P uptaking adsorbent.

Automated summary

This study investigated the physical properties and P adsorption performance of various iron hydroxides prepared by different methods. Among the iron hydroxides, those prepared with NH3/NH4Cl buffer (Fe(A)) showed the highest P adsorption performance. The specific surface area and OH species were found to be important factors affecting the adsorption performance.