Comparable phosphate adsorption onto some natural aluminosilicates vs. Fe(III)oxihydroxide

Abstract

In this paper, the attention was focused on the phosphate removal using the various, mostly traditional or naturally available adsorbents, few of the local repositories, which prove enhanced performance for phosphate removal. The highest capacity toward phosphate ions showed montmorillonite and Fe-oxihydroxide (GEH), while the uptake capacity of slovakite and clinoptilolite-rich tuff was about 30% lower. In dynamic regime, the best performance in phosphate uptake proved GEH. The experimentally recorded breakthrough curves were mathematically described by Yan and Thomas models. Their empirical equations were found to satisfactory describe the breakthrough curves in a fixed bed column (R²˃ 0.92); however, the both models approached to the experimentally obtained adsorption capacity data more or less only for zeolite column. The highest elution of phosphate into tap water was observed by montmorillonite (about 50%), while by clinoptilolite-rich tuff the elution using the tap water was rather low. MAS NMR measurements confirmed that mostly Ca²⁺ cations occurring in clinoptilolite-rich tuff framework dominate in Ca₃(PO₄)₂ surface precipitation.

Keywords:

• Clinoptilolite-rich tuff
• Fe-oxihydroxide (GEH)
• Slovakite
• Montmorillonite
• Phosphate removal
• Precipitation
• Complexation
• Elution
• Isotherm

Acknowledgement

This project was funded by the Slovak Scientific Council VEGA (Project # 1/0250/15) and by Agency for Science and Research (APVV) under Project # SK-CN-0033-12.