Removal of pharmaceutically active compounds (PhACs) by zero-valent iron: quantification of removal mechanisms consisting of degradation, adsorption and co-precipitation

The removal mechanisms of carbamazepine (CBZ), which is one of pharmaceutically active compounds, using zero-valent iron (ZVI) were quantified by defining three fractions, namely degradation , adsorption , and co-precipitation . The maximum total organic carbon (TOC) removal was obtained at pH 4. The results demonstrate that the adsorption on the ZVI surface is dominant in the TOC removal of CBZ for 4 & LE; pH & LE; 6 while the degradation by oxidative and reductive reactions is efficient exclusively for pH & LE; 3. TOC removal was not obtained for pH & GE; 8. The most dominant mechanism in the removal of CBZ by ZVI is the adsorption onto the iron oxides/hydroxides layer formed on ZVI surface rather than the degradation by oxidative and reductive reactions including Fenton and Fenton-like reactions for pH & GE; 4. A novel kinetic model for removal of CBZ by ZVI was developed to simulate the dynamic concentration profiles of CBZ, TOC, total Fe ions, and dissolved oxygen linked closely with each other and the contributions of degradation, adsorption, and co-precipitation in TOC removal of CBZ. Reasonable agreement between experimental data and model predictions suggests the applicability of the proposed kinetic model to quantitatively analyze the mechanisms of CBZ removal by ZVI.

Automated summary

The mechanisms of carbamazepine (CBZ) removal using zero-valent iron (ZVI) were studied in this research. The results showed that adsorption was the dominant mechanism at lower pH, while degradation by oxidative and reductive reactions played a major role at higher pH. A novel kinetic model was developed to analyze the removal of CBZ by ZVI, which showed reasonable agreement with experimental data.