Study on the dynamic adsorption and recycling of phosphorus by Fe-Mn oxide/mulberry branch biochar composite adsorbent

In this study, the Fe-Mn oxide/mulberry stem biochar composite adsorbent (FM-MBC) was used to conduct dynamic adsorption experiments on phosphate in water. The effects of pH value (3.0, 4.5, and 6.0), initial concentration of phosphorus (10, 20, and 30 mg L − 1 ), adsorbent bed height (2, 3, and 4 cm), and solution flow rate (1, 2, and 3 mL min − 1 ) were investigated to analyze the breakthrough curves. The results showed that as the initial phosphorus concentration and flow rate increased, and the bed height decreased, the breakthrough time was shortened. This indicates that higher initial phosphorus concentrations and flow rates, as well as lower bed heights, led to faster breakthrough of phosphate ions in the FM-MBC adsorbent. Additionally, it was observed that increasing the pH value was not conducive to the adsorption of phosphorus by the FM-MBC adsorbent. To analyze the experimental data, three different models [Yoon Nelson, Thomas, Adams-Bohart and Bed depth service time (BDST)] were fitted to the dynamic adsorption data under different experimental conditions. These models were used to predict the breakthrough curves and evaluate the model parameters of the fixed bed for process design reference. Among the four models, the Thomas model showed good agreement with the experimental data, indicating its suitability for describing the dynamic adsorption process of phosphate ions using FM-MBC. The saturated fixed-bed column including FM-MBC were regenerated with NaOH and HCl, which 0.3 mol L − 1 NaOH solution had the best regeneration effect. Overall, the results of the study demonstrated that FM-MBC has excellent adsorption properties for removing phosphate from aqueous solutions.