The collaborative incentive effect in adsorption-photocatalysis: A special perspective on phosphorus recovery and reuse

Metal element-based adsorbents for phosphorus capture: Chaperone effect, performance and mechanism

Excessive phosphorus (P) enters the water bodies via wastewater discharges or agricultural runoff, triggering serious environmental problems such as eutrophication. In contrast, P as an irreplaceable key resource, presents notable supply-demand contradictions due to ineffective recovery mechanisms. Hence, constructing a system that simultaneously reduce P contaminants and effective recycling has profound theoretical and practical implications. Metal element-based adsorbents, including metal (hydro) oxides, layered double hydroxides (LDHs) and metal-organic frameworks (MOFs), exhibit a significant chaperone effect stemming from strong orbital hybridization between their intrinsic Lewis acid sites and P (Lewis base). This review aims to parse the structure-effect relationship between metal element-based adsorbents and P, and explores how to optimize the P removal properties. Special emphasis is given to the formation of the metal-P chemical bond, which not only depends on the type of metal in the adsorbent but also closely relates to its surface activity and pore structure. Then, we delve into the intrinsic mechanisms behind these adsorbents' remarkable adsorption capacity and precise targeting. Finally, we offer an insightful discussion of the prospects and challenges of metal element-based adsorbents in terms of precise material control, large-scale production, P-directed adsorption and effective utilization.

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 prepared and fully characterized by SEM-EDS, XRD, BET, and XPS. The solution pH (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 the breakthrough time was shortened as the initial phosphorus concentration, the flow rate increased and the bed height decreased. Higher initial phosphorus concentrations, flow rates, and lower bed heights, led to a 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. Dynamic adsorption data were fitted to four models (Yoon-Nelson, Thomas, Adams-Bohart, and Bed Depth Service Time), and the R2 values of the Thomas and Yoon-Nelson models exhibited minimal variation, suggesting that the dynamic adsorption process of FM-MBC was rather intricate. The saturated fixed-bed column (including FM-MBC) was regenerated with NaOH or HCl, and it was found that a 0.1 mol L-1 NaOH solution had the best regeneration effect. XRD analysis showed that the reaction product between the FM-MBC composite and phosphate anions was Fe3(PO4)2·H2O. Moreover, the experimental results that FM-MBC can successfully be used to remove phosphorus from actual wastewater.