Radix Astragali residue-derived porous amino-laced double-network hydrogel for efficient Pb(II) removal: Performance and modeling

Valorizing solid waste for heavy metal adsorption is highly desirable to avoid global natural resources depletion. In this study, we developed a new protocol to valorize Radix Astragali residue (one of the Chinese medicine residues) into a low-cost, chemically robust, and highly permeable (ca. 90%) amino-laced porous double-network hydrogel (NH2-CNIFs/PAA) for efficient Pb(II) adsorption. The NH2-CNIFs/PAA showed (i) excellent Pb(II) adsorption capacity (i.e., 994.5 mg g(-1), similar to 4.8 mmol g(-1)), (ii) fast adsorption kinetics (k(f) = 2.01 x10(-5) m s(-1)), (iii) broad working pH range (2.0-6.0), and (iv) excellent regeneration capability (similar to 15 cycles). (v) excellent performance in various real water matrices on Pb(II) removal. Moreover, its high selectivity (distribution coefficient K-d similar to 2.4 x10(6) mL g(-1)) toward Pb(II) was owing to the present of abundant amino groups (-NH2). Furthermore, the fix-bed column test indicated the NH2-CNIFs/PAA can effectively remove 114.6 bed volumes (influent concentration similar to 5000 mu g L-1) with an enrichment factor 10.9. The full-scale system modeling (i.e., pore surface diffusion model (PSDM)) has been applied to predict the NH2-CNFs/PAA performance on Pb(II) removal. Overall, we have provided an alternative win-win scenario that can resolve the Chinese medicine residues disposal issue by valorizing it into high performance gel-based adsorbents for efficient heavy metal removal.

Automated summary

In this study, a new protocol was developed to transform Chinese medicine residues into a high-performance adsorbent for heavy metal removal. The adsorbent demonstrated excellent adsorption capacity, fast kinetics, wide pH range, and good regeneration capability.