Tailored construction of β-cyclodextrin covalently-supported tannic acid polymer nanosponge towards highly selective lead recovery

Low-cost and high-selective adsorbents is desirable but challenging for recovering heavy metal ions from actual wastewater. In this work, we developed a novel beta-cyclodextrin covalently-crosslinked tannic acid (TA@CD) polymer nanosponge via a simple condensation reaction, and then realized the selective capture of Pb2+ from complex wastewater. TA@CD demonstrated a strong affinity for Pb2+ compared to other coexisting metal ions with a high selective coefficient of 1143 (approximately 188 times higher than that of other polymer, metal based and bio-based adsorption materials), which can be attributed to the phenolic hydroxyl groups of TA that can effectively bind with Pb2+ to form a relatively stable structure. In the typical adsorption experiments, a high adsorption saturation capacity of 136.8 mg g(-1) on Pb2+ at an initial concentration of 200 mg/L (maximum capacity was 116.5 mg/g) and an ultrafast removal efficiency of 81% Pb2+ within 3 min were achieved by TA@CD (adsorption finished within 50 min), due to the abundant exposed TA adsorption sites and the efficient mass transfer rate supported by CD. With the favorable adsorption and regeneration performance, in the dynamic treatment process with a fixed-bed reactor pack of TA@CD nanosponge, the treatment volume of Pb2+-con-taining simulated wastewater can up to 9860 bed volume (BV) with only 176.5 mL eluent production. This work provides a feasible approach to design economic and directional adsorbents with the potential to selectively recover heavy metal ions from actual wastewater.

Automated summary

A novel low-cost and high-selective adsorbent was developed for the recovery of heavy metal ions from complex wastewater. The adsorbent demonstrated high selectivity and fast removal efficiency, making it a potential candidate for the selective recovery of Pb2+ ions.