Cryogels based on waste dragon fruit peel pectin for Pb2+ efficient adsorption

The development of simple and efficient novel adsorption technologies has made them highly attractive. However, the biosafety of adsorbents for human body and environment has gradually raised concerns, limiting their practical application scenarios. In this study, dragon fruit peel pectin (DFP) and gellan gum (GG) were used to construct environmentally friendly and highly biosafe dual network cross-linking cryogel (GG/DFP) as efficient adsorbent for Pb²⁺. Through texture, rheology and swelling experiments, it was demonstrated that the double crosslinking network structure formed by GG and DFP greatly enhanced the strength of cryogel. The crosslinking networks and porous structures were demonstrated by SEM and BET. Moreover, GG/DFP had a favorable Pb²⁺ adsorption capacity under different conditions, and the maximum adsorption amount was up to 93.56 mg/g. Adsorption kinetics results indicated that the pseudo-second-order model provided a better fit to the data. Adsorption equilibrium analysis was consistent with the Langmuir and Sips models. XPS analysis confirmed that it possessed multiple adsorption pathways such as physical adsorption, chelating, coordination, and ion-exchange. This work provides a promising alternative for the efficient and environmentally friendly removal of Pb²⁺ from water resources and human gastrointestinal tract, as well as new insights for the high-value utilization of dragon fruit peel waste.