Structure-activity relationships and rational screening of cyclodextrin polymer-confined nZVI activators for efficient persulfate oxidation of recalcitrant organic pollutants in water.

The preparations of cyclodextrin polymer-confined nZVI activators (CDP-nZVI) with both structural modifiability and pollutant selectivity for water decontamination face the challenge of revealing the structure-activity relationships of CDP-nZVI. Here we developed structure-activity relationship models of both the Fe content and activation potential of CDP-nZVI activators for efficient PS oxidation of recalcitrant pollutants in water. Both models (R2 = 0.927/0.801, n = 28, P < 0.001) were primarily constituted by CD types, Fe3+/2+ dosages, and dosage ratios of the tailoring reagent (citric acid-CA) to the cross-linking reagent (epichlorohydrin-EPI). In the polymeric network, the confinement of CD units on Fe ion reduction and nZVI nucleation/growth resulted in the formation of cracked nZVI with small particle sizes and thin oxide shells, and the extents increased in the order of α-CD < HP-β-CD < β-CD < γ-CD. CA tailored the polymeric network and enhanced its accessibility to Fe ions, both of which favored CD confinement effects. In contrast to the uncontrollable cross-linking synthesis of conventional CDP materials, CDP-nZVI was facilely synthesized and accurately preconditioned (R2 = 0.926/0.969). CDP-nZVI (E1) that was rationally screened activated PS and degraded naphthalene (Nap) in water by > 90% during 16 Nap/PS supplements and following 5 regeneration cycles. CDP-nZVI (E1)/PS efficiently removed PAHs, phenols, benzene series, pesticides and antibiotics in river water and wastewater by > 96%, and completely decontaminated 104 pore volumes of Nap-contaminated river water in a continuous-flow reactor. This study provides mechanistic insights into the precondition and optimization of CDP-metal sorbents and catalysts for water decontamination.