One-pot preparations of cyclodextrin polymer-entrapped nano zero-valent iron for the removal of p-nitrophenol in water

Nano zero-valent iron (nZVI) materials usually have low selectivity in water toward target contaminants (e.g., p-nitrophenol) and nontarget water constituents (e.g., nitrates and dissolved organic matter-DOM). Here we prepared the selective nZVI entrapped in the matrix of cyclodextrin polymer (CDP), using in situ impregnation and aqueous KBH4 reduction of FeCl3 in the matrix of CDP. The nZVI-CDP composites feature the network structure of CDP with mainly 40–80 nm nZVI particles entrapped in the network and 300 nm iron particles coated on the network surface. nZVI entrapped displays high stability and selective CDP facilitates the access of p-nitrophenol to nZVI, both accounting for the high selectivity of the composites. Chemical degradation of the nZVI materials, combined with adsorption, contributed to the p-nitrophenol removal. The nZVI materials usually exhibited similar or higher p-nitrophenol removal at different levels of nitrates, DOM or sulfides. Column experiments showed that the nZVI materials completely decontaminated 63 column volumes of groundwater containing p-nitrophenol, 6-fold higher than mixed nZVI and CDP. The nZVI materials were estimated to have potential performance duration of averaging 109 d, indicating the long-term performance in groundwater.