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 pre -pared 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.