Single- and multi-component adsorption of selected contaminants of emerging concern from water and some of their metabolites onto hierarchical porous copper(II)-zeolite -activated carbon composite

Abstract

A copper(II) functionalized hierarchical faujasite zeolite/activated carbon composite adsorbent (Cu-CFAU) was prepared in an attempt to develop a platform for the effective removal of contaminants of emerging concern (CECs: caffeine, carbamazepine, naproxen, and metabolites clofibric acid, 10,11-epoxy-carbamazepine, o-desmethyl-naproxen, paraxanthine, salicylic acid) from water at ambient conditions. CFAU was prepared hydrothermally via seeded in situ growth of zeolite crystals within the pores of an activated carbon (AC, Darco-KB-G) and subsequently exchanged with copper(II). The materials were characterized using XRD, TEM, TGA, porosimetry, and elemental analysis. TEM, TGA and textural properties showed direct evidence of the in situ growth of the zeolite phase. Performance of the CFAU composite for CECs equilibrium adsorption was addressed in both single- and multi-component fashion and for CECs aqueous phase concentrations covering the μg L−1 – mg L−1 range. Cu-CFAU displayed the best overall adsorption working capacities, probably due to greater affinity for all CECs by relying on complexation interaction with the transition metal sites along with an enhancement of electrostatic and hydrophobic-hydrophilic interactions. Compared to AC, the composite excelled in adsorbing ionic CECs and was able to offer at least equal capacity toward neutral CECs. Compared to other adsorbents reported so far in the literature, the Cu-CFAU offers adsorption capacities that are larger by an order of magnitude in many cases. Preliminary tests for the reusability of the composite after various adsorption/desorption cycles suggest that Cu-CFAU might be regenerated via thermal treatment under inert atmosphere when the adsorbed CEC possesses a relative low melting point.