Cobalt/zinc based metal organic frameworks as an effective adsorbent for improved removal of As(V) and Cr(VI) in a wide pH range

Herein, a Co/Zn based metal organic frameworks (ZIF-67/ZIF-8) adsorbent was synthesized through a facile method and used for the removal of As(V) and Cr(VI) ions. The adsorbent was characterized by Brunauer Emmett and Teller (BET), X-ray photoelectron spectroscopy (XPS), high resolution scanning electron microscopy (HR-SEM) equipped with energy dispersive spectroscopy (EDS), transmission electron scanning microscopy (TEM) and X-ray diffraction (XRD). The XPS results confirmed that a mixed metal MOF ZIF-67/ZIF-8 was formed. Several isotherm models were studied and the obtained results indicated a homogeneous monolayer adsorption described by Langmuir isotherm with maximum capacities of 69.4 and 71.4 mg g−1 for Cr(VI) and As(V) respectively. The adsorbent selectively removed both oxyanions in real water samples, i.e., a complex matrix that contained other metals and anions. The ZIF-67/ZIF-8 showed excellent adsorption properties towards the two targeted heavy metals therefore can be a great adsorbent in wastewater treatment.