Adsorption and separation performance of tungsten and molybdenum on modified zirconium based metal organic frameworks UiO-66-CTAB

A modified zirconium (Zr)-based metal organic framework (UiO-66-CTAB) was synthesized by solvothermal method, and used for the adsorption and separation of molybdenum (Mo) and tungsten (W). Under the optimized conditions, UiO-66-CTAB with uniform pore size and containing particles with tetrahedral cage structure could be obtained. UiO-66-CTAB showed BET surface area and micropore volume of 873.848 m2·g−1 and 0.403 cm3·g−1, respectively, with the particle size range of 200–300 nm. It acquired positive charge at pH < 7, thus it could get easily connected with the negatively charged Mo species. The material shows excellent adsorption of Mo and its effective separation from W in acidic solution. It is beneficial for separation at room temperature under the optimal contact time of 3 h. The adsorption capacity for Mo (QMo) was 355 mg·g−1 and the highest separation factor (βMo/W) was 51.4. Comprehensive analysis of XRD, SEM, FT-IR spectroscopy, XPS, and thermodynamic results indicate that the adsorption mechanism involved the selectivity of the effect of pore size, stronger affinity of the metal point Zr for Mo, and coordination interaction between the N atom of CTAB and Mo element, which allowed more Mo-homopoly acid ions to enter the cage and significantly hindered the entrance of W-homopoly acid ions into the UiO-66-CTAB. The adsorbent UiO-66-CTAB can be considered as a potential candidate for new and green adsorbent materials for the separation and recovery of W and Mo in the treatment of ores, wastes, and wastewater, which is beneficial for environmental protection.