Preparation of chromium fumarate metal-organic frameworks for removal of pharmaceutical compounds from water

Pharmaceutical pollution in water is the major cause of antibiotic resistance, so remediation of water from pharmaceuticals is a very important issue. Different methods are used for this purpose, with adsorption as one of the most preferred. Different adsorbents have been used for water treatment processes. Metal-organic frameworks that have highly porous structures have gained attention in the last decades. In this study, novel chromium fumarate (Cr-Fum) was prepared, and the efficiency of Cr-Fum was tested by ciprofloxacin (CPX) adsorption. Cr-Fum was prepared under reflux and characterized by scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), thermal analysis (TGA), and differential scanning calorimetry (DSC). The general approach of the process was monolayer adsorption at low temperature and heterogeneous adsorption at high temperature. 2.5 mg of adsorbent was adsorbed 4.97 mg/g and 11.47% of CPX. 10 mg of Cr-Fum was adsorbed 0.82 mg/g and 7.27% of CPX. Partition coefficients were calculated and 0.07 mg/g/mu M was found at 298 K. The reaction followed pseudo-first- and pseudo-second-order kinetic models. Thermodynamic analysis showed that the reaction is spontaneous and exothermic. Additional ions caused decreasing CPX adsorption, but this study showed that Cr-Fum has NaCl adsorption capacity. In future studies, NaCl adsorption should be investigated. Desorption studies were applied to Cr-Fum after the adsorption processes. 0.1 M NaOH and phosphate buffer (pH=7.4) solution were used as desorption eluents. The desorption period was chosen as 6 h. NaOH solution desorbed 67.38% of CPX at first cycle and buffer solution desorbed 26.87% of CPX at second cycle.