Fe-Zr MOFs as an effective adsorbent for Cr(VI) removal from aqueous solution

Recently, the Cr(VI) contamination in drinking water has become a severe problem for human beings and aquatic life. The objective of this work is to develop an efficient adsorbent of iron zirconium bimetallic metal-organic frameworks (Fe-Zr MOFs) by a simple co-precipitation process and use it for Cr(VI) removal from aqueous solution. The morphologies, binding groups, microstructures, and textural properties of Fe-Zr MOFs were analysed with the Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, X-ray Diffraction (XRD), and N2 adsorption–desorption instrumental techniques, respectively. Under the optimum condition of pH 3, the concentration of Cr(VI) ion is 10 F, time 150 min, and adsorbent dose of 0.250 g/L, the Fe-Zr MOFs were able to remove 95% of Cr(VI) from aqueous solution. The adsorption capacity of Fe-Zr MOFs was 123.40 mg/g as found from the Langmuir isotherm model. The chemisorption nature of the Cr(VI) adsorption on the Fe-Zr MOFs surface was confirmed by the pseudo-second-order kinetic model with a correlation coefficient of 0.95. The Fe-Zr MOFs were also able to remove Cr(VI) even in the presence of other anions with the order of Cl− > NO3− > CO32− > SO42− > PO43− respectively. The material could be reused for several cycles, as above 90% of regeneration was done with 0.1 M NaOH solution. Pore diffusion, electrostatic attraction, and chemical coordination mechanisms were the main interactions between Cr(VI) ions and the Fe-Zr MOFs surface. Hence, the Fe-Zr MOFs can be applied as a promising adsorbent for the treatment of Cr(VI) contaminated polluted water.