Optimization of nitrate removal from aqueous solutions using clinoptilolite /CoFe2O4 by surface response methodology

The purpose of this study was to investigate the efficiency of clinoptilolite modified with magnetic CoFe2O4nanoparticles as an adsorbent in the removal of nitrate from aqueous solutions. Clinoptilolite and clinoptilolite/ CoFe2O4werecharacterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) analysis and Barrett-Joyner- Halenda (BJH), and vibrating sample magnetometer (VSM) techniques. The average particle size calculated by the Debye–Scherrer for clinoptilolite and clinoptilolite/CoFe2O4 were about 31 nm and 42 nm, respectively.Based on the (SEM) results,the average particle size was comparable with the Debye Scherrer calculated crystallite size. BET shows that the surface area increased from 18.42 to 25.95 m2 g-1 by the modified clinoptilolite surface. The clinoptilolite/CoFe2O4 has saturation magnetization 0.97 emu/g.Thenitrate adsorption capacity was evaluated by clinoptilolite and clinoptilolite/CoFe2O4.Based on the results, the adsorption capacity of the clinoptilolite/CoFe2O4had a higher adsorption capacity than the unmodified clinoptilolitewhich can be attributed to its higher surface area. The effect of different variables on the nitrate removal process, such as temperature, time and mass of adsorbent, was optimized using the surface response methodology (RSM) with the Box-Behnken(BBD) method. The study showed that the maximum removal percentage of nitrate was 97.03% at 55 °C, 40.36 h, and 0.27 g mass of adsorbent.