Fe-exchanged nano-bentonite outperforms Fe3O4 nanoparticles in removing nitrate and bicarbonate from wastewater

Nitrate (NO3-) and bicarbonate (HCO3-) are harmful for the water quality and can potentially create negative impacts to aquatic organisms, crops and humans. This study deals with the removal of NO3- and HCO3- from contaminated wastewater using Fe-exchanged nano-bentonite and Fe3O4 nanoparticles. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, surface area measurement and particle size analysis revealed that the adsorbents fall under the nano-scale size range with high specific surface area, and Fe was successfully exchanged in the nano-bentonite clay. The kinetics of adsorption was well defined by pseudo-first order and pseudo-second order kinetic models for both NO3- and HCO3-. The Fe-exchanged nano-bentonite was a better performing adsorbent of the oxyanions than Fe3O4 nanoparticles. According to the Sips isothermal model, the Fe-exchanged nano-bentonite exhibited the highest NO3- and HCO3- adsorption potential of 64.76 mg g(-1) and 9.73 meq g(-1), respectively, while the respective values for Fe3O4 nanoparticles were 49.90 mg g(-1) and 3.07 meq g(-1). Thus, inexpensiveness and easy preparation process of Fe-exchanged nanobentonite make it attractive for NO3- and HCO3- removal from contaminated wastewater with significant environmental and economic benefits.