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

• Published in: Journal of hazardous materials Vol. 376; pp. 141 - 152
• Main Authors: Mukhopadhyay, Raj, Adhikari, Tapan, Sarkar, Binoy, Barman, Arijit, Paul, Ranjan, Patra, Ashok K., Sharma, Parbodh C., Kumar, Parveen
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.08.2019
• Subjects: Nano-bentonite; Nitrate pollution; Oxyanion adsorption; Wastewater treatment; Water alkalinity; Nano-bentonite; Nitrate pollution; Water alkalinity; Oxyanion adsorption; Wastewater treatment
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2019.05.025

•Fe-exchanged nano-bentonite removed NO3− and HCO3− from contaminated water.•NO3− and HCO3− sorption reached equilibrium within 2 and 2.5 h, respectively.•Maximum adsorption of NO3− and HCO3− occurred at pH 6.0.•NO3− & HCO3− adsorption potentials were 64.76 mg g-1 & 9.73 meq g-1, respectively.•Lewis acid-base reaction, outer sphere complexation & ligand exchange were involved. 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 nano-bentonite make it attractive for NO3− and HCO3− removal from contaminated wastewater with significant environmental and economic benefits.