Regenerable chitosan-embedded magnetic iron oxide beads for nitrate removal from industrial wastewater

Abstract

Industrial sites worldwide significantly contribute to water pollution. Nitrates are a common effluent pollutant from such sites. Effective means to remove nitrate ions (NO₃⁻) from polluted waters are needed. Chitosan beads, which are a non-toxic, biocompatible, and biodegradable polymer, are used for this purpose in this research. Iron-oxide nanoparticles are synthesized via the co-precipitation route and embedded into chitosan by chemical co-precipitation to form ion exchange chitosan beads (IECBs) for NO₃⁻ removal. The performance of the IECBs in a batch system was studied against NO₃⁻ adsorption from industrial water. Morphological, structural, and chemical characterization was performed by SEM, EDX mapping, BET, XRD, and FTIR, while the extent of NO₃⁻ adsorption was quantified using UV-vis spectroscopy. Different factors influencing the adsorption of NO₃⁻ on the IECBs were investigated, including the adsorbent dosage, pH of the solution, initial concentration, and interaction time. It is demonstrated that pseudo-second-order isothermal and kinetic models were best fits to the experimental data. It was found that the IECBs had a maximum adsorption capacity of 47.07 mg g⁻¹ and could load up to ∼93% of the NO₃⁻ from the batch system. The regeneration efficiency for the IECBs over 5 cycles remained high in the range of 93% to 79%, indicating their potential for industrial water treatment use.