Ammonium is a pollutant that enters the environment from increasing ammonia production and subsequent emissions released as ammonia gas, which can contaminate waterways and soil as NH₄⁺ ions. In this study, a facile synthesis procedure was suggested for preparing high-performance ammonium adsorbent. Prussian blue analogue, viz. copper hexacyanoferrate (CuHCF), was immobilized in situ on a weakly acidic cation exchange resin (WAC) without any pretreatment to prepare the composite material WAC-CuHCF to assess its selective adsorption of NH₄⁺ from aqueous solution. CuHCF appears to be located on the surface of WAC, allowing access to NH₄⁺ for adsorption. The reaction kinetics of NH₄⁺ adsorption on WAC-CuHCF was consistent with the pseudo second-order model, and the adsorption isotherm followed the Langmuir isotherm model. WAC-CuHCF exhibited successful adsorption ability over a wide pH range, with maximum adsorption observed at pH 8. The adsorption efficiency of NH₄⁺ changed only slightly in the presence of Na⁺ and decreased by only ~10% in the presence of K⁺. The ability of WAC-CuHCF to regenerate was also assessed in the column test, and the regenerated adsorbent was found to adsorb and desorb NH₄⁺ to essentially the same extent. Thus, WAC-CuHCF developed in this study, which could be prepared in a facile synthesis method, is promising as a regenerative adsorbent material for the selective adsorption of NH₄⁺ ions over a wide pH range and can be applied for wastewater treatment and environmental remediation.

Tae-Hyun Kim

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