Facile surface modification of 3D-printed biopolymer filter via acetone treatment for enhanced copper hexacyanoferrate immobilization and selective ammonium capture

Ammonium contamination poses a significant environmental concern due to its adverse impacts on aquatic ecosystems, including oxygen depletion, reproductive disorders in aquatic organisms, and the proliferation of harmful algal blooms that release toxic compounds. These effects deteriorate water quality and threaten ecosystem stability, underscoring the need for effective and selective ammonium removal strategies. In this study, copper hexacyanoferrate (CuHCF), a Prussian blue analogue with strong affinity for ammonium ions, was immobilized onto acetone-pretreated three-dimensional (3D)-printed polylactic acid (PLA) filters. Acetone pretreatment chemically etched the PLA surface, increasing surface porosity and hydrophilicity, thereby enhancing surface reactivity for subsequent functionalization and CuHCF immobilization. This surface engineering strategy enabled uniform and stable distribution of CuHCF particles on the biopolymer scaffold, resulting in improved adsorption performance and structural stability. The fabricated filter exhibited an ammonium adsorption capacity of 1.91 mg/g and maintained over 90% regeneration efficiency across five adsorption–desorption cycles. Continuous column experiments further demonstrated stable operation for up to 40 h without significant performance deterioration. Overall, this work presents a simple and scalable approach for fabricating 3D-structured adsorbents via acetone-assisted surface modification, offering a practical platform for selective ammonium recovery and resource-oriented water treatment applications.