A novel scalable polycationic melamine sponge-based filtration matrix for continuous ultrafast adsorption of anionic...

Effective capturing of anionic pollutants from wastewater under industrial operating conditions, which requires high processing flux and fast adsorption rate remains a challenge. Here, a commercially available melamine sponge (MS) with reticulated 3D macroporous structures was covalently modified with positively charged moieties using a single step functionalization under mild conditions. The developed novel polycationic melamine sponge (MS⁺) was formed by a nucleophilic addition reaction between glycidyltrimethylammonium chloride (GMTA) and MS, followed by a self-propagation of GMTA. The produced MS⁺ possessed strong electrostatic interactions with different anions such as Rose Bengal (RB) and phosphates (P) under a wide pH range (3-11). The MS⁺ exhibited promoted static adsorption efficiencies of 400 mg g^-1 (P) and 600 mg g^-1 (RB), within 5 min and 60 s, respectively. Furthermore, the MS⁺ showed high stability and recyclability for up to 15 cycles of uses, and the recycling process was environmentally friendly by using 1 M NaCl as a releasing solution. Benefiting from fast flow through the macroporous MS⁺ and highly positive charged skeleton, the MS⁺ was applied for rapid dynamic enrichment process of P from real manure wastewater with an enrichment factor of 4.4. Utilization of the MS⁺ as the substrate brings additional advantages such as low cost, availability, and flexibility to fit into existing filtration devices. The developed MS⁺ could be expanded for enrichments of other anionic species from various polluted water sources.