A recyclable elastic foam composite with spatially separated adsorption sites for simultaneous capture of multiple contaminants in complex wastewater

Simultaneous treatment of multiple pollutants in complex wastewater remains a major challenge in current water environment management. Herein, a monolithic composite adsorbent was designed and synthesized by in-situ one-step polymerization of hexachlorocyclotriphosphazene and polyethyleneimine on the surface of an elastic melamine foam (MF) at room temperature. The resulting MF@PCP was well characterized by SEM, FT-IR, XPS and N-2 analysis and its adsorption performance was systematically evaluated by using typical heavy metals, anionic dye and antibiotics as model contaminants in the single/binary systems. Characterization results showed that MF@PCP owned a highly open porous structure and spatially separated double adsorption sites (phosphazene rings and amine/imine groups), which could quickly and efficiently capture targeted contaminants from different pathways. The batch adsorption experiment results showed that MF@PCP had high adsorption capacities of 66.05, 132.8, 646, 691, 702, 784 mg/g for Cu(II), Cr(VI), methyl orange (MO), acid chrome blue K (ACBK), congo red (CR), and diclofenac sodium (DCF) in the single pollutant systems, respectively. Pseudo-second-order kinetic and intraparticle diffusion model could well describe the fast adsorption process of contaminants by MF@PCP. Meanwhile, in the binary systems (Cu(II)-Cr(VI), Cu(II)-ACBK and Cu(II)-DCF), the amount of one contaminant adsorbed by MF@PCP was significantly enhanced by the co-existence of another contaminant. FT-IR, UV-vis and XPS analysis confirmed that the designed MF@PCP adsorbent had a synergistic removal effect on metal ions, anionic dyes and diclofenac sodium based on multiple interaction mechanism. Additionally, in the simulated multi-component sewage treatment experiment, MF@PCP exhibited satisfactory adsorption performance including fast total adsorption, superior reusability and good stability. MF@PCP is expected to be a promising adsorbent for the treatment of complex wastewater.