Fabrication of porous resins via solubility differences for adsorption of cadmium (II)

Abstract By exploiting the different solubilities of triphenylphosphine in water, resins and organic solvents, porous melamine–formaldehyde (pMF) and porous urea–formaldehyde (pUF) resin materials could be successfully fabricated and used for adsorption of cadmium (II) (Cd(II)) cations. The obtained pMF and pUF materials had specific surface areas of 77.5 m 2  g −1 and 79.0 m 2  g −1 , respectively, and were able to be recycled and reused to greatly reduce raw material consumption. Due to their porous structures and high amine density, the prepared materials exhibited high removal efficiencies (94%, pMF; 90%, pUF) and adsorption capacities (3.33 mg g −1 , pMF; 3.12 mg g −1 , pUF) of Cd(II). The effect of pH, adsorption time, ion concentration, amount of adsorbent and interfering ions on Cd(II) adsorption, and adsorption thermodynamics and kinetics were investigated. The results showed that the adsorption behaviors of Cd(II) on pMF and pUF followed Langmuir and pseudo-second-order kinetic models. Furthermore, the pMF and pUF showed efficient removal of Pb(II) (90.29%, pMF; 91.32%, pUF), Cu(II) (71.47%, pMF; 83.28%, pUF) and Cr(III) (92.28%, pMF; 88.69%, pUF), while the recycled pMF and pUF showed high removal efficiencies of 88.36% (Cd(II), pMF) and 88.04% (Cd(II), pUF) even after five cycles. Their high removal efficiencies and adsorption capacities, simple and convenient synthesis, and affordability make pMF and pUF especially competitive in the arena of heavy metal ions remediation.