A facile, cost-effective, and scalable “urea cross-linking reaction” was developed to fabricate superhydrophobic melamine sponge (SMS) as efficient oils- and organic solvents-absorbent material. Primarily, a readily-available key intermediate of isocyanate-terminated poly(dimethyl siloxane) (iPD) was heated to proceed crosslinking reaction, generating flexible, hydrophobic films with urea cross-linking points. Moreover, this key iPD can be used to modify melamine sponge (MS), by heating to have its isocyanate terminals react with the secondary amine groups of MS, rendering covalent urea bonds over the surface of MS skeleton. The resultant SMS exhibits a high water contact angle (WCA) of 153.4o and excellent volumetric absorption capacity (1.163 ~ 1.661 m3/m3) for different oils and organic solvents and can be repeatedly used for 30 sorption-squeezing cycles with high absorption capacity retention (85.1 ~ 98.7 %), depending on the polarity and density of the employed organic solvents and oils, and high selectivity. This property of the material remains intact even after various standard chemical and physical insults. The fabrication procedure of SMS is simple and cost-effective and the anti-wetting, robust, recyclable SMS is efficient in the separation of various oils and organic solvent/water mixtures, therefore, this study provides attractive and potential methodology for use in scalable environmental cleanup and remediation.
A novel adsorbent, urea porous polymer (UPP), for uptake of heavy metal ions from aqueous solutions was first fabricated via cross-linking reaction N1,N1-Bis(4-aminophenyl)benzene-1,4-diamine (TPA3NH2) and two or three functional isocyanate groups into toluene and tetrahydrofuran (THF) co-solutions, U2 and U3. The UPP microspheres of 0.3-1.0 μm in mean diameter were of uniformly wrinkle-like topography and sphere-like sketched out by SEM, whose surface after decoration by urea linkage was stable and beneficial to metal ion capture. Its chemical composition, microstructure, and thermal property were characterized by solid state 13C NMR, FTIR, XRD, XPS, BET, and TGA techniques, take U3 for example, the achieved quantitative results mainly included disappearance of isocyanate 2265 cm-1, specific surface area (114.2 m2/g), CO2 capture (1.95 mmole/g) pore diameter (8.56 nm), and mass loss at the char yield (43%), which indicated a successful synthesis, well-defined structure, and good thermos ability. Adsorption tests of U3 were performed in Pb(II) solutions at various pH values, contact time, and initial concentrations, exhibiting an excellent adsorption capability. Its maximum adsorption capacity calculated by formula was 129.7 mg Pb(II)/g, which was higher than those of most available adsorbents. Additionally, several potential bonding modes and adsorption sites for both metal ions were also proposed. Furthermore, the aU3 exhibited excellent thermal properties (58%), BET analysis (1483.8 m2/g) and CO2 capture (4.21 mmole/g). Overall, UPP materials not only with large surface areas and pore volumes are environmentally friendly materials having great potential in gas storage (CO2) applications but also with outstanding adsorption performance toward Pb(II) might serve as a new absorbent for wastewater purification.