Evaluation of Intrinsic-Type and Hydrophobic Three-Dimensional Melamine/Polyvinyl-Alcohol Formaldehyde Sponges Containing a Hierarchical Porous Structure for Emulsion Separation

Abstract

Emulsion separation of emulsified oil wastewater has been an urgent problem from both environmental and economic perspectives to be dealt with. Here, to overcome the emulsion separation material-prepared process involving expensive equipment and consuming large energy and the composite componentfunctionalized running off problem during application, a series of intrinsic-type and hydrophobically functionalized three-dimensional (3D) melamine/polyvinyl-alcohol formaldehyde (MF/PVF-Cn-x) sponges containing interpenetrating polymer networks (IPNs) and a hierarchical porous structure were synthesized by introducing a PVF network into a commercial melamine (MF) sponge by coacetalation crosslinking reaction first and further acylating chlorination chemical grafting reactions. Water contact angles of as-prepared sponges were higher than 114.7°. Cross-sectional SEM morphological observation and pore size distribution curves demonstrated that interpenetrating polymer networks (IPN) and a hierarchical porous structure were constructed successfully. Their pore size scope was from 1 to 100 μm, and the average pore size was around 20 μm (15.7 and 25.1 μm), which was similar to a stable emulsion droplet size of 20 μm, which satisfied the size sieving requirement for emulsion separation. Compared with the separation performance of 2D membrane materials, MF/PVF-Cn-x 3D hierarchical porous materials exhibited excellent separation performance and antifouling property. Among them, the MF/PVF-C16-46.8% sponge had the most prominent emulsion separation performance with a flux of 9.55 × 10 4 L m −2 h −1 bar −1 and an efficiency of nearly 100%. Furthermore, the separation flux of MF/PVF-Cn-x was still higher than 2.22 × 10 4 L m −2 h −1 bar −1 and the efficiency was nearly 100% after seven cycles. On the other hand, the mechanical properties of MF/PVF-Cn-x sponges were strengthened by the introduced PVF network, and their compress stress was higher than 3.2 MPa. All the comprehensive performances made MF/PVF-Cn-x sponges become a suitable candidate as a highly effective emulsion separation material.

Preparation of Hydrophobic Functionalized Poly(vinyl alcohol) Formaldehyde-Based Composite Sponges for Highly Effective Water-in-Oil Emulsion Separation

“…Meanwhile, the compressive strengths of the PVF/PVA-Mac-PXMA sponges were much higher than those of the original one and PVF/PVA, and the maximum stress of the PVF/PVA-Mac-PEMA sponge was 14.65 MPa (ε = 70%), which was almost six times as high as that of the pristine PVF sponge. However, the maximum stress of PVF/PVA-Mac-PPMA and PVF/PVA-Mac-PBMA was slightly decreased, which was probably attributed to the fact that the introduced polymer segments are acting as plasticizers . Moreover, the PVF/PVA-Mac-PEMA sponge was taken as a typical sample to carry on cyclic σ–ε curves in the wet state.…”

“…First, the original PVF and PVF/PVA composite sponges were prepared by PVA foaming, and the detailed preparation process can be found in our previous report. , Then, 50 g of PVF/PVA sponge was immersed in 300 mL of acetonitrile solution, and then 0.2 mol of pyridine as a catalyst and 1.0 mol of methacryloyl chloride as a reaction reagent were poured into the solution. The reaction was conducted at 30 °C for 6 h. Subsequently, the prepared samples were subjected to multiple washes with acetonitrile to eliminate any unreacted reagents and then dried at 60 °C until a consistent weight was achieved.…”

“…However, the maximum stress of PVF/PVA-Mac-PPMA and PVF/PVA-Mac-PBMA was slightly decreased, which was probably attributed to the fact that the introduced polymer segments are acting as plasticizers. 37 Moreover, the PVF/PVA-Mac-PEMA sponge was taken as a typical sample to carry on cyclic σ−ε curves in the wet state. As shown in Figure 3b, the σ−ε curve of it showed a nonlinear and closed hysteresis, which followed typical viscoelastic and highly deformable materials, such as rubber.…”