(3)Applications
The melamine sponge is a popular material widely used in industry and our everyday life. For instance, its porous structure, excellent water capacity and stable properties enables it to be applied in noise resistance, water-oil separation and refractory materials.
1.Oil-Water Separation
1)Background
①Nowadays, the illegal emission of toxic chemical compounds in sea has become a crucial threat to the oceanic system.
②The conventional materials[1] like powdery zeolites and activated carbon exhibits low efficiency and is difficult to remove.
③The melamine sponge is an excellent substitution of the previous example because of its huge liquid capacity and considerable water/oil splitting ability.
2)How the sponge works [2]
Melamine sponge is a high-energy material [3] that tends to be hydrophilic and oleophobic. Its large water contact angle and porosity [4] enable its ability of oil selectivity and oil-water separation. To be specific, the sponge absorbs water which is as over 100 times as its own weight. Therefore, when it is immerged into oil/water mixtures, the water will permeate into its porous microstructure driven by gravity, decreasing the contact area between the oil molecules and the sponge surface. As a result, oil splitting in water is achieved.
3)Experimental data for water separation
The table 1 below indicates that the melamine sponge exhibits relatively excellent separation efficiency for various organic chemicals, especially for aliphatic ones as well as their derivatives. However, the addition of Fe3O4 impurity decreases the absorbing capacity, as is shown in figure 1.
Table 1. The separation efficiency for different types of organics.[5]
Figure 1. The water capacities for the influence of impurity on different types of organics.[6]
[1] X.-F. Zhang, L. Song, X. Chen, Y. Wang, Y. Feng, and J. Yao, “Zirconium ion modified melamine sponge for oil and organic solvent cleanup,” Journal of Colloid and Interface Science, vol. 566, pp. 242–247, Apr. 2020, doi: https://doi.org/10.1016/j.jcis.2020.01.101.
[2] C.-F. Wang, H.-C. Huang, and L.-T. Chen, “Protonated Melamine Sponge for Effective Oil/Water Separation,” Scientific Reports, vol. 5, no. 1, Sep. 2015, doi: https://doi.org/10.1038/srep14294.
[3] Y.Feng and J. Yao, “Design of Melamine Sponge-Based Three-Dimensional Porous Materials toward Applications,” Industrial & Engineering Chemistry Research, vol. 57, no. 22, pp.7322–7330, May 2018, doi: https://doi.org/10.1021/acs.iecr.8b01232.
[4] [5] [6] Z.Yin et al.,“An environmentally benign approach to prepare superhydrophobic magnetic melamine sponge for effective oil/water separation,” Separation and Purification Technology, vol. 236, pp. 116308–116308, Apr. 2020, doi: https://doi.org/10.1016/j.seppur.2019.116308.