# Wastewater Treatment by Polymeric Microspheres: A Review
## 2 Synthetic Polymer
The peak of sulfuric acid groups from XPS analysis showed that the strong interaction between sulfuric acid groups and metal ions is the main cause of the great adsorption capacity. The micron structure of SPS microsphere resolved the excessive hydrophilia issue caused by rich sulphonic acid groups and easily separated; thus, the microsphere has unparalleled advantages regarding nanoscale adsorbents. The microsphere maintained good recycle capacity after five regeneration cycles without any loss in adsorption capacity. Organic-inorganic materials with spherical shapes consisting of DVB and triethoxyvinyl-silane (TEVS) were synthesized and investigated for the removal of organic compounds from wastewater [39]. DVB was used as a crosslinking monomer and TEVS was used as a silane coupling agent, and the influence of their molar ratio was investigated. As shown in Figure 4, SEM image shows that the DVB:TEVS = 1:2 ratio microsphere was largely deviated from the ideal spherical form, and a 2:1 microsphere ratio showed a regular shape with a uniform and smooth surface. The adsorption properties were also different toward nitrobenzene, 4-nitropenol, and phenol. For all microspheres, nitrobenzene showed the strongest decrease of adsorbate concentration and the lowest decrease for phenol, which is related to adsorbate solubility/hydrophobicity. For nitrobenzene, 2:1 microsphere showed the greatest adsorbate loss, while for 4-nitropenol and phenol, 1:1 microsphere showed the greatest loss. TG and DTG curves showed that DVB-TEVS materials are thermally stable up to 330 \({}^{\circ}\)C and that the main destruction occurs over 450 \({}^{\circ}\)C, indicating their applicability in a comparatively wide temperature range. The remarkable selectivity toward various organic adsorbates makes it a promising adsorbent. Finally, the effect of ionic liquid in the polymeric microsphere was tested in regards to wastewater treatment. Pyridine polyionic liquid porous microspheres (PPLM) were prepared for the selective adsorption of anionic organic dyes from industrial wastewater [40]. A P(VP-DVB)-6 microsphere was chosen as the optimal adsorbent based on adsorption conditions and operational requirements ascribed to its optimal comprehensive properties. The adsorption capacities for Congo Red (CR), Bromophenol blue (BPB), Sunset Yellow (SY), Alizarin red R (AR), Safranine T (ST), and MB of P(VP-DVB)-6 microsphere were evaluated via UV-vis spectrophotometer, and it was found that it had outstanding selective adsorption effects for three anionic dyes (CR, SY, and BPB). The absorptions for SY and BPB were further investigated and fitted to the PSO kinetic model. The adsorption rate was affected by the concentration of both dye and adsorbent. The whole adsorption process occurred through two states: the surface adsorption and the intraparticle diffusion. The adsorption fit the Langmuir isotherm model, indicating that the adsorption was single molecular layer adsorption. Figure 4: SEM images of DVB:TEVS = 1:2 (**a–c**), DVB:TEVS = 1:1 microspheres (**d–f**) and DVB:TEVS = 2:1 microspheres (**g–i**) in different magnification (Reproduced from [PERSON] et al. [39], 2021, MDPI).