Design and preparation of functional azo linked polymers for the adsorptive removal of bisphenol A from water: Performance and analysis of the mechanism

Sulfonated polyHIPE/nanoclay composites with hierarchically porous structure for efficient removal of endocrine‐disrupting hormone from aqueous solution

“…There was relatively greater adsorption performance (91.2% removal) obtained at 0.05 M than at 0 M (90.5% removal). The slight increase in the adsorptive removal was ascribed to the electrostatic shielding effect on the composite surface (Berhane et al, 2016; Dong et al, 2022). The ionic strength could decrease the negative electric field around the polymeric surface and provide easier interaction of BPA molecules with the adsorbent (Guo et al, 2022).…”

“…In addition, similar removal efficiencies were obtained at 0.1 M (90.4% removal) and 0.2 M (89.2% removal) NaCl concentrations, revealing that the BPA adsorption was driven by both hydrogen bonds and hydrophobic interactions. However, a further increase in the ionic strength to 0.3 M led to a decrease in the BPA adsorption (83.5% removal) because of the fact that higher salinity induced the breakage of hydrogen bridges and “squeezing‐out effect” between BPA and p(HIPE)/NClay@S (Dong et al, 2022; Shi et al, 2022). The “salting‐out effect” was based on a theory that the solubility and hydrophobicity of bisphenol molecules could decrease at higher ionic strength which boosted the interactions within adsorbate and adsorbent, leading to increased removal performance (Berhane et al, 2016; Shi et al, 2022).…”

“…Figure 9c–d shows the high‐resolution C1s XPS spectra of p(HIPE)/NClay@S before and after BPA adsorption. The peaks located at 283.8, 284.5, 285.3, 288.1, and 291.2 eV corresponded to the C=O, C=C, C–O, O–C=O, and π – π bonds, respectively (Dong et al, 2022; Liu et al, 2021). After BPA adsorption (Figure 9d), the proportion of C=C bonds (~284 eV) decreased, whereas the peak related to the π – π satellite area disappeared, demonstrating that the π – π stacking interactions played a crucial role in the adsorption mechanism.…”

“…The changes in the proportion of the oxygen F I G U R E 8 Effect of solution pH on the bisphenol A (BPA) adsorption on p(HIPE)/NClay@S (C i : 20 mg/L, adsorbent dosage: 1 g/L, pH 2-11, T = 298 ± 2 K, adsorption time 24 h). chemical states could be ascribed from the formation of hydrogen bonds of O-HÁ Á ÁO or C-HÁ Á ÁO between -OH groups of the polymeric composite and -H from the benzene ring of BPA (Dong et al, 2022). On the other hand, the proportion of O=C bonds decreased indicating the breakage of the double bonds, whereas the ratio of C-O bonds increased after BPA adsorption, implying that the oxygen-containing groups were crucial for the BPA adsorption on p(HIPE)/NClay@S. It was reported that the oxygen-containing groups including -OH or S=O (-SO 3 H) of sulfonic acid groups over the polymeric structure might result in reduced electron drawing ability of oxygen atoms (Gong et al, 2022;Liu et al, 2021).…”

“…de Farias et al (2022) reported that the hydrophobic interactions were the main adsorption mechanism between organoclay and BPA molecules in which the hydrophobic clay surface acted as a partition phase, promoting the adsorption of bisphenol molecules via van der Waals forces. Dong et al (2022) hypothesized that the azo and benzene rings of the polymeric surface could generate a hydrophobic porous cavity, providing hydrophobic interaction with two hydrophobic benzene rings of BPA. Therefore, it was assumed that the hydrophobic interactions partially contributed to the adsorption of BPA onto p(HIPE)/NClay@S.…”