Hong-Yu Luo,Min Zhang,Nai-Chao Si,Min-Jia Meng,Li Yan,Wen-Jing Zhu,Chun-Xiang Li
In this study, novel molecularly imprinted open porous membranes (MIOPMs) were prepared using the Pickering HIPEs template method and molecular imprinting technology for selective adsorption and separation of methyl 4-hydroxybenzoate (M4HB). The template M4HB, functional monomers, crosslinker and plastifier 2-ethylhexyl acrylate (2-EHA) were contained in the oil phase. Hydrophobic silica nanoparticles (HNP-SiO 2 ) were employed as a stabilizer to establish stable W/O Pickering HIPEs with nonionic surfactant sorbitantrioleate (Span 85). The results of SEM and FTIR indicated that the optimal MIOPMs were prepared successfully and possessed open and interconnecting pores. Then, the MIOPMs were used as sorbents for M4HB. The correlation coefficient ( R 2 ) values for the Langmuir–Freundlich isotherm model and pseudo-second-order kinetic model fitting to the adsorption equilibrium and kinetic data respectively were all higher than 0.95. The maximum adsorption capacity and the time of rapid adsorption for MIOPM 4 were 4.146 mg g −1 and 100 min, respectively. In addition, the permeability separation factor of MIOPMs for M4HB compared to a structurally related analog methyl 2-hydroxybenzoate (M2HB) could reach 3.122.
Junqiang Zhang,Jiliang Ma,Gaojie Jiao,Kangning Liu,Rui Cui,Shangru Zhai,Runcang Sun
Designing an adsorbent with excellent practical application on uranium extraction from seawater is extremely difficult but urgent. Here, the poly(amidoxime) (PAO)/polyvinyl alcohol (PVA)/methyl 4-hydroxybenzoate (MeP) hydrogel (named as PP@MeP-H) was prepared using a simple and controllable ultralow temperature-solvent exchange two step strategy. With assistance of solvent exchange, MeP nanospheres anchored on the hydrogel network showed excellent antibacterial activity during the uranium adsorption from seawater. Furthermore, the hydrogel with 3D network porous structure allows uranium to easily and rapidly spread into its interior owing to its abundant porous and anti-biological pollution ion channels, which ensures maximum utilization of the effective adsorption sites on this adsorbent. The superior uranium extraction capacity achieved 162.64 mg g −1 , and the sample shows excellent stability and reusability . Interestingly, when the pH close to natural seawater , PP@MeP-H showed the highest uranium adsorption activity (153.30 mg g −1 ), and for 500 L of natural seawater, the uranium adsorption capacity achieved 3.12 mg g −1 after 21 days. Furthermore, experimental results showed that the O and N atoms of amidoxime group act as main bonding sites for uranium adsorption. As the discussed above, PP@MeP-H has excellent potential of uranium adsorption from natural seawater.
Oxygen vacancies (OVs) were introduced into Ni-based layered double hydroxides (LDHs) through Cu doping, and the catalytic performance of the resulting Ni x Cu-LDHs were investigated for peroxymonosulfate (PMS) activation and methyl 4-hydroxybenzoate (MeP) degradation. Compared with that of Ni-LDH, the catalytic performance of Ni x Cu-LDHs were significantly enhanced and increased with increasing OV content in the catalysts, indicating that Cu doping introduced OVs into Ni x Cu-LDHs and greatly improved their catalytic activity with PMS. Quenching experiments and EPR analyses confirmed that oxidation processes dominated by superoxide radicals (O 2 •− ) and singlet oxygen ( 1 O 2 ), rather than sulfate radicals (SO 4 •− ) or hydroxyl radicals (•OH) used by traditional LDH catalysts, were responsible for MeP degradation by Ni 15 Cu-LDHs. In addition, quenching experiments with different systems showed the fate of reduced SO 4 •− and •OH, and demonstrated that O 2 •− and 1 O 2 concentrations grew with increasing OV content, confirming that the presence of OVs affected the process of PMS activation. Notably, O 2 •− mainly originated from adsorbed oxygen or dissolved oxygen (DO) by acquiring electrons from OVs in Ni 15 Cu-LDHs, since OVs possess abundant localized electrons. Consequently, an OV-mediated oxidative mechanism was proposed for Ni 15 Cu-LDHs/PMS. This study provides new clues for enhancing the catalytic performance of LDH catalysts by introducing OVs via metal doping in PMS-based AOPs systems.
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