Regulatable pervaporation performance of Zn-MOFs/polydimethylsiloxane mixed matrix pervaporation membranes

Pervaporation(PV)is an emerging separation technique for liquid mixture.Mixed matrix membranes(MMMs)often demonstrate trade-off relationship between separation factor and flux.In this study,by changing the organic linkers(2-methyl imidazolate,imidazole-2-carboxaldehyde,2-ethyl imidazolate),ZIF-8,ZIF-90 and MAF-6 were prepared and filled in polydimethylsiloxane(PDMS)membranes for dealcoholization of 5%(mass)n-butanol solution,and the membranes properties and pervaporation performances were adjusted.Compared with the pure PDMS membrane,the addition of ZIF-8 resulted in a 9%increase in flux(1136 g·m^(-2)·h^(-1))and a 22.5%increase in separation factor(28.3),displaying antitrade-off effect.For the MAF-6/PDMS MMMs(2.0%mass loading),the pervaporation separation index(PSI)and separation factor were 32347 g·m^(-2)·h^(-1) and 58.6 respectively(increased by 34%and 154%in contrast with that of the pure PDMS membrane),and the corresponding permeation flux was 552 g·m^(-2)·h^(-1),presenting great potential in the removal butanol from water.It was deduced that the large aperture size combined with moderate hydrophobicity of metal–organic frameworks(MOFs)favor the concurrent increase in permeability and selectivity.

Sensitive and environmental friendly sensor on porphyrin functionalized chitosan fiber membrane for Hg^(2+)

Mercury is the most toxic and harmful heavy metal pollutant, and it is essential to detect and remove mercury from beverages. Inducing the porphyrin molecules into the chitosan structure, a novel membrane sensor tetrakis(4-carboxyphenyl)porphyrin-grafted chitosan fiber membrane (TCPP-CS) was prepared by electrospinning method and applied to recognize Hg^(2+) contaminant selectively. Compared with other common metal ions (Pb^(2+), Cu^(2+), Fe^(3+), Cr^(3+), Mg^(2+), and Zn^(2+)), the colorimetric sensor has specific color development and sensitivity to Hg^(2+) and the detection limit of the sensor reaches 1 × 10^(−5) mol·L^(−1). The response time of the membrane is 5 s, and it can be specifically colored in various pH environments convenient for practical application. Hg^(2+) resulted in a visual color change of the fiber membrane from brown to yellow-green, indicating a potential interaction between the porphyrin-functionalized chitosan fiber membrane and Hg^(2+) ions, and the wavelength shift of the UV–visible spectrum can be observed. It has the advantages of simplicity, rapidity, high selectivity, and high sensitivity, providing a new method for removing and detecting heavy metals in traditional Chinese medicine and drinks.

Exfoliated Mg–Al–Fe layered double hydroxides/polyether sulfone mixed matrix membranes for adsorption of phosphate and fluoride from aqueous solutions

Mg–Al–Fe layered double hydroxides（LDHs） were exfoliated and incorporated in polyether sulfone membranes for the removal of phosphate and fluoride for the first time. The exfoliation methods, coagulation bath, LDH amount, interfering ions, adsorption isotherm,desorption and reuse of the membranes were investigated. It was found that LDHs could be quickly exfoliated in formamide/N,N-dimethylformamide（DMF） solvent mixtures with sodium carboxymethyl cellulose as a stabilizer. The membranes displayed much higher adsorption capacity for phosphate（5.61 mg/g） and faster adsorption rate than the unexfoliated materials. With increased DMF content in the coagulation bath, the static and dynamic adsorption capacity rose. Interference from Cl-and SO4^（2-）（50 mg/L） on adsorption of phosphates was not apparent. The membranes displayed excellent reusability in dynamic adsorption/desorption. The membranes also showed high adsorption capacity for fluorides（1.61 mg/g）.

Synthesis of polyaluminum chloride with a membrane reactor:Process characteristics and membrane fouling

Polyaluminum chloride was synthesized with a membrane reactor,in which NaOH was added into AlCl 3 solution through the membrane’s micropores to reduce the NaOH droplets size.The content of the most efficient species increased to about 80%.The process characteristics in the reaction （i.e.,flow velocity,pressure drop）,and membrane fouling and cleaning were investigated.The evolution of both flow velocity and pressure drop during the reaction were related to changes in species distribution and solution viscosity.The process characteristics were well interpreted in terms of the Bernoulli equation.After reaction,the membranes were recovered by cleaning with diluted hydrochloride acid.This study is crucial for process design and scale-up of membrane reactors.

Catalytic bubble-free hydrogenation reduction of azo dye by porous membranes loaded with palladium nanoparticles

Catalytic bubble-free hydrogenation reduction of azo dye by porous membranes loaded with palladium （Pd） nanoparticles was studied for the first time. The effects of Pd loading, dye concentration and reuse repetitions of membranes were investigated. In reduction, the dye concentration decreased whereas the pH rose gradually. An optimal Pd loading was found. The catalytic membranes were able to be reused more than 3 times.