Noninvasive Real-Time Monitoring of Wetting Progression in Membrane Distillation Using Impedance Spectroscopy.

Membrane distillation (MD) is a promising technology for the treatment of high salinity wastewater using a hydrophobic membrane; however, the occurrence of wetting due to surfactants in polluted or low surface tension liquid impedes MD application. Common monitoring approaches, such as conductivity and flux measurement, cannot explain the wetting phenomenon that occurs during the wetting process in detail. Recently, impedance spectroscopy has been proposed for early wetting detection, as it depends on the change of water/air composition in the membrane pores. An earlier and larger variation was observed with precise signal detection. In this study, we proposed an analytical approach to estimate the wetting front, which is the average feed intrusion distance, by the impedance value recorded in real-time operation. With this proposed approach, the wetting mechanism in the presence of a surfactant and the effect of pore size on a commercial polyvinylidene fluoride membrane could be quantified, which cannot be explained in detail using conductivity and flux measurements.

In-situ 3D fouling visualization of membrane distillation treating industrial textile wastewater by optical coherence tomography imaging.

Membrane fouling, which is caused by the deposition of particles on the membrane surface or pores, reduces system performance in membrane distillation (MD) applications, resulting in increased operational costs, poor recovery, and system failure. Optical Coherence Tomography enables in-situ foulant monitoring in both 2D and 3D, however, the 2D images can only determine fouling layer thickness in severe fouling. Therefore, in this study, an advanced 3D imaging analysis technique using intensity range filters was proposed to quantify fouling layer formation during MD through the use of a single 3D image. This approach not only reduces computational power requirements, but also successfully separated the fouling layer from the membrane at the microscale. Thus, the thickness, fouling index, and fouling layer coverage can be evaluated in real time. To test this approach, Polyvinylidene fluoride (C-PVDF) and polytetrafluoroethylene (C-PTFE) membranes were used to treat a feed consisting of industrial textile wastewater. Thin and disperse foulants was observed on the C-PTFE, with a 22 µm thick fouling layer which could not be observed using 2D images after 24 h. Moreover, the C-PTFE demonstrated better antifouling ability than the C-PVDF as demonstrated by its lower fouling index, which was also supported by surface energy characterization. This work demonstrates the significant potential of 3D imagery in the long-term monitoring of membrane fouling process to improve membrane antifouling performance in MD applications, which can lead to lowered operational costs and improved system stability.

Correction: Iridium(iii) polypyridine complexes with a disulfide linker as biological sensors and cytotoxic agents.

Correction for 'Iridium(iii) polypyridine complexes with a disulfide linker as biological sensors and cytotoxic agents' by Steve Po-Yam Li et al., Dalton Trans., 2019, DOI: 10.1039/c9dt00793h.

Modification of 1,2,4,5-tetrazine with cationic rhenium(I) polypyridine units to afford phosphorogenic bioorthogonal probes with enhanced reaction kinetics.

New phosphorogenic bioorthogonal probes derived from mononuclear and binuclear rhenium(I) polypyridine complexes containing a 1,2,4,5-tetrazine moiety were designed; these complexes displayed substantial dienophile-induced emission enhancement, and accelerated reaction kinetics and could target a protein conjugate in living cells.

Rhenium(I) polypyridine diamine complexes as intracellular phosphorogenic sensors: synthesis, characterization, emissive behavior, biological properties, and nitric oxide sensing.

We report the development of a series of rhenium(I) polypyridine complexes appended with an electron-rich diaminoaromatic moiety as phosphorogenic sensors for nitric oxide (NO). The diamine complexes [Re(N^N)(CO)3 (py-DA)][PF6 ] (py-DA=3-(N-(2-amino-5-methoxyphenyl)aminomethyl)pyridine; N^N=1,10-phenanthroline (phen) (1 a), 3,4,7,8-tetramethyl-1,10-phenanthroline (Me4 -phen) (2 a), 4,7-diphenyl-1,10-phenanthroline (Ph2 -phen) (3 a)) have been synthesized and characterized. In contrast to common rhenium(I) diimines, these diamine complexes were very weakly emissive due to quenching of the triplet metal-to-ligand charge-transfer ((3) MLCT) emission by the diaminoaromatic moiety through photoinduced electron transfer (PET). Upon treatment with NO, the complexes were converted into the triazole derivatives [Re(N^N)(CO)3 (py-triazole)][PF6 ] (py-triazole=3-((6-methoxybenzotriazol-1-yl)methyl)pyridine; N^N=phen (1 b), Me4 -phen (2 b), Ph2 -phen (3 b)), resulting in significant emission enhancement (I/I0 ≈60). The diamine complexes exhibited high reaction selectivity to NO, and their emission intensity was found to be independent on pH. Also, these complexes were effectively internalized by HeLa cells and RAW264.7 macrophages with negligible cytotoxicity. Additionally, the use of complex 3 a as an intracellular phosphorogenic sensor for NO has been demonstrated.