Removal of Microplastics in a Hybrid Treatment Process of Ceramic Microfiltration and Photocatalyst-Mounted PES Spheres with Air Backwashing.

Microplastics (MPs), which are defined as plastics with a size of less than 5 mm, cannot be treated completely in wastewater treatment plants (WWTPs) and discharged to a water body because they are too small in size. It has been reported that MPs can have adverse effects on human beings and water ecosystems. There is a need to combine existing drinking water treatment plants (DWTPs) and WWTPs with the traditional treatment process and technology with high removal efficiency of MPs or to develop a new technology to separate MPs from water and wastewater. In this study, the effects of MPs (polyethylene (PE), 125 µm) and organic matter (humic acid) were researched in a hybrid treatment process of ceramic microfiltration (MF) and photocatalyst (TiO2)-mounted polyether sulfone (PES) spheres with air backwashing. The roles of the MF, photooxidation, and adsorption of PES spheres were confirmed in a single MF process (MF), an MF process with UV irradiation (MF+UV), MF and PES sphere adsorption without UV irradiation (MF+PES), and a hybrid process incorporating MF and PES spheres with UV irradiation (MF+PES+UV). The impact of the air backwashing cycle (filtration time, FT) on filtration characteristics and treatment efficiencies in the hybrid process was studied. In the MF process, membrane fouling increased with increasing organic matter (HA, humic acid). The treatment efficiency of MPs increased; however, that of dissolved organic matter (DOM) decreased with increasing HA. As MPs increased, the membrane fouling decreased; however, total filtration volume (VT) remained almost constant. The treatment efficiency of MPs increased a little, and that of DOM showed a dropping trend. In the hybrid process, the membrane fouling was controlled via the adsorption and UV photooxidation of the PES spheres, and the DOM treatment efficiency increased by combining processes from MF to MF+PES+UV. The optimal FT was 10 min at BT 10 s in this hybrid process. The results could be applied to separate MPs effectively in DWTPs/WWTPs.

Sustained activation of persulfate by slow release of Fe(II) from silica-coated nanosized zero-valent iron for in situ chemical oxidation.

Sustained activation of persulfate through the slow release of Fe(II) from silica-coated nanosized zero-valent iron (nZVI) particles (nZVI@SiO2) was investigated. Slow release of Fe(II) prevented radical scavenging by excess Fe(II) and increased the radical yield, which improved the stoichiometric efficiency of phenol degradation. Sulfate and hydroxyl radicals were found to be the main oxidative species produced during phenol degradation and were found to make comparable contributions to oxidation. The nZVI@SiO2 particle silica shell thickness controlled the release of Fe(II) and therefore the sustained activation of persulfate and was strongly affected by the synthesis conditions, including the [Si]/[Fe] ratio and silica supply rate. Optimal sustained phenol degradation was achieved when nZVI@SiO2 particles were synthesized using a [Si]/[Fe] ratio of 0.5 and a tetraethyl orthosilicate supply rate of 0.5 mL/min, and this was attributed to the nZVI@SiO2 particles giving an optimal Fe(II) release rate and therefore a high persulfate activation rate and a high phenol removal efficiency. Sustained persulfate activation induced by Fe(II) being slowly released was described well by single-stage first-order kinetics rather than two-stage first-order kinetics typical of unmodified nZVI/persulfate systems. Persulfate was found still to be activated by iron (oxyhydr)oxides minerals after the nZVI@SiO2 particles had been exhausted but the persulfate sustained activation induced by the slow release of Fe(II) played a crucial role in determining the overall degradation efficiency. The results highlight the importance of the slow release of Fe(II) from nZVI-based materials for in situ chemical oxidation through sustained persulfate activation.

[Clinical usefulness of bile cytology obtained from biliary drainage tube for diagnosing cholangiocarcinoma].

BACKGROUND/AIMS: Biliary drainage is performed in many patients with cholangiocarcinoma (CCA) to relieve obstructive jaundice. For those who have undergone biliary drainage, bile cytology can be easily performed since the access is already achieved. This study aims to determine the clinical usefulness of bile cytology for the diagnosis of CCA and to evaluate factors affecting its diagnostic yield. METHODS: A total of 766 consecutive patients with CCA underwent bile cytology via endoscopic nasobiliary drainage or percutaneous transhepatic biliary drainage from January 2000 to June 2012. Data were collected by retrospectively reviewing the medical records. We evaluated the diagnostic yield of bile cytology with/without other sampling methods including brush cytology and endobiliary forcep biopsy, and the optimal number of repeated bile sampling. Several factors affecting diagnostic yield were then analyzed. RESULTS: The sensitivity of bile cytology, endobiliary forceps biopsy, and a combination of both sampling methods were 24.7% (189/766), 74.4% (259/348), and 77.9% (271/348), respectively. The cumulative positive rate of bile sampling increased from 40.7% (77/189) at first sampling to 93.1% (176/189) at third sampling. On multivariate analysis, factors associated with positive bile cytology were perihilar tumor location, intraductal growing tumor type, tumor extent ≥ 20 mm, poorly differentiated grade tumor, and three or more samplings. CONCLUSIONS: Although bile cytology itself has a low sensitivity in diagnosing CCA, it has an additive role when combined with endobiliary forceps biopsy. Due to the relative ease and low cost, bile cytology can be considered a reasonable complementary diagnostic tool for diagnosing CCA.