Molecular-level insights into the mitigation of magnesium-natural organic matter induced ultrafiltration membrane fouling by high-dose calcium based on DFT calculation.

While magnesium cation (Mg2+) universally coexists with natural organic matter (NOM) in the water environment, influence of Mg2+ on NOM fouling in membrane filtration process is still unclear. This work was therefore performed to investigate effects of Mg2+ on NOM (sodium alginate (SA) as a model substance) fouling and role of Ca2+ in mitigating fouling from Mg2+ in the ultrafiltration (UF) water treatment process. Filtration tests showed two interesting fouling phenomena: (1) membrane fouling caused by combination of Mg2+ and SA maintained at a high value with the increased Mg2+ concentration; (2) the high fouling property of Mg2+ can be significantly improved by the prominent addition of calcium cation (Ca2+). It was found that changes of foulant morphology played essential roles through thermodynamic mechanisms represented by the Flory-Huggins lattice theory. Density functional theory (DFT) calculation showed that the combination of SA and Mg2+ tends to coordinate two terminal carboxyl groups in SA, beneficial to stretching alginate chains and forming a stable gel network at low doses. In addition, intramolecular coordination is difficult to occur between SA and Mg2+ due to the high hydration repulsion radius of Mg2+. Therefore, a dense and thick gel network remained even under high Mg2+concentration. Furthermore, due to the higher binding affinity of Ca2+ over Mg2+, high doses of Ca2+ trigger a transition of the stable SA-Mg2+ gel network to other configurations where flocculation and aggregation occur, thereby reducing the specific filtration resistance. The proposed thermodynamic mechanism satisfactorily explained the above interesting fouling behaviors, facilitating to development of new solutions to control membrane fouling.

The biological performance of a novel microalgal-bacterial membrane photobioreactor: Effects of HRT and N/P ratio.

A microalgal-bacterial membrane photobioreactor (MB-MPBR) was developed for simultaneous COD and nutrients (N and P) removals from synthetic municipal wastewater in a single stage for a long-term operation over 350 days. The effects of hydraulic retention time (HRT) and N/P ratio on the biological performance were systematically evaluated for the first time. The results showed that a lower N/P ratio (3.9:1) and shorter HRT (2 d) promoted more biomass production, as compared to a high HRT (3 d) and a high N/P ratio (9.7:1). The highest biomass concentration (2.55 ± 0.14 g L-1) and productivity (127.5 mg L-1·d-1) were achieved at N/P ratio of 3.9:1 and HRT of 2 d due to the highest nitrogen and phosphorus loadings under such conditions. A COD and ammonia-N removal efficiency of over 96% and 99%, respectively, were achieved regardless of HRTs and N/P ratios. In the absence of nitrogen or phosphorus deficiency, shorter HRT (2 d) yielded a higher nitrogen and phosphorus uptake but lower removal efficiency. In addition, the imbalance N/P ratio (9.7:1) would decrease nitrogen or phosphorus removal. Overall, the results suggested that it was feasible to simultaneously achieve complete or high removal of COD, nitrogen, and phosphorous in MB-MPBR under the appropriate conditions. This study demonstrated for the first time that MB-MPBR is a promising technology that could achieve a high-quality effluent meeting the discharge standards of COD and nutrients in one single step.

Insight into the mechanisms for hexavalent chromium reduction and sulfisoxazole degradation catalyzed by graphitic carbon nitride: The Yin and Yang in the photo-assisted processes.

As robust polymeric catalysts, graphitic carbon nitride (g-C3N4) has been known to have great application potential in environmental remediation. However, the mechanisms in the photo-assisted catalytic processes during the reduction or oxidation of pollutants are still difficult to discern and therefore not well studied. In this work, visible-assisted catalytic reduction of hexavalent chromium (Cr(VI)) or oxidation of sulfisoxazole (SIZ) by g-C3N4 with the addition of formic acid (FA) or potassium peroxydisulfate (PS) were systematically investigated. Effects of operation parameters such as g-C3N4 dosage, FA concentration, Cr(VI) concentration, solution pH, PS concentration were studied. The results showed g-C3N4 can be effective and robust catalyst for both the reduction (Yin) and oxidation (Yang) reactions in the environmental remediation. Mechanisms were studied by using electron spin resonance (ESR) spectroscopy. The results revealed the CO 2- is the predominant radical for Cr(VI) reduction in the g-C3N4/FA/Vis system and the SO4- and OH are all the main radicals for the oxidation of SIZ in the g-C3N4/PS/Vis system. The photo-generated carriers by g-C3N4, act as radical initiator, were responsible for the production of the reactive radical species in aqueous solution. This work not only shed a new light on the application of semiconductor polymers for the removal of micropollutants and also will expand the applicability of the polymeric photocatalysts for environmental remediation.

Neuroprotective effects of Yiqihuoxue calm wind capsule on ischemic stroke in rats.

Stroke remains the third leading cause of death and of adult disability worldwide. Vascular occlusion, followed by ischemic cascade, leads to irreversible tissue injury. Recombinant tissue plasminogen activator is the only FDA approved drug for the current treatment of acute ischemic stroke. However, traditional Chinese medicine has a long history and rich clinical experience in the treatment and rehabilitation of ischemic stroke. Using a classical middle cerebral artery occlusion (MCAO) stroke model, we tested the effectiveness of Yiqihuoxue calm wind (YCW) capsule on neurological function, gross pathology and oxidative stress status in MCAO rats. YCW capsule (3.36 and 6.72 g·kg-1 of crude drug) could significantly lower Longa's score and superoxide dismutase (SOD) level, together with less necrotic cells and infarcted area. In addition to elevated MDA and downregulated iNOS expression, YCW capsule exhibited its neuroprotective effects via free radical scavenging and NO inhibition.

Interaction of green tea polyphenol epigallocatechin-3-gallate with sunitinib: potential risk of diminished sunitinib bioavailability.

Sunitinib, a novel oral multi-targeted tyrosine kinase inhibitor for patients with metastatic renal cell carcinoma (mRCC) and advanced gastrointestinal stromal tumor, has a good prospect for clinical application and is being investigated for the potential therapy of other tumors. We observed the phenomenon that drinking tea interfered with symptom control in an mRCC patient treated with sunitinib and speculated that green tea or its components might interact with sunitinib. This study was performed to investigate whether epigallocatechin-3-gallate (EGCG), the major constituent of green tea, interacted with sunitinib. The interaction between EGCG and sunitinib was examined in vitro and in vivo. (1)H nuclear magnetic resonance ((1)H-NMR) spectroscopy and mass spectrometry (MS) were used to analyze the interaction between these two molecules and whether a new compound was formed. Solutions of sunitinib and EGCG were intragastrically administered to rats to investigate whether the plasma concentrations of sunitinib were affected by EGCG. In this study, we noticed that a precipitate was formed when the solutions of sunitinib and EGCG were mixed under both neutral and acidic conditions. (1)H-NMR spectra indicated an interaction between EGCG and sunitinib, but no new compound was observed by MS. Sticky semisolid contents were found in the stomachs of sunitinib and EGCG co-administrated mice. The AUC(0-∞) and C (max) of plasma sunitinib were markedly reduced by co-administration of EGCG to rats. Our study firstly showed that EGCG interacted with sunitinib and reduced the bioavailability of sunitinib. This finding has significant practical implications for tea-drinking habit during sunitinib administration.