Release characteristics of heavy metals from electrolytic manganese residue under varying environmental factors.

High levels of manganese (Mn) and other heavy metals from electrolytic manganese residue (EMR) stockpiled would be released into the environment under natural conditions. A batch-leaching test was carried out to investigate the release characteristics of heavy metals from EMR with different storage times under simulated environmental conditions such as acid rain with different pH (3.0, 4.5, 5.6, and 7.0) at contact times of 1, 2, 4, 6, and 12 h; liquid to solid ratio (L/S) (5:1, 10:1, 20:1, and 30:1); and temperature (15, 25, 35, and 45 °C). The results showed that low pH (3.0 and 4.5) and high temperature (35 and 45 °C) could significantly promote heavy metal leaching from EMRs and increasing the L/S ratio above 20:1 mL/g significantly decreased heavy metal leachate concentrations due to dilution effect. Cr, Mn, and Pb concentrations in leachate increased almost continuously throughout the leaching process, while Zn decreased slightly at the 12th hour. Meanwhile, heavy metal concentrations in EMR1 (fresh EMR) were higher than in EMR2 (out stockpiled for more than 3 months). The concentrations of Mn, Pb, and Zn in leachates from EMRs at pH 3.0 and 4.5 leaching far exceeded the allowable maximum discharge concentrations for pollutants of the integrated wastewater discharge standard in China (GB8978-1996) by 57.5-59.0, 1.3-4.3, and 1.1-1.8 and 53.5-56.0, 3.04-7.25, and 1.0-1.91 times, respectively. Additionally, the Mn concentrations from both EMR leachates at pH 7.0 were above the national safe emission threshold. The morphological structure of EMRs changed after leaching, and XRD analysis showed the disappearance of MnO2, SiO2, FeS2, and CaSO4. The XPS revealed that Cr, Mn, Pb, and Zn existed as Cr3+, MnO, PbSO4, and ZnSiO3, respectively, after leaching. The study concluded that Mn, Pb, and Zn from EMRS leached by acid rain might pose a high potential environmental risk. Therefore, developing appropriate disposal techniques for EMR is necessary to prevent heavy metal pollution.

Insights into the Luminescence Thermochromism of a Triarylboron Derivative: The Role of Intramolecular Group Interaction.

The organic fluorescent probes for temperature have received increasing interest due to their extremely high spatial and temporal resolution. A few of triarylboron derivatives, as almost the only molecular probes consisting of a single luminophore, have the ability to change their luminescent color at different temperatures. The mechanism of their luminescence thermochromism is controversial. Herein, several spectral experiments, along with time-dependent density functional theory (TDDFT) and coupled-cluster (CC) calculations, are carried out to elucidate the temperature-dependent luminescence. The CC rather than the TDDFT methods give a relatively reasonable explanation for the experimental results. Consequently, the thermochromism is now considered as the result of conformational thermal equilibria that occur in both the excited and ground states. Besides, an unusual conformer with intramolecular excimer characteristic plays a crucial role in the attractive luminescence behavior.

Pasteurization of fruit juices of different pH values by combined high hydrostatic pressure and carbon dioxide.

The inactivation of the selected vegetative bacteria Escherichia coli, Listeria innocua, and Lactobacillus plantarum by high hydrostatic pressure (HHP) in physiological saline (PS) and in four fruit juices with pHs ranging from 3.4 to 6.3, with or without dissolved CO(2), was investigated. The inactivation effect of HHP on the bacteria was greatly enhanced by dissolved CO(2). Effective inactivation (>7 log) was achieved at 250 MPa for E. coli and 350 MPa for L. innocua and L. plantarum in the presence of 0.2 M CO(2) at room temperature for 15 min in PS, with additional inactivation of more than 4 log for all three bacteria species compared with the results with HHP treatment alone. The combined inactivation by HHP and CO(2) in tomato juice of pH 4.2 and carrot juice of pH 6.3 showed minor differences compared with that in PS. By comparison, the combined effect in orange juice of pH 3.8 was considerably promoted, while the HHP inactivation was enhanced only to a limited extent. In another orange juice with a pH of 3.4, all three strains lost their pressure resistance. HHP alone completely inactivated E. coli at relatively mild pressures of 200 MPa and L. innocua and L. plantarum at 300 MPa. Observations of the survival of the bacteria in treated juices also showed that the combined treatment caused more sublethal injury, which increased further inactivation at a relatively mild pH of 4.2 during storage. The results indicated that the combined treatment of HHP with dissolved CO(2) may provide an effective method for the preservation of low- or medium-acid fruit and vegetable juices at relatively low pressures. HHP alone inactivated bacteria effectively in high-acid fruit juice.

Inactivation of Staphylococcus aureus and Escherichia coli by the synergistic action of high hydrostatic pressure and dissolved CO2.

This study focused on the synergistic inactivation effects of combined treatment of HHP and dissolved CO2 on microorganisms. The aim was to reduce the treatment pressure of the traditional HHP technology and make it more economically feasible. The combined treatment showed a strong bactericidal effect on Staphylococcus aureus and Escherichia coli in liquid culture, which usually have high levels of barotolerance under pressure alone. To identify the influence of CO2, a new setup to dissolve, retain and measure the concentration of CO2 was constructed. The results demonstrated that an inactivation rate of more than 8 log units was obtained for E. coli both at 300 MPa with 1.2 NL/L CO2 and at 250 MPa with 3.2 NL/L CO2, while only 2.2 and 1.8 log reductions were observed at 300 MPa and 250 MPa, respectively, for the HHP treatments alone. For S. aureus, the inactivation rate of more than 7 log units was found at 350 MPa with 3.8 NL/L CO2, while only a 0.9 log reduction was achieved at this pressure in the absence of CO2. The SEM photographs showed seriously deformed cells after the synergistic treatments. In contrast, the cells treated with individual HHP maintained a relatively smooth surface with invaginations. Propidium iodide staining and fluorescence observation was performed after pressure treatments. The results demonstrated that the combination of CO2 with HHP also promoted pressure induced cell membrane permeabilization greatly. It was deduced that the enrichment of CO2 on the cell surface and its penetration into the cells at high pressure accounted for the membrane damage and cell death.

Fluorescence detection of total count of Escherichia coli and Staphylococcus aureus on water-soluble CdSe quantum dots coupled with bacteria.

The aim of this paper was to demonstrate a fluorescence measurement method for rapid detection of two bacterial count by using water-soluble quantum dots (QDs) as a fluorescence marker, and spectrofluorometer acted as detection apparatus, while Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were as detection target bacteria. Highly luminescent water-soluble CdSe QDs were first prepared by using thioglycolic acid (TGA) as a ligand, and were then covalently coupled with target bacteria. The bacterial cell images were obtained using fluorescence microscopy. Our results showed that CdSe QDs prepared in water phase were highly luminescent, stable, and successfully conjugated with E. coli and S. aureus. The fluorescence method could detect 10(2)-10(7)CFU/mL total count of E. coli and S. aureus in 1-2h and the low detection limit is 10(2)CFU/mL. A linear relationship of the fluorescence peak intensity and log total count of E. coli and S. aureus have been established using the equation Y=118.68X-141.75 (r=0.9907).

[Determination of 1-deoxynojirimycin in Morus alba L. leaves using reversed-phase high performance liquid chromatography fluorescence detection with pre-column derivatization].

A rapid, reliable and suitable method for the determination of 1-deoxynojirimycin (DNJ) in Morus alba L. leaves has been developed. The DNJ in 100 mg dried leaves was extracted twice with 10 mL aqueous 0.05 mol/L HCl, then derivatized by 6-aminoquinoiyi-N-hydroxysuccinimidyl carbamate (AQC) in K3BO3 buffer (pH 8.5), and analyzed using a high performance liquid chromatograph equipped with a fluorescence detector. The analyte was eluted with a mobile phase of 0.02 mol/L potassium dihydrogen phosphate buffer-acetonitrile (85: 15, v/v) at the rate of 1.0 mL/min. The derivatized DNJ was well dissolved from the hydrolysis products of AQC. The linearity ranged from 0.5 to 25 mg/L, and the detection limit was 0.02 mg/L (S/N = 3). The content of DNJ in Morus alba L. leaves was 0.12%, the recovery was 96.1%-98.6%.