Peroxymonosulfate Activation by Facile Fabrication of α-MnO2 for Rhodamine B Degradation: Reaction Kinetics and Mechanism.

The persulfate-based advanced oxidation process has been an effective method for refractory organic pollutants' degradation in aqueous phase. Herein, α-MnO2 with nanowire morphology was facially fabricated via a one-step hydrothermal method and successfully activated peroxymonosulfate (PMS) for Rhodamine B (RhB) degradation. Influencing factors, including the hydrothermal parameter, PMS concentration, α-MnO2 dosage, RhB concentration, initial pH, and anions, were systematically investigated. The corresponding reaction kinetics were further fitted by the pseudo-first-order kinetic. The RhB degradation mechanism via α-MnO2 activating PMS was proposed according to a series of quenching experiments and the UV-vis scanning spectrum. Results showed that α-MnO2 could effectively activate PMS to degrade RhB and has good repeatability. The catalytic RhB degradation reaction was accelerated by increasing the catalyst dosage and the PMS concentration. The effective RhB degradation performance can be attributed to the high content of surface hydroxyl groups and the greater reducibility of α-MnO2, and the contribution of different ROS (reactive oxygen species) was 1O2 > O2·- > SO4·- > ·OH.

Distribution, risk assessment of heavy metals in sediments, and their potential risk on water supply safety of a drinking water reservoir, middle China.

Heavy metals in reservoir sediments were analyzed to assess the pollution level and to understand the potential risk on water supply safety. Heavy metals in sediments will enter the biological chain through bio-enrichment and bio-amplification in water and eventually pose a threat to the safety of drinking water supply. Analysis of eight sampling sites in JG (Jian gang) drinking water reservoir of the sediments showed that from Feb 2018 to Aug 2019 heavy metals including Pb, Ni, Cu, Zn, Mo, and Cr increased by 1.09-17.2%. Vertical distributions of heavy metals indicated that the concentrations increased gradually by 9.6-35.8%. Risk assessment code analysis indicated that Pb, Zn, and Mo were of high risk in the main reservoir area. What is more, enrichment factors of Ni and Mo were 2.76-3.81 and 5.86-9.41, respectively, showing the characteristics of exogenous input. The continuous monitoring results of the bottom water showed that the concentration of heavy metals in the bottom water exceeded the environmental quality standard value of surface water in China, and exceeded the standard by 1.76 times (Pb), 1.43 times (Zn), and 2.04 times (Mo), respectively. Heavy metals in the sediments of JG Reservoir, especially in the main reservoir area, have a potential risk of release from the sediment to the overlying water. Water supply reservoir as a source of drinking water, its quality is directly related to human health and production activities. Therefore, this first study on JG Reservoir is of great significance for the protection of drinking water safety and human health.

Catalytic Gasification of Sewage Sludge in Supercritical Water: Influence of K2CO3 and H2O2 on Hydrogen Production and Phosphorus Yield.

In this work, the catalytic gasification of sewage sludge in supercritical water was investigated in a batch reactor (460 °C, 27 MPa, 6 min), and the separate and combined effects of the catalyst on the H2 production and phosphorus yield were investigated. The experimental results indicated that K2CO3 alone improved the H2 yield, gasification efficiency (GE), and carbon gasification efficiency (CE). The largest H2 yield of 54.28 mol/kg was achieved, which was approximately three times that without a catalyst. Furthermore, the inorganic phosphorus (IP) yield increased with the addition of K2CO3. However, when H2O2 was added, the H2 yield quickly decreased with increasing H2O2 coefficient, and more than 97.8% of organic phosphorus (OP) was converted into IP. The H2 yield increased with the addition of various K2CO3/H2O2 ratios, whereas the IP yield decreased.

Zinc-iron silicate for heterogeneous catalytic ozonation of acrylic acid: efficiency and mechanism.

This research aimed at researching the degradation of acrylic acid (AA) in aqueous solution, by catalytic and non-catalytic ozonation processes performed in a semi-continuous reactor. Zinc-iron silicate was synthesized and characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) analysis, Fourier transformation infrared (FT-IR) and energy dispersive spectrometry (EDS). The characterization studies showed that Fe-Si binary oxide, Zn-Si binary oxide, ZnO and Fe2O3 deposits were formed on the surface of poor crystallinity zinc-iron silicate which contained abundant functional groups. Catalytic ozonation test results revealed that zinc-iron silicate exhibited high catalytic activity and stability in catalytic ozonation of AA in aqueous solution. The inclusion of zinc-iron silicate in the ozonation process enhanced AA decomposition by 28.7% and TOC removal by 20%, compared to the ozonation alone. The main AA removal mechanisms involved direct oxidation by ozone and indirect oxidation by hydroxyl radicals generated by the ozone chain reaction accelerated by zinc-iron silicate. The surface characteristics and chemical composition are significant factors determining the catalytic activity of zinc-iron silicate.

Field Research on Mixing Aeration in a Drinking Water Reservoir: Performance and Microbial Community Structure.

Field research on the performance of pollutant removal and the structure of the microbial community was carried out on a drinking water reservoir. After one month of operation of a water-lifting aeration system, the water temperature difference between the bottom and the surface decreased from 9.9 to 3.1 °C, and the concentration of the dissolved oxygen (DO) in the bottom layer increased from 0 to 4.2 mg/L. The existing stratification in the reservoir was successfully eliminated. Total nitrogen (TN), total phosphorus (TP), and total organic carbon (TOC) concentrations were reduced by 47.8%, 66.7%, and 22.9%, respectively. High-throughput sequencing showed that Proteobacteria, Bacteroides, and Actinomycetes accounted for 67.52% to 78.74% of the total bacterial population. Differences in the bacterial changes were observed between the enhanced area and the control area. With the operation of the water-lifting aeration system, the populations of bacteria of the main genera varied temporally and spatially. Principal component analysis pointed out a clear evolution in the vertical distribution of the microbial structure controlled by the operation of the aeration system. Permutational analysis of variance showed a significant difference in the microbial community (p < 0.01). Redundancy analysis showed that physical (water temperature, DO) and chemical environmental factors (Chl-a, TOC, TN) were the key factors affecting the changes in the microbial communities in the reservoir water. In addition, a hierarchical partitioning analysis indicated that T, Chl-a, ORP, TOC, pH, and DO accounted for 24.1%, 8.7%, 6.7%, 6.2%, 5.8%, and 5.1% of such changes, respectively. These results are consistent with the ABT (aggregated boosted tree) analysis for the variations in the functional bacterial community, and provide a theoretical basis for the development and application of biotechnology.

Baseline Characteristics and Treatment Patterns of the Patients Recruited to the China Registry of Hepatitis B.

Background and Aims: Chronic hepatitis B virus (HBV) infection remains a major public health problem globally. Here, we describe the baseline characteristics and treatment profiles of HBV-infected patients recruited to the China Registry of Hepatitis B. Methods: Inclusion criteria were patients with different stages of chronic HBV infection and complete key data. Exclusion criteria were patients with hepatocellular carcinoma. The baseline clinical, laboratory and treatment profiles were analyzed. Results: Finally, 40,431 patients were included. The median age was 43 years, with 65.2% being men and 51.3% being positive for hepatitis B e antigen (HBeAg). The most common initial diagnosis was chronic hepatitis B (81.0%), followed by cirrhosis (9.3%), inactive carrier of hepatitis B surface antigen (HBsAg) (6.7%), and immune tolerant phase of hepatitis B infection (3.0%). Among the 21,228 patients who were on treatment, 88.0%, 10.0% and 2.0% received nucleos(t)ide analogues (NAs), interferon or combination of NAs and interferon, respectively. The proportion of patients who received preferred NAs (entecavir or tenofovir disoproxil fumarate) had increased from 13.5% in 2003 to 79.7% in 2016. Conclusions: We concluded that middle-aged men accounted for most of the patients with chronic hepatitis B in this cross-sectional study. About half of the patients were HBeAg-positive. NAs were the most commonly used therapy, and use of the preferred NAs had steadily increased in the past decade.

Degradation of landfill leachate using transpiring-wall supercritical water oxidation (SCWO) reactor.

Oxidation of landfill leachate wastewater was studied in a transpiring-wall SCWO reactor, operated under varied temperature and pressure 320-430 °C, 18-30 MPa. Effect of temperature and pressure on COD and BOD removal efficiency was investigated. COD and BOD removal efficiency being 99.23%, 98.06% were achieved at 430 °C, 30 MPa, which increased with temperature and pressure. The modified pseudo first-order rate model was regressed from experimental data, taking into account the induction time (t(ind)) effect. The resulting pre-exponential factor A and activation energy E(a) were 34.86 s(-1) and 32.1 kJ mol(-1), respectively, assuming that the reaction order for feed wastewater (based on COD) and oxidant were first order and zero order, respectively.

Oxidation of industrial dyeing wastewater by supercritical water oxidation in transpiring-wall reactor.

Industrial dyeing wastewater was oxidized in supercritical water in a transpiring-wall reactor, using hydrogen peroxide as an oxidant. Experiments were performed at 595 to 704 K and 18 to 30 MPa, with an oxidant dosage ratio ranging from 0.6 to 2.0. A chemical oxygen demand (COD) removal of more than 98.4% was achieved at 704 K and 28 MPa, with a retention time less than 35 seconds, which increased with the temperature, pressure, and oxidant. A modified first-order rate expression was regressed from experimental data, taking into account the influence of induction time. The resulting pre-exponential factor, A, and activation energy, Ea, were 1.07 seconds(-1) and 12.12 kJ x mol(-1), respectively, while the reaction order for feed wastewater (based on COD) and oxidant were assumed to be 1 and 0, respectively. Gas chromatography/mass spectrometry analysis for effluents indicated that carbon dioxide, carbon monoxide, and nitrogen were the main reaction products, and phenol; benzenecarboxylic acid; 1, 2-benzenedicarboxylic acid; and isoquinoline were detected as intermediates.