Facile Designed Manganese Oxide/Biochar for Efficient Salinity Gradient Energy Recovery in Concentration Flow Cells and Influences of Mono/Multivalent Ions.

Development of effective, environmentally friendly, facile large-scale processing, and low-cost materials is critical for renewable energy production. Here, MnOx/biochar composites were synthesized by a simple pyrolysis method and showed high performance for salinity gradient (SG) energy harvest in concentration flow cells (CFCs). The peak power density of CFCs with MnOx/biochar electrodes was up to 5.67 W m-2 (ave. = 0.91 W m-2) and stabilized for 500 cycles when using 1 and 30 g L-1 NaCl, which was attributed to their high specific capacitances and low electrode resistances. This power output was higher than all other reported MnO2 electrodes for SG energy harvest due to the synergistic effects between MnOx and biochar. When using a mixture with a molar fraction of 90% NaCl and 10% KCl (or Na2SO4, MgCl2, MgSO4, and CaCl2) in both feed solutions, the peak power density decreased by 2.3-40.1% compared to 100% NaCl solution with Ca2+ and Mg2+ showing the most pronounced negative effects. Our results demonstrated that the facile designed MnOx/biochar composite can be used for efficient SG energy recovery in CFCs with good stability, low cost, and less environmental impacts. When using natural waters as the feed solutions, pretreatment would be needed.

Differences in quinone redox system of humic substances between endemic and disease-free areas in Kashin-Beck disease-affected Changdu Region, Tibet, China.

Kashin-Beck disease (KBD) is an endemic disease in China with the highest incidence rate in Tibet region. Promoted generation of oxygen free radicals by semiquinone structure of humic substance (HS) in drinking water was considered to be one of its pathogeneses. Therefore, detailed analysis of HS was performed in water and sediment samples collected from three endemic and three disease-free areas in Changdu Region, Tibet, China. After purification of the HS in the samples, the fractions of HS were characterized using electron paramagnetic resonance, 13C nuclear magnetic resonance, fluorescence spectroscopy with parallel factor analysis and Fourier transform infrared spectroscopy (FTIR). The organic carbon content of HS did not show a significant difference between endemic and disease-free areas or correlation with KBD-associated morbidity. Except FTIR, all techniques succeeded in characterization of the quinone redox system, indicating their validity and consistency. The quinone redox system in aquatic HS exhibited significantly higher level of the following indexes in endemic areas than disease-free areas: semiquinone radical content of fulvic acid (FA) (p < 0.05), aromaticity of FA (p < 0.05), fluorescence intensity (per gram carbon) of reduced quinone-like component of FA (p < 0.05) and humic acid (HA) (p < 0.1). Semiquinone radical content (r = 0.781, p < 0.1), aromaticity of FA (r = 0.891, p < 0.05), intensity of oxidized quinone-like component (r = 0.875, p < 0.05) and reduced quinone-like component of FA (r = 0.793 p < 0.1) showed medium to strong correlation with KBD-associated morbidity. Generally, the content of reduced quinone and aquatic FA showed stronger differences between endemic and disease-free areas than oxidized quinone and aquatic HA, respectively. The quinone redox system in sediment HS did not show any significant relationship with KBD. The present study is a successful attempt to combine the three indexes, semiquinone radical content, aromaticity and fluorescence intensity, in characterizing quinone redox system in HS, facilitating more comprehensive understanding of the characteristics of HS in KBD-affected regions.

Pseudocapacitive Behaviors of Polypyrrole Grafted Activated Carbon and MnO2 Electrodes to Enable Fast and Efficient Membrane-Free Capacitive Deionization.

Capacitive deionization (CDI) has emerged as a promising technique for brackish water desalination. Here, composites of polypyrrole grafted activated carbon (Ppy/AC) were prepared via in situ chemical oxidative polymerization of pyrrole on AC particles. The Ppy/AC cathode was then coupled with a MnO2 anode for desalination in a membrane-free CDI cell. Both the Ppy/AC and MnO2 electrodes exhibited pseudocapacitive behaviors, which can selectively and reversibly intercalate Cl- (Ppy/AC) and Na+ (MnO2) ions. Compared to AC electrodes, the specific capacitances of Ppy/AC electrodes increased concurrently with the pyrrole ratios from 0 to 10%, while the charge transfer and ionic diffusion resistances decreased. As a result, the 10%Ppy/AC-MnO2 cell showed a maximum salt removal capacity of 52.93 mg g-1 (total mass of active materials) and 34.15 mg g-1 (total mass of electrodes), which was higher than those of conventional, membrane, and hybrid CDI cells. More notably, the salt removal rate of the 10%Ppy/AC-MnO2 cell (max 0.46 mg g-1 s-1 to the total mass of active materials and 0.30 mg g-1 s-1 to the total mass of electrodes) was nearly 1 order of magnitude higher than those in most previous CDI studies, and this fast and efficient desalination performance was stabilized over 50 cycles.

Pharmaceuticals and personal care products in water, sediments, aquatic organisms, and fish feeds in the Pearl River Delta: Occurrence, distribution, potential sources, and health risk assessment.

This study investigated the occurrence, distribution, and potential sources of 34 pharmaceuticals and personal care products (PPCPs) in water, sediments, aquatic organisms (fish and shellfish), and fish feeds from the mariculture areas of the Pearl River Delta (PRD). The health risk presented by this class of compounds was also assessed in relation to their intake via seafood consumption. Of the 34 PPCPs, a total of 9, 21, 14, and 28 PPCPs were detected in water, sediments, fish feeds, and aquatic organisms, respectively. Trimethoprim, norfloxacin, ofloxacin, and spectinomycin were detected in all matrices. The levels of PPCPs in water and sediment samples were relatively low. Spectinomycin, paracetamol, ciprofloxacin, norfloxacin, and ibuprofen were the most frequently detected PPCPs in feeds. Ibuprofen and ketoprofen were widely detected in aquatic organisms, with average concentrations of 562 and 267 ng/g wet weight, respectively. The residual levels of PPCPs in shellfish such as ME (mussel, Mytilus edulis) and OS (oyster, Ostrea gigas) were significantly higher (p < 0.05) than those in other species including CA (topmouth culter, Culter alburnus) and EO (orbfish, Ephippus orbis). Correlation analysis indicated that the medicated feeds were a potential source of PPCPs in the mariculture areas of the PRD, but other anthropogenic sources should not be ignored. Based on maximum residue limits and acceptable daily intake, the health risks presented to humans via seafood consumption are negligible. However, as multiple antibiotics were frequently detected in the mariculture environment, aquatic organisms, and feeds, the induction and dissemination of antimicrobial resistance associated with antibiotic usage in aquaculture would be of great concern. It is necessary to establish a centralized management system and control the use of veterinary drugs in mariculture to protect the aquaculture environment and ensure the safety of seafood.