Vanadium(V) is an emerging contaminant in the most recent Environmental Protection Agency’s candidate contaminant list (CCL4). The redox chemistry of vanadium controls its occurrence in the aquatic ...environment, but the impact of vanadium(V) speciation on the redox properties remains largely unknown. This study utilized the rotating ring-disk electrode technique to examine the reduction kinetics of four pH- and concentration-dependent vanadium(V) species in the presence and the absence of phosphate. Results showed that the reduction of VO2 +, H x V4O12+x (4+x)– (V4), and HVO4 2– proceeded via a one-electron transfer, while that of Na x H y V10O28 (6–x–y)– (V10) underwent a two-electron transfer. Koutecky–Levich and Tafel analyses showed that the intrinsic reduction rate constants followed the order of V10 > VO2 + > V4 > HVO4 2–. Ring-electrode collection efficiency indicated that the reduction product of V10 was stable, while those of VO2 +, HVO4 2–, and V4 had short half-lives that ranged from milliseconds to seconds. With molar ratios of phosphate to vanadium(V) varying from 0 to 1, phosphate accelerated the reduction kinetics of V10 and V4 and enhanced the stability of the reduction products of VO2 +, V4, and HVO4 2–. This study suggests that phosphate complexation could enhance the reductive removal of vanadium(V) and inhibit the reoxidation of its reduction product in water treatment.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Persulfate (S2O8 2–)-based in situ chemical oxidation (ISCO) has gained more attention in recent years due to the generation of highly reactive and selective sulfate radical (SO4 •–). This study ...examined the effects of important groundwater chemical parameters, i.e., alkalinity, pH, and chloride on benzene degradation via heterogeneous persulfate activation by three Fe(III)- and Mn(IV)-containing aquifer minerals: ferrihydrite, goethite, and pyrolusite. A comprehensive kinetic model was established to elucidate the mechanisms of radical generation and mineral surface complexation. Results showed that an increase of alkalinity up to 10 meq/L decreased the rates of persulfate decomposition and benzene degradation, which was associated with the formation of unreactive surface carbonato complexes. An increase in pH generally accelerated persulfate decomposition due to enhanced formation of reactive surface hydroxo complexation. A change in the chloride level up to 5 mM had a negligibly effect on the reaction kinetics. Kinetics modeling also suggested that SO4 •– was transformed to hydroxyl radical (HO•) and carbonate radical (CO3 •–) at higher pHs. Furthermore, the yields of two major products of benzene oxidation, i.e., phenol and aldehyde, were positively correlated with the branching ratio of SO4 •– reacting with benzene, but inversely correlated with that of HO• or CO3 •–, indicating that SO4 •– preferentially oxidized benzene via pathways involving fewer hydroxylation steps compared to HO• or CO3 •–.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Long non-coding RNA (lncRNA) was originally defined as the representative of the non-coding RNAs and unable to encode. However, recent reports suggest that some lncRNAs actually contain open reading ...frames that encode peptides. These coding products play important roles in the pathogenesis of many diseases. Here, we summarize the regulatory pathways of mammalian lncRNA-encoded peptides in influencing muscle function, mRNA stability, gene expression, and so on. We also address the promoting and inhibiting functions of the peptides in different cancers and other diseases. Then we introduce the computational predicting methods and data resources to predict the coding ability of lncRNA. The intention of this review is to provide references for further coding research and contribute to reveal the potential prospects for targeted tumor therapy.
Persulfate (S2O8 2–) is being used increasingly for in situ chemical oxidation (ISCO) of organic contaminants in groundwater, despite an incomplete understanding of the mechanism through which it is ...converted into reactive species. In particular, the decomposition of persulfate by naturally occurring mineral surfaces has not been studied in detail. To gain insight into the reaction rates and mechanism of persulfate decomposition in the subsurface, and to identify possible approaches for improving its efficacy, the decomposition of persulfate was investigated in the presence of pure metal oxides, clays, and representative aquifer solids collected from field sites in the presence and absence of benzene. Under conditions typical of groundwater, Fe(III)- and Mn(IV)-oxides catalytically converted persulfate into sulfate radical (SO4 •–) and hydroxyl radical (HO•) over time scales of several weeks at rates that were 2–20 times faster than those observed in metal-free systems. Amorphous ferrihydrite was the most reactive iron mineral with respect to persulfate decomposition, with reaction rates proportional to solid mass and surface area. As a result of radical chain reactions, the rate of persulfate decomposition increased by as much as 100 times when benzene concentrations exceeded 0.1 mM. Due to its relatively slow rate of decomposition in the subsurface, it can be advantageous to inject persulfate into groundwater, allowing it to migrate to zones of low hydraulic conductivity where clays, metal oxides, and contaminants will accelerate its conversion into reactive oxidants.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Dissolved organic nitrogen (DON) accounts for a large fraction of the total nitrogen discharged to surface waters by municipal wastewater treatment plants designed for biological nutrient removal ...(BNR). Previous research indicates that some but not all of the DON in wastewater effluent is available to bacteria and algae over time scales that are relevant to rivers and estuaries. To separate bioavailable DON from nitrate and less reactive DON species, an XAD-8 resin coupled with an anion exchange treatment was employed prior to chemical analysis and algal bioassays. Analysis of effluent samples from a range of municipal BNR plants (total DON concentrations ranging from 0.7 to 1.8 mg N/L) employing a range of technologies indicated that hydrophilic DON, which typically accounted for approximately 80% of the total DON, stimulated algal growth, whereas hydrophobic DON, which accounted for the remaining DON, remained at nearly constant concentrations and had little or no effect on algal growth during a 14-day incubation period. The hydrophobic DON exhibits characteristics of humic substances, and is likely to persist for long periods in the aquatic environment. The distinct differences between these two classes of DON may provide a basis for considering them separately in water quality models and effluent discharge regulations.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
With the ability to switch transform the mechanical stimuli of epidermal deformations to electrical signals, epidermal strain sensors can be widely applied to monitor physiological signals, detect ...body movements and control robots. Epidermal strain sensors are required to conform to the human body under complex motions typically from tiny epidermal deformations (<1% strain) to large body movements (10–75% strain). In this study, a compliant, self-adhesive and self-healing epidermal strain sensor was fabricated with the addition of polydopamine into polyvinyl alcohol hydrogel. Due to the compliant and self-adhesive characteristics, the as-prepared strain sensors can fix well onto the epidermis without adhesive tape, perceiving extremely gentle deformations (0.1% strain), such as pulse beats, vibration of the throat, and facial expression changes. This highly stretchable strain sensor can also monitor the large motions (up to 500% strain) of legs and fingers. Moreover, owing to the reversible boron ester bond, the hydrogel has super self-healablity (self-healed in 250 ms at ambient temperature, 25 °C), which makes our sensors more humanoid. At last, thanks to its excellent ability to detect a large range of strains, the self-healing epidermal strain sensor is effective in monitoring physiological signals and body movements.
A sequential combination of membrane treatment and UV-based advanced oxidation processes (UV/AOP) has become the industry standard for potable water reuse. Chloramines are used as membrane ...antifouling agents and therefore carried over into the UV/AOP. In addition, persulfate (S2O8 2–) is an emerging oxidant that can be added into a UV/AOP, thus creating radicals generated from both chloramines and persulfate for water treatment. This study investigated the simultaneous photolysis of S2O8 2– and monochloramine (NH2Cl) on the removal of 1,4-dioxane (1,4-D) for potable-water reuse. The dual oxidant effects of NH2Cl and S2O8 2– on 1,4-D degradation were examined at various levels of oxidant dosage, chloride, and solution pH. Results showed that a NH2Cl-to-S2O8 2– molar ratio of 0.1 was optimal, beyond which the scavenging by NH2Cl of HO•, SO4 •–, and Cl2 •– radicals decreased the 1,4-D degradation rate. At the optimal ratio, the degradation rate of 1,4-D increased linearly with the total oxidant dose up to 6 mM. The combined photolysis of NH2Cl and S2O8 2– was sensitive to the solution pH due to a disproportionation of NH2Cl at pH lower than 6 into less-photoreactive dichloramine (NHCl2) and radical scavenging by NH4 +. The presence of chloride transformed HO• and SO4 •– to Cl2 •– that is less-reactive with 1,4-D, while the presence of dissolved O2 promoted gaseous nitrogen production. Results from this study suggest that the presence of chloramines can be beneficial to persulfate photolysis in the removal of 1,4-D; however, the treatment efficiency depends on a careful control of an optimal NH2Cl dosage and a minimal chloride residue.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Solar thermophotovoltaics (STPV), which utilizes the full spectrum of solar energy, possesses a high theoretical system efficiency of 85.4% that well beats the Shockley-Queisser limit of traditional ...photovoltaics. However, the experimental efficiency reported so far is still less than 10% due to a variety of optical and/or thermal losses. Based on the system efficiency analysis, we first summarize the key components of ideal STPV, which can be divided into the material/structure level and system level. We then introduce new types of solar powered thermophotovoltaics and hybrid STPV systems integrated with other energy conversion systems. A perspective is provided at the end to discuss the challenges and opportunities.
Sulfate radical (SO4 •‑) is a strong, short-lived oxidant that is produced when persulfate (S2O8 2–) reacts with transition metal oxides during in situ chemical oxidation (ISCO) of contaminated ...groundwater. Although engineers are aware of the ability of transition metal oxides to activate persulfate, the operation of ISCO remediation systems is hampered by an inadequate understanding of the factors that control SO4 •– production and the overall efficiency of the process. To address these shortcomings, we assessed the stoichiometric efficiency and products of transition metal-catalyzed persulfate oxidation of benzene with pure iron- and manganese-containing minerals, clays, and aquifer solids. For most metal-containing solids, the stoichiometric efficiency, as determined by the loss of benzene relative to the loss of persulfate, approached the theoretical maximum. Rates of production of SO4 •– or hydroxyl radical (HO•) generated from radical chain reactions were affected by the concentration of benzene, with rates of S2O8 2– decomposition increasing as the benzene concentration increased. Under conditions selected to minimize the loss of initial transformation products through reaction with radicals, the production of phenol only accounted for 30%–60% of the benzene lost in the presence of O2. The remaining products included a ring-cleavage product that appeared to contain an α,β-unsaturated aldehyde functional group. In the absence of O2, the concentration of the ring-cleavage product increased relative to phenol. The formation of the ring-cleavage product warrants further studies of its toxicity and persistence in the subsurface.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
PDF
