Effects of water constituents on the stability of gas diffusion electrode during electrochemical hydrogen peroxide production for water and wastewater treatment.

Electrochemically producing hydrogen peroxide (H2O2) from oxygen reduction reaction (ORR) with natural air diffusion electrode (NADE) is an attractive way to supply H2O2 for decentralized water treatment. In this study, the stability of NADE during H2O2 electroproduction in varying water matrices were evaluated, including synthetic electrolyte solutions (0.05 M Na2SO4) with or without calcium ions (Ca2+, 200 mg/L) and/or humic acid (HA, 40 mg/L), as well as a selected municipal wastewater (92.7 mg/L Ca2+, 3.6 mg/L Mg2+, and 23.9 mg/L total organic carbon). The results show that NADEs maintained a good stability during H2O2 electroproduction in Na2SO4 solutions regardless of the presence of HA. However, Ca2+ (and Mg2+) could form significant amounts of mineral precipitates on the surface and in the internal pores of NADEs during H2O2 electroproduction. These mineral precipitates can negatively influence H2O2 production by impeding the oxygen, electron, and proton transfer processes involved in ORR to H2O2. Moreover, the mineral precipitates shifted the NADEs from hydrophobic to hydrophilic, which may promote H2O2 reduction to H2O at the NADEs. Consequently, the apparent current efficiencies of H2O2 production decreased substantially from initially ∼90% to 50%-70% as the NADEs were continuously used for 60 h in the Ca-containing solutions and selected wastewater. These results indicate that water constituents that are commonly present in real water matrices, especially Ca2+, can cause serious deterioration of NADE stability during H2O2 electroproduction. Therefore, proper strategies are needed to mitigate electrode fouling during H2O2 electroproduction with NADEs in practical water and wastewater treatment.

The complete chloroplast genome sequence of corn and economic analysis on production costs profits in Zhengzhou city.

Corn is one of the main food crops in China. The problem of corn production cost benefit has always been the most concerned issue of farmers. In this paper, economic analysis of corn production cost benefit is conducted, and the chloroplast genome sequence is studied. The complete chloroplast genome sequence of corn was characterized from Illumina pair-end sequencing. The chloroplast genome of corn was 140,382 bp in length, containing a large single-copy region (LSC) of 82,156 bp, a small single-copy region (SSC) of 15,952 bp, and two inverted repeat (IR) regions of 21,137 bp. The overall GC content is 36.80%, while the correponding values of the LSC, SSC, and IR regions are 34.5%, 30.5%, and 42.5%, respectively. The genome contains 118 complete genes, including 85 protein-coding genes (78 protein-coding gene species), 25 tRNA genes (19 tRNA species) and 8 rRNA genes (4 rRNA species). The Neighbour-joining phylogenetic analysis showed that corn and Zea mays cultivar B73 clustered together as sisters to other Zea species.

[Effects of 6-BA and AsA on photosynthesis photoinhibition of attached poplar leaves under osmotic stress of root].

In order to know more about the relationships between photosynthesis photoinhibition and reactive oxygen species metabolism, the effects of 6-benzyladenine (6-BA) and ascorbate (AsA) on net photosynthetic rate (Pn), apparent quantum yield (AQY), superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities, O2-* generation rate, and H2O2 and malondialdehyde (MDA) contents were studied with attached leaves of poplar clone seedlings under osmotic stress of root. Under osmotic stress, the photosynthesis photoinhibition of attached poplar leaves, judged by the significant decrease of Pn and AQY, was aggravated, and the balance of reactive oxygen species metabolism was destroyed. The superoxide dismutase (SOD) activity increased, but ascorbate peroxidase (APX) activity decreased. In the meantime, the O2-* generation rate and the contents of H2O2 and malondialdehyde (MDA) increased. When osmotic stressed poplar seedlings were pretreated with 6-BA and AsA, the activities of SOD and APX increased, O2-* generation rate and H2O2 and MDA contents decreased, and photosynthesis photoinhibition was alleviated. The contents of reactive oxygen species and MDA in poplar leaves were negatively correlated with net photosynthetic rate and apparent quantum yield. It's indicated that the photosynthesis photoinhibition of attached leaves of poplar clone seedlings had intrinsic relations with the accumulation of reactive oxygen species under osmotic stress of root, and the alleviation effects of 6-BA and AsA on photosynthesis photoinhibition were related to their promotion effects to the scavenging system of reactive oxygen species.