Rice powder template for hausmannite Mn3O4 nanoparticles and its application to aqueous zinc ion battery.

In this study, a simple calcination route was adopted to prepare hausmannite Mn3O4 nanoparticles using rice powder as soft bio-template. Prepared Mn3O4 was characterized by Fourier Transform Infra-Red Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray microanalysis (EDX), Powder X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET) and Solid state UV-Vis spectroscopic techniques. Mn-O stretching in tetrahedral site was confirmed by FTIR and Raman spectra. % of Mn and O content supported Mn3O4 formation. The crystallinity and grain size was found to be 68.76% and 16.43 nm, respectively; tetragonal crystal system was also cleared by XRD. TEM clarified the planes of crystal formed which supported the XRD results and BET demonstrated mesoporous nature of prepared Mn3O4 having low pore volume. Low optical band gap of 3.24 eV of prepared Mn3O4 nanoparticles indicated semiconductor property and was used as cathode material to fabricate CR-2032 coin cell of Aqueous Rechargeable Zinc Ion Battery (ARZIB). A reversible cyclic voltammogram (CV) showed good zinc ion storage performance. Low cell resistance was confirmed by Electrochemical Impedance Spectroscopy (EIS). The coin cell delivered high specific discharge capacity of 240.75 mAhg-1 at 0.1 Ag-1 current density. The coulombic efficiency was found to be 99.98%. It also delivered excellent capacity retention 94.45% and 64.81% after 300 and 1000 charge-discharge cycles, respectively. This work offers a facile and cost effective approach for preparing cathode material of ARZIBs.

Health Risk Assessment and Comparative Studies on Some Fish Species Cultured in Traditional and Biofloc Fish Farms.

The present study aimed at (a) determining the concentration of macro-minerals and toxic metals in fish species collected from biofloc and traditional fish farms; (b) assessing the contribution of macro-minerals to our daily diet; and (c) evaluating the health risks of children and adults based on the US Environmental Protection Agency (USEPA) deterministic model. Significantly higher concentrations of macro-minerals and significantly lower levels of toxic metals (at < 0.05 level) were found in most of the biofloc fish species compared to the market fish samples. The values of the target hazard quotient (THQ) were less than 1.0 for all individual trace metals in all species, which indicated that there were no noncarcinogenic health risks. Furthermore, the value of the hazard index (HI) in three samples of Tilapia from the market exceeded the recommended value of 1.0, while all samples from the biofloc fish tank were within the maximum tolerable limit, which suggested that the daily consumption of Tilapia fishes from the market may result in considerable harmful effects. Target cancer risk (TCR) for Pb in all of the studied samples was within the range of 10-6 and 10-4, hence the adults and children would not experience any kinds of carcinogenic effects. The result obtained from this comparative study revealed that the consumption of fish species from both local market and biofloc fish farms was almost safe, but the value of TCR in Pb was higher in traditional fish samples than that of biofloc tanks, hence fish samples from biofloc farms were more suitable for consumption.