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Microorganisms play an important role in immobilizing and detoxifying excessive Mn; however, there is so far a lack of sufficient information concerning highly Mn(II)-tolerant bacteria. The present study was conducted to analyze the bio-sorption characteristics of a strain (HM8) isolated from manganese ore wastes. Analytical data from the 16S rDNA sequence determination showed that the species, HM8, had a 99% similarity to Ralstonia pickettii. Results from the designed physiological, biochemical and isothermal adsorption tests indicated that HM8 did not only grow well at a Mn(II) concentration level of 10,000 mg/L but also removed 1,002.83 mg/L of Mn(II) from the bulk solution of the culture, showing that the isolated strain possessed strong capabilities to tolerate and remove Mn(II). In the isothermal bio-sorption experiments performed to investigate the effects of relevant factors on Mn(II) sorption, the highest Mn(II) removal rate was obtained at the contact time 72 h, temperature 40°C, and pH 6.0, while the differences in both strain growth and Mn(II) removal rate between different inoculated HM8 doses were found to be insignificant within the tested range. Scanning electron microscopy showed that, under Mn(II) stress, HM8 cells appeared irregular and cracked, with apparent wrinkles on the surface. The peaks in the Fourier transform infrared spectra showed that hydroxyl and carboxyl groups were the main functional groups for Mn(II) adsorption. The experimental data supported the practical application of HM8 as a biological adsorbent for remediation of heavily Mn contaminated sites. [ABSTRACT FROM AUTHOR]

In the present work, a series of magnetically separable Fe3O4/g-C3N4/MoO3 nanocomposite catalysts were prepared. The as-prepared catalysts were characterized by XRD, EDX, TEM, FT-IR, UV-Vis DRS, TGA, PL, BET and VSM. The photocatalytic activity of photocatalytic materials was evaluated by catalytic degradation of tetracycline solution under visible light irradiation. Furthermore, the influences of weight percent of MoO3 and scavengers of the reactive species on the degradation activity were investigated. The results showed that the Fe3O4/g-C3N4/MoO3 (30%) nanocomposites exhibited highest removal ability for TC, 94% TC was removed during the treatment. Photocatalytic activity of Fe3O4/g-C3N4/MoO3 (30%) was about 6.9, 5, and 19.9-fold higher than those of the MoO3, g-C3N4, and Fe3O4/g-C3N4 samples, respectively. The excellent photocatalytic performance was mainly attributed to the Z-scheme structure formed between MoO3 and g-C3N4, which enhanced the efficient separation of the electron-hole and sufficient utilization charge carriers for generating active radials. The highly improved activity was also partially beneficial from the increase in adsorption of the photocatalysts in visible range due to the combinaion of Fe3O4. Superoxide ions (·O2−) was the primary reactive species for the photocatalytic degradation of TC, as degradation rate were decreased to 6% in solution containing benzoquinone (BQ). Data indicate that the novel Fe3O4/g-C3N4/MoO3 was favorable for the degradation of high concentrations of tetracycline in water. [ABSTRACT FROM AUTHOR]

A method for grafting ethylenediamine to a magnetic graphene oxide composite (EDA-GO@Fe3O4) was developed for Cr(VI) decontamination. The physicochemical properties of EDA-GO@Fe3O4 were characterized using HRTEM, EDS, FT-IR, TG-DSC, and XPS. The effects of pH, sorbent dose, foreign anions, time, Cr(VI) concentration, and temperature on decontamination process were studied. The solution pH can largely affect the decontamination process. The pseudo-second-order model is suitable for being applied to fit the adsorption processes of Cr(VI) with GO@Fe3O4 and EDA-GO@Fe3O4. The intra-particle diffusion is not the rate-controlling step. Isotherm experimental data can be described using the Freundlich model. The effects of multiple factors on the Cr(VI) decontamination was investigated by a 25−1 fractional factorial design (FFD). The adsorption process can significantly be affected by the main effects of A (pH), B (Cr(VI) concentration), and E (Adsorbent dose). The combined factors of AB (pH × Cr(VI) concentration), AE (pH × Adsorbent dose), and BC (Cr(VI) concentration × Temperature) had larger effects than other factors on Cr(VI) removal. These results indicated that EDA-GO@Fe3O4 is a potential and suitable candidate for treatment of heavy metal wastewater. [ABSTRACT FROM AUTHOR]