In this study, super-fine powdered activated carbon (SPAC) has been proposed and investigated as a novel catalyst for the catalytic ozonation of oxalate for the first time. SPAC was prepared from commercial granular activated carbon (GAC) by ball milling. SPAC exhibited high external surface area with a far greater member of meso- and macropores (563% increase in volume). The catalytic performances of activated carbons (ACs) of 8 sizes were compared and the rate constant for pseudo first-order total organic carbon removal increased from 0.012 min–1 to 0.568 min–1 (47-fold increase) with the decrease in size of AC from 20 to 40 mesh (863 mm) to SPAC (~1.0 mm). Furthermore, the diffusion resistance of SPAC decreased 17-fold compared with GAC. The ratio of oxalate degradation by surface reaction increased by 57%. The rate of transformation of ozone to radicals by SPAC was 330 times that of GAC. The results suggest that a series of changes stimulated by ball milling, including a larger ratio of external surface area, less diffusion resistance, significant surface reaction and potential oxidized surface all contributed to enhancing catalytic ozonation performance. This study demonstrated that SPAC is a simple and effective catalyst for enhancing catalytic ozonation efficacy.
Electrochemically active bacteria (EAB) on the cathodes of microbial electrolysis cells (MECs) can remove metals from the catholyte, but the response of these indigenous EAB toward exotic metals has not been examined, particularly from the perspective of the co-presence of Cd(II) and Cr(VI) in a wastewater. Four known indigenous Cd-tolerant EAB of Ochrobactrum sp X1, Pseudomonas sp X3, Pseudomonas delhiensis X5, and Ochrobactrum anthropi X7 removed more Cd(II) and less Cr(VI) in the simultaneous presence of Cd(II) and Cr(VI), compared to the controls with individual Cd(II) or single Cr(VI). Response of these EAB toward exotic Cr(VI) was related to the associated subcellular metal distribution based on the sensing of fluorescence probes. EAB cell membrane harbored more cadmium than chromium and cytoplasm located more chromium than cadmium, among which the imaging of intracelluler Cr(III) ions increased over time, contrary to the decreased trend for Cd(II) ions. Compared to the controls with single Cd(II), exotic Cr(VI) decreased the imaging of Cd(II) ions in the EAB at an initial 2 h and negligibly affected thereafter. However, Cd(II) diminished the imaging of Cr (III) ions in the EAB over time, compared to the controls with individual Cr(VI). Current accelerated the harboring of cadmium at an initial 2 h and directed the accumulation of chromium in EAB over time. This study provides a viable approach for simultaneously quantitatively imaging Cd(II) and Cr (III) ions in EAB and thus gives valuable insights into the response of indigenous Cd-tolerant EAB toward exotic Cr(VI) in MECs.
To enhance the phytoremediation ability of the heavy metal accumulator Perilla frutescens, melatonin (MT) was applied at different concentrations (0, 25, 50, 100, 150, and 200?μmol/L) to P. frutescens growing in cadmium (Cd) contaminated soil (10?mg/kg). The MT treatments increased the root and shoot biomasses of P. frutescens, with the maximum increase in the 150?μmol/L MT treatment (79.51% and 36.18% higher, respectively, than those of the control). The MT treatments also enhanced superoxide dismutase activity, peroxidase activity, and the soluble protein concentration of P. frutescens, and 100–200?μmol/L MT increased the chlorophyll a, chlorophyll b, and total chlorophyll concentrations in P. frutescens. The MT treatments increased the Cd concentrations in roots and shoots of P. frutescens in a dose-dependent manner. Different MT concentrations increased the Cd accumulation amounts of roots and shoots of P. frutescens, with the maxima accumulation amounts in the 150?μmol/L MT treatment (226.98% and 85.89% higher, respectively, than those of the control). These results show that MT can promote the growth and phytoremediation ability of P. frutescens growing in Cd-contaminated soil, and the optimum MT dose is 150?μmol/L. 相似文献
Environmental Geochemistry and Health - MicroRNAs (miRNAs) are a class of small, noncoding RNA species that play crucial roles across many biological processes and in the pathogenesis of major... 相似文献
