Fabrication of Ag3PO4/TiO2@molecular sieve (MS) ternary composites with remarkably enhanced visible light-responded photocatalytic activity and mechanism insight.

In this study, Ag3PO4/TiO2@molecular sieve (MS) ternary composites were fabricated via in-situ deposition and hydrothermal growth method for photocatalytic degradation of formaldehyde and sodium isobutyl xanthate (SIBX) under visible light irradiation. XRD, PL, UV-vis, UPS, SEM-EDS and XPS techniques were adopted to characterize the composite. The results show that the MS material was indexed as zeolite P and Ag3PO4-TiO2 hybrid structure could improve the absorption of visible light and greatly inhibit the recombination of photogenerated charge carriers by introducing 3 times TiO2. After evaluating the photocatalytic activity and kinetics model, it is found that photocatalytic activity is consistent with the apparent first-order kinetic model. The Ag3PO4/TiO2-3@MS ternary composite under visible light irradiation appears the highest removal rate with 97.9% of formaldehyde and 96.7% of SIBX, respectively. Furthermore, the reusability of the photocatalyst was investigated by successive reuse. After five reuses, the removal rates reached 97.3% and 94.6% within 105 min for formaldehyde and SIBX, respectively. At last, the proposed mechanism of the photocatalytic reaction and the degradation routes of formaldehyde and SIBX were systematically discussed.

Removal of chemical oxygen demand (COD) and heavy metals by catalytic ozonation-microbial fuel cell and Acidithiobacillus ferrooxidans leaching in flotation wastewater (FW).

A catalytic ozonation-microbial fuel cell and Acidithiobacillus ferrooxidans leaching process was used in treating flotation wastewater to remove chemical oxygen demand (COD) and heavy metals in this study. The results indicated that when adding 1 g/L of manganese/modified activated carbon catalyst and 1.5 g/min ozone flow, the COD could be degraded from 2,043.67 mg/L to 711.4 mg/L. After that, the COD could continue decreasing down to 72.56 mg/L through an air-cathode single chamber microbial fuel cell (SCMFCs), coated with 0.4 mg/cm2 platinum catalyst, after 15 days. Meanwhile, the maximum voltages and the ultimate power density of the SCMFCs reached 378.96 mV and 7,608.35 mW/m2, respectively. For filter residue, when 1.2 g/L Fe3+, 10% (m/v) filter residue, and 10% Acidithiobacillus ferrooxidans were added, the copper leaching rate could reach 92.69% after 7 days if the pH values were adjusted to 1.9. Furthermore, the other heavy metals were also decreased to a level lower than the pollution control standard (Chinese standard GB3838-2002). The leaching parameters in terms of pH, redox potential, and cyclic voltammetry showed that the addition of an appropriate concentration of Fe3+ to the leaching systems was beneficial to copper dissolution.

Adsorption-photocatalytic degradation and kinetic of sodium isobutyl xanthate using the nitrogen and cerium co-doping TiO2-coated activated carbon.

At present, the excessive use of sodium isobutyl xanthate (SIBX) in mineral processing has caused serious environmental problems, drawing ever-growing concern in China. A nitrogen and cerium co-doped TiO2-coated activated carbon (Ce/N-TiO2@AC) heterojunction were prepared through the sol-gel method to address these problems. The photocatalyst was characterized using XRD, TEM, SEM-EDS, PL, UV-Vis, XPS and a series of photoelectrochemical techniques. The results show that Ce/N-TiO2@AC photocatalyst possess a stable anatase phase, narrow band gap energy (2.24-2.61 eV) and high charge transport process. The photocatalytic activity of the photocatalyst was evaluated based on photodegradation kinetic studies of SIBX in aqueous solution, and it is found that it followed the Langmuir-Hinshelwood model very well. The Ce/N-TiO2@AC photocatalyst with 2% Ce appears to be the highest removal rate with 96.3% of SIBX and an apparent rate constant of 78.4 × 10-3 min-1. The reusability experiment for its potential applications was studied, and the removal rate of SIBX reached 95.8% after the fifth cycle. Besides, the proposed mechanism and degradation routes of SIBX were systematically studied, and certificate the concentration of SO2-4 ions in the final water sample was 95.9 mg/L, which was basically consistent with the theoretical value.

Red gypsum utilization and acidic wastewater treatment based on metal self-enrichment process.

The massive accumulation of red gypsum has brought great harm to human and environment. In order to achieve low-cost and high-benefit resource utilization of red gypsum, a method of metal self-enrichment during the cycle and transformation of red gypsum was proposed. The carbon dioxide and ammonia water react with red gypsum to manufacture ammonium sulfate and solid phase products. And solid phase products neutralize pickling wastewater to produce metal-enriched red gypsum for the next cycle. After the cycle, solid phase product with one circulation (containing 39.45% Fe and 7.37% Ca) and two circulation (containing 45.79% Fe, 4.75% Ca) could be obtained, which can be used as the proportioning of metallurgical sinter. The self-enrichment process not only realizes the comprehensive utilization of red gypsum, but also solves the treatment of acidic wastewater.