Efficient removal of tetracycline hydrochloride through novel Fe/BiOBr/Bi_(2)WO_(6) photocatalyst prepared by dual-strategy under visible-light irradiation

It is important to investigate whether combining two modification strategies has a synergistic effect on the activity of photocatalysts.In this manuscript,Fe-doped BiOBr/Bi_(2)WO_(6) heterojunctions were synthesized by a one-pot solvothermal method,and excellent photocatalytic performance was obtained for the degradation of tetracycline hydrochloride(TCH)in water without the addition of surfactant.Combining experiments and characterization,the synergistic effect between Fe ion doping and the BiOBr/Bi_(2)WO_(6) heterojunction was elucidated.The Fe/BiOBr/Bi_(2)WO_(6) composite photocatalyst had a beneficial void structure,enhanced visible light response,and could inhibit the recombination of photogenerated support well,which improved the photocatalytic activity.The presented experiments demonstrate that Fe/BiOBr/Bi_(2)WO_(6) removes 97% of TCH from aqueous solution,while pure BiOBr and Bi_(2)WO_(6) only remove 56% and 65% of TCH,respectively.Finally,the separation and transfer mechanisms of photoexcited carriers were determined in conjunction with the experimental results.This study provides a new direction for the design of efficient photocatalysts through the use of a dual co-modification strategy.

Performance of biotrickling filters packed with structured or cubic polyurethane sponges for VOC removal

Two identical bench-scale biotrickling filters （BTFs）, BTF 1 and BTF 2, were evaluated for toluene removal at various gas empty bed contact times （EBCTs） and organic loadings. BTF 1 and BTF 2 were packed with structured and cubic synthetic polyurethane sponges, respectively. At a constant toluene loading of 16 g/（m3.hr）, toluene removal efficiencies decreased from 98.8% to 64.3% for BTF 1 and from 98.4% to 74.1% for BTF 2 as gas EBCT decreased from 30 to 5 sec. When the toluene loading increased from 35 to 140 g/（m3.hr） at a gas EBCT of 30 sec, the removal efficiencies decreased from 99.1% to 77.4% for BTF 1 and from 99.0% to 81.5% for BTF 2. The pressure drop for both BTFs increased with increased air flow rate, and did not significantly vary while the toluene loading was increased under similar operation conditions. BTF 1 and BTF 2 could start up successfully within 19 and 27 days, respectively, when packed with fresh sponge media, and the performances could be restored in 3-7 days after biomass was removed and wasted from the media. BTF 2 displayed higher removal efficiency even under shorter EBCT or higher loading rate than BTF1 when other operation conditions were similar, while it showed lower pressure drop than BTF 1 during the whole period of operation. These results demonstrated that both BTFs could treat waste gas containing toluene effectively.