Yang Wang,Lina Zhou,Hui Li,Hailong Zhu,Teng Zhang,Menglun Yin,Qiuyue Xiang,Chen Hou
The photocatalytic (PC) degradation process of volatile organic compounds (VOCs) has been consistently restricted by the rapid recombination of photogenerated electrons and holes. To solve this problem, in this study, a novel photoelectrocatalytic (PEC) coupled system was constructed by integrating a single-chamber direct glucose fuel cell (SDGFC), which is capable of self-generating electricity, into the conventional PC system. The coupling system can inhibit the recombination of photogenerated electrons and holes by continuously generating a current without an applied power source. In addition, nitrogen-doped carbon quantum dots (N-CQDs) were prepared using biomass gelatin. This was employed as a PC material for the catalytic layer of the air cathode in the above coupling system, and the efficient degradation of benzene series (BTEX) was made easy by regulating the content of the N element. Notably, the N-CQDs under the optimal regulation ratio showed excellent optical properties and degradation performance, achieving an impressive PEC degradation rate of over 80 % for BTEX within 180 min. High-performance N-CQDs complement the novel PEC coupling system of self-generating electricity and provide robust support for BTEX degradation.
Juping You,Mine Du,Han Chen,Xinying Zhang,Shihan Zhang,Jianmeng Chen,Zhuowei Cheng,Dongzhi Chen,Jiexu Ye
A new isolate identified as Rhodococcus sp. ZJUT312 via taxonomic and 16S rRNA analysis was used for the efficient degradation of benzene, toluene, ethylbenzene, and xylene (BTEX). The strain ZJUT312 was able to degrade all the BTEX. Their average biodegradation rates followed the order o -xylene > ethylbenzene > toluene > benzene > m -xylene > p -xylene. The degradation rate of o -xylene reached as high as 0.117 mmol L −1 h −1 , which was one to two orders of magnitude higher than that of all other reported o -xylene degrading bacteria. GC-MS analysis revealed that o -xylene degradation pathway mainly proceeded with 2-methylbenzylalcohol as an intermediate and CO 2 as a final product. Mass balance analysis of the carbon element indicated that approximately 59% the o -xylene carbons were transferred to cell biomass and about 20% were mineralized into CO 2 . Furthermore, the o -xylene degradation kinetics fitted well with Haldane's model. The maximum specific degradation rate (0.953 h −1 ) was approximately 2.25 times higher than the reported data in the literature.
l -cysteine-modified Fe 3 O 4 nanoparticles ( l -cys@nFe 3 O 4 ) were synthesized successfully and used as catalyst to activate persulfate (PS) for benzene, toluene, ethylbenzene, and xylenes (BTEX) degradation. The composite was fully characterized, and the l -cys@nFe 3 O 4 had more protrusions and l -cys was combined on the surface of nFe 3 O 4 . The removals of BTEX were 78.2%, 85.1%, 85.3%, 81.2%, respectively, in PS/ l -cys@nFe 3 O 4 system, while only 52.7% 57.8%, 60.8%, and 56.3% of BTEX removals reached under the same condition for nFe 3 O 4 chelated with l -cys in 48 h. Four successive cycles of BTEX degradation were completed in PS/ l -cys@nFe 3 O 4 system. The synergistic mechanisms of BTEX degradation in PS/ l -cys@nFe 3 O 4 system were investigated by electron paramagnetic resonance (EPR), benzoic acid (BA) probe and X-ray photoelectron spectroscopy (XPS) tests. S Fe bond in l -cys-Fe complexes promoted the electron transfer between nFe 3 O 4 core and the solution, iron and iron at the interface, thereby promoting the Fe 3+ /Fe 2+ cycle and the catalytic capacity of nFe 3 O 4 . The optimal pH of PS/ l -cys@nFe 3 O 4 system was 3, while HCO 3 − and Cl − exhibited negative influences on BTEX degradation. Only 14.2%, 15.5%, 15.9%, and 15.6% BTEX had been removed in the presence of 0.12-M PS and 8.0 g/L l -cys@nFe 3 O 4 under the actual groundwater condition. However, expanding the dosage of PS and l -cys@nFe 3 O 4 was an effective strategy to overcome the adverse effect. Practitioner Points L-cys@nFe 3 O 4 were synthesized successfully and used as catalyst to activate PS for BTEX degradation. Four successive cycles of BTEX degradation were completed in PS/L-cys@nFe 3 O 4 system. lS―Fe bond in L-cys@nFe 3 O 4 promoted the electron transfer between PS and nFe 3 O 4 core.
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