Effects of carbon-silicon structure on photochemical activity of biochars,Chemosphere

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Effects of carbon-silicon structure on photochemical activity of biochars
Chemosphere ( IF 8.1 ) Pub Date : 2023-11-13 , DOI: 10.1016/j.chemosphere.2023.140719
Siwei Guo ₁ , Lun Lu ₂ , Baoliang Chen ₁

Affiliation

Biochar has raised increasing concerns because of its great environmental impacts. It is known that the photocatalytic property of biochar is related to its carbon component and dissolved black carbon, but the effect of silicon component is ignored, and the effect of silicon and carbon phases was far less studied. This study systematically explored the photochemistry of silicon-rich and silicon-deficient biochar under light irradiation by using hexavalent chromium (Cr(VI)) and sulfadiazine as representative pollutants for photoreduction and photooxidation, respectively. It was found that biochar had photoreduction activity under the enhancement of electron donors, and 80.1% Cr(VI) can be removed by biochar with crystalline silicon and carbon (i.e., RH900) after 12 h irradiation. Meanwhile after low temperature pyrolysis, biochar with amorphous silicon and carbon (i.e., RH600) had great photooxidation capacity, and 71.90% organic pollutant was degraded within 24 h. The reaction was illustrated by transient photocurrent response, and hydroxyl radical generation measurement, and other tests. A new photochemical mechanism of the synergy between silicon and carbon model was proposed to elucidate the redox reactions of pollutants under the light. Graphitic carbon or crystalline silicon formed under high temperature played a role of valence band which was excited under light irradiation and the effect of electron donors to benefit photoreduction, while amorphous silicon formed under low temperature facilitated photooxidation process by increasing reactive oxygen species concentration. This study provided a gist for biochar production and application in the field of photocatalysis, and contributed to the broader understanding of biochar geochemical behavior in natural sunlit system.

中文翻译：

碳硅结构对生物炭光化学活性的影响

生物炭因其巨大的环境影响而引起越来越多的关注。众所周知，生物炭的光催化性能与其碳组分和溶解黑炭有关，但忽略了硅组分的影响，对硅相和碳相的影响研究也少之又少。本研究分别以六价铬（Cr(VI)）和磺胺嘧啶为代表污染物进行光还原和光氧化，系统地探讨了光照射下富硅和缺硅生物炭的光化学反应。结果发现，生物炭在电子给体的增强下具有光还原活性，含晶硅和碳的生物炭（即RH900）照射12 h后可去除80.1%的Cr(VI)。同时，非晶硅碳生物炭（即RH600）经过低温热解后，具有很强的光氧化能力，24 h内降解了71.90%的有机污染物。通过瞬态光电流响应、羟基自由基产生测量和其他测试来说明该反应。提出了硅和碳模型协同作用的新光化学机制，以阐明污染物在光下的氧化还原反应。高温下形成的石墨碳或晶体硅起到光照射下激发的价带作用以及电子供体的作用有利于光还原，而低温下形成的非晶硅则通过增加活性氧浓度来促进光氧化过程。该研究为生物炭的生产和在光催化领域的应用提供了依据，并有助于更广泛地了解生物炭在自然阳光照射系统中的地球化学行为。

更新日期：2023-11-13

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