Advanced oxidation processes (AOPs) are powerful methods for treating substrates using radicals that are generated in situ. This study reviewed applications of AOPs in enhancement of biohydrogen production. The AOPs are applied in substrate pretreatment because of their ability to break the complex structure of lignocellulosic biomass for ease of subsequent hydrolysis. The mechanism of solubilization of complex organics resulting in increased biodegradability of substrate during pretreatment has been suggested. Documented studies indicate that up to 98% color removal from organic wastewater is possible by the use of AOPs. Furthermore, a combination of AOPs with biological processes can achieve more than 90% COD removal from biohydrogen production effluent. Sonication, microwave-enhanced AOPs, and electrochemical treatment are the most applied AOPs in enrichment of biohydrogen with up to fivefold increase in biohydrogen yield achieved after electrochemical pre-treatment. The mechanism of enhancement of hydrogen yield in dark fermentation after pretreatment of the substrate and inoculum with AOPs has been proposed. The excess sludge produced during hydrogen fermentation can be pretreated with ozone and ultrasound before biomethanation process. More studies on co-production of biohydrogen and electricity through electrochemical oxidation in fuel cells are necessary. This study proposes the integration of AOPs with conventional processes in biorefinery production approach with aim of improving biohydrogen yields, co-producing it with other biofuels, and reducing the process costs. Future studies should focus on the scale-up of AOPs for commercial applications. Comparative studies on energy requirements for various AOPs applications are lacking and should be carried out.

Graphical abstract

高级氧化工艺（AOP）是使用原位产生的自由基处理基材的有效方法。这项研究回顾了AOP在增强生物氢生产中的应用。由于AOP能够破坏木质纤维素生物质的复杂结构，易于后续水解，因此可用于底物预处理。已经提出了在预处理过程中复杂有机物的增溶机理，导致底物的生物降解性提高。有记录的研究表明，使用AOP可以从有机废水中去除多达98％的颜色。此外，将AOP与生物工艺相结合可以从生物制氢废水中去除90％以上的COD。超声处理，微波增强型AOP，电化学处理和电化学处理是在生物氢富集中应用最广泛的AOP，电化学预处理后生物氢产量提高了五倍。已经提出了在用AOP对底物和接种物进行预处理之后的黑暗发酵中提高氢产量的机理。氢发酵过程中产生的过量污泥可以在生物甲烷化过程之前用臭氧和超声波进行预处理。有必要对燃料电池中通过电化学氧化共同生产生物氢和电力进行更多的研究。这项研究提出了将AOPs与常规工艺整合到生物精炼生产方法中的目的，目的在于提高生物氢的产量，与其他生物燃料共同生产氢并降低工艺成本。未来的研究应集中于扩大AOP的商业应用范围。缺乏各种AOP应用的能量需求的比较研究，应该进行。

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