Emerging Trends and Knowledge Structure of Advanced Oxidation Processes for Chemical Industry Wastewater Treatment: A Bibliometric Mapping Study

Abstract

Advanced Oxidation Processes (AOPs) are increasingly applied to chemical industry wastewater because they generate reactive radical species capable of degrading refractory and toxic organic pollutants that conventional biological treatment cannot fully remove. However, the development, knowledge structure, and emerging directions of this specific research field remain insufficiently mapped. This study aims to analyze the scientific landscape, research evolution, and thematic trends of AOP-based treatment for chemical industry wastewater through bibliometric mapping, and to identify the specific knowledge gaps that distinguish this sectoral focus from prior, more broadly scoped bibliometric reviews. An initial pool of 2,017 records was retrieved from the Web of Science database using keyword combinations related to wastewater, chemical industries, and AOPs, then screened and refined to 1,000 documents for analysis. Bibliometrix, VOSviewer, CiteSpace, and OriginLab were used to examine publication trends, collaboration networks, keyword co-occurrence, citation and co-citation patterns, thematic evolution, and conceptual structures. The findings show a marked increase in publications since 2017, with China as the leading contributor in publication output and international collaboration. Dominant themes include pollutant degradation, photocatalysis, ozonation, electrochemical oxidation, and radical-based mechanisms, while emerging topics involve persulfate activation, carbon-based materials, nanocatalysts, and emerging contaminants such as pharmaceuticals and personal care products. The field remains grounded in radical chemistry while shifting toward integrated, hybrid wastewater treatment systems. This study provides a structured, sector-specific overview of research gaps and future directions to support the sustainable, economically feasible implementation of AOPs in chemical industry wastewater treatment.