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The growing global concern with water resources management has driven the search for more effective treatments for industrial effluents. The produced water is inserted in this scenario as one of the largest effluents generated by the oil industry. Besides, it cannot be discarded or reused without proper treatment due to its complex and toxic chemical composition. A bibliometric study was performed on the Scopus database from inception to 2020 in order to map the evolution of scientific publications related to the advanced oxidation processes based on reactions with ozone and Fenton's reagent. The results reinforced the efficiency of such processes for treating the produced water and the increasing of publications in the last few years, although the first document appeared only in 1995. China was the leading country in this research area, followed by Brazil and the USA. The most relevant journals were the Environmental Science & Technology and the Journal of Hazardous Materials. The research trends pointed out that the use of Fenton, photo-Fenton, and ozonation processes has been associated with other treatment methods to enhance the removal of contaminants in the produced water samples. However, the documents selected revealed the limitation on these processes due to the high costs with energy consumption. The present study can help other researchers mainly due to the few studies in this area, which demonstrates the importance of this prospection to support the development and application of advanced oxidation processes on produced water treatments. [ABSTRACT FROM AUTHOR]

Several industrial sectors produce tons of effluents daily containing a high amount of hazardous chemical pollutants that pose a major threat to the environment and human health. Current wastewater treatment methods, such as flocculation and activated carbon adsorption, have drawbacks linked to high material cost and too much energy consumption. Thus, the search for renewable, biodegradable, and efficient materials has been the object of research aimed at replacing the conventional materials used to cheapen processes and reduce environmental impacts. Lignin stands out in this context as it has low cost and high availability. Therefore, several scientific researches were developed to harness the potential of lignin, especially as adsorbent, for the removal of chemical agents from effluents. This paper presents a bibliometric review performed on the Scopus database, showing the evolution of studies related to the applicability of lignin in the removal of chemical pollutants in waters over the last five years. Data regarding annual publications, languages, journals, countries, institutions, keywords, and subjects were analyzed. The realized screening selected 130 articles that met the previously defined criteria. Results indicated a strong collaboration between countries and China's substantial contribution to the documents. The analysis also has shown that lignin is mainly used as adsorbent material, sorbent, flocculant agent, and hydrogel and presents important results and information for future researchers on this topic. [ABSTRACT FROM AUTHOR]