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Cellulose (2021) 28:9857–9871
Fig. 2 Subject areas with most articles related to cellulose based flocculants and coagulants
existing wastewater treatment technologies (Oyewo et al. 2020). While most research and review papers deal with flocculation in the context of wastewater treatments, the importance of cell flocs in microbiological systems should not be disregarded. It has been shown, for instance, that the flocculation of cellu- lose-producing bacteria is enhanced by cellulose itself, and thus the biotechnologist often needs to choose an additive, such as carboxymethyl cellulose, to disperse fibers (Andrade et al. 2019). This kind of consideration partly explains the contribution of Biology to the topic.
multidisciplinary approach. Strategies often involve physical combinations with other materials (Lee et al. 2012), chemical modifications of cellulose (Koshani et al. 2020) and/or both. As an example of hybrid material, cellulose can be bound to magnetite powder to obtain a valuable flocculation agent for a palm oil mill effluent (Mohamed Noor et al. 2018). Likewise, the presence of Ag 2 O or TiO 2 along the cellulose backbone provides usefulness for simultaneous pho- todegradation (Koshani et al. 2020). As for chemical modifications, they include not only the typical etherifications of hydroxyl groups towards anionic (carboxymethylation) or cationic (quaternary ammo- nium moieties) derivatives, but also more inspired solutions. For instance, seeking the performance of polyacrylamides, which are poorly biodegradable, and at the same time the biodegradability of polysaccharides, acrylamide units can be grafted onto carboxymethyl cellulose (Miyata et al. 1975). All things considered, Materials Science and Chem- istry are mainly found in terms of strategy, while Environmental Science and Engineering encompass frequent objectives of coagulation-flocculation, namely environmental concerns and the need for treating industrial effluents. We particularly remark the abundance of reviews within the area of Envi- ronmental Science. Such reviews mainly study the application of different wastewater treatments to grant the safe disposal of effluents or to make water drinkable, comparing innovative proposals to current methods (Matilainen et al. 2010; Verma et al. 2012; Lee et al. 2014; Teh et al. 2016; Wei et al. 2018). Allegedly, and considering they can be prepared in a wide variety of ways (powder, suspension, solution, etc.), cellulose-based agents are compatible with the
Ranking of countries, institutions, authors, and journals by number of publications
As can be seen from Fig. 3, the main contributor to the scientific production in relation to the use of cellulose as coagulant and flocculant is China, with over 100 publications, which accounts for more than twice the number of publications of the second most prolific country: Japan. The USA, Canada and India come next, with over 25 publications each. China is also the country with the highest number of institu- tions that carry out research in this area as well as the biggest funder of this research area, as can be seen in figures S3 and S4, respectively. To analyse the main contributors to research on cellulosic flocculants and coagulants, the ten most prolific authors in the field have been identified. The classification of the authors and their most relevant contributions are listed in Table 1. As can be seen from Table 1, most of the authors with most publications are in China, which is to be expected
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