## 2 Structure and Bibliometric Analysis  
The review is focused on the removal of fluoride and arsenic from the water through an adsorption treatment based on the use of rice cultivation waste. First, the precious by-products generated during rice processing are analyzed, underlining the importance of their sustainable recovery. The chemical and physical properties of rice husk, rice husk ash, and rice straw are then described, focusing on their adsorption capacity. Subsequently, the characteristics of fluoride and arsenic are briefly shown, considering in particular (i) the effects on human health, and (ii) the main causes of water pollution; at this point, the importance of removing these pollutants from groundwater has emerged even more to ensure water safe consumption. The scientific literature was then analyzed to collect studies and experiences on the use of rice by-products as adsorbent materials for the removal first of fluoride and then of arsenic from water. Finally, in the paragraph \"Final remarks and future outlooks\", the authors described the main pros and cons observed in the discussion of this issue, suggesting some possible prospects for future research. For a brief bibliometric analysis, the authors took inspiration from the studies carried out by [PERSON] et al. [39] and [PERSON] et al. [40]. The search for documents of the scientific literature was carried out thanks to Scopus(r) (Elsevier, Amsterdam, The Netherlands) database exploiting different keywords. In all the searches carried out, in the \"Document type\" field, articles, conference papers, conference reviews, and chapter books have been taken into consideration; in the \"Language\" field, however, only English was chosen. First, focusing in general on the adsorption treatment of fluorine and arsenic into drinking water, the following keywords have been entered: \"fluoride AND adsorption AND drinking water\", \"arsenic AND adsorption AND drinking water\". In this case, the bibliometric research focuses on documents published from 2000 to 2022. Figure 1 shows the trend in the number of publications. As it can be observed, there has been a constant growth of interest from the scientific community on the study of this topic from 2000 to today. However, it is to be noted that in the early 2000s, there were more publications regarding arsenic while in recent years, the focus on fluorine has increased, approaching the numbers relating to arsenic. Subsequently, the keywords \"fluoride AND adsorption AND waste AND drinking water\", \"arsenic AND adsorption AND waste AND drinking water\", and then \"fluoride AND rice AND adsorption AND drinking water\", \"arsenic AND rice adsorption AND drinking water\" were used, with the aim of (i) considering more specifically the use of recycled adsorbent materials in drinking water sector, and (ii) focusing on low-cost by  
Figure 1: Number of publications per year from 2000 to 2022 searching on Scopus®: “fluoride AND adsorption AND drinking water”, “arsenic AND adsorption AND drinking water”. “Fluorine + arsenic” is the sum of the papers relating to fluoride and the papers relating to arsenic. products deriving from the rice industry. Figure 2 compares the three bibliographic searches carried out, both the latter two described (\"By-product adsorption\" and \"Rice by-product adsorption\" in Figure 2), and the first concerning, in general, the adsorption treatment for the removal of fluoride and arsenic from drinking water (\"Adsorption\" in Figure 2), evaluating the results of both fluorine and arsenic all together. It can be observed that over the years, the increase in studies on alternative adsorption materials has occurred in synergy with adsorption in general; in fact, publications on the use of by-products have always consistently represented around 20% of the total over the years. The documents from the year 2000 to today were considered, but as it can be seen from Figure 2, the first publications on the use of rice husk and rice straw as adsorbent materials appeared only in 2007.