## 6 Final Remarks and Future Outlooks
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Type of** & **Type of** & **Type of** & **Experimental Conditions** & **Maximum Removal (\%)** & **Adsorption Capacity** & **References** \\
**adsorbent** & **Water** & **Arsenic** & & pH = 7 & & \\  & & & Temperature = 298 K & & & \\
**Rice polish/rice bran** & \multirow{4}{*}{\begin{tabular}{} \end{tabular} } & \multirow{4}{*}{\begin{tabular}{} \end{tabular} } & \multirow{4}{*}{As(III)} & Initial concentration = 1000 \(\mu\)g/L & \multirow{4}{*}{-} & \multirow{4}{*}{67 \(\mu\)g/g} & [131] \\  & & & Flow rate = 1.66 mL/min & & & \\  & & & Column diameter = 2 cm & & & \\  & & & Bed height = 25 cm & & & \\ \hline \multirow{4}{*}{\
\begin{tabular}{} \end{tabular} } & \multirow{4}{*}{
\begin{tabular}{} \end{tabular} } & \multirow{4}{*}{As(V)} & pH = 4 & & \\  & & Temperature = 298 K & & & \\
**Rice polish/rice bran** & \multirow{4}{*}{
\begin{tabular}{} \end{tabular} } & \multirow{4}{*}{As(V)} & Initial concentration = 1000 \(\mu\)g/L & \multirow{4}{*}{-} & \multirow{4}{*}{79 \(\mu\)g/g} & [131] \\  & & & Flow rate = 1.66 mL/min & & & \\  & & & Column diameter = 2 cm & & & \\  & & Bed height = 25 cm & & & \\ \hline \end{tabular}
\end{table} 
Table 12: \(Cont.\)(FeCl\({}_{3}\) doped pyrolysis) from 64.9 to 263.21 m\({}^{2}\)/g [135]. These values are encouraging but still lower than the specific surface of conventional carbon materials, which can exceed 2000 m\({}^{2}\)/g. The inevitable cost increases due to these modification treatments which increase adsorption efficiency should not be overlooked. In the future, it will be necessary to identify possible compromises between the optimization of the production process and the cost reduction, with the aim of making real an effective applicability of biochar [136]. [PERSON] et al. [137] underlined one of the main disadvantages related to the use of fine biochar particles, that is, the difficulty of recovery/collection after being used and therefore, the possible redispersion in the environment with consequent secondary pollution. To solve this limitation and to improve the adsorption process in general, it is possible to couple the adsorbent materials with some metals (such as iron, manganese, aluminum), also in the field of nanotechnologies. This approach can be applied to exploit the excellent magnetic separation capacity and the possibility of increasing the surface area of the biochar. Future research is needed to explore and learn more about the use of metals and nanoparticles, in particular, their effective and suitable application, and their economic and environmental sustainability. The stability of biochar is a property to be taken into consideration as there may be a possible dissolution of organic matter by the adsorbent material in the water to be treated. The stability of the biochar may depend on the type of raw material used and on the experimental conditions of the physical and chemical activation processes [138]. As [PERSON] et al. [139] pointed out, it would be advisable to further investigate the possible regeneration and recovery of adsorbent materials after use to make their application more sustainable, both from an economic and environmental point of view. This can represent an excellent strategy to allow both (i) the reuse of the spent adsorbent material and therefore increase its life cycle, and (ii) the study of any improvement or worsening of its adsorption capacity. In summary, as also underlined by [PERSON] et al. [134], to ensure the up-scaling of biochar from recovered by-products, it is necessary to act following some logical steps: (i) select a local raw material with reduced environmental/economic impact, (ii) identify an advantageous thermal conversion method for the environment and with controlled costs, (iii) provide, if necessary, biochar modification treatments to improve its contaminant adsorption efficiency, and (iv) apply customized technology specific to the situation/place of intervention to maximize the results of the process.