## 3 Results and Discussion
### Economic and Environmental Assessment
The cost of chemical activation strongly depends on the carbonaceous precursor and the activation agent, ranging within values between 8.60 USD/kg (\(\approx\)7.9 EUR/kg) and 2.33 USD/kg (\(\approx\)2.1 EUR/kg) [76]. In conclusion, while Na2 CO3 activation significantly enhances performance and reduces costs, careful consideration of citric acid concentrations is necessary to maintain economic viability. These findings indicate that the development of optimized adsorbent materials can lead to effective and affordable solutions for environmental remediation, making them attractive options for treating hazardous contaminants like heavy metals and organic anthropogenic pollutants of emerging concern. The environmental impact of the four char preparation methods was estimated, considering not only the adsorption efficiency but also the environmental performance under different scenarios. The environmental impact assessment was undertaken following a streamlined life cycle assessment (LCA) methodology. LCA is widely used to determine the environmental impact of processes, considering upstream and downstream emissions and the resources consumed. Four plausible scenarios were modeled based on the treatment of 1 g of char, i.e., the functional unit defined for this study. The inputs and outputs employed to build the data inventory include the reagents consumed, heating, and emissions to water, as shown in Table S1. The upstream and downstream emissions and use of resources were collated from the commercial database ecoinvent 3.10 using the allocation, cut-off by the \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multirow{2}{*}{**Yield (\%)**} & **Preparation Costs** & **Lead Removal** & **Acetaminophen** \\  & & **(EUR/kg Material) 1** & **Costs (EUR/kg) 2** & **Removal Costs (EUR/kg) 2** \\ \hline Char & - & 4.7 & 2214.0 & 1046.3 \\ char-CA-1.0 & 67.7 & 14.9 & 5008.9 & 5029.0 \\ AC & 31.7 & 13.8 & 1169.7 & 582.4 \\ AC-CA-0.5 & 31.1 & 17.5 & 1506.8 & 906.9 \\ AC-CA-1.0 & 31.4 & 21.3 & 1714.5 & 1258.1 \\ AC-CA-1.5 & 30.9 & 25.1 & 2493.9 & 1172.5 \\ \hline \hline \end{tabular}  
* Preparation costs per kg of material prepared; 2 material costs associated with the treatment per kg of contaminant removed.  
\end{table} 
Table 7: Effects of activation and citric acid modification on preparation and treatment costs. classification system model. The software SimaPro 9.6.0.1 was applied to manage the data and perform life cycle calculations. The comparative results are presented in Figure 7.  
The results depicted in Figure 7 demonstrate that the scenarios involving citric acid utilization have an environmental impact that is markedly higher than that observed in scenarios that do not employ citric acid. This conclusion applies to all environmental impact categories. Overall, the environmental impact of washing and modifying the char with citric acid is 12 times higher than that of washing alone. Additionally, the environmental impact of washing, activating, and modifying the char with citric acid is 1.4 times higher than just the activated char. For all environmental impact categories, the scenario exhibiting the highest impact is one including washing, activation, and functionalization with citric acid. Furthermore, the process of activation makes a considerable contribution to the overall environmental impact. In all scenarios, the most significant contributor to the overall environmental impact is human carcinogenic toxicity, followed by freshwater and marine ecotoxicity. This is largely attributable to the high energy requirements of the drying processes. In conclusion, although modifying the char with citric acid may enhance the adsorption performance, it also considerably increases the environmental impact. Therefore, citric acid usage leads to enhanced adsorption uptake and minimizes the preparation and removal costs; however, its use results in detrimental consequences from an environmental point of view [77; 78; 79].