# Removal of Contaminants in Water with Scallop Shell Waste
## 3 Results
### Remotion of Water Waste Contaminants
Results indicate that northern scallop shell waste has a high potential in water  
Figure 11: Surface charge of calcium carbonate and caffeic acid at different pH values. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Caffeic Acid Concentration (ppm)** & **Adsorption (\%)** & **Starting pH** & **Final pH** \\ \hline
10 & 69.2 \(\pm\) 0.4 & 4.4 & 6.8 \\
20 & 34.9 \(\pm\) 0.3 & 4.4 & 8.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Effect of contaminant concentration on adsorption percentage and pH variation. decontamination applications, as many of the adsorbents reported on Table 6 are either synthetized by using several chemical reactives [62; 63; 64; 65; 66], have a high energy consumption [67; 68; 69; 70; 71], or require large infrastructures [69; 70; 71; 72] compared to scallop shell waste, which is processed at a low energy cost and does not require complex infrastructure nor any additional chemical reactive. Figure 12 shows the pore size distribution of the different particle size ranges of scallop shell waste (BS, MS, and SS) used in this study, which was determined by the Barret-Joyner-Halenda (BJH) method. It can be seen that the removal percentage of caffeic acid (CA) and arsenic(III) is higher in the material with a lower surface area (SS). However, the pore size distribution (nm) plays an important role as BS and MS materials have larger specific surfaces, but according to pore size distribution, the pores in these materials present sizes between 3 and 12 nm, much smaller than the SS material (7.5 and 30 nm). The BS and MS samples exhibited a much more limited pore size distribution, presenting pores only up to 20 nm. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**adsorbent** & **pH** & \
\begin{tabular}{c} **CA Removal Percentage** \\ **(\%)** \\ \end{tabular} &
\begin{tabular}{c} **As(III) Removal** \\ **Percentage (\%)** \\ \end{tabular} & **Reference** \\ \hline BS & 4.3 & 0 & 10.0 & This work \\ MS & 4.3 & 88.0 & 17.0 & This work \\ SS & 4.3 & 100.0 & 23.0 & This work \\ Chitosan & 5.0 & 12.0 & - & [73] \\ Magnetic Activated Carbon & 3.0 & 97.0 & - & [74] \\ Polystyrene Crosslinked with Divinylbenzene & - & 91.0 & - & [75] \\ TiO\({}_{2}\)-Mt-Ce-Mn & 7.0-8.0 & - & 97.88 & [64] \\ Fe\({}_{3}\)O\({}_{4}\)@Cu/Ce & 5.0 & - & 75.0 & [68] \\ Chitosan & 8.5 & - & 71.7 & [70] \\ Chitosan & 5.0–10.0 & - & \textgreater{}95.0 & [72] \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Comparison of capacity of contaminants removal percentages of Chilean scallop shell waste with other adsorbents. Figure 12: Pore size distribution using different particle size ranges of scallop shells residues (BS, MS, and SS). The present study shows a direct correlation between the textural properties of scallop shell waste, especially with pore size distribution, and the removal of contaminants in the water. A larger pore size favors a high removal percentage of target contaminants caffeic acid and arsenic(III) from water, regardless of the specific surface area of the material. Properties such as morphology, chemical composition, and functional groups do not strongly affect the removal of pollutants using this waste as material for water treatment.