## 3 Results
### Methylene Blue Water Pollutant Removal  
For proof-of-concept, filter paper doped with PSS was tested for its methylene blue (MB) removal efficiency. This test aimed to assess how effectively PSS, crosslinked with varying amounts of MBAA and DVB, could remove MB from the solution. By crosslinking the PSS with these agents inside the filter paper, the polymer becomes more robust and potentially more effective at capturing and filtering out MB due to the enhanced network structure.  
The removal efficiency of MB was quantified by comparing different filter papers doped with PSS that had been crosslinked with either MBAA or DVB at various concentrations. As shown in Table 1, the results are the MB removal rates after a single filtration. The study found that PSS crosslinked with 0.5% DVB demonstrated the highest MB removal efficiency, suggesting that this specific concentration of DVB forms an optimal network within the PSS matrix for capturing MB. This highlights the potential of using DVB-crosslinked PSS for applications requiring effective filtration and removal of dye pollutants, such as wastewater treatment.  
Subsequently, four consecutive filtrations were also performed using blank filter paper and filter paper doped with PSS crosslinked with 0.5% DVB. The results, shown in Table 2, indicate that the PSS/DVB-coated filter paper removed 99.4% of MB after four filtrations, compared to 78.5% removal by the blank filter paper.  
Following the initial filtration tests, four consecutive filtrations were performed to further evaluate the long-term MB removal efficiency of the PSS-coated filter paper. Specifically, the one crosslinked with 0.5% DVB, compared to blank filter paper without any PSS coating. This series of tests aimed to determine the sustained filtration capacity and effectiveness of the PSS/DVB system over multiple cycles, simulating practical use scenarios where a filter would need to handle more than one round of filtration.  
As presented in Table 2, the results were compelling. After four consecutive filtrations, the PSS-coated filter paper crosslinked with 0.5% DVB achieved a remarkable 99.4% removal  
\begin{table}
\begin{tabular}{c c c} \hline
**Crosslinker** & **Ratio** & **MB Removal Rate (\%)** \\ \hline MBAA & 0.1\% & 58.22 \\  & 0.25\% & 58.50 \\  & 0.5\% & 63.35 \\ \hline DVB & 0.1\% & 58.54 \\  & 0.25\% & 63.65 \\  & 0.5\% & 68.83 \\ \hline \end{tabular}
\end{table}
Table 1: MB removal rates after the first filtration using both PSS/MBAA and PSS/DVB. The uncertainty is determined as \(\pm\)2%.  
Figure 4: Hydrophilicity test of the PSS/DVB and PSS/MBAA polymer network. (**a**) left slide is for PSS/DVB and the right slide is PSS/MBAA. (**b**) left slide is for PSS/DVB and the right slide is PSS/MBAA.  
of MB from the solution. This contrasts significantly with the blank filter paper, which only removed 78.5% of MB under the same conditions. The difference in removal efficiency demonstrates the enhanced capability of the PSS/DVB coating in consistently capturing and removing MB molecules over multiple filtration cycles. This performance can be attributed to the stable, crosslinked network of PSS created by DVB, which provides more active sites for MB adsorption and prevents the polymer from dissolving or degrading during filtration. As previously noted, the increased hydrophilicity of the material also likely contributes to its enhanced affinity for MB, facilitating greater contact and interaction between the dye molecules and the filter surface.  
Overall, the PSS/DVB-coated filter paper's ability to maintain higher removal efficiency across multiple filtration rounds highlights its potential for practical water purification and dye pollutant removal applications. The durability and effectiveness of this crosslinked system make it a promising candidate for use in large-scale or industrial filtration systems where repeated usage is critical.