## 3 Results and Discussion
### Comparative Analysis  
The ion-exchange process has advantages, such as lower sludge production and high selectivity and specificity as compared to other process. As discussed above, various polymeric ion-exchangers have been used for metal removal from water; however, the motive of this study was to construct a better ion exchanger at a low cost. Thus, we developed a natural-resource-based ion exchanger. Compared to many other discussed ion exchangers, it can be said that the present ion exchanger is sustainable, cheap, and environmentally benign. As a current ion-exchanger was used for the removal of metal ions from a natural water resource, its comparative study is a bit difficult due to the competitive ion effect. Apart from this, due to the different operation conditions for each study, it is very difficult to compare one ion exchanger with another. As far as adsorption efficiency is concerned, we tried to perform a comparative study in this study. The present ion-exchanger displayed comparable removal efficiency with other reported ion exchangers. It can be seen in the Table 3 that the current ion exchanger has better removal efficiency compared to the previous reported ion-exchangers. The removal efficiency of TKP, a precursor of the TTAPA resin, was also examined, and it was observed that the developed resin showed enhanced efficiency in comparison to TKP (Table 3). Thus, it can be said that the present ion-exchanger can be the better option for wastewater treatment.  
\begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Order** & **Ion Exchanger** & **Experimental Conditions** & **Ions** & **\% Removal** & **References** \\ \hline
1. & \begin{tabular}{l} Tamarind-tripropylamine \\ resin (TTA) \\ \end{tabular} & \begin{tabular}{l} pH = 7.0; Dose = 0.4 g/L; \\ Contact time = 3 h; 25 \({}^{\circ}\)C \\ \end{tabular} & \begin{tabular}{l} Pb(II) \\ Cd(II) \\ \end{tabular} & 53.38 & [56] \\ \cline{2-6}  & & \begin{tabular}{l} Zn(II) \\ \end{tabular} & 74.88 & \\ \cline{2-6}  & & \
\begin{tabular}{l} Cu(II) \\ \end{tabular} & 77.84 & \\ \cline{2-6}  & &
\begin{tabular}{l} Fe(II) \\ \end{tabular} & 83.42 & \\ \hline
2. & \begin{tabular}{l} Raw pineapple waste biomass ion \\ exchange (RPWB) \\ \end{tabular} & \
\begin{tabular}{l} pH = 3.5; 30 mg of RPWB with \\ 20 mL of 11 mg/L Fe(II) solution \\ \end{tabular} &
\begin{tabular}{l} Fe(II) \\ \end{tabular} & 47\% & [25] \\ \hline
3. & \begin{tabular}{l} Saponified pineapple waste \\ biomass ion exchange (SPWB) \\ \end{tabular} & \
\begin{tabular}{l} pH = 3.0; 30 mg of SPWB with \\ 20 mL of 11 mg/L Fe(II) solution \\ \end{tabular} &
\begin{tabular}{l} 94\% \\ \end{tabular} & \\ \hline
4. & \
\begin{tabular}{l} Purolite C 100 \\ \end{tabular} & - &
\begin{tabular}{l} Pb(II) \\ \end{tabular} & 99.17 & [57] \\ \hline
5. & \begin{tabular}{l} Amberjet 1200 Na \\ \end{tabular} & \
\begin{tabular}{l} 800, 1000, \\ 1250 mg/L \\ \end{tabular} &
\begin{tabular}{l} Pb(II) \\ \end{tabular} & 99.0 & [58] \\ \hline \hline \end{tabular}
\end{table}
Table 3: Comparative analysis of TTAPA with other ion exchangers.  
Figure 8: Results for (**a**) the column separation of metal ions using the H-TTAPA resin and (**b**) the reusability of regenerated H-TTAPA.