## 3 Results and Discussion
### Characterization of Bio-Coagulant of Deshelled Carica Papaya Seeds
#### 3.1.2 FTIR Spectroscopy  
Effectiveness of natural polyelectrolytes in destabilizing the colloidal particles rely on the degree of ionization and copolymerization of the functional groups. Additionally, its effectiveness also depends on the quantity of substituted groups present in that structural polymer [27, 28]. The functional group in the deshelled _Carica papaya_ seeds powder bio-coagulant were identified in the FT-IR spectrum range 500-4000 cm\({}^{-1}\) (Figure 1). The 3000 cm\({}^{-1}\) peak was linked to -OH of polysaccharides groups [29] while the band at 2925 cm\({}^{-1}\) and 2855 cm\({}^{-1}\) are relative to the stretching of OH groups band to methyl group (C-OH) [30]. Wavenumber 1747 cm\({}^{-1}\) corresponded to C=O carbonyl group of carboxylic acid whereas 1657 cm\({}^{-1}\) which indicates stretching of carboxylic acid (-C=O) with inter-molecular hydrogen bond [29]. The bands at 1466 cm\({}^{-1}\) and 1379 cm\({}^{-1}\) were  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Independent Variables**} & \multicolumn{5}{c}{**Level of Independent Variables**} \\ \cline{2-6}  & \(-\alpha\) & \(-\)**1** & **0** & **+1** & **+\(\alpha\)** \\ \hline A: Dosage (mg/L) & 26.3 & 50 & 125 & 200 & 223.7 \\ B: pH & 3.6 & 4.0 (3.0) \({}^{\star}\) & 5.3 & 6.5 (7.0) \({}^{\star}\) & 6.9 \\ C: Initial Turbidity (NTU) & 36.8 & 100 & 300 & 500 & 563.2 \\ \hline \hline \end{tabular} \({}^{\star}\)pH used in the factorial analyses to obtain the Pareto effect.  
\end{table}
Table 2: Coded and real levels of independent variables in the CCD.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Bio-Coagulant**} & \multirow{2}{*}{**Protein (mg/mL)**} &
\begin{tabular}{c} **With or W/out** \\ **Purification** \\ \end{tabular} & \multirow{2}{*}{**References**} \\ \hline Deshelled _Carica papaya_ seeds & 0.363 & No & This study \\ _Quercus robur_ & 0.540 & No & [PERSON] et al. [23] \\ _Pauseolus vulgaris_ & 0.081 & Yes & [PERSON] et al. [24] \\ _Moringa oleifera_ & 0.371 & Yes & [PERSON] et al. [22] \\ _Moringa oleifera_ & 0.739 & Yes & [PERSON] et al. [25] \\ Chestnut & 0.420 & Yes & [PERSON] et al. [26] \\ Acorn & 0.440 & Yes & [PERSON] et al. [26] \\ \hline \hline \end{tabular}
\end{table}
Table 3: Comparison of protein content comprised bio-coagulant deshelled _Carica papaya_ seeds and other bio-coagulants.  
attributed to -C-O group [30]. Bands at 1242 cm\({}^{-1}\) and 1163 cm\({}^{-1}\) were relative to ether, ester or phenol groups [31].  
The presence of a large number of functional groups in deshellled _Carica papaya_ seeds powder indicates its potential to adsorb a wide range of contaminants and, therefore, capable of facilitating the removal of suspended and dissolved substances from water. The FTIR spectra analysis revealed that OH, C=O and C-O are the dominant functional groups of the studied bio-coagulant which enabled the protein to be an efficient polyelectrolyte. In addition, the charge density of deshelled _Carica papaya_ seed was recorded as a weak-positive charge of +0.4 meq/g (polycation), which strengthen the possibility of the deshelled _Carica papaya_ seeds in becoming potential bio-coagulant. The negatively charged colloids may interact with positively charged bio-coagulant for active coagulation activity via charge neutralization as the coagulation mechanism.