## 3 Results and Discussion
### Automated Column Sorption System
#### 3.2.1 Sampling Sequence and Flow Rate
Immediately after SC1 is filled and before 30-mL collection, the switch to Mode-II diverts the flow to begin filling the second sorption column (C2). Once both columns are filled, the flow is divided in Mode-III at the top outlet of C1, between SC1 and SC2, while maintaining consistent contact throughout the system. Again, during \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multirow{2}{*}{**MODE**} & \multirow{2}{*}{**Start Time (min:s)**} & \multicolumn{2}{c}{**End Time (mins)**} \\ \cline{3-5}  & & & **SC1** & **SC2** \\ \hline \multirow{2}{*}{C1-A} & I & 15:10 & 18:50 & - \\  & II & 18:50 & & \\ \hline \multirow{2}{*}{Cx-B} & III & 36:40 & 42:42 & 42:49 \\  & II & 42:50 & & \\ \hline \multirow{2}{*}{Cx-1} & III & 48:04 & 54:10 & 54:27 \\  & II & 54:27 & & \\ \hline \multirow{2}{*}{Cx-2} & III & 59:39 & 66:15 & 66:34 \\  & II & 66:34 & & \\ \hline \multirow{2}{*}{Cx-3} & III & 71:37 & 77:55 & 78:19 \\  & II & 78:20 & & \\ \hline \multirow{2}{*}{Cx-4} & III & 83:24 & 89:56 & 89:56 \\  & II & 89:57 & & \\ \hline \multirow{2}{*}{Cx-5} & III & 95:05 & 101:32 & 101:45 \\  & II & 101:46 & & \\ \hline \multirow{2}{*}{Cx-6} & III & 106:52 & 112:53 & 113:10 \\  & II & 113:11 & & \\ \hline \multirow{2}{*}{TW1} & & 115:45 & & \\ \hline \multirow{2}{*}{Cx-7} & III & 118:10 & 123:45 & 123:56 \\  & II & 123:57 & & \\ \hline \multirow{2}{*}{Cx-8} & III & 129:00 & 136:07 & 136:19 \\  & II & 136:20 & & \\ \hline \multirow{2}{*}{Cx-9} & III & 141:22 & 147:29 & 147:34 \\  & II & 147:35 & & \\ \hline \multirow{2}{*}{Cx-10} & III & 152:40 & 158:35 & 158:45 \\  & II & 158:46 & & \\ \hline \multirow{2}{*}{Cx-11} & III & 163:45 & 169:40 & 169:45 \\  & II & 169:46 & & \\ \hline \multirow{2}{*}{Cx-12} & III & 174:50 & 181:06 & 181:04 \\  & II & 181:10 & & \\ \hline \multirow{2}{*}{Cx-13} & III & 186:11 & 192:08 & 192:36 \\  & II & & PUMP OFF & \\ \hline \multirow{2}{*}{TW2} & & 195:00 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Sorption system sampling sequence. Mode-III, C1 receives the same inlet flow rate, but the sampling chambers SC1 and SC2 receives this division of flow. It is column C2 that receives a variable flow rate during the analysis period, set by the adjustable division timer. Based on the filling start time (36:40 min:s) of C1-B and C2-B, and the end time of collection (192:36 min:s) for C1-13 and C2-13, a geometric mean flow rate between Mode-II and Mode-III in C2 is established as 5.39 mL/min. With these unique flow rates recognized for both columns, their corresponding EBCTs are established by Equation (4) to yield:  
\[\text{EBCT}_{1}=\frac{\text{d}^{2}\pi\text{H}}{4(\text{Q}_{\text{C1}})}= \frac{(2.61\text{ cm})^{2}\pi(30.48\text{ cm})}{4(8.18\text{ cm}^{3}/\text{min})}\cong\text{ }20:00\text{ min}:\text{s}\]  
\[\text{EBCT}_{2}=\frac{\text{d}^{2}\pi\text{H}}{4(\text{Q}_{\text{C2,AVG}})}= \frac{(2.61\text{ cm})^{2}\pi(30.48\text{ cm})}{4(5.39\text{ cm}^{3}/\text{min})}\cong\text{ }30:20\text{ min}:\text{s}\]  
Due to the relatively slow kinetics of zeolites, long residence times are required. Any solution volume-element in contact with a given zeolite bed layer is for only a limited time period, which is usually insufficient to reach the equilibrium state. The failure of zeolite to attain local equilibrium causes a lower uptake of HMIs from solution [11]. The detention time that the fluid element is in contact with the fixed-bed per sorption column is a result of the flow rate selected in this present study. This trend between the columns provides insight into the overall treatment availability of the zeolite material in this very unique configuration.