# Evaluation of Agricultural Soil-Improving Zeolite for Improving Irrigation Water Quality
## 3 Results and Discussion
### Central Composite Rotatable Design (CCRD)  
The results revealed distinct behaviors for each of the studied species. While several tested conditions achieved 100% removal of boron (B), sodium (Na) removal percentages were considerably lower, ranging from 10% to 24%. In one of the trials, desorption or release of sodium was observed, leading to a final sodium concentration 147% higher than the initial concentration (Table 5). This underscores the suitability of the factorial design for boron removal via zeolite but emphasizes its limited efficacy for combined sodium removal. The results suggest the interaction and influence of the presence of other chemical species, \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Water Simples** & \
\begin{tabular}{c} **Limit Irrigation** \\ **Water (FAO)** \\ \end{tabular} &
\begin{tabular}{c} **Restriction Use** \\ **(FAO)** \\ \end{tabular} \\ \hline
**pH** & & 6–8.5 & - \\ \hline
**CE (dS/m)** & 1.3 (0.2) & 0–3 & Medium \\ \hline
**Ca2+ (meq/L)** & 15.1 (2.8) & 0–20 & - \\ \hline
**Na+ (meq/L)** & 9.7 (0.2) & 0–40 & High \\ \hline
**Mg2+ (meq/L)** & 1.1 (0.4) & 0–5 & - \\ \hline
**CO3\({}^{2}\) (meq/L)** & \textless{}0.1 & 0–0.1 & - \\ \hline
**CI (meq/L)** & 5.24 (1.4) & 0–30 & Medium \\ \hline
**NO3 (mg/L)** & 6.6 (1.2) & 0–10 & Medium \\ \hline
**NH+4 (mg/L)** & 5.4 (0.9) & 0–2 & - \\ \hline
**K+ (mg/L)** & 10.2 (1.0) & 0–2 & - \\ \hline
**B (mg/L)** & 0.75 (0.3) & 0–2 & High \\ \hline
**SAR (meq/L)** & 9.2 & 0–15 & Medium \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Chemical characterization of irrigation water before treatment. Values compared with FAO irrigation water-quality standards [11]. The results represent the mean values (n = 5), with standard deviations in parentheses. both in the irrigation water samples and in the zeolite composition itself [24]. [PERSON] et al. [60] previously reported cyclic episodes of sodium adsorption/desorption in zeolite compounds, primarily due to the large ionic diameter of the sodium cation (1.02 A), causing a significant expansion of the material volume to accommodate sodium. However, the same study indicated the potential for sedation and desodiation of zeolitic materials during multiple cycles. The divergent behavior of species with zeolite was once again confirmed in the estimation of significant effects at a 95% confidence interval. As observed in Table 6, for sodium, none of the studied dependent variables or their interaction proved to be significant. In contrast, for boron removal via zeolite, both linear and quadratic forms of contact time were statistically significant. \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline  & **Coefficient** & **Effect** & **Standard Error** & **t (2)** & \(p\)**-Value** \\ \hline  & \multicolumn{4}{c}{**[Na]**} & & \\ \hline Zeolite content (L) & Q\({}_{1}\) & 0.39 & 0.28 & 1.39 & 0.21 \\ \hline Zeolite content (Q) & Q\({}_{1}\)\({}^{2}\) & \(-\)0.21 & 0.31 & \(-\)0.67 & 0.52 \\ \hline Contact time (L) & Q\({}_{2}\)\({}^{2}\) & \(-\)0.42 & 0.28 & \(-\)1.49 & 0.18 \\ \hline Contact time (Q) & Q\({}_{2}\)\({}^{2}\) & \(-\)0.18 & 0.31 & \(-\)0.56 & 0.59 \\ \hline Zeolite content vs. contact time & Q\({}_{1}\) vs. Q\({}_{2}\) & 0.87 & 0.40 & 2.21 & 0.06 \\ \hline \multicolumn{5}{c}{**[B]**} & & \\ \hline Zeolite content (L) & Q\({}_{1}\) & \(-\)0.08 & 0.07 & \(-\)1.1 & 0.32 \\ \hline Zeolite content (Q) & Q\({}_{12}\) & \(-\)0.08 & 0.08 & \(-\)0.96 & 0.37 \\ \hline Contact time (L) & Q\({}_{2}\) & 0.19 & 0.07 & 2.6 & 0.04 \\ \hline Contact time (Q) & Q\({}_{22}\) & \(-\)0.24 & 0.08 & \(-\)2.89 & 0.02 \\ \hline Zeolite content vs. contact time & Q\({}_{1}\) vs. Q\({}_{2}\) & \(-\)0.16 & 0.1 & \(-\)1.52 & 0.17 \\ \hline \end{tabular}
\end{table} 
Table 6: Estimated effects for variables in sodium (Na) and boron (B) removal via zeolite.