# Ni/Zn Layered Double Hydroxide (LDH) Micro/Nanosystems and Their Azorubine Adsorption Performance
## 5 Conclusions  
In summary, Ni/Zn layered double hydroxide based nanohybrid was obtained using low-cost template-free hydrothermal process at 180 \({}^{\circ}\)C growth temperature during 6 h via  
Figure 8: Adsorption isotherms of Az dye on Ni/Zn LDH nanohybrid for two models: (**a**) Langmuir and (**b**) Freundlich model. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Models**} & \multirow{2}{*}{
\begin{tabular}{c} **Isotherm** \\ **Constants** \\ \end{tabular} } & \multicolumn{4}{c}{**Temperature K**} \\ \cline{3-5}  & & **288 K** & **298 K** & **318 K** \\ \hline \multirow{4}{*}{Langmuir} & q\({}_{\text{e-exp}}\) [mg g\({}^{-1}\)] & 223.44 & 236.74 & 243.94 \\  & R\({}^{2}\) & 0.9952 & 0.9934 & 0.9871 \\  & K\({}_{\text{L}}\) [l mg\({}^{-1}\)] & 0.376 & 0.270 & 0.099 \\  & Q\({}_{\text{max}}\) [mg g\({}^{-1}\)] & 227.273 & 243.902 & 294.118 \\  & R\({}_{\text{L}}\) & 0.050 & 0.069 & 0.167 \\ \hline \multirow{2}{*}{Freundlich} & R\({}^{2}\) & 0.9694 & 0.9779 & 0.8626 \\  & K\({}_{\text{F}}\) (mg g\({}^{-1}\)) & 71.58 & 72.35 & 43.12 \\ \cline{1-1}  & N & 3.128 & 3.123 & 2.097 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Langmuir and Freundlich constants for Az adsorption onto Ni/Zn LDH nanohybrid. the formation of two phases based of nickel hydrate hydroxide (\(\alpha^{*}-\)Ni(OH)\({}_{2}\) 0.75 H\({}_{2}\)O) and zinc carbonate (Zn\({}_{5}\)(CO\({}_{3}\))\({}_{2}\) (OH)\({}_{6}\)), where the FTIR results also indicate the presence of functional groups that favor their electrostatic attraction with the anionic dye. This multiscale porous hydroxide based nanohybrid with irregular-like nanoflakes in 3D spongeous shape hierarchical micro/nanostructures which possess very interesting specific surface area around 110 m\({}^{2}\) g\({}^{-1}\)with reasonable pore volume and pore size distribution between [0.16-0.85 cm\({}^{3}\) g\({}^{-1}\)] and [12-32 nm], respectively, is accompanied by mixed oxidation states with two kinds of anions Ni\({}^{2+}\) (or Zn\({}^{2+}\)) and Ni\({}^{3+}\) (or Zn\({}^{3+}\)), allowing it to be a very good nanoadsorbent. The Az adsorption ability of this new kind of nanoadsorbent was systematically investigated using kinetic and equilibrium studies as well as by examining the effect of dosage adsorbents, initial adsorbate concentration, initial pH, temperature, etc. Thus, the capacity sorption of Az increases with increasing Az concentration, with a very fast sorption process whereby an equilibrium time of 60 min was obtained. The adsorption behavior of dye onto this Ni/Zn LDH nanohybrid was obviously influenced by the pH with the best removal efficiency at pH range from 6 to 7. We also, noted that our new nanoadsorbent presents an important adsorption capacity (\(\sim\)223 mgg\({}^{-1}\)) compared to other materials. Moreover, the sorption kinetic data were more suitable with the pseudo-first-order (PFO) kinetic model. [PERSON] adsorption isotherm model showed the best compatibility with the experimental data in comparison with other isotherm models. Conceptualization, A.N.-M. and O.G. ; methodology, A.N.-M.; validation, A.N.-M. and O.G. ; investigation, A.N.-M. and O.G. ; resources, S.D. and N.H.; writing--original draft preparation, A.N.-M. and O.G. ; writing--review and editing, A.N.-M. and O.G. ; supervision, A.H. and M.G. ; Samples analysis, D.B. and J.E.-H. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. Informed Consent Statement: Informed consent was obtained from all subjects involved in the study. Not applicable. The present work is based on the research carried out at LEREC laboratory, Badji Mokhtar-Annaba University under Directorate General for Scientific Research and Technological Development (DGRSDT)--Algeria.