# Application of Nanofluids in CO\({}_{2}\) Absorption: A Review
## 4 Classification of Nanofluids Based on Base Liquid
### Water-Based Nanofluid
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Researchers**} & \multirow{2}{*}{**Base Fluid**} & \multirow{2}{*}{**Nanoparticle**} & \multicolumn{2}{c}{**Size of**} & \multirow{2}{*}{**Contactor Type**} & \multirow{2}{*}{**Enhancement \%**} & \multirow{2}{*}{
\begin{tabular}{c} **Absorbent** \\ **Loading** \\ \end{tabular} } \\  & & & & & & & \\ \hline [PERSON] et al. [111] & Water & Fe\({}_{3}\)O\({}_{4}\)@SiO\({}_{2}\)-SNH\({}_{2}\) & 50 & Bubble column & 70.3 & 0.4 wt.\% \\ [PERSON] et al. [90] & Water & SiO\({}_{2}\) & 30 & Bubble column & 24 & 0.021 wt.\% \\ [PERSON] et al. [128] & Water & FCNT * & 10 & Bubble column & 36 & 4 vol\% \\ [PERSON] et al. [84] & Water & SiO\({}_{2}\) & 15 & Batch vessel & 21 & 0.1 wt.\% \\  & Water & Al\({}_{2}\)O\({}_{3}\) & 20 & Batch vessel & 18 & 0.1 wt.\% \\  & & Fe\({}_{3}\)O\({}_{4}\) & 4 & & 24 & 0.02 wt.\% \\  & & CNT & * & & 34 & 0.02 wt.\% \\ [PERSON] et al. [32] & Water & Fe\({}_{3}\)O\({}_{4}\) & 4 & HFMC & 43.8 & 0.15 wt.\% \\  & & CNT & * & & 38 & 0.1 wt.\% \\  & & SiO\({}_{2}\) & 15 & & 25.9 & 0.05 wt.\% \\  & & Al\({}_{2}\)O\({}_{3}\) & 20 & & 3 & 0.05 wt.\% \\ [PERSON] et al. [88] & Water & SiO\({}_{2}\) & 30-40 & Bubble column & 7 & 0.1 wt.\% \\ Water & ZnO & 11.5 & & 14 & 0.1 wt.\% \\ [PERSON] et al. [129] & Water & Al\({}_{2}\)O\({}_{3}\) & 15-20 & Packed column & 14 & 0.05 vol\% \\  & Al\({}_{2}\)O\({}_{3}\)-SiO\({}_{2}\) & 10-15 & & 10 & 0.05 vol\% \\ [PERSON] et al. [34] & Water & Fe\({}_{3}\)O\({}_{4}\) & 8 & Packed column & 12 & 0.005 vol\% \\  & & NiO & 50 & & 9.5 & 0.01 vol\% \\ [PERSON] et al. [127] & Water & Al\({}_{2}\)O\({}_{3}\) & 25 & WWC & 40–55 & 1 vol\% \\ [PERSON] et al. [93] & Water & SiO\({}_{2}\) & 62 & Bubble column & 40 & 0.01 wt.\% \\ [PERSON] [130] & Water & CNT & * & HFMC & 45\({}^{1}\) & 0.25 wt.\% \\ [PERSON] et al. [131] & Water & SiO\({}_{2}\) & 15 & HFMC & 16 & 0.05 wt.\% \\  & & CNT & * & & 34 & 0.05 wt.\% \\ [PERSON] et al. [29] & DI Water & ZnO & 10-30 & PP HFMC & 130 & 0.15 wt.\% \\  & & TiO\({}_{2}\) & 21 & & 60 & 0.15 wt.\% \\  & & MWCNT & 10-20 & & 60 & 0.15 wt.\% \\ [PERSON] et al. [116] & Water & nMWCNT & 11.6 & Stirred reactor & 25.1 & 0.02 wt.\% \\ [PERSON] et al. [24] & DI Water & TiO\({}_{2}\) & ¡50 & Stirred cell reactor & 39.81 & 0.1 wt.\% \\ Al\({}_{2}\)O\({}_{3}\) & ¡40 & & 22.3 & 0.14 wt.\% \\ [PERSON] et al. [132] & Water & DETA@ECH@ Fe\({}_{3}\)O\({}_{4}\) & 40 & Batch equilibrium & & 77.3 & 0.5 wt.\% \\ [PERSON] et al. [133] & Water & EGO & 20 & Bubble column & diminished to zero & ¡0.02 wt.\% \\ [PERSON] et al. [134] & DI Water & Fe\({}_{3}\)O\({}_{4}\)@SiO\({}_{2}\)-lysine & 17-20 & Bubble Column & 88 & 0.125 wt.\% \\ [PERSON] et al. [135] & Water & Al\({}_{2}\)O\({}_{3}\) & 20–60 & Single-Bubble Column & 117 & 0.1 wt.\% \\  & & Fe\({}_{2}\)O\({}_{3}\) & 30–80 & & 103 & 1 wt.\% \\  & & SiO\({}_{2}\) & 20–60 & & 88 & 0.01 wt.\% \\ [PERSON] et al. [136] & DI Water & Al\({}_{2}\)O\({}_{3}\) & 45 & Bubble Column & 23.5 & 0.01 vol\% \\ [PERSON] et al. [137] & DI Water & \(\alpha\)- Al\({}_{2}\)O\({}_{3}\) & 80 & HFMC & 12.2 & 0.02 vol\% \\  & & \(\gamma\)- Al\({}_{2}\)O\({}_{3}\) & 20 & & 21.6 & 0.02 vol\% \\ [PERSON] et al. [31] & DI Water & CNT & * & HFMC & 40 & 0.5 wt.\% \\  & & SiO\({}_{2}\) & 10–15 & & 20 & 0.5 wt.\% \\ [PERSON] et al. [138] & DI Water & SiO\({}_{2}\) & 15 & Stirred cell reactor & 13.1 & 0.01 vol\% \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Overview of water-based nanofluids for improvement of CO\({}_{2}\) absorption. Nanofluids containing different nanoparticles like SiO\({}_{2}\), Fe\({}_{3}\)O\({}_{4}\), carbon nanotubes, or Al\({}_{2}\)O\({}_{3}\) in a base fluid including amine-based solutions or deionized water were also used for gas absorption in a membrane contactor.