# Unlocking the Detoxification of Phenanthrene from Water Using Alkali-Activated Slag Mortar
## 2 Materials and Methods
### Sorption Experiment  
Analyzing phenanthrene (PHE) in aqueous solutions is challenging due to its low solubility. To address this, polyethylene (PE) passive samplers were utilized for assessing PHE sorption. It has been found that the equilibrium time between polyethylene and water for PHE is less than 10 h [19]. Therefore, a sorption experiment was conducted \begin{table}
\begin{tabular}{c c} \hline
**Component** & **wt\%** \\ \hline CaO & 42.4 \\ SiO\({}_{2}\) & 33.5 \\ Al\({}_{2}\)O\({}_{3}\) & 11.3 \\ MgO & 8.5 \\ SO\({}_{3}\) & 1.9 \\ TiO\({}_{2}\) & 0.7 \\ Na\({}_{2}\)O & 0.4 \\ K\({}_{2}\)O & 0.4 \\ Fe\({}_{2}\)O\({}_{3}\) & 0.4 \\ MnO & 0.2 \\ ZrO\({}_{2}\) & 0.1 \\ SrO & 0.1 \\ Cl & 0.1 \\ \hline \end{tabular}
\end{table} 
Table 1: Chemical composition of ground granulated blast furnace slag. for more than 10 h to ensure equilibrium between PE and water. PE strips measuring 2.5 cm \(\times\) 5.0 cm were cleaned by immersing them in hexane for 24 h, followed by acetone for 30 min, and then rinsed in deionized water for another 30 min. After cleaning, the PE strips were dried with lab tissue and stored at 4 \({}^{\circ}\)C until they were ready for use. For the sorption kinetics experiment, the AAS using 8% of Na\({}_{2}\)O was introduced to 200 mL of a PHE solution with a concentration of 0.9 mg/L, with the pH set at 5.5. To prevent microbial activity, NaN\({}_{3}\) was added to achieve a final concentration of 100 mg/L. The PE was then placed in the solution. At specified time intervals, the PE samplers were retrieved, wiped with lab tissue, and extracted with 20 mL of hexane for 24 h. To explore the rate-controlling step in sorption processes, the kinetic data were analyzed using the pseudo-first-order (PFO) and pseudo-second-order (PSO) models [20]. The equations are expressed as follows:  
Pseudo-first-order:  
\[\ln(Q_{e}-Q_{t})=\ln Q_{e}-K_{1}t. \tag{1}\]  
Pseudo-second-order:  
\[\frac{t}{Q_{t}}=\frac{1}{K_{2}Q_{e}^{2}}+\frac{t}{Q_{e}} \tag{2}\]  
where \(Q_{t}\) (mg/g) and \(Q_{e}\) (mg/g) represent the amounts of PHE adsorbed at time \(t\) (h) and at equilibrium, respectively; \(K_{1}\) is the PFO constant (1/min); and \(K_{2}\) is the PSO rate constant (g/mg/min). For the sorption equilibrium study, PHE concentrations ranged from 0.05 to 0.9 mg/L. The solid/liquid ratio was fixed at 0.1 g/L. For the study of the effect of pH on PHE removal efficiency, the pH was adjusted from 3 to 9 using HCl and NaOH solutions. In cases of the coexistence of hydrophobic organic carbons, a concentration of 0.05 mg/L was used for each of the following: PHE, PYR, NAP, DiBP, and DBP. After 240 h, the PE strips were retrieved and extracted with hexane. The PHE sorption isotherm data were fitted with the Langmuir and Freundlich sorption models. Each equation is expressed as follows:  
[PERSON] equation:  
\[Q_{e}=\frac{Q_{m}K_{L}C_{e}}{1+K_{L}C_{e}} \tag{3}\]  
Freundlich equation:  
\[Q_{e}=K_{\mathrm{F}}C_{e}^{\frac{1}{n_{\mathrm{F}}}} \tag{4}\]  
where \(Q_{e}\) (mg/g) represents the amount of PHE adsorbed at equilibrium, calculated from Equation (1), \(C_{e}\) (mL/g) denotes the equilibrium concentration in the PE, \(Q_{m}\) stands for the theoretical maximum sorption capacity of PHE in mg/g, \(K_{L}\) is the Langmuir equilibrium constant, relating to the free energy of exchange in L/mg, and \(K_{\mathrm{F}}\) ((mg/g) (L/mg)\({}^{1/n}\)) and \(n_{\mathrm{F}}\) are empirical constants of the Freundlich model, while \(n_{S}\) is a constant related to heterogeneous systems [21]. To evaluate the effect of real water on PHE sorption, 0.05 mg/L of PHE was spiked into uncontaminated lake water, river water, groundwater, and seawater. The solid/liquid ratio was fixed at 1.0 g/L. The concentration of PHE in the solution before and after sorption was determined based on the PHE extracted from the PE passive sampler at 240 h. The extracted samples were concentrated under a nitrogen gas flow before analysis.