# Innovative Vaporization of Wood Panel Waste into Activated Biochar for Efficient Phenol Adsorption
## 3 Results and Discussion
### Kinetics and Isotherms of Phenol Adsorption
The adsorption rate constant (K\({}_{2}\)) significantly increases with pyrolysis temperature, ranging from 4.63 \(\times\) 10\({}^{-5}\) mg/(g\(\cdot\)h) for BWP750 to 1.55 \(\times\) 10\({}^{-7}\) mg/(g\(\cdot\)h) for BWP950. This indicates higher diffusion rates of phenol molecules into the mesopores of the biochar, consistent with the increased mesopore volume from 0.028 cm\({}^{3}\)/g (BWP750) to 0.139 cm\({}^{3}\)/g (BWP950). The adsorption isotherm data (Table 3) fit well with the Langmuir model (R\({}^{2}\) = 0.99), suggesting monolayer adsorption of phenol molecules on homogenous surface sites of the biochar. The maximum adsorption capacity (Q\({}_{\text{max}}\)) increases proportionally with pyrolysis temperature, reaching 178.57 mg/g for BWP950 compared to 144.93 mg/g for BWP850. This increase is mainly attributed to the increased specific surface area (SBET = 866 m\({}^{2}\)/g) and higher carbon content (81.2%) obtained at 950 \({}^{\circ}\)C. Higher pyrolysis temperatures promote the carbonization process while reducing oxygen-containing functional groups (from 23.4% [BWP] to 13.4% [BWP950]), resulting in a more hydrophobic surface with a higher affinity for phenol adsorption. This process is explained by the increased graphitization degree and reduced polar functional groups on the biochar surface, which facilitate hydrophobic interactions and \(\pi\)-\(\pi\) electron donor-acceptor (EDA) interactions between phenol molecules and the biochar surface [63]. \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline \multirow{2}{*}{**Biochar**} & \multicolumn{3}{c}{**Pseudo-First-Order**} & \multicolumn{3}{c}{**Pseudo-Second-Order**} & \multicolumn{3}{c}{**Elovich’s Equation**} \\ \cline{2-9}  & **qe** & **K\({}_{1}\) h\({}^{-1}\)** & **R\({}^{2}\)** & **qe** & **mg/g** & **K\({}_{2}\) mg/(gh)** & **R\({}^{2}\)** & **\(\alpha\) mg/(gh)** & **\(\beta\)** & **R\({}^{2}\)** \\ \hline BWP750 & 27.63 & 0.581 & 0.67 & 49.751 & 4.63 \(\times\) 10\({}^{-5}\) & 0.80 & 7.275 \(\times\) 10\({}^{3}\) & 0.282 & 0.17 \\ \hline BWP850 & 35.34 & \(-\)0.071 & 0.67 & 142.86 & 1.16 \(\times\) 10\({}^{-6}\) & 0.99 & 5.742 \(\times\) 10\({}^{5}\) & 0.105 & 0.98 \\ \hline BWP950 & 34.27 & \(-\)0.071 & 0.99 & 172.41 & 1.55 \(\times\) 10\({}^{-7}\) & 1 & 3.836 \(\times\) 10\({}^{7}\) & 0.112 & 0.94 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Kinetic parameters obtained from phenol adsorption on biochars. Table 4 presents a comparative overview of phenol adsorption capacities across various biochars and activated carbons. The adsorption capacities span a broad range, from 98.6 mg/g for ZnCl\({}_{2}\)-activated black wattle bark biochar to 471.2 mg/g for CO\({}_{2}\)-activated, acid-washed wheat straw biochar. These differences are mainly attributed to variations in precursor composition, surface area, pore size distribution, and activation methods (e.g., chemical vs. physical) as well as adsorption test conditions (pH, adsorbent: effluent dosage, initial concentration). Notably, the WPW-derived biochar activated at 950 \({}^{\circ}\)C (BWP950) demonstrates 171.9 mg/g adsorption capacity and 866 m\({}^{2}\)/g surface area without the use of chemical agents such as KOH, ZnCl\({}_{2}\), or EDTA. Although this performance is moderate compared to highly engineered adsorbents, the use of reconstituted wood waste as a precursor offers significant economic and environmental advantages. Taken together, the results in Table 4 support the potential of industrial waste vaporization via thermal activation to yield biochars with suitable properties for wastewater treatment applications. Furthermore, whereas most studies of high-performance materials have applied shorter contact times (10-240 min), activated biochars in our study achieved competitive capacity even with a longer equilibrium time (48 h), suggesting strong surface interactions and the potential for continuous flow applications.