# Innovative Vaporization of Wood Panel Waste into Activated Biochar for Efficient Phenol Adsorption
## 3 Results and Discussion
### Analysis of Metal and Heavy Metal Leading Behavior  
Reconstituted WPW normally contains heavy metals, which are considered pollutants and which can significantly harm the environment and human health, depending on their concentration [70]. The metals present in the WPW are in raw, pyrolyzed, and activated states. Table 5 presents the metal analysis results for the different samples. The obtained values are the average of three measurements. The highest metal concentrations in the WPW are for Ca and K (2513 mg/kg and 811 mg/kg, respectively), followed by Na (684 mg/kg) and Fe (319 mg/kg). Concentrations of Cd, Co, Cu, and Pb are below the detection limit for the applied method. The metal contents found in the WPW have high concentrations compared to those reported in the literature. For example, [PERSON] et al. [71] determined that uncontaminated solid wood presented lower metal concentrations compared to WPW, probably due to the presence of a melamine-formaldehyde coating bonded to both surfaces of the WPW. Indeed, [PERSON] and [PERSON] [72] found that Si and Ti were the two most abundant metals in \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Material** & & & & \\ (Precursor, Activation) & & & & \\ \hline Magnetic Fe–Zn biochar & & & & \\ activated with KOH & 1122 & 458.9 & pH 6, 25 \({}^{\circ}\)C, 480 min, 0.5 g/L, & [22] \\ (co-pyrolysis) & & & 100 mg/L & \\ \hline Wheat straw biochar (HF wash + 10\% CO\({}_{2}\) activation at 900 \({}^{\circ}\)C) & 492.6 & 471.2 & pH 7, 25 \({}^{\circ}\)C, 240 min, 1 g/L, & [23] \\ \hline Bamboo-derived & & & & \\ nitrogen-doping magnetic & & & & \\ porous hydrochroat coactivated & & & & \\ by K\({}_{2}\)FeO\({}_{4}\) and CaCO\({}_{3}\) & & & & \\ \hline Almond shell-activated biochar & & & & \\ (chemical activation with & 1050 & 161.0 & pH 7, 25 \({}^{\circ}\)C, 60 min, 1 g/L, & [25] \\ EDTA-4 Na/KOH at 750 \({}^{\circ}\)C) & & & & \\ \hline Black wattle bark-activated & & & & \\ carbon (black wattle bark, & 414.1 & 98.6 & pH 6.5, 55 \({}^{\circ}\)C, 120 min, 1 g/L, & [64] \\ ZnCl\({}_{2}\)-activated, pyrolysis) & & & & \\ \hline Sawdust-activated carbon & & & & \\ (physical activation via steam & 1053 & 158.9 & pH 4, 25 \({}^{\circ}\)C, 10 min, 0.5 g/L, & [65] \\ at 900 \({}^{\circ}\)C) & & & 100 mg/L & [66] \\ \hline Sunflower stalk-activated & & & & \\ biochar (chemical activation with KOH) & 452 & 333.0 & pH 6, 25 \({}^{\circ}\)C, 30 min, 0.5 g/L, & [66] \\ \hline Rice husk biochar activated & & & & \\ with KOH and modified by & 1368 & 215.3 & pH 5, 25 \({}^{\circ}\)C, 10 min, 0.5 g/L, & [67] \\ EDTA-4 Na (M-AC) & & & & \\ \hline Activated carbon (PET plastic, & & & & \\ H\({}_{3}\)PO\({}_{4}\)-activated) & 655.6 & 114.9 & pH 7, 25 \({}^{\circ}\)C, 120 min, 0.4 g/L, & [68] \\ \hline Magnetic Fe\({}_{3}\)O\({}_{4}\)/ZIF-8 MOF & & & & \\ composite (magnetic ZIF-8 & & & & \\ adsorbent) & & & & \\ \hline WPW-activated biochar at & & & & \\ 950 \({}^{\circ}\)C (BWP950) & 866 & 171.9 & pH 6, 25 \({}^{\circ}\)C, 48 h, 1 g/L, & \\ (without adding a chemical) & & & & 200 mg/L & This study \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparative summary of phenol adsorption by various biochar materials. furniture wood waste, followed by Ca, K, Na, and Fe, at lower concentrations than those found in the present study: 1590, 340, 300, and 280 mg/kg, respectively. The metal present in WPW could also come from the panel manufacturing process, which involves cutting and/or grinding tools [73]. Table 5 also shows the effects of pyrolysis and activation in terms of changes in metal concentrations. The concentrations of most metals increase after pyrolysis, and more so after activation. This is because endogenous, non-volatile heavy metals from biochar feedstocks remain in the biochar structure during the thermochemical processes [74]. Furthermore, the higher the activation temperature, the higher the concentration of metals in the activated biochar, because metals do not volatilize, whereas organic matter is degraded and removed during pyrolysis and activation [75].