## 4 Conclusions  
Low-temperature, flash-vacuum pyrolysis of an agro-waste, crisp persimmon peel, was performed. CPP200 prepared at 200 \({}^{\circ}\)C was negatively charged due to its oxygen-containing groups, which could efficiently interact with positively charged cationic dye (MB) to achieve selective adsorption. Under optimized experimental conditions (initial concentration of MB = 60 mg/L, T \(\geq\) 313 K, time = 90 min, adsorbent dosage = 5 mg), the maximum adsorption capacity of CPP200 reached 77.11 mg/g. The adsorption of MB by CPP200 was spontaneous and endothermic, which could be best described by a linear pseudo-second-order kinetic model as well as a linear Langmuir isothermal model. SEM, elemental mapping, FT-IR spectroscopy, XPS, zeta potential and SSA analyses were used to characterize the physicochemical properties of CPP200 and propose its adsorption mechanism. The experimental data indicated that oxygen-containing groups such as -C=O, -COOH and -OH groups dominated the adsorption of MB by CPP200. The low-temperature, flash vacuum pyrolysis method has shown energy-saving and environmentally-friendly features. Obviously, CPP-derived BCs can be rapidly and conveniently produced, and can thus be used as cost-saving adsorbents for future industrial and practical applications. **Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/molecules27165160/s1](https://www.mdpi.com/article/10.3390/molecules27165160/s1)]([https://www.mdpi.com/article/10.3390/molecules27165160/s1](https://www.mdpi.com/article/10.3390/molecules27165160/s1)), Figure S1: Fitted adsorption kinetic curves by pseudo-first-order models: (A) Linear form; (B) Non-linear form. Fitted adsorption kinetic curves by pseudo-second-order models: (C) Linear form; (D) Non-linear form; Figure S2: The experimental data of CPP200 toward MB and the fitting curves of [PERSON] isotherm model: (A) Linear form; (B) Non-linear form. The experimental data of CPP200 toward MB and the fitting curves of [PERSON] isotherm model: (C) Linear form; (D) Non-linear form; Figure S3: Experimental data and the fitted curve of ln\(k_{d}\) versus 1/T calculated from van't Hoff plots of adsorption of MB onto \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**adsorbent** & **Activated Method/** & **Temp. (K)** & **adsorbent** & **C\({}_{\text{MB}}\) (mg/L)** & **\(\mathbf{q_{\text{max}}}\)** & **References** \\  & **Activator** & & **Dosage** & & **(mg/g)** & **(mg/g)** & **References** \\ \hline Persimmon fruit peel & Furnace (700 \({}^{\circ}\)C, N\({}_{2}\)) & 298 & 2.0 g/L & 1600 & 303 & [18] \\ Dragon fruit peel & KOH/Furnace (700 \({}^{\circ}\)C, N\({}_{2}\)) & 323 & 0.08 g/0.1 L & 200 & 175.0 & [62] \\ Apricot stones & NaOH and Citric acid/Oven & 298 & 0.15 g/0.05 L & 160 & 18.95 & [65] \\ Pulp and Paper & Zn(L)/Tube furnace & 298 & 0.01 g/0.01 L & 1000 & 590.20 & [66] \\ Sludge & (700 \({}^{\circ}\)C, N\({}_{2}\)) & 298 & 0.01 g/0.01 L & 34.1 & 183.3 & [67] \\ Corn cob & H\({}_{3}\)PO\({}_{3}\)Microwave oven & 312.9 & 0.1 g/0.1 L & 34.1 & 183.3 & [67] \\ Corn stalk & KOH and H\({}_{3}\)PO4/Muffle & 298 & 0.015 g/0.03 L & 200 & 372.3, 105 & [68] \\ Crisp persimmon peel & Vacuum tube furnace (200 \({}^{\circ}\)C) & 313 & 0.005 g/0.02 L & 60 & 77.11 & This study \\ \hline \hline \end{tabular}
\end{table} 
Table 2: A comparison of adsorption capacities of CPP200 for MB with other previously reported carbon-based adsorbents under optimal experimental conditions. CPP200; Table S1: Adsorption kinetic parameters for the adsorption of MB onto CPP200; Video S1: title; Table S2: Adsorption isothermal parameters for the adsorption of MB onto CPP200; Table S3: Thermodynamic parameters of MB adsorption onto CPP200; Table S4: Molecular structure, molecular weight and maximum absorbance of dyes. Conceptualization, J.-G.Y. ; methodology, J.-G.Y. ; validation, L.-Q.X., J.-G.Y. and X.-Y.J. ; formal analysis, L.-Q.X. ; investigation, L.-Q.X. ; resources, J.-G.Y. ; data curation, L.-Q.X.