In this work, birch bark (BB) was used for the first time to prepare porous biochars via different one-step methods including direct activation (BBB) and N-doping co-activation (N-BBB). The specific surface area and total pore volume of BBB and N-BBB were 2502.3 and 2292.7 m²/g, and 1.1389 and 1.0356 cm³/g, respectively. When removing synthetic methyl orange (MO) dye and heavy metal Cr⁶⁺, both BBB and N-BBB showed excellent treatment ability. The maximum adsorption capacities of BBB and N-BBB were 836.9 and 858.3 mg/g for MO, and 141.1 and 169.1 mg/g for Cr⁶⁺, respectively, which were higher than most previously reported biochar adsorbents. The probable adsorption mechanisms, including pore filling, π–π interaction, H-bond interaction, and electrostatic attraction, supported the biochars’ demonstrated high performance. In addition, after five recycles, the removal rates remained above 80%, which showed the high stability of the biochars. This work verified the feasibility of the one-step N-doping co-activation method to prepare high-performance biochars, and two kinds of biochars with excellent performance (BBB and N-BBB) were prepared. More importantly, this method provides new directions and ideas for the development and utilization of other biomasses.

A porous carbon material was prepared from quinoa husk (QH) by carbonization and chemical activation with KOH. A series of experiments, including SEM (Scanning electron microscopy), FT-IR (Fourier transform infrared), XRD (X-ray diffraction), Raman, X-ray photoelectron spectroscopy (XPS), and N₂ adsorption/desorption, were carried out on the porous carbon produced from quinoa husk (PC–QH). The results showed that PC–QH was mainly composed of activated carbon and graphite. Moreover, PC–QH exhibited a high level of porosity with a BET (the Brunauer–Emmett–Teller theory) surface area of 1713 m² g⁻¹. As a representative dye, malachite green (MG) was selected to evaluate the performance of PC–QH to absorb the contaminants in dyeing wastewater. In batch adsorption experiments, PC–QH exhibited a high adsorption rate toward malachite green (MG). An uptake capacity of 599.90 mg g⁻¹ was achieved in the initial 5 min, and the MG adsorption capacity of PC–QH reached 1365.10 mg g⁻¹, which was higher than many other adsorbents. The adsorption data were well fitted with the Freundlich isotherm model and the pseudo-second-order kinetic model. PC–QH also displayed a high absorption rate to rhodamine B (RhB), methyl violet (MV), methylene blue (MB), and methyl orange (MO). The results in this study suggest that PC–QH can be a promising adsorbent for quick treatment of dyeing wastewater.

In this work, fungal hyphae (FH, Irpex lacteus) was used as the carbon resource for the preparation of porous carbon materials (PCFH) using mixed alkali as the activator. The SEM, N₂ adsorption/desorption, FT-IR, XRD, Raman, and XPS were used to characterize the structure and surface properties of PCFH. The results showed that the PCFH not only has a huge Brunauer–Emmett–Teller (BET) surface area (2480 m² g⁻¹), but also has abundant functional groups containing carbon, oxygen, and nitrogen. Rhodamine B (RhB) was selected to evaluate the adsorption properties of the PCFH prepared under different conditions in dyeing wastewater. A fast adsorption rate was observed, and an uptake capacity of 765 mg g⁻¹ was achieved in the initial 5 min. The maximum adsorption capacity of PCFH to RhB reached 1912 mg g⁻¹ at the pH value of 9, which could efficiently remove RhB from the aqueous solution. The adsorption process was fitted better by a pseudo-second order model, and the adsorption isotherm for the RhB was well fitted by the Freundlich model. Moreover, the probable mechanism of adsorption was analyzed. In short, the good adsorption performance of PCFH indicated that it has a broad application prospect for dye water pollution control.