Preparation Of Magnetic Biochar Research Articles

Preparation of magnetic biochar used bioleached sludge to enhance tetracycline removal in a heterogeneous Fenton-like system

The environmental application of iron (Fe)-rich acidic sludge generated after bioleaching is still a challenge. Pyrolysis offers a promising avenue for converting this sludge into biochar. In this study, magnetic biochar (BLS-BC7) was prepared from acidic Fe-rich sludge and employed as a catalyst for tetracycline (TC) degradation by hydrogen peroxide (H2O2). Furthermore, compared with the original sludge-based biochar, BLS-BC exhibited a 2.3 times higher specific surface area, providing more active sites for the catalytic reactions. The scanning electron microscopy and Raman results indicated that BLS-BC7 was coated with a large number of particles on its surface, presenting a rough appearance with a high degree of defects, thereby providing more active sites for biochar. Characterization via photoelectron spectroscopy, elemental analysis, and Fourier transform infrared spectroscopy results indicated that BLS-BC contained a higher amount of oxygen functional groups, along with an increased content of CO and the formation of Fe–O, facilitating H2O2 activation to generate reactive oxygen species (ROS). Additionally, quenching experiments and electron paramagnetic resonance spectroscopy demonstrated the generation of multiple ROS such as 1O2, ·OH, and O2−·, in the BLS-BC7/H2O2 system. This resulted in a TC removal rate of 100 % within 120 min, with a mineralization rate of 53.4 %. The biochar exhibited easy recoverability and strong reusability, maintaining a TC removal rate of 91.3 % after five cycles of experiments. The X-ray diffraction patterns before and after the reaction showed that BLS-BC7 exhibited strong stability, with no apparent change in peak positions before and after use.

Corrigendum: Water Sci Technol (2023) 87 (2): 492-507: Preparation of magnetic biochar and its catalytic role in degradation of Cu-EDTA by heterogeneous Fenton reaction, Yu Jiang, Xinyu Liu, Shikai Huang, Huifang Wu, Haiyan Liu, Shenzhe Liu, Jiale Xu, Kun Wang.

Corrigendum: Water Sci Technol (2023) 87 (2): 492-507: Preparation of magnetic biochar and its catalytic role in degradation of Cu-EDTA by heterogeneous Fenton reaction, Yu Jiang, Xinyu Liu, Shikai Huang, Huifang Wu, Haiyan Liu, Shenzhe Liu, Jiale Xu, Kun Wang.

Preparation of magnetic biochar and its catalytic role in degradation of Cu-EDTA by heterogeneous Fenton reaction.

In this study, magnetic biochar (Fe-BC) was synthesized from phoenix tree leaves and FeSO4·7H2O by impregnation-pyrolysis method, and was used to activate H2O2 to degrade Cu-EDTA. The effects of preparation parameters on the degradation of Cu-EDTA by Fe-BC/H2O2 system were investigated by degradation experiments and characterization methods (SEM, BET, FTIR, XRD and XPS). The results showed that the magnetic biochar prepared under the pyrolysis temperature of 400 °C, pyrolysis time of 3 h and iron content of 3 wt% had the best catalytic activity. Within 120 min, the breaking efficiency of Cu-EDTA binding, precipitation efficiency of Cu2+ and removal efficiency of TOC could reach 78.48, 71.65 and 46.54% at the conditions of adding 1.0 g/L magnetic biochar and 25 mM H2O2 and the iron dissolution was only 0.32 mg/L. The characterization results and comparison experiments demonstrated that the catalytic effect of magnetic biochar not only depends on the transfer of electrons to H2O2 by the loaded iron oxides, but also the active oxygen functional groups (OFGs) and persistent free radicals (PFRs) contained on the surface can transfer electrons to H2O2 or even dissolved oxygen to produce an amount of hydroxyl radicals (·OH) and superoxide anion radicals (O2·-).

Nitrogen-doped magnetic biochar made with K3[Fe(C2O4)3] to adsorb dyes: Experimental approach and density functional theory modeling

Magnetic biochar displays promising applications in dye wastewater treatment since it can be effectively separated by magnetism. However, the preparation of magnetic biochar with a large specific surface area is complicated and the effects of ferrous and/or ferric ions on dye adsorption are not clear enough. Herein, a facile one-pot approach of magnetic self-nitrogen-doped biochar fabrication was developed, using K3[Fe(C2O4)3] as an activator and iron supplier. Magnetic self-nitrogen-doped biochar could be easily separated with a magnet. Magnetic self-nitrogen-doped biochar had a large specific surface area (1034 m2/g) and excellent adsorption capacities for Congo red (1360 mg/g) and Rhodamine B (320 mg/g). From thermodynamics studies, Congo red adsorption on magnetic self-nitrogen-doped biochar is better than Rhodamine B. Based on the larger adsorption energies, magnetic self-nitrogen-doped biochar has a relatively stronger binding ability for Congo red than Rhodamine B, and the ferrous ions loaded on biochar surface are more beneficial for dye adsorption than ferric ones.

Immobilization of Cd and Pb in soil facilitated by magnetic biochar: metal speciation and microbial community evolution.

The preparation of magnetic biochar from sewage sludge and rice straw for heavy metal contaminated soil remediation has greater application prospects, but its remediation mechanism was rarely considered by combining soil physicochemical properties with microbial community. In this study, the effects of magnetic sewage sludge biochar (SSB) and rice straw biochar (RSB) on Cd and Pb immobilization in paddy soil were compared and analyzed by 60-day soil incubation experiments. The results illustrated that DTPA-Cd and DTPA-Pb were reduced by 51.53% (43.07%) and 53.57% (50.47%), while the percentage of residual fraction of the BCR procedure was enhanced by 31.27% (30.78%) of Cd and 27.25% (23.22%) of Pb in the SSB (RSB) treatment, respectively. Fe was detected on both SSB and RSB surfaces, but SSB had rougher and a larger specific surface area compared to RSB. The addition of SSB and RSB in paddy soil increased soil pH and TOC content, and affected the diversity and species of soil microbial community. Compared with the CK group, the relative abundance of Proteobacteria, Bacteroidota, and Lysobacter decreased, and the relative abundance of Actinobacteriota, Pontibacter, and Alkaliphilus increased with SSB and RSB treatments, all of which reflected the bioavailability of Cd and Pb reduction.

Preparation of magnetic biochar with different magnetization sequences for efficient removal of oxytetracycline from aqueous solution

Magnetic modification has been widely applied to solve the difficulty of separating the powdered material from an aqueous medium after use. But knowledge on magnetization sequence to the properties of materials and their performance is still inadequate. To make up for this vacancy, in this study, the magnetic biochars with different magnetization sequences (Pre-MCS and Post-MCS) were prepared and employed in the adsorptive removal of oxytetracycline (OTC) wastewater. Characterizations, adsorption performance and mechanisms, as well as cycle performance of the prepared biochar were investigated. Results indicated that the Post-MCS not only had the highest OTC adsorption capacity (21.8 mg/g) but also exhibited the best separation performance. Mechanism analysis revealed that the chemisorption dominated the adsorption process of OTC on the studied biochars, besides, the electrostatic attraction and physisorption also had a certain contribution to the adsorption mechanism. Furthermore, the optimized biochar (Post-MCS) had acceptable reusability and remained ~61.9% of the adsorption capacity of fresh Post-MCS biochar. Therefore, the Pre-MCS can be considered as a promising adsorbent for the removal of OTC due to its high adsorption capacity and good separation performance.

The relationship of structure and organic matter adsorption characteristics by magnetic cattle manure biochar prepared at different pyrolysis temperatures

Abstract The preparation of magnetic biochar from cattle manure is an effective way for resource utilization. Fe3+-impregnated magnetic biochar for organic matter adsorption was synthesized by pyrolysis at 200, 400, and 600 °C respectively to investigate the influence of pyrolysis temperature on the structure and adsorption properties of magnetic biochar and their interrelationship. Congo red (CR) and Methylene blue (MB) were chosen to a representative of acidic and alkaline organics. The analyses showed that the number of functional groups decreased, and the specific surface area and iron oxides content increased with the increase of pyrolysis temperature. Fe3+ was loaded on biochar in form of γ-Fe2O3 and converted into Fe3O4 when the pyrolysis temperature rose from 400 to 600 °C. As the pyrolysis temperature increased from 200 to 600 °C, the adsorption capacities of magnetic biochar to MB first decreased and then increased, whereas that to CR increased gradually. There are three main structural factors affecting the adsorption properties of magnetic biochar: surface area, functional groups, and iron oxides content. The adsorption of magnetic biochar to MB is mainly related to the competitive mechanism of surface area and functional groups. The main factor affecting the adsorption of MB by MCMB200 (magnetic biochar prepared at 200 °C) and MCMB600 (magnetic biochar prepared at 600 °C) is functional groups and surface area, respectively. The adsorption of CR by magnetic biochar is mainly related to the synergistic mechanism of surface area and iron oxides content.