Phosphorus doped cyanobacterial biochar catalyzes efficient persulfate oxidation of the antibiotic norfloxacin

A comprehensive review of modified biochar-based advanced oxidation processes for environmental pollution remediation: efficiency, mechanism, toxicity assessment

Biochar (BC) has been demonstrated efficacy in activating oxidants to enhance environmental contaminant degradation. However, performance limitations of pristine biochar, including insufficient active sites and low electron transfer efficiency, primarily stemming from feedstock heterogeneity and pyrolytic parameter variations, resulting in suboptimal activation efficiency in practical applications. Recent studies demonstrated that targeted functionalization strategies, such as heteroatom doping, metal loading, and acid/alkali modification, could significantly improving activation performance of biochar, which was critical for advancing biochar-based advanced oxidation processes. In this review, the modification methods of biochar and their applications in activating diverse oxidants for water purification, soil remediation, air pollutant mitigation, and antimicrobial disinfection were summarized. Additionally, the differences in mechanisms among modified biochars for activating different oxidants in pollutant degradation were systematically illustrated. This review indicated that both free radicals and non-free radicals pathway played key roles in pollutant removal, either individually or through synergistic effects. Furthermore, potential challenges in applying modified biochar-based AOPs at a practical scale were also discussed. This review have shown that the presence of natural substances and impurities in these environments can deplete active components, resulting in reduced pollutant degradation efficiencies compared to controlled laboratory conditions. The current review illustrated that the toxicity of modified biochar was related to feedstocks and pyrolysis processes. Meanwhile, the toxicity of degradation intermediates could significantly reduce using modified biochar-based AOPs. Overall, this review provide insights for future research in this field.

Cu/N co-doped biochar activating PMS for selective degrading paracetamol via a non-radical pathway dominated by singlet oxygen and electron transfer

The non-free radical oxidation pathway (PMS-NOPs) of peroxymonosulfate (PMS) holds significant promise for practical wastewater treatment applications, owing to its low oxidation potential, high PMS utilization rate, and robust anti-interference capability in the degradation of pollutants. A novel activator copper nitrogen co-doped porous biochar (Cu-N-BC) with rich defect edges and functional groups was obtained by adding Cu and N to the biochar matrix generated by sodium alginate through pyrolysis in this study. Under the condition of 1 mM PMS, 30 mg/L activator was used to activate PMS and achieve efficient degradation of 10 mg/L paracetamol (PCT) within 15 min, with a high reaction rate constants (kobs) of 0.391 min-1. The activation mechanism of the Cu-N-BC/PMS/PCT system was a non-radical activation pathway with the dominance of singlet oxygen (1O2) and the presence of catalyst-mediated electron transfer. The graphite nitrogen, pyridine nitrogen, and Cu-N coordination introduced by Cu/N co-doping, as well as the carbon skeleton and CO functional group of biochar, were considered active sites that promote the 1O2 generation. The Cu-N-BC/PMS system exhibits strong stability, eco-friendliness, effective mineralization, and interference resistance across diverse pH levels (3-11) and interfering ions, including Cl-, H2PO4-, NO3-, SO42-, and humic acid. Remarkably, it efficiently degrades PCT in tap and lake water, achieving a notable 63.73% TOC mineralization rate, with leached copper ions below 0.02 mg/L. This research introduces a novel method for obtaining metal nitrogen carbon activators and enhances understanding of PMS non-radical activation pathways and active sites.

Unveiling activation mechanism of persulfate by homologous hemp-derived biochar catalysts for enhanced tetracycline wastewater remediation

Advancements in biochar activating persulfate advanced oxidation processes (PS-AOP), have gained significant attention. However, the understanding of biochar-based catalysts in activating PS remains limited. Herein, biochar (BC) and N-doped biochar (NBC) were synthesized from hemp for activating PS to treat tetracycline (TC) wastewater and analyzed their mechanisms separately. Surprisingly, N-doped in biochar leads to a change in the activation mechanism of PS. The BC-PS system operates mainly through a radical pathway, advantageous for treating soil organic pollution (68%) with pH adaptability (less than 10% variation). Nevertheless, the NBC-PS system primarily employs an electron transfer non-radical pathway, demonstrating stability (only 7% performance degradation over four cycles) and enhanced resistance to anionic interference (less than 10% variation) in organic wastewater treatment. This study provides a technical reference and theoretical foundation for enhancing biochar activation of PS in the removal of organic pollutants from aquatic and terrestrial environments.

The application of P-modified biochar in wastewater remediation: A state-of-the-art review

Phosphorus modified biochar (P-BC) is an effective adsorbent for wastewater remediation, which has attracted widespread attention due to its low cost, vast source, unique surface structure, and abundant functional groups. However, there is currently no comprehensive analysis and review of P-BC in wastewater remediation. In this study, a detailed introduction is given to the synthesis method of P-BC, as well as the effects of pyrolysis temperature and residence time on physical and chemical properties and adsorption performance of the material. Meanwhile, a comprehensive investigation and evaluation were conducted on the different biomass types and phosphorus sources used to synthesize P-BC. This article also systematically compared the adsorption efficiency differences between P-BC and raw biochar, and summarized the adsorption mechanism of P-BC in removing pollutants from wastewater. In addition, the effects of P-BC composite with other materials (element co-doping, polysaccharide stabilizers, microbial loading, etc.) on physical and chemical properties and pollutant adsorption capacity of the materials were investigated. Some emerging applications of P-BC were also introduced, including supercapacitors, CO2 adsorbents, carbon sequestration, soil heavy metal remediation, and soil fertility improvement. Finally, some valuable suggestions and prospects were proposed for the future research direction of P-BC to achieve the goal of multiple utilization.

Zinc and sulfur functionalized biochar as a peroxydisulfate activator via deferred ultraviolet irradiation for tetracycline removal

To enhance the degradation of tetracycline class (TC) residuals of high-concentration from pharmaceutical wastewater, a novel zinc (Zn) and sulfur (S) functionalized biochar (SC-Zn), as a peroxydisulfate (PDS) activator, was prepared by two-step pyrolysis using ZnSO4 accumulated water-hyacinth. Results showed that the removal rate of 50, 150, and 250 mg per L TC reached 100%, 99.22% and 94.83% respectively, by the SC-Zn/PDS system at a dosage of 0.3 g per L SC-Zn and 1.2 mM PDS, via the deferred ultraviolet (UV) irradiation design. Such excellent performance for TC removal was due to the synergetic activation of PDS by the biochar activator and UV-irradiation with biochar as a responsive photocatalyst. The functionalization of the co-doped Zn and S endowed the biochar SC-Zn with a significantly enhanced catalytic performance, since Zn was inferred to be the dominant catalytic site for SO4˙- generation, while S played a key role in the synergism with Zn by acting as the primary adsorption site for the reaction substrates. The employed SC-Zn/PDS/UV system had excellent anti-interference under different environmental backgrounds, and compared with the removal rate of TC by adsorption of SC-Zn, the increasing rate in the SC-Zn/PDS/UV system (18.75%) was higher than the sum of the increases in the SC-Zn/PDS (9.87%) and SC-Zn/UV systems (3.34%), furtherly verifying the systematic superiority of this synergy effect. This study aimed to prepare a high-performance functionalized biochar activator and elucidate the rational design of deferred UV-irradiation of PDS activation to efficiently remove high-concentration antibiotic pollutants.