Magnetic MgFe2O4/biochar derived from pomelo peel as a persulfate activator for levofloxacin degradation: Effects and mechanistic consideration

Magnetic biochar serves as adsorbents and catalyst supports for the removal of antibiotics from wastewater: A review

Numerous antibiotics are being released into the natural environment through wastewater. As antibiotic usage increases annually, its detrimental impact on the environment is escalating. Addressing environmental sustainability and human health requires significant attention towards antibiotic removal. In recent years, magnetic biochar (MBC) has gained widespread application in water treatment due to its exceptional adsorption and catalytic degradation capabilities. Antibiotics such as sulfamethoxazole (SMX), tetracycline (TC), ciprofloxacin (CIP), and others commonly exhibit an adsorption capacity by MBC ranging from 5 mg/g to 900 mg/g. Moreover, MBC typically removes over 90% of these antibiotics within 60 min. The effectiveness of antibiotic removal is significantly influenced by various preparation and modification methods. Furthermore, the incorporation of magnetism enables the material to be recycled and reused multiple times, thereby reducing consumption costs. This article discusses recent studies on antibiotic removal using MBC. It has been observed that variations in the selection of raw material and preparation procedures significantly affect antibiotic removal, while the mechanisms involved in antibiotic removal remain ambiguous. Additionally, it has been noted that the removal process may lead to secondary pollution and high preparation costs. Therefore, this review comprehensively outlines the utilization of MBC in the removal of antibiotics from wastewater, including aspects such as modification, preparation, removal mechanism, and factors influencing removal, and providing recommendations for antibiotic development. The aim is to offer researchers a clear understanding to advance the field of MBC materials.

Biochar-based functional materials for the abatement of emerging pollutants from aquatic matrices

Biochar has emerged as a versatile and efficient multi-functional material, serving as both an adsorbent and catalyst in removing emerging pollutants (EPs) from aquatic matrices. However, pristine biochar's catalytic and adsorption capabilities are hindered by its poor surface functionality and small pore size. Addressing these limitations involves the development of functionalized biochar, a strategic approach aimed at enhancing its physicochemical properties and improving adsorption and catalytic efficiencies. Despite a growing interest in this field, there is a notable gap in existing literature, with no review explicitly concentrating on the efficacy of biochar-based functional materials (BCFMs) for removing EPs in aquatic environments. This comprehensive review aims to fill this void by delving into the engineering considerations essential for designing BCFMs with enhanced physiochemical properties. The focus extends to understanding the treatment efficiency of EPs through mechanisms such as adsorption or catalytic degradation. The review systematically outlines the underlying mechanisms involved in the adsorption and catalytic degradation of EPs by BCFMs. By shedding light on the prospects of BCFMs as a promising multi-functional material, the review underscores the imperative for sustained research efforts. It emphasizes the need for continued exploration into the practical implications of BCFMs, especially under environmentally relevant pollutant concentrations. This holistic approach seeks to contribute to advancing knowledge and applying biochar-based solutions in addressing the challenges posed by emerging pollutants in aquatic ecosystems.

Endogenous iron-enriched biochar derived from steel mill wastewater sludge for tetracycline removal: Heavy metals stabilization, adsorption performance and mechanism

Steel mill wastewater sludge, as an iron-enriched solid waste, was expected to be converted into iron-enriched biochar with acceptable environmental risk by pyrolysis. The purpose of our study was to evaluate the chemical speciation transformation of heavy metals in biochar under various pyrolysis temperatures and its reutilization for tetracycline (TC) removal. The experimental data indicated that pyrolysis temperature was a key factor affecting the heavy metals speciation and bioavailability in biochar, and biochar with pyrolysis temperature at 450 °C was the most feasible for reutilization without potential risk. The endogenous iron-enriched biochar (FSB450) showed highly efficient adsorption towards TC, and its maximum adsorption capacity could reach 240.38 mg g-1, which should be attributed to its excellent mesoporous structure, abundant functional groups and endogenous iron cycling. The endogenous iron was converted to a stable iron oxide crystalline phase (Fe3O4 and MgFe2O4) by pyrolysis, which underwent a valence transition to form a coordination complex with TC by electron shuttling in the FSB450 matrix. The study provides a win-win approach for resource utilization of steel wastewater sludge and treatment of antibiotic contamination in wastewater.

Insight into the degradation of carbamazepine by electrochemical-pressure UV-activated peroxodisulphate process: kinetics, radicals, and degradation pathway

In this work, to improve the performance of peroxodisulphate-advanced oxidation, an electrochemical oxidation-assisted UV light-activated peroxodisulphate system (E/UV/PDS) was used to degrade carbamazepine. The degradation of carbamazepine by PDS, E/PDS, UV/PDS and E/UV/PDS systems was compared, and their synergistic effects were analysed. The influence of single factors, such as PDS addition, initial pH, DS voltage, target initial concentration, etc., on the degradation of the E/UV/PDS system was discussed, and the optimal degradation process parameters were given. The active substances were determined by free radical inhibition experiments, such as 1O2, SO 4 - ⋅ and ⋅ OH . It was proved that 1O2 contributes much more to the degradation of carbamazepine than SO 4 - ⋅ and ⋅ OH . The degradation pathway of carbamazepine was proposed. Finally, the degradation mechanism of carbamazepine in the E/UV/PDS system was speculated. The results indicate that the electrochemical combined with the E/UV/PDS system is of great potential application value in the removal of antibiotic drug pollution and environmental purification.

Advances and challenges in the removal of organic pollutants via sulfate radical-based advanced oxidation processes by Fe-based metal-organic frameworks: A review

Organic contaminants, notorious for their complexity and resistance to degradation, are prevalent in aquatic environments, posing severe threats to ecosystems. Sulfate radical-based advanced oxidation processes (SR-AOPs), known for their stability and high effectiveness, have become a common choice for treating organic wastewater. Metal-organic framework materials (MOFs) have garnered substantial attention due to their facile chemical manipulation, unique structural configurations, and other favorable properties. Therefore, this article critically reviews recent advances in research involving the utilization of Fe-based MOFs (Fe-MOFs) and their derivatives in SR-AOPs. Specifically, it highlights the manipulation of influencing factors within the system to enhance the degradation of organic pollutants. The mechanisms and applications underlying the degradation of organic pollutants in the SR-AOPs system are also elucidated.

Activating peroxymonosulfate with Fe-doped biochar for efficient removal of tetracycline: Dual action of reactive oxygen species and electron transfer

If pharmaceutical wastewater is not managed effectively, the presence of residual antibiotics will result in significant environmental contamination. In addition, inadequate utilization of agricultural waste represents a squandering of resources. The objective of this research was to assess the efficacy of iron-doped biochar (Fe-BC) derived from peanut shells in degrading high concentrations of Tetracycline (TC) wastewater through activated peroxymonosulfate. Fe-BC demonstrated significant efficacy, achieving a removal efficiency of 87.5% for TC within 60 min without the need to adjust the initial pH (20 mg/L TC, 2 mM PMS, 0.5 g/L catalyst). The degradation mechanism of TC in this system involved a dual action, namely Reactive Oxygen Species (ROS) and electron transfer. The primary active sites were the Fe species, which facilitated the generation of SO4•-, •OH, O2•-, and 1O2. The presence of Fe species and the C=C structure in the Fe-BC catalyst support the electron transfer. Degradation pathways were elucidated through the identification of intermediate products and calculation of the Fukui index. The Toxicity Estimator Software Tool (T.E.S.T.) suggested that the intermediates exhibited lower levels of toxicity. Furthermore, the system exhibited exceptional capabilities in real water and circulation experiments, offering significant economic advantages. This investigation provides an efficient strategy for resource recycling and the treatment of high-concentration antibiotic wastewater.

Decolorization and degradation of various dyes and dye-containing wastewater treatment by electron beam radiation technology: An overview

The treatment of dye-containing wastewater generated from textile industries is still a challenge, and various technologies, including physical, chemical and biological ones have been used. In recent years, the ionizing radiation (usually including gamma ray generated by radionuclide, such as 60Co and 137Cs, and electron beam generated by electron accelerator) technology has received increasing attention for degrading refractory or toxic organic pollutants in wastewater because of its unique advantages, such as no chemical additives, fast reaction rate, strong degradation capacity, high efficiency, flexibility, controllability. Compared to the conventional wastewater treatment processes, ionizing radiation technology, as a disruptive wastewater treatment technology, is more efficient for the decolorization and degradation of dyes and the treatment of dye-containing wastewater. In this paper, the recent advances in the treatment of dye-containing wastewater by ionizing radiation, in particular by electron beam (EB) radiation were summarized and analyzed, focusing on the decolorization and degradation of various dyes. Firstly, the formation of various reactive species induced by radiation and their interactions with dye molecules, as well as the influencing factors on the removal efficiency of dyes were discussed. Secondly, the researches on the treating dye-containing wastewater by electron beam radiation technology were systematically reviewed. Then, the decolorization and degradation mechanisms by electron beam radiation were further discussed in detail. And the integrated processes that would contribute to the advancement of this technology in practical applications were examined. More importantly, the recent advances of electron beam radiation technology from laboratory to application were reviewed, especially successful operation of dye-containing wastewater treatment facilities in China. And eventually, current challenges, future research directions, and outlooks of electron beam radiation technology were proposed for further advancing this technology for the sustainable development of water resources.

Removal of bisphenol A in a heterogeneous Fenton system via biochar synthesized using different Fe precursors: Properties, effects, and mechanisms

The reactivity and mechanism of the Fe-doped biochar (FeBC) Fenton reaction are typically influenced by the amount and type of Fe species in materials. This study investigated the effects of different Fe precursors (FeSO4, Fe(NO)3, FeCl2, and FeCl3) used to prepare Fenton catalyst FeBCs (FeSBC, FeNBC, FeC2BC, and FeC3BC) on the physicochemical characteristics, pH resistance, and reactivity for bisphenol A (BPA) removal. In addition to the FeSBC/H2O2 (0.007 min-1) system, FeNBC/H2O2 (1.143 min-1), FeC2BC/H2O2 (0.278 min-1), and FeC3BC/H2O2 (0.556 min-1) completely removed BPA within 20 min under the optimal conditions (FeBCs: 0.1 g/L; H2O2: 1 mM; BPA: 20 mg/L; pH 3). FeBCs/H2O2 systems demonstrated good stability and resistance to inorganic anions and natural organic matter under appropriate initial pH conditions. However, FeC2BC and FeC3BC exhibited better pH applicability than FeNBC. Characterization results indicated that the physicochemical properties of FeBCs were dependent on the Fe precursor, which correlated with the degree of Fe corrosion and the production of distinct reactive oxygen species (ROS). Quenching experiments and electron spin resonance detection results indicated that OH, 1O2, and O2- species were all engaged in BPA removal; the ROS concentrations were significantly influenced by the initial pH and Fe precursor. The results indicate that Fe precursors significantly impact the performance and characteristics of Fe-based biochar materials, which are tailorable to specific applications.

Enhanced adsorption performance of oxytetracycline in aqueous solutions by Mg-Fe modified suaeda-based magnetic biochar

Oxytetracycline (OTC) in the waste water can be removed by biochar adsorption. How to separate the biochar adsorbed antibiotics from the wastewater was also a problem. The nontoxic magnetic biochar was prepared from Suaeda biochar (800SBC) by mafic bimetal modification, and used for the removal of OTC. The results of XRD and VSM indicated that the main composition of biochar was ferrite. Then through batch adsorption experiments, the adsorption kinetics, isothermal adsorption, thermodynamics, and coexisting ion and adsorbent regeneration experiments were studied. Through the fitting of the adsorption model, it was found that Mg-Fe@800SBC(1:1) and 800SBC belonged to chemisorption. 800SBC was consistent with the Langmuir model, mainly monolayer adsorption, and Mg-Fe@800SBC(1:1) was consistent with the Freundlich model, mainly multilayer adsorption. The adsorption processes of the two materials were spontaneous, endothermic and entropic decreasing processes. The maximum adsorption capacity of the Mg-Fe@800SBC(1:1) for OTC from the Sips L-F model was 82.83 mg/g. Through various characterizations of magnetic biochar, it was found that the adsorption mechanism of the modified biochar included the hydrogen bonds between the oxygen-containing functional group of biochar and the -NH2 group of OTC, π-π EDA interaction, electrostatic attraction and complexation. Coexistence anions (CO32- and PO43-) have a negative effect on the adsorption process.

Sulfadiazine removal efficiency with persulfate driven by electron-rich Cu-beta zeolites

Surface electron transport and transfer of catalysts have important consequences for persulfate (PS) activation in PS system. In this paper, an electron-rich Cu-beta zeolites catalyst was synthesized utilizing a straightforward solid-state ion exchange technique to efficiently degrade sulfadiazine. The X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FTIR) results revealed that Cu element substitutes Al element and enters the beta molecular sieve framework smoothly. Furthermore, the X-ray photoelectron spectroscopy (XPS) measurements demonstrated that the Cu-beta catalyst is primarily Cu0. Cu-beta zeolites catalyst can exhibit excellent catalytic activity to degrade sulfadiazine with the oxidant of PS. The optimal sulfadiazine removal performance was explored by adjusting reaction parameters, including sulfadiazine concentration, catalyst dosage, oxidant dosage, and solution pH. The sulfadiazine removal efficiency in the Cu-beta zeolites/PS system could reach 90.5% at the optimal reaction condition ([PS]0 = 0.5 g/L, [Cu-beta zeolites]0 = 1.0 g/L, pH = 7.0) with 50 mg/L of sulfadiazine. Meanwhile, The degradation efficiency was less affected by anionic interference (Cl-, SO4-, HCO3-). The surface electron transport and transfer of the Cu-beta zeolites catalyst were significant causes for the remarkable degradation performance. According to electron paramagnetic resonance (EPR) and quenching studies, the Cu-beta zeolites/PS system was mostly dominated by SO4•- in the degradation of sulfadiazine. Furthermore, two possible pathways for sulfadiazine degradation were proposed according to the analysis of intermediate products detected by the liquid chromatography-mass spectrometry (LC-MS).

Degradation of sulfanilamide in aqueous solution by ionizing radiation: Performance and mechanism

Sulfonamide (SA) is an emerging contaminants and the efficient treatment of SA containing wastewater remains a challenge. Herein, SA degradation by gamma irradiation has been systematacially studied. SA (10 mg/L) could be totally removed with 1.5 kGy irradiation. Quenching experiments demonstrated that •OH and eaq- were the predominant for SA degradation. SA degradation was reduced with initial concentration increasing, and the removal was faster with pH increasing in the range of 3.1-10.8. The coexisting matters affected SA degradation through changing reactive species, and the introduction of SO42- and Cl- enhanced SA degradation, while CO32- had a negative impact on SA degradation, and the degradation was insignificantly affected when adding humic acid. Gamma irradiation could remain effective in real water matrixes. In conjunction with LC-MS analysis and DFT calculation, possible degradation pathways for SA were proposed. Gamma irradiation could reduce the toxicity of SA, while several byproducts with more toxic were also formed. Furthermore, gamma/priodate (PI) process was promising to enhance SA degradation and mineralization. k value increased by 1.85 times, and mineralization rate increased from 19.51% to 79.19% when adding PI. This study suggested that ionizing radiation was efficient to eliminate SA in wastewater.

Recent advances in the synthesis and application of magnetic biochar for wastewater treatment

Magnetic biochar (MBC) is a novel bio-carbon material with both desired properties as adsorbent and magnetic characteristics. This review provides an up-to-date summary and discussion on the latest development of MBC, which covers the progress on its synthesis, application, and techno-economic analysis. The review indicates that the direct hydrothermal synthesis has been catching more research attention to produce MBC due to its mild reaction conditions. Instead of the Fe-loaded MBC, there is a trend of using Mn for the magnetization. For the MBC application, how to improve its adsorption performance for water decontamination, ideally to match that of the biochar (BC) or activated carbon, is important. In addition, more studies on the environmental impacts of MBC and life-cycle assessment decoding the process optimization options are necessary. This review will provide valuable references for the development of MBC and MBC-based materials for wastewater treatment.

Production of MgFe2O4/activated carbons derived from a harmful grass Cynodon dactylon and their utilization for ciprofloxacin removal

Cynodon dactylon, an invasive species, exhibits its robust adaptability, reproduction and nutrient regime against the local species. Taking advantage of this harmful grass as a raw precursor to produce valuable materials for wastewater treatment has paid much attention. Herein, we report on the fabrication of Cynodom dactylon derived MgFe2O4@AC with a main goal of effective removal of ciprofloxacin antibiotic from water. Our findings showed that MgFe2O4@ACK1 composites attained mesoporous textures, high specific surface areas (884.3-991.6 m2 g-1), and MgFe2O4-20%@ACK1 was the most effective with a very high removal efficiency of 96.7%. The Elovich model was suitable for describing the kinetic of adsorption with (Radj)2 of 0.9988. Meanwhile, the isotherm data obeyed the Langmuir model corresponding to (Radj)2 of 0.9993. Qmax value of MgFe2O4-20%@ACK1 was determined at 211.67 mg g-1. The proposed adsorption mechanism primarily comprises five routes as follows, (i) pore-filling, (ii) π-π interaction, (iii) electrostatic interaction, (iv) hydrogen bonding, and (v) hydrophobic interaction. MgFe2O4-20%@ACK1 adsorbent could reuse with three cycles. We recommend that MgFe2O4/ACs derived from Cynodom dactylon could be high-efficiency adsorbents for the elimination of antibiotics.

A walnut shell biochar-nano zero-valent iron composite membrane for the degradation of carbamazepine via persulfate activation

In this study, novel walnut shell biochar-nano zero-valent iron nanocomposites (WSBC-nZVI) were synthesized using a combined pyrolysis/reduction process. WSBC-nZVI displayed a high removal efficiency (86 %) for carbamazepine (CBZ) compared with walnut shell biochar (70 %) and nano zero-valent iron (76 %) in the presence of persulfate (PS) (0.5 g/L catalyst, 10 mg/L CBZ, 1 mM persulfate). Subsequently, WSBC-nZVI was applied for the fabrication of the membrane using a phase inversion method. The membrane demonstrated an excellent removal efficiency of 91 % for CBZ in a dead-end system (2 mg/L CBZ, 1 mM persulfate). In addition, the effect of various operating conditions on the degradation efficiency in the membrane/persulfate system was investigated. The optimum pH was close to neutral, and an increase in CBZ concentration from 1 mg/L to 10 mg/L led to a drop in removal efficiency from 100 % to 24 %. The degradation mechanisms indicated that oxidative species, including 1O2, OH, SO4-, and O2-, all contribute to the degradation of CBZ, while the role of 1O2 is highlighted. The CBZ degradation products were also investigated, and the possible pathways and the predicted toxicity of intermediates were proposed. Furthermore, the practical use of the membrane was validated by the treatment of real wastewater.

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

In this study, cyanobacterial biochars (CBs) enriched/doped with non-metallic elements were prepared by pyrolysis of biomass amended with different N, S, and P containing compounds. Their catalytic reactivity was tested for persulfate oxidation of the antibiotic norfloxacin (NOR). N and S doping failed to improve CB catalytic reactivity, while P doping increased reactivity 5 times compared with un-doped biochar. Biochars produced with organic phosphorus dopants showed the highest reactivity. Post-acid-washing improved catalytic reactivity. In particular, 950 ℃ acid-washed triphenyl-phosphate doped CB showed the largest degradation rate and reached 79% NOR mineralization in 2 h. Main attributes for P-doped CBs high reactivity were large specific surface areas (up to 655 m2/g), high adsorption, high C-P-O content, graphitic P and non-radical degradation pathway (electron transfer). This study demonstrates a new way to reuse waste biomass by producing efficient P-doped metal-free biochars and presents a basic framework for designing carbon-based catalysts for organic pollutant degradation.

A smart and sustainable pathway for abatement of single and binary mixtures of dyes through magnetically retrievable Ca4Fe9O17 anchored on Biochar matrix

In this work, the author developed Ca4Fe9O17/biochar (CFB) via a green method through a facile co-precipitation procedure involving egg shells as calcium precursor and investigating its performance in single as well as binary solution of methylene blue (MB) and rhodamine B (RhB). The CFB nanocomposite was characterized by XRD, SEM, TEM, XPS, Raman, FTIR, BET, and VSM. ESR studies show the presence of hydroxyl (·OH) and superoxide (O2·¯) radicals, which are primary radical species for pollutant degradation. The average crystalline size of CFB nanocomposites was found to be 32.992 nm using XRD, whereas TEM analysis indicates a particle diameter of 35-36 nm. The degradation efficacy of MB and RhB dyes was achieved at 99.2% and 98.6%, respectively, in a single solution, whereas 99.4% and 99.2%, respectively, in a binary solution within 36 min. Additionally, an iron cluster was formed during the degradation process of MB dye. The degradation of organic contaminants and generation of iron clusters from the degraded dye products were both expedited by the remarkable extension effect of the Ca4Fe9O17 in the CFB nanocomposites. The three processes were achieved using CFB nanocomposite: (1) the advanced oxidation process; (2) degradation of MB and RhB dye in single as well as binary solution with enhanced efficiency, (3) the production of the iron cluster from degraded products. Thus, these three steps constitute a smart and sustainable way that leads to an effective effluent water treatment system and the generation of iron clusters preventing secondary pollution.

Simultaneous adsorption of ciprofloxacin and Cu2+ using Fe and N co-doped biochar: Competition and selective separation

The treatment of combined antibiotics and heavy metals pollution is a critical challenge. Herein, iron and nitrogen co-doped biochar (Fe/N-BC) was synthesized using rape straw as precursor, and applied for the adsorption of ciprofloxacin (CIP) and Cu2+ in single and binary systems. The qmax for CIP and Cu2+ were 46.45 mg g-1 and 30.77 mg g-1, respectively. Adsorption decreased in a binary matrix, indicating that there was a competitive effect between CIP and Cu2+, which might be due to CIP and Cu2+ sharing similar active adsorption sites on Fe/N-BC. Interestingly, CIP and Cu2+ co-adsorption was a pH-dependent process. Fe/N-BC has potential to highly selectively separate CIP/Cu2+ from mixed solutions through adjusting pH values. Furthermore, adsorption mechanisms were systematically investigated in this research. This research could help to provide a deeper understanding of the synchronously removing specific antibiotics and heavy metals by biochar adsorbents.

Deep insight into selective adsorption behavior and mechanism of novel deep eutectic solvent functionalized bio-sorbent towards methcathinone: Experiments and DFT calculation

This work designed and synthesized novelly selective, highly efficient and friendly environmental biochar nanomaterial (ZMBC@ChCl-EG) by screening suitable deep eutectic solvent (DES) as the functional monomer via Density Functional Theory (DFT). The prepared ZMBC@ChCl-EG achieved the highly efficient adsorption of methcathinone (MC) and exhibited excellent selectivity as well as good reusability. Selectivity analysis concluded that the distribution coefficient value (K_D) of ZMBC@ChCl-EG towards MC was 3.247 L/g, which was about 3 times higher than that of ZMBC, corresponding to stronger selective adsorption capacity. The studies of isothermal and kinetics indicated that ZMBC@ChCl-EG had an excellent adsorption capacity towards MC and the adsorption was mainly chemically controlled. In addition, DFT was used to calculate the binding energies between MC and each component. The binding energies were -10.57 kcal/mol for ChCl-EG/MC, -3.15∼-9.51 kcal/mol for BCs/MC, -2.33 kcal/mol for ZIF-8/MC, respectively, suggesting that DES played a major role in enhancing methcathinone adsorption. Lastly, the adsorption mechanisms were revealed by variables experiment combined with characterizations and DFT calculation. The main mechanisms were hydrogen bonding and π-π interaction.

Detection and removal technologies for ammonium and antibiotics in agricultural wastewater: Recent advances and prospective

With the extensive development of industrial livestock and poultry production, a considerable part of agricultural wastewater containing tremendous ammonium and antibiotics have been indiscriminately released into the aquatic systems, causing serious harms to ecosystem and human health. In this review, ammonium detection technologies, including spectroscopy and fluorescence methods, and sensors were systematically summarized. Antibiotics analysis methodologies were critically reviewed, including chromatographic methods coupled with mass spectrometry, electrochemical sensors, fluorescence sensors, and biosensors. Current progress in remediation methods for ammonium removal were discussed and analyzed, including chemical precipitation, breakpoint chlorination, air stripping, reverse osmosis, adsorption, advanced oxidation processes (AOPs), and biological methods. Antibiotics removal approaches were comprehensively reviewed, including physical, AOPs, and biological processes. Furthermore, the simultaneous removal strategies for ammonium and antibiotics were reviewed and discussed, including physical adsorption processes, AOPs, biological processes. Finally, research gaps and the future perspectives were discussed. Through conducting comprehensive review, future research priorities include: (1) to improve the stabilities and adaptabilities of detection and analysis techniques for ammonium and antibiotics, (2) to develop innovative, efficient, and low cost approaches for simultaneous removal of ammonium and antibiotics, and (3) to explore the underlying mechanisms that governs the simultaneous removal of ammonium and antibiotics. This review could facilitate the evolution of innovative and efficient technologies for ammonium and antibiotics treatment in agricultural wastewater.

Insights into the mechanism of persulfate activation with biochar composite loaded with Fe for 2,4-dinitrotoluene degradation

Iron in biochar composite loaded with Fe (Fex@biochar) is crucial for persulfate activation. However, the iron dosages-driven mechanism linked to the speciation, electrochemical property, and persulfate activation with Fex@biochar remains ambiguous. We synthesized and characterized a series of Fex@biochar and evaluated its catalytic performance in 2,4-dinitrotoluene removal experiments. With increasing FeCl₃ dosage, iron speciation in Fex@biochar changed from γ-Fe₂O₃ to Fe₃O₄, and the variation in functional groups was as follows: Fe-O, aliphatic C-O-H, O-H, aliphatic C-H, aromatic CC or CO, and C-N. The electron accepting capacity of Fex@biochar increased as the FeCl₃ dosage increased from 10 to 100 mM but decreased at 300 and 500 mM FeCl₃. 2,4-dinitrotoluene removal first increased and subsequently decreased, reaching 100% in the persulfate/Fe100@biochar system. The Fe100@biochar also showed good stability and reusability for PS activation, verified by five test cycles. The mechanism analysis indicated that the iron dosage altered the Fe (Ⅲ) content and electron accepting capacity of Fex@biochar during pyrolysis, further controlling persulfate activation and 2,4-dinitrotoluene removal. These results support the preparation of eco-friendly Fex@biochar catalysts.

Degradation of levofloxacin in wastewater by photoelectric and ultrasonic synergy with TiO2/g-C3N4@AC combined electrode

A novel particle combined electrode named TiO₂/g-C₃N₄@AC (TGCN-AC) was prepared by loading TiO₂ and g-C₃N₄ on activated carbon through gel method, which was used to degrade levofloxacin (LEF) in pharmaceutical wastewater by photoelectric process. The remarkable physicochemical features of particle electrodes were verified by using diverse characterization techniques including SEM-EDS, XRD, FT-IR, BET and pH_ZPC. EIS-CV and photocurrent showed excellent electrocatalysis and photoelectrocatalysis performance of particle electrodes. The photocatalytic characteristics and fluorescence properties of the particle electrode were proved by UV-vis DRS and PL spectra measurements. Combined with Tauc's plot and Mott-Schottky plots curves, the E_CB and E_VB of particle electrodes were determined. The experiments on different influence factors such as pH, ultrasonic, aeration, current density and the concentration of LEF were carried out in the photoelectric reactor. Under the conditions of pH values 3.0, 200 W ultrasonic, 8 L/min aeration, the mass ratio of g-C₃N₄ and TiO₂ is 8%, after 4.0 h of photoelectric process, about 94.76% of LEF (20 mg/L) in water was degraded. TGCN-AC also has excellent reusability. The degradation rate of LEF can still reach 71.17% after repeated use for 6 times. Scavenger studies showed that h⁺ and O^2- were the main active species. By observing the colony size of E. coli, it was proved that the LEF in the effluent had no antibacterial activity. The degradation pathways of LEF was analyzed and drawn by HPLC-MS spectra.

Escherichia coli inactivation in water by sulfate radical-based oxidation process using FeCl3-activated biochar/persulfate system

Pathogenic microbes in water present great risks to environments, water resources, and human health. In the present study, for the first time, a FeCl₃-activated bermudagrass-derived biochar (FA-BC) was applied to activate persulfate (PS) for E. coli inactivation. The PS activation was ascribed to the presence of Fe⁰ and Fe₃O₄ on the surface of FA-BC, and SO₄^·- radicals were proved to be the main role for E. coli inactivation using FA-BC activated PS system (FA-BC/PS). Decreasing the pH (5-9) and increasing the PS concentration (50-300 mg/L), reaction temperature (20-50 °C), and FA-BC dosage (100-500 mg/L) resulted in the enhancement of disinfection efficiency of E. coli using FA-BC/PS. 6.21 log reductions of E. coli were achieved within 20 min under the optimal conditions (500 mg/L FA-BC, 200 mg/L PS, pH 7, and 20 °C with 10⁷ CFU/mL E. coli in DI water). The FA-BC/PS effectively eliminated various initial concentrations of E. coli (10⁵-10⁸ CFU/mL). The E. coli inactivation rate decreased from 0.1426 min^-1 to 0.0883, 0.1268 min^-1, and 0.1093 min^-1 with the presence of 10 mg/L humic acid, 100 mg/L Cl^-, and 100 mg/L HCO₃^-, respectively. In addition, after three cycles of disinfection tests using FA-BC/PS, the E. coli inactivation rate only slightly decreased from 0.1426 to 0.1288 min^-1. The FA-BC/PS also effectively removed the E. coli in real stormwater with a 99.2 % inactivation efficiency within 180 min. The FA-BC/PS in fixed-bed column tests revealed the continuous and high inactivation of E. coli in water. Increasing the FA-BC amount (1.5 %-5 %) and PS concentration (50-200 mg/L) and decreasing the flow rate (2-4 mL/min) caused the lower E. coli concentration in effluent. Therefore, the FA-BC/PS can be considered as a promising and efficient technique for water disinfection.

Hydrothermal synthesis of sewage sludge biochar for activation of persulfate for antibiotic removal: Efficiency, stability and mechanism

The use of biochar materials as catalysts to activate persulfate (PS) for the degradation of antibiotics has attracted much attention. In this study, a carbonaceous material (Cu/Zn-SBC) was prepared from sewage sludge by hydrothermal modification. The efficiency of PS activation by Cu/Zn-SBC was investigated using tetracycline (TC) as the model antibiotic. In the Cu/Zn-SBC + PS system, the TC removal rate reached 90.13% at 10 min and exceeded 99% within 4 h. This not only met the requirement of removing large amounts of pollutants in a short time but also achieved the complete removal of pollutants in the subsequent time. Additionally, the Cu/Zn-SBC + PS system was found to be dominated by radical and nonradical pathways. Cu, hydroxyl and carboxyl groups on the surface of Cu/Zn-SBC promoted the production of free radicals and non-free radicals. Under several changes in reaction conditions and water environment factors, the TC removal rate remained above 85% within 10 min. Furthermore, the removal rate of TC was still 85.79% when Cu/Zn-SBC combined with PS was reused twice and 77.14% when reused four times. This study provides an ideal solution for the treatment of sewage sludge, and offers a stable and efficient material for removing antibiotics from wastewater.

Degradation of organic pollutants from water by biochar-assisted advanced oxidation processes: Mechanisms and applications

Biochar has shown large potential in environmental remediation because of its low cost, large specific surface area, porosity, and high conductivity. Biochar-assisted advanced oxidation processes (BC-AOPs) have recently attracted increasing attention to the remediation of organic pollutants from water. However, the effects of biochar properties on catalytic performance need to be further explored. There are still controversial and knowledge gaps in the reaction mechanisms of BC-AOPs, and regeneration methods of biochar catalysts are lacking. Therefore, it is necessary to systematically review the latest research progress of BC-AOPs in the treatment of organic pollutants in water. In this review, first of all, the effects of biochar properties on catalytic activity are summarized. The biochar properties can be optimized by changing the feedstocks, preparation conditions, and modification methods. Secondly, the catalytic active sites and degradation mechanisms are explored in different BC-AOPs. Different influencing factors on the degradation process are analyzed. Then, the applications of BC-AOPs in environmental remediation and regeneration methods of different biochar catalysts are summarized. Finally, the development prospects and challenges of biochar catalysts in environmental remediation are put forward, and some suggestions for future development are proposed.

Phosphate removal from aqueous solutions with a zirconium-loaded magnetic biochar composite: performance, recyclability, and mechanism

Phosphate (P) removal is significant for water pollution control. In this paper, a novel penicillin biochar modified with zirconium (ZMBC) was synthesized and used to adsorb P in water. The results showed that ZMBC had a porous structure and magnetic properties, and the zirconium (Zr) was mainly present in the form of an amorphous oxide. P adsorption displayed strong pH dependence. The Freundlich model described the adsorption process well, and the saturated adsorption capacity was 27.97 mg/g (25 ℃, pH = 7). The adsorption kinetics were consistent with the pseudo-second-order model, and the adsorption rates were jointly controlled by the surface adsorption stage and intraparticle diffusion stage. Coexisting anion experiments showed that CO₃^2- inhibited P adsorption, reducing the adsorption capacity by 62.63%. The adsorbed P was easily desorbed by washing with a 1 M NaOH solution, and after 5 cycles, the adsorbent had almost the same capacity. The mechanism for P adsorption was inner-sphere complexation and electrostatic adsorption.

Resource utilization of chicken manure to produce biochar for effective removal of levofloxacin hydrochloride through peroxymonosulfate activation: The synergetic function of graphitization and nitrogen functionality

Transforming hazardous livestock manure into biochar as an advanced oxidation processes catalyst is a two-in-one strategy to treat waste by waste. In this work, a self-modified biochar catalyst obtained from chicken manure is developed for peroxymonosulfate activation to degrade levofloxacin hydrochloride. The deterioration rate of levofloxacin hydrochloride reached 89% in 40 min, after three cycles of the catalyst, the LFX still maintained 52% degradation rate. And under low levofloxacin hydrochloride concentration, the degradation rate can reach 99% within 40 min. Apart from catalyst characterization and optimization, the effects of catalyst, peroxymonosulfate, levofloxacin hydrochloride, co-existing anions, and natural organic matter concentrations during the reaction are investigated. Additionally, the quenching experiments and electron spin resonance spectroscopy both reveal the reaction mechanism. As the graphitic nitrogen combined with the sp²-hybridized carbon in biochar was highly electronegative, thus appealing electrons from neighboring carbon networks, making the adjoining carbon atoms to be positively charged, which facilitated the degradation process. The oxidative degradation of levofloxacin hydrochloride was ascribed to non-radical routes including surface-bound radicals, h⁺ and ¹O₂ mediated oxidation, the contribution rates were 91%, 93.5%, and 96.8%, respectively. Moreover, possible degradation pathways of levofloxacin hydrochloride are studied by Density Functional Theory (DFT) and LC-MS analysis. This work provides a novel method to produce chicken manure biochar by self-modified chicken manure during biochar pyrolysis for peroxymonosulfate activation in organic contaminations abatement and reveals the combined effect of graphitization and nitrogen functionalization while providing new ideas for the resource utilization of chicken manure.

Excess sludge biochar facilitates persulfate activation for highly efficient tetracycline removal

This study proposed a novel advanced oxidation system to treat metal and antibiotic pollution in water simultaneously. Meanwhile, the enhancement effect of absorbed metal pollution on the activation of persulfate in the system was also investigated. As the most widely used and polluting material, tetracycline (TC) and metal Fe were used as the pollutant models. In this study, a carbonaceous material (BC) was prepared from excess sludge and then combined with the persulfate system (Fe/BC/PS). It was found that the best biochar was obtained when the pyrolysis temperature reached 500 °C (BC500), with the specific surface area of 39.712 m²/g. Combining it with 300 mg/L PS, the removal rate of 120 mg/L TC reached 70.6%. Moreover, the sludge biochar itself possessed numerous reaction sites and good defective structure, which provided a perfect reaction site for the variable metals absorbed by BC. They accelerated electron conduction greatly, which led to the activation of PS very active and generating far more active radicals than normal. In addition, it also proposed the rational pathway and potential mechanism of TC degradation based on the degradation intermediates. This study has a high reference value for resource utilization of sewage sludge and antibiotics removal from water.

FexN produced in pharmaceutical sludge biochar by endogenous Fe and exogenous N doping to enhance peroxymonosulfate activation for levofloxacin degradation

For preparing high performance biochar to be applicated in persulfate-based oxidation treatment of wastewater, the feasibility of deriving Fe-N biochar from pharmaceutical sludge by endogenous Fe and exogenous N doping was investigated. With exogenous urea doping, Fe_xN contained biochar (PZBC800U) was successfully derived from endogenous Fe(OH)₃ contained pharmaceutical sludge. PZBC800U effectively activated peroxymonosulfate (PMS) to remove 80 mg·L^-1 levofloxacin (LEV) within 90 min. The main mechanism of PMS activation by PZBC800U for LEV degradation was revealed as non-radical pathways dominated by ¹O₂ generation and direct electron transfer. The formation of Fe_xN combined with the increase of pyridinic-N in the biochar changed the electronic structure, improved the electron transfer ability, and thus achieved the excellent PMS activation capacity of the biochar. The vital function of endogenous Fe(OH)₃ was verified by comparing PZBC800U to Fe leached and extra Fe added controls. A total of 18 intermediates in the degradation of LEV were identified, and degradation pathways were proposed. Combined with the average local ionization energy calculation, the priority of piperazine breakage during LEV degradation was experimentally proved and mechanistically elucidated. This study provides a new insight into Fe_xN biochar preparation from pharmaceutical sludge and the mechanisms of its excellent PMS activation performance for LEV degradation.

The adsorption mechanisms of oriental plane tree biochar toward bisphenol S: A combined thermodynamic evidence, spectroscopic analysis and theoretical calculations

Garden pruning waste is becoming a problem that intensifies the garbage siege. It is of great significance to purify polluted water using biochar prepared from garden pruning waste. Herein, the interaction mechanism between BPS and oriental plane tree biochar (TBC) with different surface functional groups was investigated by adsorption experiments, spectroscopic analysis and theoretical calculations. Adsorption kinetics and isotherm of BPS on TBC can be satisfactorily fitted into pseudo-second-order kinetic and Langmuir models, respectively. A rapid adsorption kinetic toward BPS was achieved by TBC in 15 min. As compared with TBC prepared at low temperature (300 °C) (LTBC), the maximum adsorption capacity of TBC prepared at high temperature (600 °C) (HTBC) can be significantly improved from 46.7 mg g^-1 to 72.9 mg g^-1. Besides, the microstructure and surface functional groups of HTBC were characterized using SEM, BET-N_2, and XPS analysis. According to density functional theory (DFT) theoretical calculations, the higher adsorption energy of HTBC for BPS was mainly attributed to π-π interaction rather than hydrogen bonding, which was further supported by the analysis of FTIR and Raman spectra as well as the adsorption thermodynamic parameters. These findings suggested that by improving π-π interaction through high pyrolysis temperature, BPS could be removed and adsorbed by biochar with high efficacy, cost-efficiency, easy availability, and carbon-negative in nature, contributing to global carbon neutrality.

Immobilization of microbes on biochar for water and soil remediation: A review

Biochar has caught great attention over the last decade with the loose and porous structure, and carbon stability provides suitable living conditions for the growth and activity of microorganisms. This review provided a comprehensive summary of biochar immobilization microbe (BIM) in water and soil decontamination. Firstly, the bacterial immobilization techniques including adsorption, entrapping, and covalence methods were exhibited. Secondly, the applications of BIM in water and soil environmental remediation were introduced, mainly including the treatment of organic pollutants, heavy metals, and N/P, among which the most frequently immobilized microorganism was Bacillus. Then, the mechanisms of adsorption, redox, and degradation were analyzed. Finally, pertinent questions for future research of BIM technology were proposed. The purpose of this paper is to provide useful background information for the selection of better biochar fixation microorganisms for water and soil remediation.

A Mini Review on Persulfate Activation by Sustainable Biochar for the Removal of Antibiotics

Antibiotic contamination in water bodies poses ecological risks to aquatic organisms and humans and is a global environmental issue. Persulfate-based advanced oxidation processes (PS-AOPs) are efficient for the removal of antibiotics. Sustainable biochar materials have emerged as potential candidates as persulfates (Peroxymonosulfate (PMS) and Peroxydisulfate (PDS)) activation catalysts to degrade antibiotics. In this review, the feasibility of pristine biochar and modified biochar (non-metal heteroatom-doped biochar and metal-loaded biochar) for the removal of antibiotics in PS-AOPs is evaluated through a critical analysis of recent research. The removal performances of biochar materials, the underlying mechanisms, and active sites involved in the reactions are studied. Lastly, sustainability considerations for future biochar research, including Sustainable Development Goals, technical feasibility, toxicity assessment, economic and life cycle assessment, are discussed to promote the large-scale application of biochar/PS technology. This is in line with the global trends in ensuring sustainable production.

Resource utilization of tannery sludge to prepare biochar as persulfate activators for highly efficient degradation of tetracycline

In this work, a low-cost carbon-based catalyst (TSBC) was prepared by the facile one-pot pyrolysis of tannery sludge (TS) and used to activate persulfate (PS) for tetracycline (TC) removal. The results showed that TSBC-500 exhibited optimal physicochemical properties and the best performance for PS activation to remove TC from drinking water. Approximately 99.1% of TC was removed in the TSBC-500/PS system, which was considerably higher than those in the TSBC-500 adsorption and pure PS systems. Radical quenching experiments indicated that •OH and SO₄•^- played major roles in the TC removal in the TSBC-500/PS system. In addition, transition metals, functional groups, and the high degree of carbon structural defects were beneficial for PS activation to degrade TC. This study not only newly contributes to high-value utilization of TS as a PS activator but also offers an efficient method for the removal of organic pollutants.

Cu-Doped magnetic loofah biochar for tetracycline degradation via peroxymonosulfate activation

The Cu-doped deactivated magnetic biochar exhibited high PMS activation to degrade TC with a high removal rate of 97.6%.