Chloramphenicol interaction with functionalized biochar in water: sorptive mechanism, molecular imprinting effect and repeatable application

Mycelium-Doped Straw Biochars for Antibiotic Control

Straw, a predominant agricultural residue, represents a significant waste product. Harnessing its potential is of paramount importance both in terms of research and economic value. In this study, chemically pretreated corn straw was infused with distinct microbial fungal mycelium variants and subsequently transformed into a series of biochars through a process involving carbonization and activation. The findings revealed enhancements in the specific surface area and total pore volume of mycelium-doped straw biochars compared to the original corn straw biochar (BCS). Additionally, discernible disparities were observed in their physical and chemical attributes, encompassing functional groups, surface chemistry, and micro-morphology. Notably, in water-based antibiotic removal experiments focusing on tetracycline hydrochloride (TH) and chloramphenicol (CP), the mycelium-doped straw biochars outperformed BCS. Their maximum adsorption capacities for TH and CP surpassed those of alternative adsorbents, including other biochars. Impressively, even after five cycles, the biochar exhibited a removal rate exceeding 80%, attesting to its robust stability. This study successfully emphasized the efficacy of incorporating fungal mycelium to enhance the adsorption properties of straw-based biochar, introducing a new theoretical basis for the development of lignocellulosic materials.

Integration of covalent organic frameworks and molecularly imprinted polymers for selective extraction of flavonoid naringenin from grapefruit (Citrus × paradisi Macf.) peels

Grapefruit (Citrus × paradisi Macf.) peel, a by-product of the citrus-processing industry, possesses an important economic value due to the richness of bioactive compounds. In this study, boron-linked covalent organic frameworks integrated with molecularly imprinted polymers (CMIPs) were developed via a facile one-pot bulk polymerization approach for the selective extraction of naringenin from grapefruit peel extract. The obtained CMIPs possessed a three-dimensional network structure with uniform pore size distribution, large surface areas (476 m2/g), and high crystallinity. Benefiting from the hybrid functional monomer APTES-MAA, the acylamino group can coordinate with the boronate ligands of the boroxine-based framework to form B-N bands, facilitating the integration of imprinted cavities with the aromatic skeleton. The composite materials exhibited a high adsorption capacity of 153.65 mg/g, and a short adsorption equilibrium time of 30 min for naringenin, together with favorable selectivity towards other flavonoid analogues. Additionally, the CMIPs captured the template molecules through π-π* interaction and hydrogen bonding, as verified by FT-IR and XPS. Furthermore, they had good performance when employed to enrich naringenin in grapefruit peels extract compared with the common adsorbent materials including AB-8, D101, cationic exchange resin, and active carbon. This research highlights the potential of CMIPs composite materials as a promising alternative adsorbent for naringenin extraction from grapefruit peel.

Evaluation of different functionalization methodologies for improving the removal of three target antibiotics from wastewater by a brewery waste activated carbon

This work aims to increase the efficiency of an activated carbon produced from brewery waste (AC) in the removal of three target antibiotics (sulfamethoxazole (SMX), trimethoprim (TMP), and ciprofloxacin (CIP)) by surface incorporation of oxygen, nitrogen or sulfur groups. AC was produced using spent brewery grains (the most abundant waste from the brewing industry) as raw material, K2CO3 as activating agent and microwave energy for pyrolysis. Then, seven different functionalized AC were prepared, characterized for their physicochemical properties, and tested for adsorption (%) of SMX, TMP and CIP from three different matrices (ultrapure water (pH ~5-6), buffered ultrapure water (pH 8), and effluent from a municipal wastewater treatment plant (WWTP effluent (pH 8)), under batch operation. Based on the obtained results, an oxygen functionalized AC was selected for further characterization and studies on the adsorption of the target antibiotics from the WWTP effluent. Kinetic results fitted the pseudo-second order model and the equilibrium isotherms were adequately described by the Langmuir model, reaching maximum adsorption capacities (qm) of 124 ± 1 μmol g-1, 315 ± 2 μmol g-1 and 201 ± 5 μmol g-1 for SMX, TMP and CIP, respectively. The selected functionalization increased qm by up to 58 % in comparison with the non-functionalized AC. The oxygen modified AC produced from a biomass waste remarkably improved its performance for an efficient application in the removal of antibiotics from wastewater.

Chemistry of soil-type dependent soil matrices and its influence on behaviors of pharmaceutical compounds (PCs) in soils

Behaviors of pharmaceutical compounds (PCs) in soil are usually determined by experimental extrapolation of results from separate constitutes to the soil, or from a special soil to other regional soil conditions. However, such extrapolation is problematic due to variations in soil clay mineral and organic matter (OM) compositions with soil types, which dominate the interaction mechanisms of PCs in soil. It is essential to review current literature to enhance our understanding of the soil-type dependent surface chemistry of soil matrices and the environmental behavior of PCs in different soil types. Major types of soils occur globally in parallel to the latitudinal or altitudinal zonation due to regional climate conditions with distinct clay mineral and OM compositions. The soil-type dependent surface chemistry results in variations in retention, distribution, transport, and transformation PCs in soil. The mixture of PCs of different classes usually exhibited enhanced sorption due to the cooperative multilayer sorption on soil constituents, and that of the same class often caused differential adsorption capacity compared to the sorption from single compound due to competitive sorption. PCs preferentially adsorb to a soil component, or to a special soil type, and exhibit notably soil-type dependent sorption affinity, mobility, and dissipation. The soil-dependent surface chemistry of soil is critical to predict the persistence and bioavailability of PCs in soil. In the future, more detailed studies of influence of individual soil factor on the behaviors of PCs and especially the practical field site investigation are required to better understand the sorption, transport, transformation, and ecotoxicology of PCs in typical soil types.

Enhanced removal of sulfonamide antibiotics from water by phosphogypsum modified biochar composite

Antibiotic pollution has become a global eco-environmental issue. To reduce sulfonamide antibiotics in water and improve resource utilization of solid wastes, phosphogypsum modified biochar composite (PMBC) was prepared via facile one-step from distillers grains, wood chips, and phosphogypsum. The physicochemical properties of PMBC were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), Zeta potential, X-ray diffraction (XRD), etc. The influencing factors, adsorption behaviors, and mechanisms of sulfadiazine (SD) and sulfamethazine (SMT) onto PMBC were studied by batch and fixed bed column adsorption experiments. The results showed that the removal rates of SD and SMT increased with the increase of phosphogypsum proportion, while decreased with the increase of solution pH. The maximum adsorption capacities of modified distillers grain and wood chips biochars for SD were 2.98 and 4.18 mg/g, and for SMT were 4.40 and 8.91 mg/g, respectively, which was 9.0-22.3 times that of pristine biochar. Fixed bed column results demonstrated that PMBC had good adsorption capacities for SD and SMT. When the solution flow rate was 2.0 mL/min and the dosage of PMBC was 5.0 g, the removal rates of SD and SMT by modified wood chips biochar were both higher than 50% in 4 hr. The main mechanisms of SD and SMT removal by PMBC are hydrogen bonding, π-π donor-acceptor, electrostatic interaction, and hydrophobic interaction. This study provides an effective method for the removal of antibiotics in water and the resource utilization of phosphogypsum.

Influence of adsorption sites of biochar on its adsorption performance for sulfamethoxazole

In this study, the effects of various types of key adsorption sites on biochar were investigated on its adsorption capacity for sulfamethoxazole (SMX). The biochar obtained by carbonization of corncob at 800 °C (named CC800) was applied to the adsorption of SMX in aqueous environment. The adsorption of SMX by CC800 exhibited a "Three-stage downward adsorption ladder" characteristic in the whole pH range, which was attributed to the different mechanisms corresponding to different adsorption sites of CC800. The organic solvent method and heat treatment method restored the adsorption sites of CC800 after saturated adsorption. And the results revealed that the pore structure and aromatic structure under acidic conditions, and surface functional groups and pore structure under alkaline conditions were confirmed to be key SMX adsorption sites. The adsorption energies of each adsorption mechanism were calculated by density functional theory (DFT), and their order was (-)CAHB (-COO^-) > π⁺-π EDA interaction > (-)CAHB (-O^-) > pore filling mechanism > π-π EDA interaction. Based on the above studies, the adsorption performance of biochar to SMX can be improved by targeted modification of its micropore structure, surface functional groups, and aromatic structures.

A review of antibiotics and antibiotic resistance genes (ARGs) adsorption by biochar and modified biochar in water

Antibiotics have been used in massive quantities for human and animal medical treatment, and antibiotic resistance genes (ARGs) are of great concern worldwide. Antibiotics and ARGs are exposed to the natural environment through the discharge of medical wastewater, causing great harm to the environment and human health. Biochar has been widely used as a green and efficient adsorbent to remove pollutants. However, pristine and unmodified biochars are not considered sufficient and efficient to cope with the current serious water pollution. Therefore, researchers have chosen to improve the adsorption capacity of biochar through different modification methods. To have a better understanding of the application of modified biochar, this review summarizes the biochar modification methods and their performance, particularly, molecular imprinting and biochar aging are outlined as new modification methods, influencing factors of biochar and modified biochar in adsorption of antibiotics and ARGs and adsorption mechanisms, wherein adsorption mechanism of ARGs on biochar is found to be different than that of antibiotics. After that, the directions of biochar and modified biochar worthy of research and the issues that need attention are proposed. It can be noted that under the current dual carbon policy, biochar may have wider application prospects in future.

Molecular Mechanism of Chloramphenicol and Thiamphenicol Resistance Mediated by a Novel Oxidase, CmO, in Sphingomonadaceae

Antibiotic resistance mediated by bacterial enzyme inactivation plays a crucial role in the degradation of antibiotics in the environment. Chloramphenicol (CAP) resistance by enzymatic inactivation comprises nitro reduction, amide bond hydrolysis, and acetylation modification. However, the molecular mechanism of enzymatic oxidation of CAP remains unknown. Here, a novel oxidase gene, cmO, was identified and confirmed biochemically. The encoded CmO oxidase could catalyze the oxidation at the C-1' and C-3' positions of CAP and thiamphenicol (TAP) in Sphingobium sp. strain CAP-1. CmO is highly conserved in members of the family Sphingomonadaceae and shares the highest amino acid similarity of 41.05% with the biochemically identified glucose methanol choline (GMC) oxidoreductases. Molecular docking and site-directed mutagenesis analyses demonstrated that CAP was anchored inside the protein pocket of CmO with the hydrogen bonding of key residues glycine (G) 99, asparagine (N) 518, methionine (M) 474, and tyrosine (Y) 380. CAP sensitivity tests demonstrated that the acetyltransferase and CmO could enable a higher level of resistance to CAP than the amide bond-hydrolyzing esterase and nitroreductase. This study provides a better theoretical basis and a novel diagnostic gene for understanding and assessing the fate and resistance risk of CAP and TAP in the environment. IMPORTANCE Rising levels of antibiotic resistance are undermining ecological and human health as a result of the indiscriminate usage of antibiotics. Various resistance mechanisms have been characterized-for example, genes encoding proteins that degrade antibiotics-and yet, this requires further exploration. In this study, we report a novel gene encoding an oxidase involved in the inactivation of typical amphenicol antibiotics (chloramphenicol and thiamphenicol), and the molecular mechanism is elucidated. The findings provide novel data with which to understand the capabilities of bacteria to tackle antibiotic stress, as well as the complex function of enzymes in the contexts of antibiotic resistance development and antibiotic removal. The reported gene can be further employed as an indicator to monitor amphenicol's fate in the environment, thus benefiting risk assessment in this era of antibiotic resistance.

FeCl3-activated biochar catalyst for heterogeneous Fenton oxidation of antibiotic sulfamethoxazole in water

One-step FeCl₃-mediated pyrolysis/activation was developed for preparation of bermudagrass (BG)-derived FeCl₃-activated biochars (FA-BCs) from bermudagrass (BG) as a heterogenous Fenton catalyst for heterogeneous Fenton oxidation of sulfamethoxazole (SMX) in water. The FA-BC prepared at the FeCl₃ to BG mass ratio of 2 (FA-BC) exhibited higher adsorption and Fenton oxidation of SMX than other mass ratios of the FeCl₃ to BG. FA-BC presented the great surface area (835 m²/g) and high SMX adsorption capacity (195 mg SMX/g BC), which was higher than various BCs in the previous studies. Additionally, the surface of FA-BC was attached with Fe₂O₃, Fe⁰, and Fe₃O₄ after the FeCl₃ activation. Under the optimal conditions for Fenton reaction (SMX concentration, 100 mg/L; loading of FA-BC, 0.1 g/L; dose of H₂O₂, 200 mg/L; temperature, 20 °C; pH 3; reaction time, 12 h), SMX and COD removal efficiencies reached 99.94% and 65.19%, respectively. Increasing reaction temperature from 20 to 50 °C significantly improved the SMX oxidation rate from 0.46 to 1.04 h^-1. The HO· radicals were proved to play a major role during the Fenton oxidation of SMX. In addition, the SMX solution treated by Fenton oxidation showed much less toxicity than the initial SMX solution. Additionally, the reusability tests of FA-BC indicated that 89.58% removal efficiency for SMX was still achieved after 3 cycles of Fenton oxidation under the optimal conditions. Furthermore, FA-BC can also efficiently remove SMX from the dairy wastewater. Therefore, FA-BC showed a high potential to eliminate aqueous SMX through adsorption and heterogeneous Fenton oxidation.

Preparation of in-situ nitrogen-doped lignin-based porous carbon and its efficient adsorption of chloramphenicol in water

Porous carbon is an excellent absorbent for pollutants in water. Here, we report a breakthrough in performance of porous carbon based on lignin prepared using sodium lignosulfonate (SLS), potassium carbonate and melamine as precursor, activator and nitrogen source, respectively. A series of characterization tests confirmed that in-situ nitrogen doping greatly enhanced porous structure, resulting in a specific surface area of 2567.9 m² g^-1 and total pore volume of 1.499 cm³ g^-1, which is nearly twice that of non-nitrogen-doped porous carbon. Moreover, adsorption experiments revealed that at 303 K, the saturated adsorption capacity of chloramphenicol was as high as 713.7 mg g^-1, corresponding to an improvement of 33.7%. Further, the prepared porous carbon exhibited a strong anti-interference against metal ions and humic acid. The adsorption process was confirmed to be an endothermic reaction dominated by physical adsorption, indicating that an increase in temperature is conducive to adsorption. The results of this study show that nitrogen-doped lignin-based porous carbon prepared by in-situ doping is a promising material to significantly alleviate water pollution owing to its low cost, excellent pore structure and good adsorption properties.

Ground coffee waste-derived carbon for adsorptive removal of caffeine: Effect of surface chemistry and porous structure

Carbon-based adsorbents show high adsorption capacity towards caffeine due to their porosity and surface functionality. However, the main limiting factor for high performance has not been addressed; furthermore, the adsorption interaction with different active sites needs to be explored. In this study, we synthesized a hierarchical porous nitrogen-doped carbon with unique surface functionality by single-step calcination of coffee waste with KOH under N₂. The porous structure, nitrogen content, and types are optimized by varying calcination temperature and KOH concentration. The result of the adsorption experiments shows that both the nitrogen type and the pore size distribution are the limiting factors to adsorption. In addition, the effect of acidic and basic functional groups is studied in detail. The adsorption of caffeine on CW-C is dominantly governed by EDA interaction between the resonance structure of pyridonic-N and the electron-withdrawing group of the caffeine, and the dispersive force caused by the oxidized-N and delocalized π electron of caffeine. Furthermore, we demonstrate that the surface of CW-C is not suitable for the formation of electrostatic and non-electrostatic interaction with caffeine. The maximum adsorption capacity of caffeine at 25 °C is 274.2 mg/g. Moreover, we demonstrate that the unique physio-chemical properties of CW-C are capable of adsorbing other emerging contaminants such as diclofenac, where maximum adsorption capacity of 242.3 mg/g diclofenac is recorded.

Accurate Removal of Toxic Organic Pollutants from Complex Water Matrices

Characteristic emerging pollutants at low concentration have raised much attention for causing a bottleneck in water remediation, especially in complex water matrices where high concentration of interferents coexist. In the future, tailored treatment methods are therefore of increasing significance for accurate removal of target pollutants in different water matrices. This critical review focuses on the overall strategies for accurately removing highly toxic emerging pollutants in the presence of typical interferents. The main difficulties hindering the improvement of selectivity in complex matrices are analyzed, implying that it is difficult to adopt a universal approach for multiple targets and water substrates. Selective methods based on assorted principles are proposed aiming to improve the anti-interference ability. Thus, typical approaches and fundamentals to achieve selectivity are subsequently summarized including their mechanism, superiority and inferior position, application scope, improvement method and the bottlenecks. The results show that different methods may be applicable to certain conditions and target pollutants. To better understand the mechanism of each selective method and further select the appropriate method, advanced methods for qualitative and quantitative characterization of selectivity are presented. The processes of adsorption, interaction, electron transfer, and bond breaking are discussed. Some comparable selective quantitative methods are helpful for promoting the development of related fields. The research framework of selectivity removal and its fundamentals are established. Presently, although continuous advances and remarkable achievements have been attained in the selective removal of characteristic organic pollutants, there are still various substantial challenges and opportunities. It is hopeful to inspire the researches on the new generation of water and wastewater treatment technology, which can selectively and preferentially treat characteristic pollutants, and establish a reliable research framework to lead the direction of environmental science.

Occurrence, toxicity and adsorptive removal of the chloramphenicol antibiotic in water: a review

Chloramphenicol is a broad-spectrum bacterial antibiotic used against conjunctivitis, meningitis, plague, cholera, and typhoid fever. As a consequence, chloramphenicol ends up polluting the aquatic environment, wastewater treatment plants, and hospital wastewaters, thus disrupting ecosystems and inducing microbial resistance. Here, we review the occurrence, toxicity, and removal of chloramphenicol with emphasis on adsorption techniques. We present the adsorption performance of adsorbents such as biochar, activated carbon, porous carbon, metal-organic framework, composites, zeolites, minerals, molecularly imprinted polymers, and multi-walled carbon nanotubes. The effect of dose, pH, temperature, initial concentration, and contact time is discussed. Adsorption is controlled by π-π interactions, donor-acceptor interactions, hydrogen bonding, and electrostatic interactions. We also discuss isotherms, kinetics, thermodynamic data, selection of eluents, desorption efficiency, and regeneration of adsorbents. Porous carbon-based adsorbents exhibit excellent adsorption capacities of 500-1240 mg g^-1. Most adsorbents can be reused over at least four cycles.

Novel insights into the adsorption of organic contaminants by biochar: A review

With rising concerns in the practical application of biochar for the remediation of environment influenced by various organic contaminants, a critical review to facilitate insights the crucial role that biochar has played in wastewater and polluted soil decontamination is urgently needed. This research therefore aimed to describe different intriguing dimensions of biochar interactions with organic contaminants, which including: (i) an introduction of biochar preparation and the related physicochemical properties, (ii) an overview of mechanisms and factors controlling the adsorption of organic contaminants onto biochar, and (iii) a summary of the challenges and an outlook of the further research needs in this issue. In the light of the survey consequences, the appearance of biochar indicates the potential in substituting the existing costly adsorbents, and it has been proved that biochar is one promising adsorbent for organic pollutants adsorption removal from water and soil. However, some research gaps, such as dynamic adsorption, potential environmental risks, interactions between biochar and soil microbes, novel modification techniques, need to be further investigated to facilitate its practical application. This research will be conductive to better understanding the adsorption removal of organic contaminants by biochar.

Single and ternary competitive adsorption-desorption and degradation of amphenicol antibiotics in three agricultural soils

The widespread usage of veterinary antibiotics results in antibiotic contamination and increases environmental risks. This study was evaluated the single and ternary competitive adsorption-desorption and degradation of three amphenicol antibiotics (AMs): chloramphenicol (CAP), thiamphenicol (TAP), and florfenicol (FF) in three agricultural soils. The adsorption capacity of amphenicol antibiotics in the soil was weak, and the K_f value was in the range of 0.15-3.59 μg^1-1/nL^1/n kg^-1. In the single adsorption-desorption experiment, the ranked order of adsorption capacity was TAP > FF > CAP. However, in the ternary competitive adsorption experiment, the order was changed to be CAP > FF > TAP. The degradation of AMs in soils was performed at various conditions. All AMs were vulnerable to microbial degradation in soils. A higher initial concentration would reduce the degradation rate and enhance the persistence of AMs in soil. The degradation of AMs was positively influenced by changes in soil moisture content and culture temperatures up to 30 °C and decreased at higher temperatures. An equation was used to predict the leachability of AMs in soils and assess their risk to the water environment. The weak adsorption capacity and poor persistence of FF indicated that it may have a strong effect on groundwater based on the equation. It is imperative to further assess the biological impacts of FF at environmentally relevant concentrations given its mobility and extensive use in the livestock industry.

High mesoporosity phosphorus-containing biochar fabricated from Camellia oleifera shells: Impressive tetracycline adsorption performance and promotion of pyrophosphate-like surface functional groups (C-O-P bond)

In China, more than 3.5 million tons of Camellia oleifera discarded shells are produced every year. This work first prepared phosphorus-containing biochar (PBC) from C. oleifera shells and was successfully applied to the efficient removal of tetracycline (TC) from solutions. The prepared PBC exhibits superior TC adsorption capacity of 451.5 mg/g, and TC uptake rapidly reached 315.5 mg/g at the first 5 min (C₀ = 50 mg/L). Furthermore, PBC also shows excellent applicability to the broad range pH value (1-9) and superior selective removal in the presence of various high concentration coexisting ions (1 mM). Mechanisms underlying TC adsorption were also put forward, and analysis suggested that pyrophosphate-like surface functional groups (C-O-P bond) played a critical role in this process. Notably, treating pharmaceutical wastewater with PBC can efficiently reduce chemical oxygen demand (COD) and total organic carbon (TOC) concentration below the discharge standard of China (GB21904-2008).

Adsorption and regeneration on iron-activated biochar for removal of microcystin-LR

Novel iron activated biochars (FA-BCs) were prepared via simultaneous pyrolysis and activation of FeCl₃-pretreated bermudagrass (BG) for removing microcystin-LR (MC-LR) in aqueous solution. Compared to the raw BC (without activation), the surface area and adsorption capacity of FA-BC at iron impregnation ratio of 2 (2 g FeCl₃/g BG) were enhanced from 86 m²/g and 0.76 mg/g to 835 m²/g and 9.00 mg/g. Moreover, FA-BC possessed various iron oxides at its surface which provided the catalytic capacity for regeneration of MC-LR spent FA-BC and magnetic separation after the MC-LR adsorption. Possible mechanisms for the MC-LR adsorption onto FA-BC would include electrostatic attraction, π⁺-π, hydrogen bond, and hydrophobic interactions. The detailed adsorption studies indicated mainly chemisorption and intra-particle diffusion limitation would participate in the adsorption process. The thermal regeneration at 300 °C kept high regeneration efficiency (99-100%) for the MC-LR spent FA-BC during four cycles of adsorption-regeneration. In addition, the high regeneration efficiency (close to 100%) was also achieved by persulfate oxidation-driven regeneration. FA-BC also exhibited high adsorption capacity for the MC-LR from the real lake water to meet the MC-LR concentration below 1 μg/L as a safe guideline suggested by WHO.

Iron-activated bermudagrass-derived biochar for adsorption of aqueous sulfamethoxazole: Effects of iron impregnation ratio on biochar properties, adsorption, and regeneration

This work focused on the impacts of FeCl₃ impregnation ratio on the properties of FeCl₃-activated bermudagrass (BG)-derived biochars (IA-BCs), adsorption of sulfamethoxazole (SMX) onto IA-BCs and regeneration of SMX-spent IA-BC. Compared with the control BC (85.82 m²/g), IA-BCs made via pyrolysis with FeCl₃ to BG mass ratio between 1 and 3 (1-3 g FeCl₃/g BG) resulted in significantly enhancing surface area (1014-1035 m²/g), hydrophobicity, Fe content in IA-BCs (3.87-7.27%), and graphitized carbon. The properties of IA-BCs supported magnetic separation and higher adsorption (32-265 mg SMX/g BC) than the control BC (6-14 mg SMX/g BC) at various pH. Adsorption experiments indicated various adsorption mechanisms between SMX and IA-BCs via π-π EDA, hydrophobic interactions, and hydrogen bond with intraparticle diffusion limitation. The adsorption was also found to be spontaneous and exothermic. The IA-BC made at FeCl₃ to BG mass ratio of 2 (IA-BC_2.0) showed the maximum adsorption capacity for SMX (253 mg SMX/g BC) calculated from Langmuir isotherm model. Additionally, both NaOH desorption and thermal oxidation showed effective regeneration of SMX-saturated IA-BC_2.0 over multiple cycles. After three cycles of adsorption-regeneration, 64% and 62% of regeneration efficiencies were still achieved under thermal treatment at 300 °C and desorption with 0.1 M NaOH solution, respectively, indicating a cost-efficient adsorbent for the elimination of SMX in water.

Sonication alkaline-assisted preparation of Rhizopus oryzae biomass for facile bio-elimination of tetracycline antibiotic from an aqueous matrix

The present study aimed to remove tetracycline (TET) antibiotic molecule from an aqueous medium using adsorbents prepared from Rhizopus oryzae biomass. The TET adsorption process was discontinuous and the adsorbent biomass was crude and NaOH-sonication-modified Rhizopus oryzae fungi. Specific active surface area for crude and modified Rhizopus oryzae was 10.38 m²/g and 20.32 m²/g, respectively. The results showed that the maximum TET adsorption efficiency was determined at pH 4, temperature 25 °C, initial TET concentration 10 mg/L, contact time 80 min, and biomass quantity 2 g/L. The equilibrium behavior showed that the Langmuir model suitably described the process. The maximum TET adsorption capacity was determined to be 38.02 mg/g and 67.93 mg/g, respectively, indicating that the method of biomass modification promoted the bio-adsorption capacity. A higher correlation coefficient (R²) and lower RMSE for the pseudo-first-order kinetic than other models showed its ability to describe the behavior of TET bio-adsorption. The enthalpy thermodynamic parameter (ΔH°) for the TET adsorption process was determined - 63.847 kJ/mol and - 85.226 kJ/mol for the raw and modified Rhizopus oryzae, respectively. Therefore, it can be suggested that the biomass of Rhizopus oryzae especially the modified version can be effectively used for the TET removal from aqueous environments.

Chemical Activation of Forage Grass-Derived Biochar for Treatment of Aqueous Antibiotic Sulfamethoxazole

Chemically activated forage Bermudagrass-derived biochar (A-BC) was produced, characterized, and utilized for adsorption of sulfamethoxazole (SMX) in water for the first time. After NaOH activation, A-BC showed a higher surface area (1991.59 m2/g) and maximum adsorption capacity for SMX (425 mg SMX/g BC) than those of various biochars and commercial activated carbons. The detailed analysis for adsorption of SMX onto A-BC indicated the efficient sorption of SMX through π-π EDA and hydrophobic and hydrogen bond interactions. Additionally, the adsorption of SMX on A-BC was limited by pore and liquid film diffusions. The SMX adsorption on A-BC was found to be endothermic and spontaneous from thermodynamic studies. Furthermore, the highly efficient regeneration of SMX-saturated A-BC over multiple cycles was achieved by NaOH-driven desorption, indicating that the adsorption of SMX onto A-BC would have high potential for cost-effective solution for elimination of SMX from water.

The role of stereochemistry of antibiotic agents in the development of antibiotic resistance in the environment

Antibiotic resistance (ABR) is now recognised as a serious global health and economic threat that is most efficiently managed via a 'one health' approach incorporating environmental risk assessment. Although the environmental dimension of ABR has been largely overlooked, recent studies have underlined the importance of non-clinical settings in the emergence and spread of resistant strains. Despite this, several research gaps remain in regard to the development of a robust and fit-for-purpose environmental risk assessment for ABR drivers such as antibiotics (ABs). Here we explore the role the environment plays in the dissemination of ABR within the context of stereochemistry and its particular form, enantiomerism. Taking chloramphenicol as a proof of principle, we argue that stereoisomerism of ABs impacts on biological properties and the mechanisms of resistance and we discuss more broadly the importance of stereochemistry (enantiomerism in particular) with respect to antimicrobial potency and range of action.

Magnetic nanoparticles assisted dispersive liquid-liquid microextraction of chloramphenicol in water samples

This work describes the development of a new methodology based on magnetic nanoparticles assisted dispersive liquid-liquid microextraction (DLLME-MNPs) for preconcentration and extraction of chloramphenicol (CAP) antibiotic residues in water. The approach is based on the use of decanoic acid as the extraction solvent followed by the application of MNPs to magnetically retrieve the extraction solvent containing the extracted CAP. The coated MNPs were then desorbed with methanol, and the clean extract was analysed using ultraviolet-visible spectrophotometry. Several important parameters, such as the amount of decanoic acid, extraction time, stirring rate, amount of MNPs, type of desorption solvent, salt addition and sample pH, were evaluated and optimized. Optimum parameters were as follows: amount of decanoic acid: 200 mg; extraction time: 10 min; stirring rate: 800 rpm; amount of MNPs: 60 mg; desorption solvent: methanol; salt: 10%; and sample pH, 8. Under the optimum conditions, the method demonstrated acceptable linearity (R ² = 0.9933) over a concentration range of 50-1000 µg l^-1. Limit of detection and limit of quantification were 16.5 and 50.0 µg l^-1, respectively. Good analyte recovery (91-92.7%) and acceptable precision with good relative standard deviations (0.45-6.29%, n = 3) were obtained. The method was successfully applied to tap water and lake water samples. The proposed method is rapid, simple, reliable and environmentally friendly for the detection of CAP.

The Potentiality of Rice Husk-Derived Activated Carbon: From Synthesis to Application

Activated carbon (AC) has been extensively utilized as an adsorbent over the past few decades. AC has widespread applications, including the removal of different contaminants from water and wastewater, and it is also being used in capacitors, battery electrodes, catalytic supports, and gas storage materials because of its specific characteristics e.g., high surface area with electrical properties. The production of AC from naturally occurring precursors (e.g., coal, biomass, coconut shell, sugarcane bagasse, and so on) is highly interesting in terms of the material applications in chemistry; however, recently much focus has been placed on the use of agricultural wastes (e.g., rice husk) to produce AC. Rice husk (RH) is an abundant as well as cheap material which can be converted into AC for various applications. Various pollutants such as textile dyes, organic contaminants, inorganic anions, pesticides, and heavy metals can be effectively removed by RH-derived AC. In addition, RH-derived AC has been applied in supercapacitors, electrodes for Li-ion batteries, catalytic support, and energy storage, among other uses. Cost-effective synthesis of AC can be an alternative for AC production. Therefore, this review mainly covers different synthetic routes and applications of AC produced from RH precursors. Different environmental, catalytic, and energy applications have been pinpointed. Furthermore, AC regeneration, desorption, and relevant environmental concerns have also been covered. Future scopes for further research and development activities are also discussed. Overall, it was found that RH-derived AC has great potential for different applications which can be further explored at real scales, i.e., for industrial applications in the future.

Preparation and Modification of Biochar Materials and their Application in Soil Remediation

As a new functional material, biochar was usually prepared from biomass and solid wastes such as agricultural and forestry waste, sludge, livestock, and poultry manure. The wide application of biochar is due to its abilities to remove pollutants, remediate contaminated soil, and reduce greenhouse gas emissions. In this paper, the influence of preparation methods, process parameters, and modification methods on the physicochemical properties of biochar were discussed, as well as the mechanisms of biochar in the remediation of soil pollution. The biochar applications in soil remediation in the past years were summarized, such as the removal of heavy metals and persistent organic pollutants (POPs), and the improvement of soil quality. Finally, the potential risks of biochar application and the future research directions were analyzed.

Sorptive removal of dissolved organic matter in biologically-treated effluent by functionalized biochar and carbon nanotubes: Importance of sorbent functionality

The sorptive removal of dissolved organic matter (DOM) in biologically-treated effluent was studied by using multi-walled carbon nanotube (MWCNT), carboxylic functionalised MWCNT (MWCNT-COOH), hydroxyl functionalized MWCNT (MWCNT-OH) and functionalized biochar (fBC). DOM was dominated by hydrophilic fraction (79.6%) with a significantly lower hydrophobic fraction (20.4%). The sorption of hydrophobic DOM was not significantly affected by the sorbent functionality (∼10.4% variation) and sorption capacity followed the order of MWCNT > MWCNT-COOH > MWCNT-OH > fBC. In comparison, the sorption of hydrophilic fraction of DOM changed significantly (∼37.35% variation) with the change of sorbent functionality with adsorption capacity decreasing as MWCNT-OH > MWCNT-COOH > MWCNT > fBC. Furthermore, the affinity of adsorbents toward a hydrophilic compound (dinitrobenzene), a hydrophobic compound (pyrene) and humic acid was also evaluated to validate the proposed mechanisms. The results provided important insights on the type of sorbents which are most effective to remove different DOM fractions.

Microwave-assisted in-situ elimination of primary tars over biochar: Low temperature behaviours and mechanistic insights

An efficient method for microwave-assisted low temperature catalytic elimination of primary tars using cheap biochar as catalyst has been developed along with H₂ rich syngas production. Tar removal efficiency reached 94.03% after 8 min reaction at 600 °C, while the concentration of H₂ and syngas was up to 50.5 vol% and 94.5 vol% respectively, which were significantly comparable to conventional technologies at 700-900 °C. The FT-IR, ICP and EDX results indicated that the biochar surface contained O-containing functional groups and 12.6 wt% uniformly dispersed alkali and alkaline earth metals (AAEMs) in the carbon skeleton. The low temperature behaviours were attributed to the hot spots, which were induced by the increased dielectric properties of biochar and decentralized AAEMs under microwave heating. Possible reaction mechanism for the elimination of primary tars over biochar catalysts were discussed based on this experimental study.

Sorption of hydrophobic organic contaminants on functionalized biochar: Protagonist role of π-π electron-donor-acceptor interactions and hydrogen bonds

The sorption of five potent endocrine disruptors as representative hydrophobic organic contaminants (HOCs) namely estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-ethynylestradiol (EE2) and bisphenol A (BPA) on functionalized biochar (fBC) was systematically examined, with a particular focus on the importance of π-electron-donor (phenanthrene: PHEN) and π-electron-acceptors (1,3-dinitrobenzene: DNB, p-amino benzoic acid: PABA) on sorption. Experimental results suggested that hydrogen-bond formation and π-π-electron-donor-acceptor (EDA) interactions were the dominant sorption mechanisms. The sorption of HOCs decreased as E1 > E2 > EE2 > E3 > BPA based on the Freundlich and Polanyi-Mane-models. The comparison of adsorption coefficient (K_d) normalized against hexadecane-water partition coefficient (K_HW) between HOCs and PHEN indicated strong π-π-EDA interactions. π-π interactions among DNB, PHEN and HOCs were verified by the observed upfield frequency (Hz) shifts using proton nuclear magnetic resonance (¹H NMR) which identified the specific direction of π-π interactions. UV-vis spectra showed charge-transfer bands for π-donors (PHEN and HOCs) with the model π-acceptor (DNB) also demonstrating the role of π-π EDA interactions. The role of π-electron-donor and π-electron-acceptor domains in fBC was identified at different solution pH.

Toxicological interaction of multi-component mixtures to Vibrio qinghaiensis sp.-Q67 induced by at least three components

It has been stated by researchers that the antibiotic polymyxin B sulfate (POL) is a key component inducing time-dependent antagonism in freshwater luminescent bacteria, Vibrio qinghaiensis sp.-Q67, exposed in the ternary mixture system of the ionic liquids, pesticide and antibiotics. However, the previous statement is limited to ternary and quaternary mixtures without considering situations such as the binary system. In order to prove the direct inducing of antagonism by POL in a more complete and systematic way, two categories of experiments (adding POL in non-antagonistic ternary system and decomposing antagonistic ternary system with POL into the binary system) have been conducted in this paper. The results showed that quaternary mixture systems (adding POL to non-antagonism ternary mixture, up verification) exhibit antagonistic action in a majority of rays, at some point in the experiment. However, by decomposing the antagonistic ternary mixtures with POL into binary mixtures (down verification), the combined toxicities of binary mixtures at all time points in the experiment are additive. Obviously, the POL has a significant contribution to antagonism only in the ternary and quaternary mixtures, but not in the binary mixtures. We can draw a new conclusion that the antagonism of the multi-component mixtures is induced by at least three components (including POL), with complex chemical interactions. Therefore, considering POL's influence of antagonism as an example, future environmental protection practitioners and academic researchers should construct more scenarios of mixtures when assessing the influences and reactions of certain chemicals causing pollutions.

Selective detection of chloramphenicol based on molecularly imprinted solid-phase extraction in seawater from Jiaozhou Bay, China

This study highlights an efficient sample pre-treatment method for preconcentration and detection of chloramphenicol in marine water using molecularly imprinted solid-phase extraction (MISPE). Chloramphenicol molecularly imprinted microspheres were prepared and evaluated on the base of morphology, capacity and selectivity. The imprinted microspheres exhibited specific recognition and high retention capability to chloramphenicol and were applied as special solid-phase extraction adsorbents. An off-line MISPE protocol has been optimized and a creative analytical method coupled to HPLC-DAD was successfully developed for the cleanup and determination of chloramphenicol in seawater samples. Method performance was satisfactory with recoveries ranging from 81 to 90% and relative standard deviation (RSD) was <4.93% (n = 3). Accuracy of the method was assessed at three spiking concentration levels and the limit of detection was 5 ng L^-1. Finally, five seawater samples from Jiaozhou Bay of China were determined and the results showed that there was no chloramphenicol detected.

Removal of Chloramphenicol from Aqueous Solution Using Low-Cost Activated Carbon Prepared from Typha orientalis

Low-cost and efficient activated carbon (AC) was prepared from Typha orientalis via phosphoric acid activation for chloramphenicol (CAP) removal. The adsorption capacity and mechanisms of CAP on AC were investigated. The physicochemical properties of AC were characterized by an N2 adsorption/desorption isotherm, elemental analysis, Boehm’s titration and X-ray photoelectron spectroscopy (XPS). The effects of experimental parameters were investigated to study the adsorption behaviors of CAP on AC, including contact time, initial concentration, ionic strength, and initial pH. AC had a micro-mesoporous structure with a relatively large surface area (794.8 m2/g). The respective contents of acidic and basic functional groups on AC were 2.078 and 0.995 mmol/g. The adsorption kinetic that was well described by a pseudo-second-order rate model implied a chemical controlling step. The adsorption isotherm was well fitted with the Freundlich isotherm model, and the maximum CAP adsorption capacity was 0.424 mmol/g. The ionic strength and pH had minimal effects on CAP adsorption. The dominant CAP adsorption mechanisms on AC were evaluated and attributed to π-π electron-donor-acceptor (EDA) interaction, hydrophobic interaction, in conjunction with hydrogen-bonding interaction. Additionally, AC exhibited an efficient adsorption performance of CAP in a realistic water environment.