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High capacity of oxytetracycline hydrochloride removal in wastewater via Mikania micrantha Kunth-derived biochar modified by Zn/Fe-layered double hydroxide

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Abstract

Antibiotic contamination in water has been an increasing global concern, and how to effectively remove antibiotics (e.g., oxytetracycline [OTC] hydrochloride) from wastewater becomes imperative. In this study, the biochar derived from an invasive plant (Mikania micrantha Kunth) was synthesized with Zn/Fe- layered double hydroxide (LDH) by co-precipitation method (ZnFe-LDH/MBC) to remove OTC from water. ZnFe-LDH/MBC posed the highest OTC removal performance of 426.61 mg/g. ZnFe-LDH/MBC exhibited stability and efficiency in OTC adsorption at different pH levels and under interfering conditions with co-existing ions, as well as outstanding regeneration capabilities during adsorption-desorption cycles. Furthermore, the removal of OTC by ZnFe-LDH/MBC was mediated by several processes including pore filling, hydrogen bonding force, electrostatic interaction, π-π interaction, as well as complexation. Consequently, ZnFe-LDH/MBC has excellent potential for the purification of OTC pollutants that is low-cost, efficient, and environmentally friendly.

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... These findings are consistent with results reported by Li et al. [47], where biochar modified with ZnSO 4 and FeCl 3 exhibited a significant increase in specific surface area and pore volume compared to unmodified biochar. For example, the specific surface area of Mikania micrantha Kunth biochar increased from 4.2 m 2 g −1 to 54.1 m 2 g −1 after modification, with a corresponding increase in pore volume from 0.02 to 0.14 cm 3 g −1 . ...
... Fourier-transform infrared (FTIR) spectroscopy showed an absorption band at 852 cm −1 , corresponding to the bending vibration of As-OH after adsorption [39]. Furthermore, the high adsorption efficiency observed at pH 5 can be attributed to surface protonation, which promotes hydrogen bond formation between functional groups on 1Zn-1Fe-1SBC and the adsorbed ions [47]. These hydrogen bonds provide additional attractive forces, stabilizing the adsorption of arsenic ions. ...
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Arsenic (As), a highly toxic and carcinogenic heavy metal, poses significant risks to soil and water quality, while oxytetracycline (OTC), a widely used antibiotic, contributes to environmental pollution due to excessive human usage. Addressing the coexistence of multiple pollutants in the environment, this study investigates the simultaneous adsorption of As(III) and OTC using a novel bimetallic zinc-iron-modified biochar (1Zn-1Fe-1SBC). The developed adsorbent demonstrates enhanced recovery, improved adsorption efficiency, and cost-effective operation. Characterization results revealed a high carbon-to-hydrogen ratio (C/H) and a specific surface area of 1137 m2 g−1 for 1Zn-1Fe-1SBC. Isotherm modeling indicated maximum adsorption capacities of 34.7 mg g−1 for As(III) and 172.4 mg g−1 for OTC. Thermodynamic analysis confirmed that the adsorption processes for both pollutants were spontaneous (ΔG < 0), endothermic (ΔH > 0), and driven by chemical adsorption (ΔH > 80 kJ mol−1), with increased system disorder (ΔS > 0). The adsorption mechanisms involved multiple interactions, including pore filling, hydrogen bonding, electrostatic attraction, complexation, and π-π interactions. These findings underscore the potential of 1Zn-1Fe-1SBC as a promising adsorbent for the remediation of wastewater containing coexisting pollutants.
... Conventional wastewater treatment methods are not intended to remove recalcitrant and complex molecules such as antibiotics (de Ilurdoz et al., 2022;X. Li et al., 2022). Currently, a number of advanced wastewater treatment techniques such as adsorption (Fan et al., 2023;B. Wang et al., 2023), biodegradation (Kayal & Mandal, 2022), chemical oxidation (Huo et al., 2023), and photocatalytic degradation (Regulska et al., 2022) are employed to remove OTC from water. Due to the straightforward operation, hig ...
... (Huo et al., 2023), and photocatalytic degradation (Regulska et al., 2022) are employed to remove OTC from water. Due to the straightforward operation, high effectiveness, and lack of harmful byproducts, adsorption is considered to be the most feasible among these techniques for removing recalcitrant pollutants from water (de Ilurdoz et al., 2022;X. Li et al., 2022). Activated carbon (Azari et al., 2020;Barjasteh-Askari et al., 2021;Hongsawat & Prarat, 2022), clay minerals (B. Wang et al., 2023), zeolites (Başkan et al., 2022), metal oxides (Das & Panda, 2022), nanomaterials (Almufarij et al., 2022), and biochar (Vievard et al., 2023) have been used by many researchers for the adsorptive removal of ...
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Indiscriminate use of oxytetracycline is linked to the development of antibiotic-resistant genes, posing a serious threat to human health and ecosystem balance. This article reports the adsorptive elimination of oxytetracycline (OTC) from aqueous solution using a newly developed MnO2-modified pine-cone biochar (MnO2/PCBC). The MnO2/PCBC was characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, CHNS analyzer, inductively coupled plasma–optical emission spectroscopy, and Brunauer-Emmett-Teller N2 adsorption analyzer. Batch adsorption experiments, designed using the central composite design framework of response surface methodology, were conducted to investigate the influence of process variables on the adsorption of OTC onto MnO2/PCBC. The optimized conditions for achieving maximum removal (88.1%) were found to be at pH 8, MnO2/PCBC dose 0.44 g/L, initial OTC concentration 200 mg/L, and temperature 303 K. The adsorption process follows Langmuir (R²=0.95) and Freundlich (R²=0.95) isotherms and pseudo-second-order (R²=0.99) adsorption kinetics. The adsorption process was found to be endothermic (ΔH⁰ = 33.04 kJ/mol) and spontaneous in nature (ΔG⁰ from −1.33 kJ/mol at 283 K to −5.65 kJ/mol at 313 K). The synthesized MnO2/PCBC could be recycled and reused for OTC removal with a percentage removal of around 80% after fifth cycle. The results indicate an effective removal of oxytetracycline with only 0.44 g/L MnO2/PCBC with maximum adsorption capacity of 357.14 mg/g which demonstrates improved performance in comparison to many adsorbents reported in literature. This implies that MnO2/PCBC offers potential to be developed into a cost-effective technique for antibiotic removal from water. Graphical Abstract
... CA4 candidate (id: 54680782) corresponds to oxytetracycline hydrochloride (OTC low-cost antibiotic derived from tetracycline used in livestock health and aquaculture [7 Intensive use of OTCs could lead to antibiotic resistance problems in people and even le to kidney disease and cancer. Because these chemical compounds accumulate in soil, w ter, and food [79]. Therefore, pollution caused by antibiotic use is an environmental pro lem of global magnitude. ...
... Intensive use of OTCs could lead to antibiotic resistance problems in people and even lead to kidney disease and cancer. Because these chemical compounds accumulate in soil, water, and food [79]. Therefore, pollution caused by antibiotic use is an environmental problem of global magnitude. ...
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Pesticides have a significant negative impact on the environment, non-target organisms, and human health. To address these issues, sustainable pest management practices and government regulations are necessary. However, biotechnology can provide additional solutions, such as the use of polyelectrolyte complexes to encapsulate and remove pesticides from water sources. We introduce a computational methodology to evaluate the capture capabilities of Calcium-Alginate-Chitosan (CAC) nanoparticles for a broad range of pesticides. By employing ensemble-docking and molecular dynamics simulations, we investigate the intermolecular interactions and absorption/adsorption characteristics between the CAC nanoparticles and selected pesticides. Our findings reveal that charged pesticide molecules exhibit more than double capture rates compared to neutral counterparts, owing to their stronger affinity for the CAC nanoparticles. Non-covalent interactions, such as van der Waals forces, π-π stacking, and hydrogen bonds, are identified as key factors which stabilized the capture and physisorption of pesticides. Density profile analysis confirms the localization of pesticides adsorbed onto the surface or absorbed into the polymer matrix, depending on their chemical nature. The mobility and diffusion behavior of captured compounds within the nanoparticle matrix is assessed using mean square displacement and diffusion coefficients. Compounds with high capture levels exhibit limited mobility, indicative of effective absorption and adsorption. Intermolecular interaction analysis highlights the significance of hydrogen bonds and electrostatic interactions in the pesticide-polymer association. Notably, two promising candidates, an antibiotic derived from tetracycline and a rodenticide, demonstrate a strong affinity for CAC nanoparticles. This computational methodology offers a reliable and efficient screening approach for identifying effective pesticide capture agents, contributing to the development of eco-friendly strategies for pesticide removal.
... Numerous studies have also shown that OTCHs contribute to microbial death and the dissemination of antibiotic resistance genes [9], which can be transmitted to other organisms through water runoff, soil and food. In particular, OTCH, a broad-spectrum antibiotic, has a long half-life and poor chemical and biological degradation [10], highlighting the urgent need for an effective and eco-friendly method to remove it from water [11]. ...
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Tetracycline contaminants are frequently found in groundwater and surface water, which contribute to the proliferation of antibiotic resistance genes, leading to significant environmental pollution. Adsorption technology is an efficient and reproducible remediation method. In this work, a bamboo-based composite biochar was prepared by attaching zeolitic imidazole framework-67 to delignified bamboo flakes, followed by carbonization using the solvothermal method to remove oxytetracycline hydrochloride from water. The chemical and physical properties of the composite were characterized using different surface analysis techniques. The findings revealed that zeolitic imidazole framework-67 modified bamboo-based composite biochar, with a maximum adsorption capacity of 310.74 mg·g⁻¹, adhered to the pseudo-second kinetic model and Langmuir isothermal model during the adsorption of oxytetracycline hydrochloride. The adsorption process was spontaneous, exothermic, and involved monolayer chemisorption. Possible mechanisms included electrostatic interactions, hydrogen bonding, physisorption and π-π interactions. This study demonstrates that the bamboo-based composite biochar possesses excellent adsorption properties for oxytetracycline hydrochloride and could serve as a cost-effective and environmentally friendly adsorbent for removing antibiotics from water. Graphical Abstract
... Актуальность этой проблемы поставила перед учеными задачу по поиску способов очистки вод от тетрациклинов, одним из которых является сорбционное концентрирование. Технология адсорбции находит широкое применение из-за простоты, экономической выгоды, отсутствия вторичного загрязнения и широкого выбора сорбционных материалов [10]. ...
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Окситетрациклин (OTЦ) является антибиотиком, который активно исполь-зуется в медицинских целях, в сфере животноводства и сельского хозяйства. Он обладает ши-роким спектром действия и эффективен в борьбе против различных бактериальных инфекций, а также способствует стимуляции роста животных. Однако его применение имеет свои негатив-ные стороны, в частности, использование OTЦ в сельском хозяйстве приводит к его попаданию в окружающую среду, в результате чего возникает угроза для здоровья людей и экологической обстановки. Для устранения нежелательных компонент из водных объектов часто прибегают к использованию сорбентов. Одним из перспективных сорбентов для решения данной задачи является бентонитовая глина. Преимущество данного материала состоит в достаточно высокой емкости, избиратель-ности, экологической безопасности, низкой стоимости и доступности. В работе в качестве сор-бента использована бентонитовая глина Левашинского месторождения Республики Дагестан. Установлено, что окситетрациклин наиболее полно извлекается из водной среды с рН 2.5 за 45 мин, при этом сорбционная емкость достигает 402 мг/г глины. Ключевые слова: бентонитовая глина, окситетрациклин, антибиотик, сорбция, очистка воды. Окситетрациклин (ОТЦ)-это антибиотик широкого спектра действия, исполь-зуемый для терапии в медицине и сельском хозяйстве при лечении различных бактери-альных инфекционных заболеваний, а также в качестве стимулятора роста в животно-водстве. В целом антибиотики используются для лечения и профилактики инфекцион-ных заболеваний как у людей, так и у животных. С начала 1990-х годов сельхозпроиз-водители активно применяли антибиотики, чтобы улучшить рост и эффективность кормления, а также снизить вероятность развития некоторых заболеваний [1]. Высокая антибактериальная активность и относительно низкая стоимость тетра-циклинов привели к масштабному использованию человеком, что, в свою очередь, по-служило причиной увеличения их присутствия в окружающей среде. По масштабам применения они занимают одно из первых мест среди других ветеринарных антибио-тиков [2; 3]. Согласно расчетам аналитиков DISCOVERY Research Group, в 2019 г. в России было произведено 93 000 тонн тетрациклина [4]. Относительно небольшие количества антибиотиков группы тетрациклинов усва-иваются организмом животных, в то время как большая часть выводится в виде неме-таболизированного исходного соединения. Выделение исходных соединений для тет-рациклинов составляет от 70 % до 90 %. Остатки тетрациклинов могут сохраняться в окружающей среде в течение длительного времени. Лабораторное исследование устой
... The resulting supernatants were filtered through 0.45 μm filter membranes and evaluated using a spectrophotometer (UV-1280; Shimadzu, China) at 700 nm. The adsorption capacity of the sample was calculated using Equation (1-1), and pseudo-first-order, pseudo-second-order, and intra-particle diffusion models were used to determine the kinetics of phosphate adsorption: [24] pseudo-first-order: lnðq e À q t Þ ¼ lnq e À K 1 t (1-4) pseudo-second-order: ...
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Phosphorus is an important element for plant growth. The efficient use and recovery of phosphorus is crucial due to limited phosphate resource reserves. This study explored the potential application of an in situ Ca and Mg co‐doped biochar derived from tobacco stem to reclaim and reuse phosphate from aqueous solutions. We performed various batch adsorption experiments and industrial analysis based on different parameters. The findings indicate that biochar prepared using the raw material particle size range of 0.85–2 mm and pyrolyzed at 800 °C presented good pore structure and specific surface area. Ca and Mg elements in biochar exhibited great influence on its phosphate adsorption property. The maximum phosphate adsorption capacity of the tobacco stem‐based biochar was 54.66 mg/g, and the experimental data agreed with the Langmuir equation, suggesting monolayer adsorption. The adsorption process conformed to the pseudo‐second‐order kinetic equation, indicating that chemisorption was the dominant adsorption process and that the adsorption was controlled by intra‐particle diffusion. Furthermore, phosphate adsorbed on tobacco stem‐based in situ Ca and Mg co‐doped biochar was released under acidic, alkaline, and neutral conditions. Therefore, in situ Ca and Mg co‐doped biochar prepared from tobacco stems is a potential environmentally friendly and low‐cost adsorbent for phosphorus recovery.
... Unfortunately, although research is advancing in the generation of knowledge, there are limitations that prevent the application of some processes at the industrial level. This is the case of adsorption using organic wastes, which, despite being the current trend in research due to their promising characteristics as adsorbents, present considerable differences with respect to their behavior [10]. Among the factors that influence the behavior of adsorbents are the type of contaminant and the number of components in the medium. ...
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Adsorption is nowadays an efficient technology for the removal of pollutants such as tetracycline (TC) and oxytetracycline (OTC) in water. Using mathematical tools such as modeling allows for a more in-depth understanding of the process to improve it to the point where it can be used in industry. In this work, the behavior of the bicomponent adsorption equilibrium of TC and OTC on rice husk ash and its mathematical estimation was studied. Two groups of data were used in this research: in group 1, the initial concentration of OTC was fixed, and the initial concentration of TC varied, and in group 2, TC was fixed, and OTC varied. Adsorption conditions were C0 = 20-160 mg L-1; pH = original solution; mads = 1.6 g; Vsol = 100 mL; T = 298K; agitation speed v = 300 rpm. The estimation model was of the additive type, which considered one term for each component and the Langmuir and Freundlich adsorption isotherms. The experimental data were processed in R Open software and the parameter used as the goodness of fit was the residual standard error (RSE). The four models obtained from the combination of the two components and the isotherms presented an RSE of less than 0.3, which indicates that the estimation of the adsorption equilibrium in the mixture had high precision. For group 1, the models that best fitted the experimental data were those corresponding to Langmuir-Langmuir and Langmuir-Freundlich interactions, whereas, for group 2 data they were Langmuir-Freundlich and Freundlich-Freundlich. The adsorption behavior in the mixture for TC was of Langmuir type and OTC had a behavior closer to the Freundlich isotherm. The interaction coefficients allowed us to determine that the mixing effect between the components was synergistic. The adsorption equilibrium on a bicomponent mixture of TC and OTC on rice husk ash was estimated with minimal error through a hybrid model.
... The equilibrium adsorption isotherm could be described well by different isotherm models to explain the interaction between adsorbate and adsorbent ( Fig. 4 and Table S6 †). 63 The adsorption isotherms of MB adsorbed by NaCBC 300 have been tted with all the equilibrium data in Fig. 4. The correlation coefficient value of Freundlich isotherm model (R 2 = 0.92) was higher than that of Langmuir isotherm model (R 2 = 0.89), indicating that the Freundlich isotherm model was more suitable for the isothermal behavior during the adsorption process. This result demonstrated that multilayer adsorption was more inclined to be the equilibrium adsorption mechanism of MB by NaCBC 300 . ...
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As an efficient and cost-effective adsorbent, biochar has been widely used in the adsorption and removal of dyes. In this study, a simple NaOH-modified biochar with the pyrolysis temperature of 300 °C (NaCBC300) was synthesized, characterized, and investigated for the adsorption performances and mechanisms of methylene blue (MB). NaCBC300 exhibited excellent MB adsorption performance with maximum removal efficiency and adsorption capacity of 99.98% and 290.71 mg g⁻¹, which were three and four times higher than biochar without modification, respectively. This might be attributed to the increased content of –OH and the formation of irregular flakes after NaOH modification. The Freundlich isotherm suggested multilayer adsorption between NaCBC300 and MB. Spectroscopic characterizations demonstrated that multiple mechanisms including π–π interaction, H-bonding, and pore-filling were involved in the adsorption. According to density functional theory (DFT) calculations, electrostatic interaction between NaCBC300 and MB was verified. The highest possibility of the attraction between NaCBC300 and MB was between –COOH in NaCBC300 and R–N(CH3)2 in MB. This work improved our understanding of the mechanism for MB adsorption by modified biochar and provided practical and theoretical guidance for adsorbent preparation with high adsorption ability for dyes.
... This increases the longevity and effectiveness of BC@ LDH for long-term stability. Li et al. (2022) reported improved removal of antibiotics (426.61 mg/g) compared to pristine biochar and LDH. ...
... The value of I D /I G used to estimate the carbon defect was 0.85, 0.82, 0.79, and 0.77 for BC, Zn-Al-LDH/biochar, Mg-Al-LDH/biochar, and Mg-Fe-LDH/biochar, respectively. Li et al. discussed the potential mechanism based on Raman analysis (Li et al., 2022e). The peaks at 1585 cm − 1 and 1356 cm − 1 of ZnFe-LDH/biochar in Raman spectrum moved to 1572 cm − 1 and 1371 cm − 1 , indicating that the π-π interaction was involved in oxytetracycline absorption. ...
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... Table S5: specific surface areas and porosity characteristics of fresh PKC-4 and used PKC-4. References [44,[56][57][58][59][60][61][62][63] are cited in the supplementary materials. ...
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In this study, MnPc intercalated Zn/Fe layered double hydroxides (MnPc/ZF-LDH) were synthesized by pillared intercalation modification with different MnPc intercalation amounts and used for the selective transformation and removal of As(III) from the arsenate-phosphate mixed solution. Fe-N bonds were constructed by the complexation of MnPc and iron ions on the Zn/Fe layered double hydroxides (ZF-LDH) interface. The DFT calculation results show that the binding energy of Fe-N bonded to arsenite (-3.75 eV) was higher than that of phosphate (-3.16 eV), resulting in MnPc/ZnFe-LDH exhibiting high As(III) selective adsorption performance and anchoring it rapidly in the arsenite -phosphate mixed solution. The maximum adsorption capacity of 1MnPc/ZF-LDH for As(III) could reach 180.7 mg·g-1 under dark conditions. MnPc also acts as a photosensitizer to provide more active species for the photocatalytic reaction. A series of experiments demonstrated that MnPc/ZF-LDH exhibits high As(III) selective photocatalytic performance. A total of 10 mg·L-1 of As(III) was completely removed in the reaction system within 50 min in a single As(III) environment. In an environment with As(III) and PO43-, it achieved 80.0 % removal efficiency of As(III) and showed a good reuse effect. The introduction of MnPc could improve the utilization of visible light by the MnPc/ZnFe-LDH. The singlet oxygen generated from photoexciting MnPc leads to abundant ZnFe-LDH interface OH. In addition, MnPc/ZnFe-LDH shows good recyclability, making it a promising multifunctional material for the purification of arsenic-polluted sewage.
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The composites based on layered double hydroxides and waste resources derived biochar (LDHs-biochar) have attracted a signficant interest for the removal of antibiotics from aqueous media. The major reason behind this application is the excellent adsorption performance along with the catalytic degrdation ability of LDHs-biochar. This review summarized the basic concept and stratigies for the preparation of LDHs-biochar along with the mechanisms behind their application for removal of antibiotics from contaminated water. Various environmental conditions, including pH, temperature, concentrations are discussed herein. Newly emerging approcahes based on LDHs-biochar along with major hurdels and challenges associated with the process for removal of antibiotics are emphasized. This review will be useful for the new reaserch findings and development of LDHs-biochar based systems for large-scale water remediation application.
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Biochar-supported zero-valent iron nanocomposites have received much attention due to their application potential in environmental pollution remediation. However, in many occasions, zero-valent iron loading improves the electron transfer efficiency and catalytic oxidation capacity of biochar while blocking the original pore structure of biochar, limiting its application potential. In this study, a zero-valent iron composites with large SSA (865.86 m2/g) was prepared in one step using pre-pyrolysis of biochar powder and K2FeO4 grinding for co-pyrolysis. The processes of ZVI generation and SSA expansion during the pyrolysis were investigated. The factors affecting the removal process of Cd and OTC in water by the composites were investigated. The mechanisms of Cd fixation and OTC degradation by the composites were explored by experiments, characterization, and DFT calculations. The OTC degradation pathway was proposed by theoretical predication and LC-MS spectrometry. The results indicate that ion exchange, complexation with oxygen-containing functional groups, electrostatic attraction, and interaction with π-electrons are the main mechanisms of Cd immobilization. The degradation pathways of OTC mainly include dehydroxylation, deamination and dealkylation.
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Transition metals are usually applied for activating persulfate to degrade organic contaminants efficiently, and there are numerous researches utilizing bimetallic catalysts to harvest the higher performance. Mechanisms of reactive oxygen species (ROS) generation as well as the mutual transformation of bimetal have been reported a lot, yet the deviation of ROS contribution for contaminants degradation and the relevant role of metals seem to be explored deficiently. Herein, biochar decorated with bimetal of Co/Fe (Fe1/4Co1/2-PWBC600) was prepared for peroxymonosulfate (PMS) activation and oxytetracycline (OTC) degradation, and properties of catalysts were analyzed for elaborating the intrinsic difference of ROS generation. Results showed that the structure of ROS contribution was optimized in Fe1/4Co1/2-PWBC600/PMS system, and the co-dominance of SO4•‒ and ¹O2 realized the better OTC degradation performance compared with the merely cobalt-based catalyst. Besides, durability tests showed that Fe1/4Co1/2-PWBC600 performed much better in oxidation resistance and reusability, which was owing to the co-dominance effect and the consumption buffering of oxygen vacancies. This work offered a new insight into the synthesis of bimetallic catalysts to strengthen the properties pertinently, realizing the higher performance of pollutants degradation and catalyst lifetime.
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In this study, loofah sponge-based biochar (KLSF/C) prepared by two-step pyrolysis and KOH modification was utilized in removing oxytetracycline hydrochloride (OTCH) and chloramphenicol (CAP) in single system and binary component systems. The effects of adsorbent dosage, initial concentration, and pH value on adsorption performance were discussed. The adsorption data could be well described by the pseudo-second-order kinetic model and the Freundlich model. The maximum adsorption capacities of OTCH and CAP at 25 °C were 790.49 mg g⁻¹ and 635.79 mg g⁻¹ in the single component system and 717.15 mg g⁻¹ and 581.39 mg g⁻¹ in the binary component system, respectively. In both systems, the adsorption capacity of KLSF/C for OTCH was always higher than that for CAP. Thermodynamic studies showed that the adsorption process was exothermic and spontaneous. Intraparticle diffusion and membrane diffusion were involved in the adsorption process. Overall, KLSF/C could be considered as an ideal adsorbent in removing antibiotics from water, which provided useful guidance for turning waste into wealth.
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In this paper, coconut shell biochar (BC), pickling biochar (HBC), and nano-zero-valent iron-loaded biochar (nZVI-HBC) were prepared; these were used to remove oxytetracycline (OTC), and the removal mechanism and degradation product were analyzed. These biochars were characterized using SEM, XRD, FTIR, and XPS. The effects of biochar addition amount, pH, ion type, and ion concentration on OTC adsorption were studied by a batch adsorption experiment. Under the optimal conditions, the equilibrium adsorption capacity of nZVI-HBC to OTC was 196.70 mg·g−1. The adsorption process can be described by Langmuir isothermal adsorption equations, conforming to the pseudo-second-order dynamics model, indicating that adsorption is dominated by single-molecule chemical adsorption, and a spontaneous process of increasing heat absorption entropy. Mass spectrometry showed that the OTC removal process of nZVI-HBC included not only adsorption but also degradation. These results provide a practical and potentially valuable material for the removal of OTC.
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Biochar (BC) has exhibited a great potential to remove water contaminants due to its wide availability of raw materials, high surface area, developed pore structure, and low cost. However, the application of BC for water remediation has many limitations. Driven by the intense desire of overcoming unfavorable factors, a growing number of researchers have carried out to produce BC-based composite materials, which not only improved the physicochemical properties of BC, but also obtained a new composite material which combined the advantages of BC and other materials. This article reviewed previous researches on BC and BC-based composite materials, and discussed in terms of the preparation methods, the physicochemical properties, the performance of contaminant removal, and underlying adsorption mechanisms. Then the recent research progress in the removal of inorganic and organic contaminants by BC and BC-based materials was also systematically reviewed. Although BC-based composite materials have shown high performance in inorganic or organic pollutants removal, the potential risks (such as stability and biological toxicity) still need to be noticed and further study. At the end of this review, future prospects for the synthesis and application of BC and BC-based materials were proposed. This review will help the new researchers systematically understand the research progress of BC and BC-based composite materials in environmental remediation.
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Photocatalytic degradation of oxytetracycline hydrochloride (OTC‐HCl) in marine aquaculture wastewater and the effects of factors on the effectiveness of photocatalysts are studied in this paper by using Zn0.75Mn0.75Fe1.5O4/ZnFe2O4/ZnO under visible light and changing the molar ratio of Zn²⁺:Fe³⁺:Mn²⁺, calcination temperature of catalysts, hydrogen peroxide concentration, dose of catalysts, illumination time of photocatalytic, and initial concentration of OTC‐HCl. The degradation of OTC‐HCl in marine aquaculture wastewater was optimized by orthogonal experiment. The best effect exists when the molar ratio of Zn²⁺:Fe³⁺:Mn²⁺ was 10:1:3, the calcination temperature of photocatalyst was 400°C, the concentration of hydrogen peroxide was 0.5 g/L, the dose of catalysts was 0.6 g/L, the illumination time was 2.5 h, and the initial concentration of OTC‐HCl was 0.010g/L. The degradation rate of OTC‐HCl can reach 80.18%. Zn0.75Mn0.75Fe1.5O4/ZnFe2O4/ZnO can effectively degrade the OTC‐HCl in marine aquaculture wastewater under visible light.
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Biological invasions are responsible for substantial biodiversity declines as well as high economic losses to society and monetary expenditures associated with the management of these invasions1,2. The InvaCost database has enabled the generation of a reliable, comprehensive, standardized and easily updatable synthesis of the monetary costs of biological invasions worldwide3. Here we found that the total reported costs of invasions reached a minimum of US1.288trillion(2017USdollars)overthepastfewdecades(19702017),withanannualmeancostofUS1.288 trillion (2017 US dollars) over the past few decades (1970–2017), with an annual mean cost of US26.8 billion. Moreover, we estimate that the annual mean cost could reach US$162.7 billion in 2017. These costs remain strongly underestimated and do not show any sign of slowing down, exhibiting a consistent threefold increase per decade. We show that the documented costs are widely distributed and have strong gaps at regional and taxonomic scales, with damage costs being an order of magnitude higher than management expenditures. Research approaches that document the costs of biological invasions need to be further improved. Nonetheless, our findings call for the implementation of consistent management actions and international policy agreements that aim to reduce the burden of invasive alien species. Analysis of the InvaCost database shows that the costs of biological invasions have markedly increased between 1970 and 2017 and show no sign of slowing down, highlighting the importance of evidence-based and cost-effective management actions.
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Biochar/layered double hydroxide (LDH) composites have gained considerable attention in recent times as low-cost sustainable materials for applications in water treatment. This paper critically evaluates the latest development in applications of biochar/LDH composites in water treatment with an emphasis on adsorption and catalytic degradation of various pollutants. The adsorption of various noxious contaminants, i.e., heavy metals, dyes, anions, and pharmaceuticals onto biochar/LDH composites are described in detail by elaborating the adsorption mechanism and regeneration ability. The synergistic effect of LDH with biochar exhibited significant improvement in specific surface area, surface functional groups, structure heterogeneity, stability, and adsorption characteristics of the resulting biochar/LDH composites. The major hurdles and challenges associated with the synthesis and applications of biochar/LDH composites in water remediation are emphasized. Finally, a roadmap is suggested for future research to assure the effective applications of biochar/LDH composites in water purification.
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Mikania micrantha Kunth is an invasive alien weed and known as a plant killer around the world. Accurately and rapidly identifying M. micrantha in the wild is important for monitoring its growth status, as this helps management officials to take the necessary steps to devise a comprehensive strategy to control the invasive weed in the identified area. However, this approach still mainly depends on satellite remote sensing and manual inspection. The cost is high and the accuracy rate and efficiency are low. We acquired color images of the monitoring area in the wild environment using an Unmanned Aerial Vehicle (UAV) and proposed a novel network —MmNet— based on a deep Convolutional Neural Network (CNN) to identify M. micrantha in the images. The network consists of AlexNet Local Response Normalization (LRN), along with the GoogLeNet and continuous convolution of VGG inception models. After training and testing, the identification of 400 testing samples by MmNet is very good, with accuracy of 94.50% and time cost of 10.369 s. Moreover, in quantitative comparative analysis, the proposed MmNet not only has high accuracy and efficiency but also simple construction and outstanding repeatability. Compared with recently popular CNNs, MmNet is more suitable for the identification of M. micrantha in the wild. However, to meet the challenge of wild environments, more M. micrantha images need to be acquired for MmNet training. In addition, the classification labels need to be sorted in more detail. Altogether, this research provides some theoretical and scientific basis for the development of intelligent monitoring and early warning systems for M. micrantha and other invasive species.
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In this study, date-palm biochar MgAl-augmented double-layered hydroxide (biochar-MgAl-LDH) nanocomposite was synthesized, characterized, and used for enhancing the removal of phosphate and nitrate pollutants from wastewater. The biochar-MgAl-LDH had higher selectivity and adsorption affinity towards phosphate compared to nitrate. The adsorption kinetics of both anions were better explained by the pseudo-first-order model with a faster removal rate to attain equilibrium in a shorter time, especially at lower initial phosphate-nitrate concentration. The maximum monolayer adsorption capacities of phosphate and nitrate by the non-linear Langmuir model were 177.97 mg/g and 28.06 mg/g, respectively. The coexistence of anions (Cl − , SO 4 2− , NO 3 − , CO 3 2− and HCO 3 −) negligibly affected the removal of phosphate due to its stronger bond on the nano-composites, while the presence of Cl − and PO 4 3− reduced the nitrate removal attributed to the ions' participation in the active adsorption sites on the surface of biochar-MgAl-LDH. The excellent adsorptive performance is the main synergetic influence of the MgAl-LDH incorporation into the biochar. The regeneration tests confirmed that the biochar-MgAl composite can be restored effortlessly and has the prospective to be reused after several subsequent adsorption-desorption cycles. The biochar-LDH further demonstrated capabilities for higher removal of phosphate and nitrate from real wastewater.
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Biochar is a pyrogenous, organic material synthesized through pyrolysis of different biomass (plant or animal waste). The potential biochar applications include: (1) pollution remediation due to high CEC and specific surface area; (2) soil fertility improvement on the way of liming effect, enrichment in volatile matter and increase of pore volume, (3) carbon sequestration due to carbon and ash content, etc. Biochar properties are affected by several technological parameters, mainly pyrolysis temperature and feedstock kind, which differentiation can lead to products with a wide range of values of pH, specific surface area, pore volume, CEC, volatile matter, ash and carbon content. High pyrolysis temperature promotes the production of biochar with a strongly developed specific surface area, high porosity, pH as well as content of ash and carbon, but with low values of CEC and content of volatile matter. This is most likely due to significant degree of organic matter decomposition. Biochars produced from animal litter and solid waste feedstocks exhibit lower surface areas, carbon content, volatile matter and high CEC compared to biochars produced from crop residue and wood biomass, even at higher pyrolysis temperatures. The reason for this difference is considerable variation in lignin and cellulose content as well as in moisture content of biomass. The physicochemical properties of biochar determine application of this biomaterial as an additive to improve soil quality. This review succinctly presents the impact of pyrolysis temperature and the type of biomass on the physicochemical characteristics of biochar and its impact on soil fertility.
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The need to design low-cost adsorbents for the detoxification of industrial effluents has been a growing concern for most environmental researchers. So modelling of experimental data from adsorption processes is a very important means of predicting the mechanisms of various adsorption systems. Therefore, this paper presents an overall review of the applications of adsorption isotherms, the use of linear regression analysis, nonlinear regression analysis, and error functions for optimum adsorption data analysis.
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A biochar supported calcined-Mg/Al layered double hydroxides composite (CLDHs/BC) was synthesized by a one-pot slow pyrolysis of LDHs preloaded bagasse biomass. Multiple characterizations of the product illustrated that the calcined-Mg/Al layered double hydroxides (CLDHs) were successfully coated onto the biochar in slow pyrolysis of pre-treated biomass. The as-synthesized CLDHs/BC could efficiently remove antibiotic tetracycline from aqueous solutions. The coating of CLDHs significantly increased the adsorption ability of biochar, and CLDHs/BC exhibited more than 2 times higher adsorption capacity than that of the pristine biochar (BC) in the tested pH range. The maximum adsorption capacity of CLDHs/BC for tetracycline was 1118.12 mg/g at 318 K. The experimental results suggested that the interaction with LDHs on biochar played a dominant role in tetracycline adsorption, accompanied with π–π interaction and hydrogen bond. This study provides a feasible and simple approach for the preparation of high-performance material for antibiotics contaminated wastewater treatment in a cost-effective way.
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In this study, sycamore flocs (SF), which caused environmental and health problems, were utilized to prepare biochar. SFB2-900 obtained under the conditions of activation agent K2CO3, pyrolysis temperature 900℃ and m(K2CO3): m(BC) 2 had the strongest adsorption capacity (730 mg/g) for oxytetracycline hydrochloride (OTC-HCl). The pseudo-second-order kinetic model and Langmuir model described the adsorption kinetics and isotherms best. SFB2-900 exhibited high OTC-HCl adsorption capacity in both higher ionic strength and wide pH range. The theoretical simulation indicated that the closest interaction distance between OTC-HCl and SFB2-900 was 2.44 Å via π-π stacking configuration. Pore filling, π-π electron donor acceptor (EDA) interaction, H-bonding and electrostatic interactions were also involved in the process of OTC-HCl removal. SFB2-900 showed great removal efficiency for OTC-HCl in different water matrices and good regeneration ability. This study solved the problems caused by SF, realized waste biomass recycling, and achieved preparing high-efficient adsorbent for antibiotic.
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Efficient removal of oxytetracycline hydrochloride (OTC) from wastewater is of great significance but extremely challenging. Herein, a novel adsorbent lignin-based multi-metal ferrite biochar (FeNiZn-LBC) was synthesized through pyrolysis with controllable temperature and hydrothermal reaction using lignin of sinocalamus oldhami as raw material. The adsorption property of FeNiZn-LBC for OTC was systematically researched, and the results displayed that adsorption of FeNiZn-LBC to OTC accorded with the Langmuir model and the equilibrium adsorption capacity was 476 mg g⁻¹. Notably, FeNiZn-LBC can be regenerated with 0.100 mol L⁻¹ NaOH. Additionally, we raised rational explanations for the mechanisms of adsorption behavior based on the zeta potential and XPS spectra. The adsorption of FeNiZn-LBC for OTC was mainly controlled by the electrostatic interactions, hydrogen bonds and complexation involving FeNiZn-LBC and OTC, especially the metal-oxide bond (M-O) generated after loaded with multi-metal ferrite played a positive role in the removal of OTC from water. Our work highlighted the potential of FeNiZn-LBC for excellent adsorption of OTC in next generation.
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The presence of residual antibiotics will lead to potential environmental risks. Here cyclodextrins (CDs) were successfully used to modify graphene-based iron nanoparticles ([email protected] NPs) to enhance the absorption of oxytetracycline hydrochloride (OTC). The removal of OTC decreased in the order: γ[email protected] NPs > β[email protected] NPs > α[email protected] NPs > [email protected] NPs, with better performance than that of bare GO and Fe NPs. Characterization techniques were applied to better understand how CDs impact the structure of [email protected] NPs and improve removal performance. Raman and X-ray diffraction analysis showed that GO acted as a carrier to support Fe NPs within the grafted cyclodextrin, where GO also participated in the removal process. Cyclodextrin modified [email protected] NPs had relatively small particle sizes (15 nm), with a high surface area (61.7 m²·g⁻¹). X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy suggested that cyclodextrin acted as both a stabilizing and capping agent during green synthesis, which could protect the reactivity of Fe NPs and simultaneously reduce aggregation. A potential synthesis mechanism of cyclodextrins modified composites was also proposed, and subsequent wastewater testing indicated that γ[email protected] NPs had high potential for practical applications.
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Metal-free carbonaceous catalysts are receiving increasing attention in wastewater treatment. Here, nitrogen and sulfur co-doped carbon sphere catalysts (N,S-CSs900-OH) were synthesized using glucose and L-cysteine via a hydrothermal method and high temperature alkali activation. The N,S-CSs900-10%-OH exhibited excellent catalytic performance for the degradation of oxytetracycline (OTC). The degradation rate was 95.9% in 60 min, and the reaction equilibrium rate constant was 0.0735 min⁻¹ (k0–15 min). The synergistic effect of adsorption-promoting degradation was demonstrated in the removal process of OTC. The excellent adsorption capacity of N,S-CSs900-10%-OH ensured the efficient oxidation of OTC. N,S-CSs900-10%-OH reduced the activation energy of the OTC degradation reaction (Ea=18.23 kJ/mol). Moreover, the pyrrolic N, thiophene S and carbon skeleton played an important role in the degradation of OTC based on density function theory, and the catalytic mechanism was expounded through radical and nonradical pathways. The active species involved in the reaction were O2•−, ¹O2, SO4•− and •OH, of which O2•− was the primary reactive species. This study provides a new insight into the reaction mechanism for efficient treatment of organic pollutants using metal-free doped porous carbon materials.
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The regulation of surface electrons by non-metal doping of biochar (BC) is environmentally and ecologically significant. However, systematic studies on the regulation of surface electrons by transition metal doping are lacking. The present study is based on the observation that the removal efficiency of oxytetracycline (OTC) by Mn-doped BC is eight times higher than that of undoped BC in 20 min. The effects of Mn doping on the crystal phase formation, persistent free radicals (PFRs), electron density, molecular orbitals, and nucleophilic active sites of BC are investigated, and the intermediate products of OTC are evaluated. Mn doping enhances the signal for sp²-hybridised carbon–carbon double bond, forms more delocalised π-bonds, and promotes the formation of free radicals centred on the carbon atoms. The specific surface area of BC increases, and manganese oxide is formed on the its surface. Density functional theory calculations show that Mn doping accelerates the electron transfer of BC, provides additional electrons for the BC system, and makes this system more ionised. OTC molecules preferentially attack the nucleophilic reaction sites near Mn atoms based on molecular electrostatic potential measurements. Therefore, this study provides new insights into the surface electronic structures regulated by transition metal elements.
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The presence of emerging pollutants in water matrices is an increasing concern; therefore, the development of sustainable technologies that enable the removal of these pollutants is required. The goal of the present study was to propose a methodology to prepare a sustainable catalyst using functionalized mesoporous activated carbon and an enzyme for the removal of oxytetracycline. Four strategies of laccase immobilization were evaluated using a 3² experimental design to evaluate the enzyme immobilization efficiency. The activated carbon was functionalized with hydrochloric acid, glutaraldehyde, or carbodiimide, resulting in four different enzyme immobilization carriers. The response variables evaluated were the protein-specific load capacity and specific activity of immobilized laccase. All developed carriers successfully immobilized the enzyme; among these, the carriers treated with hydrochloric acid and glutaraldehyde had significant protein-specific capacities with yields of 90%, while the carbodiimide carrier had a yield below 40%. In addition, the hydrochloric acid-treated carrier achieved the highest specific activity (168 ± 52 U/g) and specific protein load (13.48 ± 0.90 mg/g). The antibiotic removal assays that employed this catalyst showed better performance (100%) than the free enzyme, which was used as a reference. However, the apparent antibiotic removal mechanism was found to be pollutant adsorption instead of degradation, which was ascribed to the high affinity of the hydrochloric acid-treated carrier for the studied pollutant.
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We present the chemisorption of chlortetracycline (CTC) and oxytetracycline (OTC) on theta phosphorene nanoribbon (theta-PNRibbon) based on the first-principles framework. The formation energy of theta-PNRibbon is noticed to be -3.759 eV per atom, which ensures structural stability. The theta-PNRibbon exhibits a band gap of 1.376 eV that belongs to the semiconductor. The presence of CTC and OTC molecules on a water medium requires a removal substrate. The adsorption energy for the complex structure is found to be in the range of -2.778 eV to -9.268 eV. Based on the adsorption energy and charge transfer between CTC and OTC molecules and theta-PNRibbon, the chemisorption of target molecules is observed. Also, the electronic properties of theta-PNRibbon owing to adsorption of CTC and OTC molecules are investigated with band structure and density of states studies. The findings reveal that theta-PNRibbon is one of the base substrates for the removal of CTC and OTC in the water bodies.
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The use of biomass for the synthesis of value-added products, such as functional nanomaterial for the removal of contaminants, is a challenge. In this study, hybrid bimetallic Fe/Ni nanoparticles and reduced graphene supported bimetallic Fe/Ni nanoparticles (Fe/Ni-rGO) were prepared via a one-step green synthesis using green tea extract, and thereafter evaluated for the simultaneous removal of rifampicin (RIF) and Pb(II) from aqueous solution. The efficiencies of Pb(II) and RIF removal by Fe/Ni-rGO were 87.5 and 96.8%, respectively. The removal performance of the hybrid Fe/Ni-rGO was better than either nFe/Ni, rGO, or Fe-rGO. Detailed characterization and analyses of Fe/Ni-rGO indicated that both Fe and Ni nanoparticles were evenly distributed over the surface of rGO and that aggregation of Fe, Ni nanoparticles, and stacking of rGO in the hybrid were decreased. Furthermore, while LC-TOF-MS analysis showed that RIF was degraded into small-molecule fragments, XPS showed that Pb(II) was not reduced to Pb⁰. The major conditions impacting removal efficiency, adsorption kinetics, and fit to adsorption isotherm models were examined to better understand the removal mechanism. While the adsorption of both contaminants fit well a pseudo-second-order kinetic model, the adsorption of RIF fit the Freundlich isotherm model best, while the adsorption of Pb(II) fit the Langmuir isotherm model best. Thus, the removal mechanism of both contaminants firstly being chemical adsorbed onto the surface, while nFe/Ni continues to participate in the catalytic reduction of RIF. Moreover, Fe/Ni-rGO could be reused and performed well for wastewater treatment, thus suitable as a practical resource recycling technology.
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Magnetic modification has been widely applied to solve the difficulty of separating the powdered material from an aqueous medium after use. But knowledge on magnetization sequence to the properties of materials and their performance is still inadequate. To make up for this vacancy, in this study, the magnetic biochars with different magnetization sequences (Pre-MCS and Post-MCS) were prepared and employed in the adsorptive removal of oxytetracycline (OTC) wastewater. Characterizations, adsorption performance and mechanisms, as well as cycle performance of the prepared biochar were investigated. Results indicated that the Post-MCS not only had the highest OTC adsorption capacity (21.8 mg/g) but also exhibited the best separation performance. Mechanism analysis revealed that the chemisorption dominated the adsorption process of OTC on the studied biochars, besides, the electrostatic attraction and physisorption also had a certain contribution to the adsorption mechanism. Furthermore, the optimized biochar (Post-MCS) had acceptable reusability and remained ~61.9% of the adsorption capacity of fresh Post-MCS biochar. Therefore, the Pre-MCS can be considered as a promising adsorbent for the removal of OTC due to its high adsorption capacity and good separation performance.
Article
Non-thermal plasma coupled with graphene-TiO2-Fe3O4 nanocomposites was applied to promote oxytetracycline (OTC) degradation in water. Graphene-TiO2-Fe3O4 nanocomposites were systematically characterized and calculated based on the density functional theory (DFT). Graphene-TiO2-Fe3O4 nanocomposites exhibited higher specific surface area, carrier separation rate and magnetic intensity. More importantly, graphene-TiO2-Fe3O4 nanocomposites were very prone to separation from solution. Compared to Fe3O4 and graphene-TiO2, graphene-TiO2-Fe3O4 nanocomposites further enhanced the removal efficiency of OTC. The highest removal efficiency could reach 98.1% when the doping amount of Fe3O4 was 20 wt%. The optimal parameters of catalyst dosage, peak voltage, air flow rate and pH value were 0.24 g/L, 18 kV, 4 L/min and 3.2, respectively. Compared with graphene-TiO2, the addition of graphene-TiO2-Fe3O4 nanocomposites decreased the concentration of O3 and H2O2, but increased the production of ·OH. ·OH, O3 and H2O2 played certain role for OTC elimination. The degradation process was explored by UV-Vis spectrum, three dimensional fluorescence, liquid chromatography-mass spectrometry (LC-MS), ion chromatography (IC) and discrete Fourier transform (DFT) analysis. Reactive molecular dynamical (MD) simulation was also performed to further investigate the reaction mechanisms, and the simulation show a good agreement with the experimental observation by analyzing the bond breaking and formation. The actual toxicity of OTC was alleviated after plasma-catalytic treatment.
Article
The present work provides the first attempt of using manganese dioxide loaded poly(sodium acrylate) hydrogel (MnO2@PSA) to address potential threats posed by oxytetracycline (OTC) antibiotics in aqueous environment. The MnO2@PSA was prepared via a facile approach and demonstrated enhanced removal performance even under extremely high concentrations of OTC. The outstanding performance exhibited by MnO2@PSA was attributed to synergetic effects of adsorption oxidative degradation. The synthesized composite was characterized evaluated under varying conditions. The adsorption pH was optimized at pH 5, at which the removal efficiency OTC was reached 91.46%. According to the kinetics study, the pseudo-second-order kinetic model was the best to explain the adsorption data, implying the interaction mechanisms were dominated by chemisorption. The Langmuir isotherm model was the best to explain the isotherm data, and the corresponding maximum adsorbed amount of OTC was 1,150.4 mg g-1. The MnO2@PSA was highly selective for OTC adsorption and degradation under the presence of natural organic matter and common environmental metal ions. The oxidative degradation study indicated that OTC molecules were structurally degraded into 15 intermediate products via six reaction pathways. Both the theoretical models and spectroscopic methods demonstrated the removal mechanism of OTC onto MnO2@PSA was governed by ion exchange, cation-π bonding, hydrogen-bonding, and π-π electron donor-acceptor. Overall, MnO2@PSA is an excellent and environmentally sustainable material to remove OTC from water and wastewater via the combined effects of adsorption and oxidative degradation.
Article
Kaolinite and methoxy-modified kaolinite were used as novel adsorbents for oxytetracycline (OTC) removal and recovery from aqueous media. Batch adsorption experiments were performed to study the effect of pH, ionic strengths, initial concentration, and contact time on OTC adsorption. The adsorbents were characterized using powder X-ray diffraction (PXRD), Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) before and after adsorption. Adsorption of OTC reached its maximum when solution pH increased up to 6 for 0.001 M ionic strength, above which adsorption decreased further when solution pH increased. Freundlich and Langmuir’s models best fit the equilibrium data with a strong dependency on OTC adsorption capacity giving its maximum at 36 mg g⁻¹. Binding is postulated for OTC adsorption on pristine kaolinite as a special case of Hill model with independent binding interaction of OTC adsorption onto the clay that affects the adjacent sites on the pristine kaolinite, in contrast with the adsorption of OTC on methoxy-modified kaolinite. Nitrogen peaks of the XPS spectra indicated changes in the oxidation states of C-N bonds in the N1s peaks by forming tertiary amide C-N and methoxy O-CH3 bonds which corroborated with the results from FTIR spectra. Removal efficiencies and spectroscopic results indicate that performance on methoxy-modified kaolinite is a promising modification on the clay for recovering antibiotics from wastewater.
Article
Laboratory investigations show that rates of adsorption of persistent organic compounds on granular carbon are quite low. Intraparticle diffusion of solute appears to control the rate of uptake, thus the rate is partially a function of the pore size distribution of the adsorbent, of the molecular size and configuration of the solute, and of the relative electrokinetic properties of adsorbate and adsorbent. Systemic factors such as temperature and pH will influence the rates of adsorption; rates increase with increasing temperature and decrease with increasing pH. The effect of initial concentration of solute is of considerable significance, the rate of uptake being a linear function of the square-root of concentration within the range of experimentation. Relative reaction rates also vary reciprocally with the square of the diameter of individual carbon particle for a given weight of carbon. Based on the findings of the research, fluidized-bed operation is suggested as an efficient means of using adsorption for treatment of waters and waste waters.
Article
In this study, the reduced graphene oxide-supported bimetallic palladium-zero-valent-iron (Pd/nZVI/rGO) composites were synthesized using a facile one-step liquid-phase reduction method. Physicochemical and textural properties as well as chemical composition of the as-prepared composites were firstly characterized. Transmission electron microscopy (TEM) and X-ray diffractometry (XRD) analysis revealed that the presence of rGO sheets prevented the aggregation of Pd/nZVI nanoparticles and retarded the transformation of iron corrosion products from magnetite/maghemite to lepidocrocite, inducing such nanoparticles to be dispersed more homogeneously. In addition, the loading of Pd/nZVI nanoparticles could avoid the stacking of rGO sheets effectively. The synthesized Pd/nZVI/rGO composites were then used to remove antibiotic oxytetracycline (OTC) from aqueous solutions. It was found that the introduction of an optimal amount of rGO into Pd/nZVI nanoparticles enhanced significantly OTC removal. In particular, the presence of 5 wt.% of rGO in Pd/nZVI/rGO composite (dose, 0.1 g/L) exhibited the highest OTC removal of 96.5% (initially, 100 mg/L) after 60-min reaction at pH 5.0 and 25°C. The removal of OTC by Pd/nZVI/rGO composite was contributed by adsorption process, Fenton-like reactions, and reduction reactions. The Pd/nZVI/rGO composites exhibited better reusability than pristine nZVI particles. The pathways of OTC degradation over Pd/nZVI/rGO nanocomposite were also proposed.
Article
Oxytetracycline (OTC), as one of widely applied veterinary antibiotic, has become a new environmental pollutant. To explore the feasibility of the nanocomposites of reduced graphene oxide (rGO) with the ZrO2 nanoparticles for OTC removal, two nanocomposites of monoclinic-ZrO2@rGO and tetragonal-ZrO2@rGO through controlling the dosage of triethanolamine are prepared successfully and characterized. Detail investigation of the adsorption for the family of tetracycline antibiotics on the two nanocomposites has been assessed. For comparison, the tetragonal-ZrO2@rGO (198.4 mg g–1) exhibits a higher adsorptive amount than the monoclinic-ZrO2@rGO (177.9 mg g–1), whereas two nanocomposites demonstrate a remarkably selective uptake of OTC among the family of tetracycline antibiotics due to their higher affinity towards OTC. Adsorption of OTC by in 15 minutes can reach the equilibrium and is independent on pH in the range of 4-8. The adsorption of OTC by the two nanocomposites is well matched by both pseudo-second order and Langmuir models and exhibits a favorable, endothermic and spontaneous nature. Fourier transform infrared and XRD analysis reveal the interactions between OTC and the nanocomposites such as surface complexation, π-π and cation-π bonding interactions with a crucial role.
Article
Metal-organic framework and nano carbon materials were widely used in separation field in recent years. In this study, nanocomposite of MIL-100(Fe) and multi-walled carbon nanotubes (MIL-100(Fe)-CNTs) was prepared and characterized and its adsorption property towards Oxytetracycline (OTC) was presented. MIL-100(Fe)-CNTs exhibits higher adsorption capacity compared to MIL-100(Fe), making this composite as one of the favorable adsorbents. The adsorption capacity of MIL-100(Fe)-CNTs reached 429 mg·g⁻¹ at 313 K. The langmuir model and Koble-Corrigan model were better to predict the equilibrium data while the pseudo-second-order kinetic model could well describe the kinetic process. The process was endothermic and spontaneous while the ion exchange was the main adsorption mechanism of OTC on MIL-100(Fe)-CNTs. The nanocomposite is promising to effectively remove OTC from solution.
Article
Exotic invasive plants endanger the integrity of agricultural and natural systems throughout the world. Thus, the development of cost-effective and economic application of invasive plants is warranted. Here, we characterized fifteen biochars derived from five invasive plants at different temperatures (300, 500, and 700 °C) by determining their yield, ash content, pH, CEC, surface area, elementary composition, functional groups, and mineral composition. We conducted batch adsorption experiments to investigate the adsorption capacity and efficiency for Cd²⁺ and Cu²⁺ in wastewater. Our results suggest that all invasive plants are appropriate for biochar production, temperature and plant species had interacting effects on biochar properties, and the biochars pyrolyzed at 500 and 700 °C exhibited high metal adsorption capacity in neutral (pH = 7) solutions. The adsorption kinetics can be explained adequately by a pseudo-second-order model. BBC500 (Bidens pilosa L. derived biochar at 500 °C) and MBC500 (Mikania micrantha) exhibited higher metal equilibrium adsorption capacities (38.10 and 38.02 mg g⁻¹ for Cd²⁺, 20.01 and 20.10 mg g⁻¹ for Cu²⁺) and buffer abilities to pH than other biochars pyrolyzed at 500 °C. The Langmuir model was a better fit for IBC500 (Ipomoea cairica), MBC500, and LBC500 (Lantana camara L.) compared to the Freundlich model, whereas the opposite was true for BBC500 and PBC500 (Praxelis clematidea). These results suggest that the adsorption of metals by IBC500, MBC500, and LBC500 was mainly monolayer adsorption, while that by BBC500 and PBC500 was mainly chemical adsorption. Our results are important for the utilization and control of invasive plants as well as the decontamination of aqueous pollution.
Article
In this study, biochar derived from municipal sludge was activated by zinc chloride, which was first time used as the precursor for hydrothermal synthesis of magnetic sludge biochar (Fe/Zn-SBC) for tetracycline (TC) and ciprofloxacin (CIP) removal. The maximum adsorption capacity of Fe/Zn-SBC for TC and CIP were 145 mg g-1 and 74.2 mg g-1 at 25 °C, respectively. Kinetics, isotherms, thermodynamics and characterization analysis suggested that the adsorption process was dominated by pore filling, oxygen-containing groups complexation, π-π conjugation and hydrogen bonding. Fe/Zn-SBC had the high selective adsorption capacity for TC and CIP in a wide pH range and even at the high ionic strength. The magnetic sensitivity ensured its easy separation performance. The co-processing of ultrasound and ethanol could effectively regenerate the used Fe/Zn-SBC. Also, it exhibited great environmental safety in the pH range of 3 to 12. These superiority suggested that it is a promising adsorbent for antibiotics removal.
Article
The cetyltrimethylammonium bromide (CTAB)-functionalized silica nanoparticles (MSN) were prepared using a combined sol-gel and adsorption steps. The nitrogen adsorption-desorption surface analysis shows the MSN has a lower surface area than the unmodified (or free) silica nanoparticles (FSN). The energy dispersive X-ray (EDX) and Fourier transform infrared (FTIR) analysis confirmed the presence of CTAB in MSN with maximum CTAB coverage of (0.74 ± 0.04) mmol/g. The maximum adsorption capacity of oxytetracycline (OTC) onto MSN performed in the batch adsorption process, Qe.max is 449.89 µmol g⁻¹, which is higher than FSN (57.06 µmol g⁻¹). The adsorption depends on pH value, OTC concentration, temperature, and contact time. The thermodynamic parameters indicate the process as exothermic in nature and spontaneous. The isotherm data fits well with the Redlich-Peterson model, while the pseudo-second order (PSO) kinetic model is found to be suitable to describe the kinetic data with the film diffusion as the rate-limiting step. The electrostatic, hydrogen bonding and hydrophobic interactions are mainly responsible for the OTC adsorption onto the synthesized adsorbents. The reusability studies found that the adsorbent could be recycled without drastic adsorption capacity reduction. The successful decoration of the CTAB onto the surface of the silica nanoparticles provides an effective method in the development of promising adsorbents for antibiotic removal from wastewater.
Article
In this study, Fe3O4-HA-La composite was prepared by chemical coprecipitaion method, and the oxytetracycline (OTC) adsorption efficiency of the obtained adsorbent was investigated with batch experiment. Characterization methods, including BET, SEM, XRD, FTIR, XPS and VSM, were employed to study its physiochemical properties. The batch experiment results indicated that > 90% of OTC was removed using the adsorbent Fe3O4-HA-La under wide pH range from 5 to 9. The regeneration experiment showed that after three cycles of adsorption/regeneration, Fe3O4-HA-La kept the OTC removal efficiency > 80% and saturation magnetization (Ms) value > 55 emg g⁻¹. The OTC adsorption process was better fitted with pseudo-second-order kinetic model. The OTC adsorption process was better fitted with Redlich-Peterson model (R² > 0.99). High correlation coefficient (R² > 0.97) was also observed for Langmuir model, which showed the Qmax of 23.43 mg g⁻¹. The complexation reaction between OTC and HA, La and Fe on Fe3O4-HA-La were contributed to the efficient removal of OTC by Fe3O4-HA-La.
Article
As an "up-and-coming" two-dimensional (2D) material, black phosphorus (BP) has attracted much attention due to its abundant metal-free properties and broad application prospects in photocatalysis. This study introduces a promising sunlight-driven metal-free photocatalyst for oxytetracycline hydrochloride degradation and hexavalent chromium reduction in water and wastewater. The roles of BP quantum dots (BPQDs) in the distribution of electrons and photocatalytic performances were well identified by experimental and density functional theory (DFT) calculations. As expected, the specially designed 0D/1D structure shows unusual photocatalytic efficiency toward the degradation of oxytetracycline hydrochloride (0.0276 min⁻¹) and reduction of hexavalent chromium (0.0404 min⁻¹). Reactive species, namely, O2⁻ and h⁺ comprised the primary photocatalytic mechanisms for oxytetracycline hydrochloride degradation. This work highlights that the combination of tubular g-C3N4 (TCN) with BPQDs facilitates the charge spatial separation in the photocatalytic process, and provides alternative strategy for design of highly active and metal-free nanomaterials toward environmental remediation and sustainable solar-to-chemical energy conversion.
Article
In this study, oxytetracycline (OTC) as a target pollutant in swine wastewater was removed by aerobic granular sludge (AGS). The removal rate of 300 μg/L OTC in aerobic granular sludge sequencing batch reactor (AGSBR) increased to 88.00% in 33 days and maintained stable. The chemical oxygen demand (COD), ammonium nitrogen (NH4+-N) and total phosphorus (TP) in wastewater were also efficiently removed. The removal of OTC mainly depended on the adsorption and biodegradation of AGS, and the biodegradation was increased obviously after AGS adaptation to OTC. The degradation products of OTC were analyzed by mass spectrometry. The analysis of metagenome sequencing revealed that the enzymes, such as glycosyl transferases (GTs), polysaccharide lyases (PLs) and auxiliary activities (AAs), may play an important role in the removal of OTC. The Lefse analysis showed that the Flavobacteriia, Flavobacteriales, Cryomorphaceae and Fluviicola were four kinds of microbes with significant difference in OTC feed reactor, which are considered to be drug-resistant bacteria in AGSBR. Furthermore, the dynamics of microbial community changed significantly at three levels, including the enrichment of drug-resistant microorganisms and the microorganisms that gradually reduced or even disappeared under the pressure of OTC.
Article
Pharmaceuticals are emerging pollutants present mainly in industrial and municipal wastewater. Herein, structurally variable binary and ternary metal hydroxides based on copper, manganese, and aluminum were used for the adsorptive scavenging of the oxytetracycline (OTC) antibiotic. A facile hydrothermal method was used for the synthesis of binary CuAl-hydroxide, MnAl-hydroxide, and ternary CuMnAl-hydroxide. Structural and morphological characteristics of the metal hydroxides (MHs) were studied by X-ray diffraction (XRD), Fourier transformed infrared spectrum (FTIR), X-ray photoelectron spectroscopy (XPS) and Scanning electron microscopy (SEM) analysis. The adsorptive removal for OTC was found in the order CuMnAl-hydroxide > CuAl-hydroxide > MnAl-hydroxide. The highest removal of OTC by CuMnAl-hydroxide and CuAl-hydroxide was observed at pH 7 while MnAl-hydroxide showed the optimum adsorption at pH 9. All three materials showed different saturation time and equilibrium concentration for OTC adsorption. The mechanism investigation found that strong electrostatic attraction, hydrogen bonding, and anion exchange were mainly responsible for the removal of the OTC and adsorption process followed the pseudo-second-order kinetic model and equilibrium data was best fitted to the Langmuir isotherm model. The adsorption of OTC was influenced by the presence of Cu (II) and Cr (VI) ions in the aqueous solution due to the competitive adsorption of co-ions. Moreover, the adsorption of OTC was endothermic in nature, and maximum adsorption capacity was found to be 250.07 mg/g at 50 °C.
Article
In this study, cetyl trimethylammonium bromide (CTAB) (cationic) and sodium dodecyl benzene sulfonate (SDBS) (anionic) were used to modify natural sepiolite (SEP) to obtain a type of organic sepiolite (C-S-SEP). It was further applied for adsorption of oxytetracycline (OTC), a common antibiotic in water. The changes of SEP crystal structure and physicochemical properties before and after modification were analyzed by the means of XRD, FTIR, TG, SEM/EDS, BET, XPS and zeta potential. The adsorption performance and mechanism of OTC on C-S-SEP were studied by static adsorption method. The results showed that the adsorption capacity of C-S-SEP increased significantly, and the removal rate of OTC increased from 50.26% to 99.42%. The partition coefficient of SEP and C-S-SEP was 0.356 and 2.172 mg g-1 μM-1, respectively. CTAB and SDBS were successfully loaded onto the surface of SEP without entering its interlaminar domain, and the original crystal structure of SEP was well maintained. In the range of the studied ratio, anionic and cationic surfactants had the synergistic solubilization effect. The adsorption process conformed to the pseudo-second-order kinetic model and Langmuir isothermal adsorption model. The adsorption reaction was exothermic and a process of entropy reduction. The increase of temperature was not conducive to adsorption, and the adsorption reaction was basically unaffected by the pH value. The adsorption of C-S-SEP on OTC was the result of the combination of distribution and surface adsorption. The organic modified SEP was expected to become a low-cost environmentally friendly adsorption material that can effectively remove OTC from water.
Article
Three adsorbents, namely, original biochar (CLB), montmorillonite (MMT)-biochar composite (MBC), and magnetic MMT-biochar composite (MMBC) were successfully fabricated by one step pyrolysis of original cauliflower (Brassica oleracea L.) leaves, mixture of cauliflower leaves and MMT, and FeCl3-laden mixture of cauliflower leaves and MMT under limited oxygen atmosphere, respectively. The characterizations of samples indicated that substantial MMT mineral particles and Fe3O4 nanoparticle were dispersed on the surface of MMBC. Due to the introduction of Fe3O4, MMBC performed excellent magnetization property. The adsorption experiments of oxytetracycline (OTC) indicated that the maximum adsorption ability of MMBC was 58.85 mg·g-1, which was 2.63 times as large as CLB, also, larger than that of MBC. Meanwhile, pH, ionic strength, and humic acid (HA) performed slight effects for adsorption of OTC on MMBC. In addition, MMBC still removed 92% OTC after five regeneration cycles. Finally, primary mechanisms of OTC adsorption onto MMBC were attributed to hydrogen bonding and π-π reaction, and ion exchange reaction was considered to exist. Meanwhile, functional groups including Si-O-Al, Si-O-Si, Si-O, and Fe3O4 nanoparticles would provide extra binding sites for OTC adsorption. Therefore, MMBC had an obvious potential to apply into water purification as a reliable, low-cost, and environmentally friendly adsorbent.
Article
The 100th anniversary of Langmuir’s theory of adsorption is a significant landmark for the physical chemistry and chemical engineering communities. Despite its simplicity, the Langmuir adsorption model captures the key physics of molecular interactions at interfaces and laid the foundation for further progress in understanding interfacial phenomena, developing new adsorbent materials, and designing engineering processes. The Langmuir model has had an exceptional impact on diverse fields within the chemical sciences (ranging from chemical biology to materials science), an impact that became clearer with the development of modified adsorption theories and continues to be relevant today.
Article
The growing occurrence of As(III) pollutant in surface and ground water has serious implications to human and plant life. Developing and understanding the interaction between priority pollutants and low-cost adsorbent materials is of importance in finding solution to the ever-growing threat of water pollution. In this study, pine cone biomass, an agricultural waste was chemically activated and applied as potential adsorbent for As(III) in water. Effect of sorption parameters such as pH and dose were investigated. Temperature effect on adsorption kinetics and equilibrium studies indicates ligand exchange as the main sorption mechanism with an activation energy of 26.24 kJ/mol. Ligand exchange mechanism was confirmed by FTIR, XPS and pHPZC analysis before and after adsorption and As(III)/NO3 exchange reaction. Effect of ionic strength and anion competition of several environmentally occurring anions on the uptake of As(III) by the adsorbent were also tested. The results showed that As(III) inhibition increased with pH and among the anions, PO43{\text{PO}}_{4}^{3 - } anions inhibited As(III) ion adsorption strongly while As(III) uptake was slightly increased in the presence of CO32{\text{CO}}_{3}^{2 - }, SO42{\text{SO}}_{4}^{2 - } and Cl⁻ anions.
Article
In this paper, a Zeolite Imidazole Framework-8 (ZIF-8), was investigated for the removal of a mixture of two common antibiotics, tetracycline (TC) and oxytetracycline hydrochloride (OTC). Batch experiments showed that 90.7% of TC and 82.5% of OTC were simultaneously removed using ZIF-8. The maximum adsorption capacities for TC and OTC were 303.0 and 312.5 mg g⁻¹, respectively. For both antibiotics’ adsorption followed pseudo-second-order kinetics and best fit the Langmuir adsorption model with R² of 0.963 and 0.981, for TC and OTC at 303 K, respectively. The relatively large specific surface area of ZIF-8 (1158.2 m² g⁻¹) combined with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that both antibiotics were adsorbed on to the surface of ZIF-8. X-ray powder diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy both indicated the presence of benzene ring structures, associated with both pollutants, on ZIF-8 after reaction; which confirmed adsorption was occurring. XPS also showed the presence of C[dbnd]O double bonds on the surface of ZIF-8 indicating the presence of antibiotics. The adsorption mechanism most likely involved π-π interactions between the conjugated groups in TC/OTC and the imidazole rings of ZIF-8.
Article
In the adsorption literature, the Van't Hoff equation is used in different manners without any criteria about the concepts of physical-chemistry of equilibrium for calculation of thermodynamic parameters of adsorption. Indeed, the equilibrium constant (K) should be dimensionless for being used in the Van't Hoff equation. However, this is not a simple adjustment of units, as being spread in the literature, to become K dimensionless. In this paper, it will be calculated the equilibrium constants using numeric examples and show the flaws of the thermodynamics calculations, when the value of K is wrongly calculated, and what are the expected results of the changes in enthalpy (ΔH°) and changes in the entropy (ΔS°) that are spread in the literature.
Article
Enhancement of As(III) adsorption by magnetite immobilized on pine cone (MNP-PCP) as compared with pine cone (PCP) was studied. The adsorbents were characterized using FTIR, VSM, XRD and XPS. The PCP, MNP, MNP-PCP and physical mixtures of PCP and MNP (1:1, 2:1 and 1:2) were evaluated for As(III) adsorption. The results show that the composite had better As(III) uptake, FTIR peaks at 812 to 813 cm⁻¹ show As-O bonding. Pseudo second-order model and Langmuir isotherm gave good fit with the experimental data and monolayer capacities of PCP and MNP-PCP were 14.83 and 18.02 mg/g at 299 K. The adsorption type was found to be ion exchange as obtained from Dubinin–Radushkevich parameter E with values of 11.7 and 12.13 kJ/mol for PCP and MNP-PCP, respectively at 299 K. A slight increase in As(III) uptake with increasing ionic strength and shift in pHPZC to lower values after As(III) uptake which was higher for MNP-PCP confirmed the participation of ion exchange reaction.PO4³⁻ anions only caused a reduction in As(III) uptake which was stronger in MNP-PCP. HCl and NaOH desorbed a higher percentage of As(III) from MNP-PCP (82 and 66%) and MNP-PCP gave a more stable As(III) capacity after three cycle desorption/reuse.
Article
In this work, new Cu-coated biochar composites for the adsorption of Re(VII) through complexation mechanism was synthesized successfully. The sensitivity of Cu-coated biochars to solution pH decreased greatly and the adsorption capacity was increased by 3–12 times compared with pristine biochar at pH 3–6. The environmental effect factors and mechanisms of Re(VII) adsorption onto Cu-coated biochar composites (Cu-BC) were investigated. The Re(VII) adsorption nicely fits the Redlich-Peterson isotherm model, and the recovery of Re(VII) from acidic solution by Cu-coated biochar composites follows pseudo-second-order kinetics. Besides, the thermodynamic parameters depicted the spontaneous endothermic nature for the adsorption of low concentration Re(VII). These results demonstrate that easily synthetic Cu-coated biochar composites have promising potential for the recovery of low concentration Re(VII) in acidic solution.
Article
Pollution of water by single antibiotics has been investigated in depth. However, in reality, a wide range of different contaminants is often mixed in the aquatic environment (contaminant cocktail). Here, single and competitive sorption dynamics of ionizable norfloxacin (NOR), sulfamerazine (SMR) and oxytetracycline (OTC) by both pristine and modified biochars were investigated. Sorption kinetics of the three antibiotics was faster in ternary-solute than single-solute system. Sorption efficiency was enhanced in the competitive system for NOR by the pristine biochar, and for OTC by both the pristine biochar and the modified biochar, while SMR sorption by the pristine biochar and the KOH-modified biochar was inhibited. Sorption was governed by electrostatic interactions, π-π EDA and H-bonds for antibiotics sorption by biochar. SMR and OTC sorption by biochar was influenced by cation bridging and surface complexation, respectively. This research finding will guide the development of treatment procedures for water polluted by multiple antibiotics.
Article
The presence of antibiotics in the water and wastewater has raised problems due to potential impacts on the environment and consequently their removal is of great importance. For this reason, this article aims to perform a study on the possibility of oxytetracycline (OTC) adsorption from aqueous medium by using the hydroxyapatite (HA) nanopowders as adsorbent materials. The hydroxyapatite nanopowders were synthesized by wet precipitation method by using orthophosphoric acid and calcium hydroxide as raw materials and investigated by XRD, SEM-EDX, FTIR and BET methods. The uncalcined and calcined hydroxyapatite samples have hexagonal crystal structure with crystal sizes smaller than 100nm and a specific surface area of 316m2/g and 139m2/g, respectively. The adsorption behavior of oxytetracycline, a zwitterionic antibiotic, on nanohydroxyapatite was investigated as a function of pH, contact time, adsorbent dosage and drug concentration by means of batch adsorption experiments. High oxytetracycline removal rates of about 97.58% and 89.95% for the uncalcined and calcined nanohydroxyapatites, respectively, were obtained at pH8 and ambient temperature. The adsorption process of oxytetracycline onto nanohydroxyapatite samples was found to follow a pseudo-second order and intraparticle diffusion kinetic models. The maximum adsorption capacities of 291.32mg/g and 278.27mg/g for uncalcined and calcined nanohydroxyapatite samples, respectively, have been found. The adsorption mechanism of OTC on the hydroxyapatite surface at pH8 can be established via surface complexation. The obtained results are indicative of good hydroxyapatite adsorption ability towards oxytetracycline drug.
Article
In the present investigation, the adsorptive removal of the antibiotic drug oxytetracycline (OTC) and toxic heavy metal cadmium (Cd) from aqueous solution was carried out using forest and wood-processing residues. Numerous biochars were prepared using different chemical agents (H3PO4, H2SO4, NaoH and KOH) and pyrolysis times and temperatures. Several elemental, chemical and structural characterizations were performed. The optimum conditions for pyrolysis to enable the production of biochars with well-developed porosity was 600 °C for 1 h, for both residues. The adsorption process using selected activated biochars was optimized with respect to reaction time, pH, temperature and initial load of pollutants. Under optimized operating conditions, and based on equilibrium modeling data, the biochars which showed the highest removal efficiencies of OTC and cadmium were “5M H3PO4 forest” (263.8 mg/g) and “1M NaoH forest” (79.30 mg/g), respectively. Compared to adsorbents reported in the literature, the efficiencies of those biochars are highly competitive.
Article
Activated magnetic biochar (AMB) was prepared with corn stalks, reed stalks, and willow branches by simultaneous carbonization, magnetization, and activation, and used for norfloxacin removal in water. The exploration results showed that the zeta potential was positively charged at pH 2-10. These prepared activated magnetic biochars have a large specific surface area (> 700 m2·g-1) and pore volume (> 0.3 cm3·g-1). The quasi-second-order kinetic adsorption equation could better describe the adsorption of NOR on AMB. The Langmuir isotherm showed the better fitting results on AMB. The AMB showed the strong adsorption of NOR, and the saturated adsorption capacity of corn activated magnetic biochar was the highest, 7.6249 mg·g−1. The adsorption of NOR on AMB was a spontaneous endothermic process. The effect of pH on the adsorption behaviors of NOR on AMB was not obvious, and AMB had a good adsorption effect on NOR in a wide pH range.
Article
In order to study the optimum atmosphere condition for preparing waste tea-based activated carbon by H3PO4 activation, activated carbons were prepared under nitrogen (NAC), air (AAC) and steam (SAC) atmospheres, respectively. The physicochemical properties of the three activated carbons were characterized by N2 adsorption/desorption and Fourier transform infrared spectroscopy (FTIR). AAC exhibited highest values of the Brunauer–Emmett–Teller (BET) surface area (880 m²/g) and total pore volume (0.680 cm³/g) than that of NAC (824 cm²/g and 0.666 cm³/g) and SAC (785 cm²/g and 0.629 cm³/g). Nevertheless, the adsorption results for oxytetracycline (OTC) showed that SAC had the strongest adsorption capacity than NAC and AAC. The adsorption equilibrium data for OTC adsorption onto the three activated carbons agreed well with the Freundlich model, and the adsorption kinetics were well fitted in pseudo-second-order model. Results revealed that activated carbon prepared under air atmosphere showed the largest BET surface area and activated carbon prepared under steam atmosphere showed the best adsorption capacity.
Article
Hydrothermal carbonization (HTC) of carbohydrates is an economic and sustainable technique for the synthesis of carbon materials. However, the assembly of carbohydrates with soft templates is susceptible to hydrolysis, degradation, and relatively high HTC temperature. Thus, it is still challenging to control the HTC/soft templating of carbohydrates and prepare mesoporous carbon with specific properties. Herein, a simple and effective self-transformation strategy is proposed to improve the HTC/soft templating, which introduces an insoluble melamine sulfate into the formation processes. Mechanism studies indicate that the assembly of d-fructose with soft templates is greatly promoted by coassembling with the gradually released melamine sulfate. As a result, carbonaceous composites with a flower-like structure and N-doping were synthesized. Further, ordered mesoporous carbons with N-doping are obtained after calcination. The obtained carbons exhibit outstanding ability for heavy metal adsorption and supercapacitors. Significantly, this self-transformation strategy will open up new avenues for synthesizing carbohydrate-based functional carbons.