Adsorption of tetracycline antibiotics from an aqueous solution onto graphene oxide/calcium alginate composite fibers

Adsorptive removal of oxytetracycline hydrochloride using bagasse-based biochar powder and beads

Oxytetracycline Hydrochloride (OTC), a common antibiotic used to treat specific illnesses in humans and animals, is characterized by poor absorption into cells, low volatility, and high hydrophilicity. It is a potent contaminant that poses a serious threat to the ecosystem, particularly the aquatic sources. Adsorption onto natural adsorbents is one of the most successful, economical, and ecologically friendly ways to remove antibiotics from waste water. The present work focuses on the adsorption of OTC utilizing alginate biochar beads (AlBCB) and biochar powder (BC) derived from bagasse. The influence of several factors were studies and optimized through batch studies employing BC and AlBCB. After 50 min BC displayed a removal of 97%, at an initial concentration of 10 ppm. The experimental data was discovered to follow PFO kinetics and fit with the Freundlich isotherm adsorption model. AlBCB, after a contact time of 40 min, indicated a maximum percentage removal of 86% for initial concentration of 10 ppm OTC. Al-biochar beads showed the maximum percentage removal at pH 10. 0.5 g of adsorbent was used to carry out all batch experiments at room temperature. The adsorption fitted Freundlich adsorption isotherm and intraparticle diffusion kinetics.

MOF-Modified Microrollers for Bioimaging and Sustained Antibiotic Delivery

Central nervous system (CNS) infections caused by neurosurgery or intrathecal injection of contaminated cerebrospinal fluid are a common and difficult complication. Drug-delivery microrobots are among the latest solutions proposed for antibacterial applications. However, there is a lack of research into developing microrobots with the ability to sustain antibody delivery while can move efficiently in the CNS. Here, biocompatible antibacterial metal-organic framework (MOF)-modified microrollers (MMRs) to combat CNS infections are proposed. The MMRs are iron-based metal-organic framework (NH2-MIL-101(Fe)) modified for enhanced adsorption and Fe/Al coated for magnetic actuation and biocompatibility. The MMRs have demonstrated a faster and unhindered magnetically actuated motion on the uneven biological tissue surface in an organ-on-a-chip that mimicked the CNS compared to it on smooth surface. CFD results consistently align with the experimental findings. The MMRs can be loaded with rhodamine 6G for bioimaging, allowing them to be imaged through sections of the main human tissues by fluorescence microscopy, or tetracycline hydrochloride for antibiotic delivery, allowing them to inhibit the growth of Staphylococcus aureus biofilms by sustained release of antibiotics for 9 days. This study provides a strategy to integrate high-capacity adsorption material with magnetically actuated locomotion for long-term targeted antibacterial applications in biological environments.

A waste-to-wealth conversion of plastic bottles into effective carbon-based adsorbents for removal of tetracycline antibiotic from water

Currently, plastic waste and antibiotic wastewater are two of the most critical environmental problems, calling for urgent measures to take. A waste-to-wealth strategy for the conversion of polyethylene terephthalate (PET) plastic bottles into value-added materials such as carbon composite is highly recommended to clean wastewater contaminated by antibiotics. Inspired by this idea, we develop a novel PET-AC-ZFO composite by incorporating PET plastic-derived KOH-activated carbon (AC) with ZnFe2O4 (ZFO) particles for adsorptive removal of tetracycline (TTC). PET-derived carbon (PET-C), KOH-activated PET-derived carbon (PET-AC), and PET-AC-ZFO were characterized using physicochemical analyses. Central composite design (CCD) was used to obtain a quadratic model by TTC concentration (K), adsorbent dosage (L), and pH (M). PET-AC-ZFO possessed micropores (d ≈ 2 nm) and exceptionally high surface area of 1110 m2 g-1. Nearly 90% TTC could be removed by PET-AC-ZFO composite. Bangham kinetic and Langmuir isotherm were two most fitted models. Theoretical maximum TTC adsorption capacity was 45.1 mg g-1. This study suggested the role of hydrogen bonds, pore-filling interactions, and π-π interactions as the main interactions of the adsorption process. Thus, a strategy for conversion of PET bottles into PET-AC-ZFO can contribute to both plastic recycling and antibiotic wastewater mitigation.

Machine learning and statistical physics modeling of tetracycline adsorption using activated carbon derived from Cynometra ramiflora fruit biomass

The current investigation reports the usage of adaptive neuro-fuzzy inference system (ANFIS) and artificial neural network (ANN), the two recognized machine learning techniques in modelling tetracycline (TC) adsorption onto Cynometra ramiflora fruit biomass derived activated carbon (AC). Many characterization methods utilized, confirmed the porous structure of synthesized AC. ANN and ANFIS models utilized pH, dose, initial TC concentration, mixing speed, time duration, and temperature as input parameters, whereas TC removal percentage was designated as the output parameter. The optimized configuration for the ANN model was determined as 6-8-1, while the ANFIS model employed trimf input and linear output membership functions. The obtained results showed a strong correlation, indicated by high R2 values (ANNR2: 0.9939 & ANFISR2: 0.9906) and low RMSE values (ANNRMSE: 0.0393 & ANFISRMSE: 0.0503). Apart from traditional isotherms, the dataset was fitted to statistical physics models wherein, the double-layer with a single energy satisfactorily explained the physisorption mechanism of TC adsorption. The sorption energy was 21.06 kJ/mol, and the number of TC moieties bound per site (n) was found to be 0.42, conclusive of parallel binding of TC molecules to the adsorbent surface. The adsorption capacity at saturation (Qsat) was estimated to be 466.86 mg/g - appreciably more than previously reported values. These findings collectively demonstrate that the AC derived from C. ramiflora fruit holds great potential for efficient removal of TC from a given system, and machine learning approaches can effectively model the adsorption processes.

Highly efficient hydrophobic nanocomposite in the decontamination of micropollutants and bacteria from aqueous wastes: A sustainable approach

Micro-pollutants (specifically antibiotics and personal care products) and potential bacterial contamination pose a severe threat to human health and marine life. The study derives indigenous novel fibrous hydrophobic nanocomposite, efficient in decontaminating the micro-pollutants (tetracycline (TC) and bisphenol A (BPA)) and potential pathogens (S. pyogenes and E. coli) from aqueous wastes. A facile method synthesizes the fibrous attapulgite (ATP)- poly(4-vinylpyridine-co-styrene) (PVP) framework decorated in situ with the Ag0 nanoparticles (ATP@PVP/Ag0). A greener method using the Artocarpus heterophyllus leaf extract derives the Ag0(NPs). Various analytical methods extensively characterize the materials. A comprehensive study that includes pH, concentration, background electrolytes, and ionic strength reveals the sorptive removal insights of TC and BPA utilizing the ATP@PVP solid. The elimination of tetracycline (TC) and bisphenol A (BPA) agrees well with the pseudo-second-order kinetics. The pH 3.07 and 6.06 favor removing TC and BPA with the capacity of 10.86 mg/g and 17.36 mg/g at 25 °C. The hydrogen bonding and hydrophobic interactions predominate the sorption mechanism, and the material shows remarkable stability and reusability in repeated sorption/desorption operations. Similarly, the natural water implications and flow-bed system show fair applicability of solid in decontaminating the TC and BPA in an aqueous medium. Further, the material ATP@PVP/Ag0 exhibits very high inhibition of potential pathogens S. pyogenes and E. coli and optimizes the solid dose and solution pH.

A critical review of sodium alginate-based composites in water treatment

The global freshwater crisis is a pressing issue, especially in areas with little rainfall and inner continental regions. The growing attention to water scarcity has induced increased interest in research on advanced water treatment technologies. As an abundant bioactive material in nature, sodium alginate (SA) has been widely used in water management due to its outstanding water absorption and holding ability, reversible swelling property, and pollutant adsorption performance. Building on this, progress made in using various modified forms of SA to access clean water is addressed in this review. Covering studies concern the adsorption and separation of pollutants in wastewater by SA-based absorbents and freshwater harvesting by SA-based collectors. This review explores SA-based composites' composition-structure-construction designs and emphasizes the impact of materials like inorganic materials, functional polymers, and porous matrices and how they can be exploited for water treatment. It also highlights the mechanisms of contaminants adsorption and freshwater desorption of SA-based composites. Finally, the shortcomings and future orientation of SA-based composites are proposed, including performance optimization, structural modification, application expansion, and mechanism in-depth investigation. This review aims to offer a theoretical basis and technical guidance for the use of natural materials to respond to the shortage of freshwater resources.

Synthesis and characterization of new composite from modified silica-coated MnFe2O4 nanoparticles for removal of tetracycline from aqueous solution

In this study, a new composite from silica coated MnFe2O4 nanoparticles, diethylenetriamine, 3-chloropropyl trimethoxysilane and Mg-Al Layered Double Hydroxide (Mg-Al LDH/DETA/CPTMS/SCNPs) composite was synthesized. The Mg-Al LDH/DETA/CPTMS/SCNPs composite was examined by Fourier transform infrared spectrometer (FT-IR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDS), X-ray diffraction (XRD), Thermogravimetric Analysis (TGA) and Vibrating Sample Magnetometry (VSM). The synthesized composite exhibited magnetic property with a saturation magnetization of 0.40 emu g-1. The Mg-Al LDH/DETA/CPTMS/SCNPs composite was utilized as a successful adsorbent for removal of tetracycline from aqueous solutions. The effect of various operation factors such as initial drug concentration, adsorbent dosage, pH and contact time were investigated. The optimized variable conditions such as adsorbent dose of 60 mg L-1, drug concentration of 100 mg L-1, pH = 7 and contact time 30 min were obtained. For describing the adsorption isotherms, the Langmuir, Freundlich and Temkin adsorption models were utilized. The results indicated that the adsorption isotherm is in good agreement with Langmuir model. According to the Langmuir analysis, the maximum adsorption capacity (qm) of the Mg-Al LDH/DETA/CPTMS/SCNPs composite for tetracycline was obtained to be 40.16 mg g-1. The kinetic studies revealed that the adsorption in all cases to be a pseudo second-order process. The negative value of ΔG° and the positive value of ΔH° showed the adsorption process to be spontaneous and endothermic.

Bioinspired Stevia rebaudiana Green Zinc Oxide Nanoparticles for the Adsorptive Removal of Antibiotics from Water

Green zinc oxide nanoparticles (ZnO NPs) synthesized using Stevia rebaudiana as a reducing agent were investigated as ecofriendly adsorbents for the removal of the antibiotics ciprofloxacin (CIP) and tetracycline (TET) from water. Green ZnO NPs were synthesized using a rapid novel approach that did not require annealing or calcination at high temperatures to produce mesoporous NPs with a size range of 37.36-71.33 nm, a specific surface area of 15.28 m2/g, and a negative surface charge of -15 mV at pH 5. The green ZnO NPs exhibited an antioxidant activity of 85.57% at 250 μg/mL and an antibacterial activity with MIC and MBC of 50 and 100 mg/mL, respectively, against both Escherichia coli and Staphylococcus aureus. The best adsorption performance was achieved using a 4 g/L dose and pH 5, yielding, respectively, 86.77 ± 0.82% removal and 27.07 ± 0.26 mg/g adsorption capacity for CIP at 10 mg/L and 67.86 ± 3.41% and 15.88 ± 0.37 mg/g for TET at 25 mg/L. The green ZnO NPs achieved 79.71% ± 0.28 and 61.55% ± 0.53 removal of 10 mg/L CIP and 25 mg/L TET, respectively, in a spiked tap water binary system of the two contaminants. Adsorption of CIP and TET occurred mainly via electrostatic interactions, whereby CIP was bound more strongly than TET by virtue of its charge and size. The synthesis and adsorption processes were evaluated by a stepwise regression statistical model to optimize their parameters. Lastly, the green ZnO NPs were regenerated and reused for 5 cycles, indicating their functionality as simple, reusable, and low-cost adsorbents for the removal of CIP and TET from wastewater, in accordance with SDGs #6 and 12 for the sustainable management of water.

Dual valorization of coastal biowastes for tetracycline remediation and biomethane production: A composite assisted anaerobic digestion

Harnessing coastal biowaste for dual valorization in water treatment and biofuel production holds paramount importance for sustainability and resource challenges. This study investigated the potential of engineered composite (CABC) derived from coastal biowaste-based materials for tetracycline (TC) removal and biomethane production. High-yield calcium carbonate (CaCO3; 95.65%; bivalve shells) and biochar (GA-BC; 41.50%; green macroalgae) were produced and used as precursors for CABC. The characterization results revealed presence of β-CaCO3 and ν2-CO3 aragonite in CaCO3, and composite homogeneity was achieved. The CABC exhibited a maximum TC sorption capacity of 342.26 mg/g via synergistic sorption mechanisms (i.e., surface/pore filling, electrostatic attraction, calcium ion exchange, and chelation). Supplementation of anaerobic digestion process with GA-BC, CaCO3, and CABC was investigated via three consecutive cycles. Biochemical methane potential of glucose as a sole substrate was increased from 157.50 to 217.00, 187.00, and 259.00 mL-CH4, while dual substrate (glucose+TC) treatment was increased from 94.5 to 146.5, 129.0, and 153.00 mL-CH4 for GA-BC, CaCO3, and CABC, respectively. Moreover, system stability and TC removal were increased with the addition of GA-BC (40.90%), CaCO3 (16.30%), and CABC (53.70%). Therefore, this study exemplifies the circular bioeconomy approach, demonstrating the sustainable use of biowaste-derived composite for water treatment and biofuel production.

Development of calcium phosphate-chitosan composites with improved removal capacity toward tetracycline antibiotic: Adsorption and electrokinetic properties

Two eco-friendly and highly efficient adsorbents, namely brushite-chitosan (DCPD-CS), and monetite-chitosan (DCPA-CS) composites were synthesized via a simple and low-cost method and used for tetracycline (TTC) removal. The removal behavior of TTC onto the composite particles was studied considering various parameters, including contact time, pollutant concentration, and pH. The maximum TTC adsorption capacity was 138.56 and 112.48 mg/g for the DCPD-CS and DCPA-CS, respectively. Increasing the pH to 11 significantly enhanced the adsorption capacity to 223.84 mg/g for DCPD-CS and 205.92 mg/g for DCPA-CS. The antibiotic adsorption process was well-fitted by the pseudo-second-order kinetic and Langmuir isotherm models. Electrostatic attractions, complexation, and hydrogen bonding are the main mechanisms governing the TTC removal process. Desorption tests demonstrated that the (NH4)2HPO4 solution was the most effective desorbing agent. The developed composites were more efficient than DCPD and DCPA reference samples and could be used as valuable adsorbents of TTC from contaminated wastewater.

Two-step pyrolytic preparation of biochar for the adsorption study of tetracycline in water

In this study, cow dung biomass was converted into biochar (BC). BC900 was obtained through one-step pyrolysis at 900 °C, while BC700-900 and BC900-700 were obtained via two-step pyrolysis at temperature ranges of 700-900 °C and 900-700 °C, respectively. The primary objective was to investigate the adsorption performance and application value of BCs for tetracycline (TC) in water. The samples underwent characterization using scanning electron microscopy and mapping analysis, Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. Subsequently, the effects of reaction time, adsorbent dosage, temperature, pH, and ionic strength were analyzed. Based on the fitting results of adsorption kinetics, the pyrolytic BCs exhibited a better fit with the pseudo-secondary kinetic model. The adsorption isotherm indicated monolayer adsorption on the surface of the adsorbents, with maximum adsorption capacities of 158.93 mg/g for BC900-700, 150.15 mg/g for BC700-900, and 142.56 mg/g for BC900, respectively. Furthermore, results from simulated wastewater and regeneration experiments demonstrated that BC900-700 exhibited not only excellent adsorption performance in wastewater but also remarkable regeneration capabilities. The two-step pyrolysis BCs in this study displayed a higher adsorption capacity compared to the one-step pyrolysis BCs in practical applications. These findings provide insights for further exploring the adsorption mechanism and optimizing the process.

Insights on the Synthesis of Al-MCM-41 with Optimized Si/Al Ratio for High-Performance Antibiotic Adsorption

Studies indicate that approximately two-thirds of the rivers of the world are contaminated by pharmaceutical compounds, especially antibiotics and hormones. Data reported by the World Health Organization (WHO, 2015) revealed an increase of 65% in antibiotic consumption between 2000 and 2015, with a worldwide increase of 200% expected up to 2030. Environmental contamination by antibiotics and their metabolites can cause the alteration of bacterial genes, leading to the generation of superbacteria. In this work, adsorption was explored as a strategy to mitigate antibiotic contamination, proposing the use of the Al-MCM-41 mesoporous material as an efficient and high-capacity adsorbent. Evaluation of the influence of the synthesis parameters enabled understanding of the main variables affecting the adsorption capacity of Al-MCM-41 for the removal of a typical antibiotic, amoxicillin (AMX). It was found that the adsorbent composition and specific surface area were the main factors that should be optimized in order to obtain the highest AMX removal capacity. Using statistical tools, the best Si/Al ratio in Al-MCM-41 was found to be 10.5, providing an excellent AMX uptake of 132.2 mg per gram of adsorbent. The Si/Al ratio was the most significant factor affecting the adsorption. The cation-π interactions increased with an increase of the Al content, while the interactions involving silanols (Yoshida H-bonding and dipole-dipole hydrogen bridges) decreased.

Pharmaceutical residues in the ecosystem: Antibiotic resistance, health impacts, and removal techniques

Hospital wastewater has emerged as a major category of environmental pollutants over the past two decades, but its prevalence in freshwater is less well documented than other types of contaminants. Due to compound complexity and improper operations, conventional treatment is unable to remove pharmaceuticals from hospital wastewater. Advanced treatment technologies may eliminate pharmaceuticals, but there are still concerns about cost and energy use. There should be a legal and regulatory framework in place to control the flow of hospital wastewater. Here, we review the latest scientific knowledge regarding effective pharmaceutical cleanup strategies and treatment procedures to achieve that goal. Successful treatment techniques are also highlighted, such as pre-treatment or on-site facilities that control hospital wastewater where it is used in hospitals. Due to the prioritization, the regulatory agencies will be able to assess and monitor the concentration of pharmaceutical residues in groundwater, surface water, and drinking water. Based on the data obtained, the conventional WWTPs remove 10-60% of pharmaceutical residues. However, most PhACs are eliminated during the secondary or advanced therapy stages, and an overall elimination rate higher than 90% can be achieved. This review also highlights and compares the suitability of currently used treatment technologies and identifies the merits and demerits of each technology to upgrade the system to tackle future challenges. For this reason, pharmaceutical compound rankings in regulatory agencies should be the subject of prospective studies.

Efficient Cr(VI) sequestration from aqueous solution by chemically modified Garcinia kola hull particles: characterization, isotherm, kinetic, and thermodynamic studies

There is a need for the removal of hexavalent chromium from contaminated water prior to its discharge into the environment, as part of industrial effluents, due to its toxic nature. In this present study, an adsorbent prepared via chemical modification of Garcinia kola hull particles (GK-HP) using NaOH was applied for Cr(VI) sequestration from aqueous solution. Both the raw (rGK-HP) and chemically modified Garcinia kola hull particles (cMGK-HP) were characterized using BET, SEM, XRD, FTIR, TGA, and EDS. The effects of pH, contact time, adsorbent dose, adsorbate initial concentration, and temperature on Cr(VI) sequestration were examined. The adsorbent, cMGK-HP, proved to be more effective for the adsorption process than rGK-HP with 96.25% removal efficiency at a pH of 2, a contact time of 60 min, an adsorbent dose of 5 g/L, Cr(VI) initial concentration of 20 mg/L and a temperature of 40°C. Isotherm and kinetic studies showed experimental data to be well-fitted with Langmuir isotherm and follow the pseudo-second-order kinetic model. The thermodynamic study revealed adsorption nature to be feasible, occur via physisorption, spontaneous, and exothermic. Changes in morphological structure, textural property, spectral peak, phase composition, and chemical composition of adsorbents before and after Cr(VI) sequestration from solution were proved by SEM, BET, FTIR, XRD, and EDS analyses, respectively. cMGK-HP possessed excellent reusability attribute and high thermal stability as shown by TGA. In conclusion, the adsorption capacity of cMGK-HP is better than many other adsorbents generated from agrowastes used in previous studies for Cr(VI) removal.

Adsorption and Desorption Study of Reusable Magnetic Iron Oxide Nanoparticles Modified with Justicia adhatoda Leaf Extract for the Removal of Textile Dye and Antibiotic

The release of tetracycline hydrochloride (TCH) and methylene blue (MB) dye into the aquatic system uncontrollably caused major environmental and health problems; hence, their prevention required serious attention. Adsorption process is now being researched in order to increase adsorption efficiency and reprocess to alleviate environmental issues. The use of magnetic nanoparticle as an adsorbent for wastewater treatment has a lot of prospective. A magnetic iron oxide nanoparticle surface modified by Vasaka (Justicia adhatoda) leaf extract (JA-MIONs) is used to give a fast removal approach for MB dye and TCH antibiotics. Dynamic light scattering, UV-Vis and band gap measurement, powder X-ray diffraction, Fourier-transform infrared spectroscopy, and transmission electron microscopy were operated to analyse the formation and size of these magnetic nanoparticles. The impacts of different factors such as contact time (30-150 min), adsorbate concentration (10-50 mg/L), pH (4-10), and adsorbent dose (2-10 mg) were explored. Adsorption kinetics and isotherms show that it follows the pseudo-first-order kinetic and the Freundlich isotherm, with maximum adsorption capacities of 76.92 mg/g for MB and 200 mg/g for TCH at 298 K. The reusability of the JA-MIONs eventually exhibited a decline in the adsorption percentage of MB and TCH after five and four times respectively. After the desorption-adsorption cycles, this adsorbent continued to exhibit significant adsorption capacity. This investigation furnished the significant reference data for the synthesis of JA-MIONs as a novel and auspicious adsorbent for the industrial clean-up of toxic dyes and heavily used antibiotics from water.

Efficient Uptake of Angiotensin-Converting Enzyme II Inhibitor Employing Graphene Oxide-Based Magnetic Nanoadsorbents

This paper reports a high efficiency uptake of captopril (CPT), employing magnetic graphene oxide (MGO) as the adsorbent. The graphene oxide (GO) was produced through an oxidation and exfoliation method, and the magnetization technique by the co-precipitation method. The nanomaterials were characterized by FTIR, XRD, SEM, Raman, and VSM analysis. The optimal condition was reached by employing GO·Fe3O4 at pH 3.0 (50 mg of adsorbent and 50 mg L−1 of CPT), presenting values of removal percentage and maximum adsorption capacity of 99.43% and 100.41 mg g−1, respectively. The CPT adsorption was dependent on adsorbent dosage, initial concentration of adsorbate, pH, and ionic strength. Sips and Elovich models showed the best adjustment for experimental data, suggesting that adsorption occurs in a heterogeneous surface. Thermodynamic parameters reveal a favorable, exothermic, involving a chemisorption process. The magnetic carbon nanomaterial exhibited a high efficiency after five adsorption/desorption cycles. Finally, the GO·Fe3O4 showed an excellent performance in CPT removal, allowing future application in waste management.

Adsorptive removal of levofloxacin and antibiotic resistance genes from hospital wastewater by nano-zero-valent iron and nano-copper using kinetic studies and response surface methodology

In the twenty-first century, water contamination with pharmaceutical residues is becoming a global phenomenon and a threat. Antibiotic residues and antibiotic resistance genes (ARGs) are recognized as new emerging water pollutants because they can negatively affect aquatic ecosystems and human health, thereby posing a complex environmental problem. These nano-adsorbents of the next generation can remove these pollutants at low concentrations. This study focuses on the chemical synthesis of copper oxide nanoparticles (CuONPs) and nano-zero-valent iron (nZVI) used as nano-adsorbents for levofloxacin removal from water samples and antibiotic-resistant genes. The CuONPs and nZVI are initially characterized by transmission electron microscopy, scanning electron microscopy, and X-ray diffraction. The levofloxacin adsorption isotherm on the CuONPS and nZVI shows the best fit with the Langmuir isotherm model, exhibiting correlation coefficients (R2) of 0.993 and 0.999, respectively. The adsorption activities of CuONPS and nZVI were fitted to a pseudo-second-order kinetic model with correlation coefficients (R2) of 0.983 and 0.994, respectively. The maximum levofloxacin removal capacity was observed at (89%), (84%), (89%), (88%) and (71.6) at pH 7 and adsorbent dose(0.06 mg/L), initial LEV concentration (1 mg/L), temperature 25 °C, and contact time 120 min for CuONPs. Removal efficiency was (91%), (90.6%), (91%), (89%), and (80%), at pH 7, adsorbent dose(0.06), initial LEV concentration (1 mg/L), temperature 35 °C, and contact time 120 min. The levofloxacin adsorption is an exothermic process for nZVI and CuONPs, according to thermodynamic analysis. A thermodynamic analysis indicated that each adsorption process is spontaneous. Several genera, including clinically pathogenic bacteria (e.g., Acinetobacter_baumannii, Helicobacter_pylori, Escherichia_coli, Pseudomonas_aeruginosa, Clostridium_beijerinckii, Escherichia/Shigella_coli, Helicobacter_cetorum, Lactobacillus_gasseri, Bacillus_cereus, Deinococcus_radiodurans, Rhodobacter_sphaeroides, Propionibacterium_acnes, and Bacteroides_vulgatus) were relatively abundant in hospital wastewater. Furthermore, 37 antibiotic resistance genes (ARGs) were quantified in hospital wastewater. The results demonstrated that 95.01% of nZVI and 91.4% of CuONPs are effective adsorbents for removing antibiotic-resistant bacteria from hospital effluent. The synthesized nZVI and CuONPs have excellent reusability and can be considered cost effective and eco-friendly adsorbents.

Scallop shell coated Fe2O3 nanocomposite as an eco-friendly adsorbent for tetracycline removal

ABSTRACTThe present study focused on the usability of scallop shell coated Fe₂O₃ nanoparticles as an eco-friendly new absorbent in the treatment of tetracycline (TC). The process performance in terms of TC removal was investigated at different operating conditions, i.e. at solution pH of 3-11, Fe₂O₃-scallop dosage of 0.4-2.4 g L^-1, initial TC content of 20-120 mg L^-1 and temperature of 25-55°C. Solution pH of 7 yielded the highest TC removal efficiency (99%). At this pH value, almost complete TC removal was achieved at a Fe₂O₃-scallop shell nanocomposite dose of 1.6 g L^-1 and 25°C. The responsible TC removal mechanism is suggested as the non-electrical π-π dispersion interaction between the bulk π system on the absorbent surface and TC molecules bearing both benzene rings and double bonds at this solution pH. TC removal efficiency appreciably enhanced up to the Fe₂O₃-scallop dosage of 1.6 g L^-1 being an optimum. Adsorption rate was found to be fast at lower initial TC concentrations than 40 mg L^-1. The effect of temperature on TC removal efficiency was insignificant. Adsorption followed the pseudo-second-order kinetic model. Experimental data perfectly fitted by the Langmuir equation. The maximum adsorption capacity was calculated as 49.26 mg g^-1. Thermodynamic analysis demonstrated that adsorption process was spontaneous process and endothermic. The results obtained from the present study proved the excellent performance of scallop shell coated Fe₂O₃ nanoparticles as an eco-friendly adsorbent in TC treatment.

Adsorption and transformation of tetracyclines on alpha alumina particles with surface modification by anionic surfactant

The adsorption and transformation of tetracyclines (TCs) antibiotics, including oxytetracycline (OTC), chlortetracycline (CTC), and tetracycline (TC), on the sodium dodecyl sulfate (SDS) surfactant-modified α-Al₂O₃ particles were comprehensively investigated in this study. The TCs adsorption was significantly enhanced by using the modified adsorbents compared with the use of the unmodified adsorbents. The experimental conditions were systematically optimized and found to be pH 4, NaCl 1 mM, the contact time of 180 min, and the adsorbent dosage of 25 mg. mL^-1. The high maximum adsorption capacities were approximately 320, 85, and 91 mg. g^-1 for TC, OTC, and CTC, respectively. Meanwhile, the great removal efficiencies of the three antibiotics TC, OTC, and CTC were correspondingly 91.85, 88.4, and 98.3%. The TCs adsorption isotherm and kinetics on the SDS-modified α-Al₂O₃ particles mainly governed by the electrostatic and hydrophobic interactions were clarified by a suitable two-step model, the Fourier transform infrared spectroscopy (FT-IR) and zeta potential measurements. Meanwhile, the TCs structural transformation determined by the liquid chromatography with tandem mass spectrometry (LC-MS/MS) measurement was promoted through the adsorption on the α-Al₂O₃ surface. The TCs transformation rates strongly affected by the TCs adsorption were in the order of CTC > TC > OTC. The found results are promised that the SDS-modified α-Al₂O₃ particles might behave as high-performance adsorbents to remove the TCs from aqueous solutions.

Efficient and Reusable Sorbents Based on Nanostructured BN Coatings for Water Treatment from Antibiotics

Increasing contamination of wastewater with antibiotics used in agriculture, animal husbandry, and medicine is a serious problem for all living things. To address this important issue, we have developed an efficient platform based on a high specific surface area hexagonal boron nitride (BN) coating formed by numerous nanopetals and nanoneedles. The maximum sorption capacity of 1 × 1 cm² BN coatings is 502.78 µg/g (tetracycline, TET), 315.75 µg/g (ciprofloxacin, CIP), 400.17 µg/g (amoxicillin, AMOX), and 269.7 µg/g (amphotericin B, AMP), which exceeds the sorption capacity of many known materials. Unlike nanoparticles, BN-coated Si wafers are easy to place in and remove from antibiotic-contaminated aqueous solutions, and are easy to clean. When reusing the adsorbents, 100% efficiency was observed at the same time intervals as in the first cleaning cycle: 7 days (TET) and 14 days (CIP, AMOX, AMP) at 10 µg/mL, 14 days (TET, CIP, and AMOX) and 28 days (AMP) at 50 µg/mL, and 14 days (TET) and 28 days (CIP, AMOX and AMP) at 100 µg/mL. The results obtained showed that TET and CIP are best adsorbed on the surface of BN, so TET was chosen as an example for further theoretical modeling of the sorption process. It was found that adsorption is the main mechanism, and this process is spontaneous and endothermic. This highlights the importance of a high specific surface area for the efficient removal of antibiotics from aqueous solutions.

Removal of Tetracycline Hydrochloride from Water by Visible-Light Photocatalysis Using BiFeO3/BC Materials

It is widely considered that photocatalysis is an effective and eco-friendly method of dealing with organic pollutants dissolved in water. Nonetheless, photocatalysts still have some drawbacks, such as poor visible-light absorption, easy recombination of photogenerated charge carriers, and limited active sites. In this study, bismuth ferrite coupled with biochar material (BiFeO3/BC) was simply synthesized, and its photocatalysis reactivity was systemically examined under an irradiation of λ > 400 nm. The experimental results showed that under a relatively acidic environment, the removal rate of tetracycline hydrochloride reached 95%. Using a variety of characterization investigations, we analyzed the morphology structure and chemical composition of BiFeO3/BC. In consideration of simple preparation and high respondence toward visible light, further explorations of BiFeO3/BC and its properties and optimized degradation conditions are worthwhile.

Highly Efficient Adsorption of Tetracycline Using Chitosan-Based Magnetic Adsorbent

Herein, tetracycline adsorption employing magnetic chitosan (CS·Fe₃O₄) as the adsorbent is reported. The magnetic adsorbent was synthesized by the co-precipitation method and characterized through FTIR, XRD, SEM, and VSM analyses. The experimental data showed that the highest maximum adsorption capacity was reached at pH 7.0 (211.21 mg g^-1). The efficiency of the magnetic adsorbent in tetracycline removal was dependent on the pH, initial concentration of adsorbate, and the adsorbent dosage. Additionally, the ionic strength showed a significant effect on the process. The equilibrium and kinetics studies demonstrate that Sips and Elovich models showed the best adjustment for experimental data, suggesting that the adsorption occurs in a heterogeneous surface and predominantly by chemical mechanisms. The experimental results suggest that tetracycline adsorption is mainly governed by the hydrogen bonds and cation-π interactions due to its pH dependence as well as the enhancement in the removal efficiency with the magnetite incorporation on the chitosan surface, respectively. Thermodynamic parameters indicate a spontaneous and exothermic process. Finally, magnetic chitosan proves to be efficient in TC removal even after several adsorption/desorption cycles.

Adsorption characteristics of N-rGO for multiple representative trace antibiotics in water

Antibiotics have attracted considerable attention as pollutants; however, they have not been controlled because they cannot be effectively treated via conventional water treatment. In this study, nitrogen-doped reduced graphene oxide (N-rGO) was prepared, and its adsorption performance on multiple trace antibiotics in water was investigated by considering sulfamethoxazole, levofloxacin, clindamycin, tetracycline, penicillin, and chloramphenicol as target pollutants. The results demonstrated that the adsorption process was completed within 60 min at a removal rate exceeding 80%. The adsorption process was in line with the first-order kinetic equation and the Langmuir isothermal adsorption model, with a theoretical maximum adsorption capacity of 1,265.82 mg g^-1 . Meanwhile, the effect of pH value was related to the structure of antibiotics. Simulation studies showed that anions and cations in natural water matrix did not inhibit the adsorption process, whereas humic acid adversely affected the adsorption effect. Characterizations revealed that the N-rGO surface was wrinkled with abundant and diverse oxygen-containing functional groups, which provided suitable conditions for efficient adsorption. The results indicated that N-rGO rapidly and effectively adsorbed trace antibiotics in water, thus providing a basis for constructing an adsorption-catalytic oxidation system. Overall, the proposed method is excellent for treating trace antibiotics in a water environment.

Influence of magnetite incorporation into chitosan on the adsorption of the methotrexate and in vitro cytotoxicity

Emerging pollutants are a group of substances involved in environmental contamination resulting mostly from incomplete drug metabolism, associated with inadequate disposal and ineffective effluent treatment techniques. Methotrexate (MTX), for instance, is excreted at high concentrations in unchanged form through the urine. Although the MTX is still effective in cancer and autoimmune disease treatment, this drug shows the ability of bioaccumulation and toxicity to the organism. Thus, the present work aimed to evaluate the adsorption of the MTX drug onto magnetic nanocomposites containing different amounts of incorporated magnetite (1:1, 1:5, and 1:10 wt%), combining the theoretical-experimental study as well as the in vitro cytotoxicity. Moreover, equilibrium studies (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Hill, Redlich-Peterson, and Sips), kinetic (PFO, PSO, and IPD), and thermodynamic (ΔG°, ΔH°, and ΔS°) were used to describe the experimental data, and ab initio simulations were employed in the theoretical study. Magnetic nanocomposites were synthesized by the co-precipitation method using only FeCl₂ as the iron precursor. Adsorbents were characterized by FTIR, XRD, Raman, SEM-EDS, BET, and VSM analysis. Meanwhile, cytotoxic effects on L929 and A375 cell lines were evaluated through MTT, NR, and LDH assays. The adsorption of the MTX was carried out in a typical batch system, exploring the different experimental conditions. The theoretical study suggests the occurrence of chemisorption between CS·Fe₃O₄-MTX. The maximum adsorption capacity of MTX was 285.92 mg g^-1, using 0.125 g L^-1 of CS·Fe₃O₄ 1:1, with an initial concentration of the MTX (50 mg L^-1), pH 4.0 at 293 ± 1.00 K. The best adjustment of equilibrium and kinetic data were the Sips (low values for statistical errors) and PSO (q_e = 96.73 mg g^-1) models, respectively. Thermodynamic study shows that the adsorption occurred spontaneously (ΔG° < 0), with exothermic (ΔH° =  - 4698.89 kJ mol^-1) and random at the solid-solution interface (ΔS° = 1,476,022.00 kJ mol^-1 k^-1) behavior. Finally, the in vitro study shows that magnetic nanomaterials exhibit higher cytotoxicity in melanoma cells. Therefore, the magnetic nanocomposite reveals to be not only an excellent tool for water remediation studies but also a promising platform for drug delivery.

Experimental and Theoretical Study of Sorption Capacity of Hexagonal Boron Nitride Nanoparticles: Implication for Wastewater Purification from Antibiotics

The constant accumulation of antibiotics and their degradation products in wastewater as a result of human activity poses a serious threat to humanity and other living beings. To contribute to solving this important problem, hollow hexagonal boron nitride nanoparticles (BNNPs) with a spherical shape and smooth surface were synthesized, which were characterized as an efficient adsorbent for wastewater treatment from three types of antibiotics: ciprofloxacin (CIP), tetracycline (TC), and benzylpenicillin (BP). As follows from DFT calculations, the interaction of antibiotic molecules (AM) with the BN surface is neither purely physical nor purely chemical, and negative binding energy (BE) indicates that the adsorption process is spontaneous and endothermic. The calculated electron density redistributions at the AM/BN interfaces show that antibiotics interact with BN mainly through oxygen-containing groups. In addition, this interaction causes the BN surface to bend, which increases both the BE and the contact area. The removal efficiency of antibiotics (Re, %) depends on their initial concentration. At an initial concentration of 10 µg/mL, Re₅₀ and Re₁₀₀ were observed after 24 h and 14 days, respectively. With an increase in the initial concentration to 40 μg/mL, Re₅₀ and Re₁₀₀ were achieved after 5 and 28 days (with the exception of ciprofloxacin (~80% Re)). The maximum sorption capacity of BNNPs (q_e) was determined to be 297.3 mg/g (TC), 254.8 mg/g (BP), and 238.2 mg/g (CIP), which is significantly superior to many other systems. Tetracycline is adsorbed much faster than the other two antibiotics, which is confirmed by both theoretical and experimental data. Based on the results of the DFT analysis, a simple and efficient sorbent regeneration strategy was proposed, which ensures complete removal of antibiotics after 14 (BP), 21 (TC), and 10 (CIP) days. Thus, the obtained results clearly show that BNNPs are promising sorbents for various classes of antibiotics, including aminoglycosides, tetracyclines, and β-lactams.

Enhanced adsorption performance of UiO-66 via modification with functional groups and integration into hydrogels

University of Oslo-66 (UiO-66) was a potential adsorbent for removing various pollutants from wastewater. Modifying the UiO-66 surface with different functional groups could enhance the adsorption performance. In this study, the UiO-66 modified with a functional group of -NH₂ or -NO₂ was prepared and tested to adsorb different pollutants. The results showed that -NO₂ modified UiO-66 increased the adsorption capacity of tetracycline by 17 times to 94.08 mg g^-1 compared with unmodified UiO-66. The adsorption process of UiO-66-NO₂ followed the pseudo-second-order adsorption kinetic model and Langmuir isotherm model with a maximum isotherm adsorption capacity of 127.32 mg g^-1. The adsorption interaction was hydrogen bonding and electrostatic attraction. The UiO-66-NO₂ also showed good adsorption performance to Co²⁺, Methylene blue, Congo red. Fixing UiO-66-NO₂ into hydrogel performed a stable absorption performance with a high absorption capacity (71.56 mg g^-1) to TC and a good regeneration rate (85%) after five cycles, providing a novel applicable way to remove pollutants from wastewater.

A Fast Adsorption of Azithromycin on Waste-Product-Derived Graphene Oxide Induced by H-Bonding and Electrostatic Interactions

Graphene oxide (GO) was prepared from the graphite electrode of waste dry cells, and the application of the prepared GO as a potential adsorbent for rapid and effective removal of an antibiotic, azithromycin (AZM), has been investigated. The synthesis process of GO is very simple, cost-effective, and eco-friendly. As-prepared GO is characterized by field-emission scanning electron microscopy, energy-dispersive X-ray, transmission electron microscopy, X-ray diffractometry, Fourier transform infrared spectroscopy, elemental analysis, Brunauer-Emmett-Teller sorptometry, and zeta potential analysis. The obtained GO has been employed for removal of the widely used AZM antibiotic from an aqueous solution. The quantitative analysis of AZM before and after adsorption has been carried out by liquid chromatography tandem mass spectrometry. The adsorption of AZM by GO was performed in a batch of experiments where the effects of adsorbent (GO) dose, solution pH, temperature, and contact time were investigated. Under optimum conditions (pH = 7.0, contact time = 15 min, and adsorbent dose = 0.25 g/L), 98.8% AZM was removed from the aqueous solution. The rapid and effective removal of AZM was significantly controlled by the electrostatic attractions and hydrogen bonding on the surface of GO. Adsorption isotherms of AZM onto GO were fitted well with the Freundlich isotherm model, while the kinetic data were fitted perfectly with the pseudo-second order. Therefore, the simple, cost-effective, and eco-friendly synthesis of GO from waste material could be applicable to fabricate an effective and promising low-cost adsorbent for removal of AZM from aqueous media.

Removal of Methyl Red from Aqueous Solution Using Polyethyleneimine Crosslinked Alginate Beads with Waste Foundry Dust as a Magnetic Material

In this study, a cost-effective adsorbent based on sodium alginate (SA) with waste foundry dust (WFD) was fabricated for the removal of methyl red (MR) from aqueous media. However, the utilization of WFD/SA beads to remove anionic dyes (such as MR) from effluents has limitations associated with their functional groups. To improve the adsorption performance, WFD/SA-polyethyleneimine (PEI) beads were formed via PEI crosslinking onto WFD/SA beads, which could be attributed to the formation of amide bonds from the carboxyl and amino groups due to the change of N-H bonds in the reaction. The Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) results indicated that PEI was crosslinked on the WFD/SA via a chemical reaction. In the FTIR spectra of WFD/SA-PEI, peaks of the –COO (asymmetric) stretching vibration shifted to 1598 and 1395 cm⁻¹, which could be attributed to the hydrogen-bonding effect of the N–H groups in PEI. In the N1s spectrum, three deconvoluted peaks were assigned to N in –N= (398.2 eV), –NH/–NH₂ (399.6 eV), and NO₂ (405.2 eV). WFD/SA-PEI beads were assessed and optimized for aqueous MR adsorption. The WFD/SA-PEI beads showed a high removal efficiency for MR (89.1%) at an initial concentration of 1000 mg/L, and presented a maximum MR adsorption capacity of 672.7 mg/g MR. The adsorption process showed a good fit with the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model. The amino and hydroxyl groups in the WFD/SA-PEI beads facilitate strong hydrogen bonding and electrostatic interactions. Moreover, these WFD/SA-PEI beads were easily recovered after the adsorption process.

Properties and the Application of Sludge-Based Biochar in the Removal of Phosphate and Methylene Blue from Water: Effects of Acid Treating

Sludge-based biochar could be used to remove phosphate and methylene blue (MB) from water. It is a highly efficient way to treat the sludge and contaminated water synergistically. The high ash content in sludge greatly influenced the adsorption property of the resultant biochar. In this work, the influence of carbonization-activation and acid treating on the adsorption performance of the sludge-based biochar was evaluated. The composition, structure, and surface properties of biochar were improved after acid treating. The biochar was obtained in a sequence of carbonization-activation first and then acid treating, providing the optimal adsorption property. Zn550-H and Zn750-H showed excellent adsorption capacity to phosphate and MB, respectively. The adsorption process was well described by the pseudo-first-order and pseudo-second-order kinetic models. Isothermal studies implied that it was controlled by multiple processes. What is more, sludge-based biochar performed well in the adsorption of phosphate and MB from weakly acidic to alkaline conditions, which was beneficial to utilize the sludge-based biochar in water remediation practically.

Improving the 6-Aminopenicillanic acid release process using vermiculite-alginate biocomposite bead on drug delivery system

The present study deals with developing vermiculite (VMT)-alginate (Alg) composites with different cross-linker concentrations (CaCl₂) to deliver the controlled 6-aminopenicillin acid (6-APA). The Characterization of synthesized composites was conducted by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. Optimization attempts were explored via the response surface method (RSM) to best predict the actual amount of compound. The adsorption capacity of 6-APA onto this adsorbent was found to be 208.33 mg/g, which was higher than that for other clays. The equilibrium and Kinetic studies (chemical reaction and diffusion-based models) indicated that drug absorption on VMT-Alg is homogeneous with chemical interaction. An increase in cross-linker (CaCl₂) concentration leads to improvement in the drug encapsulation efficiency while having no significant effect on loading efficiency. The in-vitro release of the pure drug shows a rapid burst release followed by 100% cumulative release within 6 h. Whereas, the synthesized drug with Alg substantially showed less release of 43% after 8 h. Release experiments revealed that the presence of the CaCl₂ delayed the release of the 6-APA less than 35% after 12 h. The kinetic release of 6-APA is followed by the Korsmeyer-Peppas model based on Fick's law mechanism due to the kinetic exponent (n < 0.5). All studied composites antibacterial activity after 24 h exposure against E. Coli and S. aureus. The antibacterial activities of composites were evaluated by the halo of no growth. The results showed that the VMT-Alg-6APA composite had strong activity against Gram-positive and Gram-negative bacteria.

Alginate-Based Smart Materials and Their Application: Recent Advances and Perspectives

Nature produces materials using available molecular building blocks following a bottom-up approach. These materials are formed with great precision and flexibility in a controlled manner. This approach offers the inspiration for manufacturing new artificial materials and devices. Synthetic artificial materials can find many important applications ranging from personalized therapeutics to solutions for environmental problems. Among these materials, responsive synthetic materials are capable of changing their structure and/or properties in response to external stimuli, and hence are termed "smart" materials. Herein, this review focuses on alginate-based smart materials and their stimuli-responsive preparation, fragmentation, and applications in diverse fields from drug delivery and tissue engineering to water purification and environmental remediation. In the first part of this report, we review stimuli-induced preparation of alginate-based materials. Stimuli-triggered decomposition of alginate materials in a controlled fashion is documented in the second part, followed by the application of smart alginate materials in diverse fields. Because of their biocompatibility, easy accessibility, and simple techniques of material formation, alginates can provide solutions for several present and future problems of humankind. However, new research is needed for novel alginate-based materials with new functionalities and well-defined properties for targeted applications.

Structural Design of Low Toxicity Metal-Organic Frameworks for Multifunction Detection of Organic and Inorganic Contaminants from Water

Metal-organic frameworks (MOFs)-based sensors for monitoring toxic substances in wastewater have attracted great attention due to the efficient and reliable performance. Here, we has synthesized two novel zinc-based MOFs [Zn(ttb)₂(H₂O)₂]_n (Zn1-ttb) and {[Zn(ttb)₂]·0.5CH₃CN}_n (Zn2-ttb) through changing the polarity of reaction solvents and finally obtained target 2D MOF material [Zn(ttb)(bdc)_0.5]_n(Zn3-ttb-bdc) by successfully introducing an ancillary ligand H₂bdc (Httb = 1-(triazo-1-ly)-4-(tetrazol-5-ylmethyl)benzene, H₂bdc = 1,4-benzenedicarboxylic acid). As-prepared Zn3-ttb-bdc exhibits high water and chemical stability as well as excellent fluorescence property. Due to the -COOH binding sites from H₂bdc, Zn3-ttb-bdc shows high sensitivity and a rapid luminescent response to a representative organic micropollutant trinitrophenol (TNP) and inorganic pollutants (Fe³⁺ and Cr₂O₇^2-) in wastewater. The mechanisms of multifunctional detection abilities of Zn3-ttb-bdc toward different types of pollutants are further studied. This work presents the structural design in preparing MOF materials for multifunctional detection performance, thus opening new perspectives for emerging MOF-based sensors as environmental monitors.

Metals and Antibiotics as Aqueous Sequestration Targets for Magnetic Polyamidoamine-Grafted SBA-15

In this study, a magnetic generation-5 polyamidoamine (G-5 PAMAM) dendrimer-functionalized SBA-15 (mPSBA) composite was synthesized by coupling amine-functionalized silica (SBA-15-NH2) and amine-functionalized magnetic nanoparticles (MNP-NH2) with the G-5 PAMAM, before characterization and aqueous sorption of As(III), Cd(II), tetracycline, and ciprofloxacin using the composite. The mPSBA characterization data exhibited the typical Si-O-Si infrared peaks from the SBA-15 backbone in addition to the acquired characteristic infrared Fe-O and amide-I/II peaks from the MNP and G-5 PAMAM dendrimers, respectively. Postsorption infrared spectra showing shifts for the amide-linked groups indicated the likely points of contaminant attachment on the composite. Its thermal stability was lower than that of SBA-15 but higher than that of SBA-15-NH, while the XRD diffractograms of the backbone SBA-15-NH and MNP were unchanged in the final composite. The mPSBA composite was a better As(III) and Cd(II) adsorbent than SBA-15 by ≈400 and 140%, respectively, with rapid uptake in the first 60 min and equilibrium achieved at 120 min. Sorption was enhanced with increasing pH (until pHpzc) and initial contaminant concentration. The process was spontaneous and endothermic; thus, increasing ambient temperature enhanced Cd(II) sorption. The sorption data fitted better to the homogeneous fractal pseudo-second-order (FPSO) kinetics model and the Brouers-Sotolongo fractal adsorption isotherm models, indicating complex sorption interactions and pore-filling/contaminant trapping within mPSBA. Further experiments using mPSBA for the uptake of tetracycline and ciprofloxacin showed 679% and 325% higher sorption, respectively, compared with that for SBA-15-NH. In addition to the added advantage of easy removal from solution/treated water after the adsorption process, mPSBA sorption capacities for these studied contaminants [As(III): 23.3 mg/g; Cd(II): 74.5 mg/g; tetracycline: 38.4 mg/g; ciprofloxacin: 23.0 mg/g] are better than those of several advanced adsorbents reported in the literature.

Effective Poly (Cyclotriphosphazene-Co-4,4'-Sulfonyldiphenol)@rGO Sheets for Tetracycline Adsorption: Fabrication, Characterization, Adsorption Kinetics and Thermodynamics

The development of excellent drug adsorbents and clarifying the interaction mechanisms between adsorbents and adsorbates are greatly desired for a clean environment. Herein, we report that a reduced graphene oxide modified sheeted polyphosphazene (rGO/poly (cyclotriphosphazene-co-4,4'-sulfonyldiphenol)) defined as PZS on rGO was used to remove the tetracycline (TC) drug from an aqueous solution. Compared to PZS microspheres, the adsorption capacity of sheeted PZS@rGO exhibited a high adsorption capacity of 496 mg/g. The adsorption equilibrium data well obeyed the Langmuir isotherm model, and the kinetics isotherm was fitted to the pseudo-second-order model. Thermodynamic analysis showed that the adsorption of TC was an exothermic, spontaneous process. Furthermore, we highlighted the importance of the surface modification of PZS by the introduction of rGO, which tremendously increased the surface area necessary for high adsorption. Along with high surface area, electrostatic attractions, H-bonding, π-π stacking and Lewis acid-base interactions were involved in the high adsorption capacity of PZS@rGO. Furthermore, we also proposed the mechanism of TC adsorption via PZS@rGO.

Effective tetracycline removal from liquid streams of dairy manure via hierarchical poly (vinyl alcohol-co-ethylene)/polyaniline metal complex nanofibrous membranes

Antibiotic residues from animal wastes enter underground and surface water streams, posing high risks to public health. Novel technologies capable of removing the residues from the matrix of concern such as animal waste should be developed. This research investigates the development of nanofiber absorbent for removing tetracycline (TC) antibiotic residues from liquid streams of dairy manure produced in a typical dairy farm. Hierarchically structured nanofibrous adsorbent was developed through growing a uniform polyaniline (PAni) nanodots on poly (vinyl alcohol-co-ethylene) (EVOH) nanofiber membrane (NFM). Moreover, Cu²⁺ ions were chelated on the developed EVOH/PAni-Cl NFM to improve TC adsorption efficiency and selectivity. The TC adsorption capacities of EVOH/PAni-Cl-Cu²⁺ and EVOH/PAni-Cl) NFM were 1100 mg g^-1 and 600 mg g^-1 within 120 min., respectively. The NFMs adsorption efficiency was investigated using dairy wastewater. Initial TC concentrations in dairy wastewater sample varied between 20 and 50 ppm. The EVOH/PAni-Cl-Cu²⁺ NFM showed TC removal of 86% from dairy manure samples at 25 ppm initial TC concentration within 60 min. during batch mode treatment. Results showed that the dynamic binding efficiency of 450 mg g^-1 can be achieved at an initial TC concentration of 50 ppm. Furthermore, the NFM displayed efficient chemical and physical stability even after 8 cycles of reusing without significant changes in its performance or hazardous Cu²⁺ leaching.

Removal of antibiotics from aqueous solution by using porous adsorbent templated from eco-friendly Pickering aqueous foams

The aqueous foam template without any solvent and only using the particles stabilizer has attracted much attention for preparation of the porous adsorbents. Herein, a novel porous adsorbent was fabricated via thermal-initiated polymerization of Pickering aqueous foams, which was stabilized by the natural sepiolite (Sep) and pine pollen, and utilized for the removal of antibiotic from aqueous solution. The stabilizing mechanism of Pickering aqueous foam of that the Sep was modified with the leaching substance from pine pollen and arranged orderly around the bubble to form a dense "shell" structure was revealed. The adsorbents possessed the hierarchical porous structure and excellent adsorption performance for antibiotic of chlorotetracycline hydrochloride (CTC) and tetracycline hydrochloride (TC). The equilibrium adsorption capacities of CTC and TC were achieved with 465.59 and 330.59 mg/g within 60 min at 25°C, respectively. The adsorption process obeyed Langmuir model and pseudo-second-order adsorption kinetic model. This work provided eco-friendly approach for fabricate porous adsorbents for wastewater treatment.