Minimizing the residual antimicrobial activity of tetracycline after adsorption into the montmorillonite: Effect of organic modification

Impact of land use-induced soil heterogeneity on the adsorption of fluoroquinolone antibiotics, tested on organic matter pools

The effects on the adsorption of fluoroquinolone antibiotics of long-term soil heterogeneity induced by land-use were investigated. Three different land use areas with their two organic matter (OM) pools were tested for the adsorption of three antibiotics widely detected in the environment (ciprofloxacin, norfloxacin, ofloxacin). The soils were separated into two size fractions, > 63 µm fraction and < 63 µm fractions for the fast and slow OM pools, respectively. Any effect of land use on adsorption was only observed in the slow pool in the increasing order: arable land, grassland, and forest. The composition of the soil organic matter (SOM) did influence adsorption in the slow pool, but not in the bulk soilsThis was, because: 1) the ratio of the slow pool was low, as in forest, 2) the ratio of the slow pool was high but its adsorption capacity was low due to its SOM composition, as in arable land and grassland. Soils containing a large slow SOM pool fraction with aliphatic dominance were found to be more likely to adsorb micropollutants. It is our contention that the release of contaminated water, sludge, manure or compost into the environment should only be undertaken after taking this into consideration.

Enhanced adsorption and colorimetric detection of tetracycline antibiotics by using functional phosphate/carbonate composite with nanoporous network coverage

This work presents efficient tetracycline (TC) antibiotics adsorption using a functional porous phosphate/carbonate composite (PCC). The PCC was fabricated by anion-exchange of phosphate on the surface of vaterite-phase calcium carbonate particle scaffolds. The PCC, having dense nanoporous network coverage with large surface area and pore volume, exhibited excellent TC adsorption in solution. Its adsorption isotherm fitted well to the Freundlich model, with a maximum adsorption capacity of 118.72 mg/g. The adsorption process was spontaneous, endothermic, and followed pseudo-second-order kinetics. From the XPS analysis, the hydrogen bonding and surface complexation were the key interactions in the process. In addition, a colorimetric TC detection method was developed considering its complexation with phosphate ions, originating from PCC dissolution, during adsorption. The method was used to detect TC in mg/L concentrations in water samples. Thus, the multifunctional PCC exhibited potential for use in TC removal and environmental remediation.

Strategic preparation of porous magnetic molecularly imprinted polymers via a simple and green method for high-performance adsorption and removal of meropenem

In this study, a facile method has been developed to synthesize a novel type of porous magnetic molecularly imprinted polymers (Fe₃O₄-MER-MMIPs) for the selective adsorption and removal of meropenem. The Fe₃O₄-MER-MMIPs, with abundant functional groups and sufficient magnetism for easy separation, are prepared in aqueous solutions. The porous carriers reduce the overall mass of the MMIPs, greatly improving their adsorption capacity per unit mass and optimizing the overall value of the adsorbents. The green preparation conditions, adsorption performance, and physical and chemical properties of Fe₃O₄-MER-MMIPs have been carefully studied. The developed submicron materials exhibit a homogeneous morphology, satisfactory superparamagnetism (60 emu g^-1), large adsorption capacity (11.49 mg g^-1), quick adsorption kinetics (40 min), and good practical implementation in human serum and environmental water. Finally, the protocol developed in this work delivers a green and feasible method for synthesizing highly efficient adsorbents for the specific adsorption and removal of other antibiotics as well.

XPS, structural and antimicrobial studies of novel functionalized halloysite nanotubes

A novel robust preparation method based on thermal salt decomposition has been elaborated for synthesis of halloysite nanotubes (HNTs) impregnated with silver and iron oxide nanoparticles. The developed method is simple, time-effective, and can be employed for large scale material fabrication. Different characterization techniques, including X-ray diffraction (XRD), scanning and transmission electron spectroscopy (SEM and TEM) and energy dispersive X-ray spectroscopy (EDS) have been used to characterize the functionalized HNTs composite materials. Surface elemental and chemical state analysis was conducted using X-ray photoelectron spectrometer (XPS). The functionalized HNTs exhibit enhanced total surface area (by 17.5%) and pore volume (by 11%) compare to the raw HNTs calculated by using the Brunauer-Emmett-Teller (BET) method. It was shown that functionalized HNTs possess high antimicrobial properties towards both gram- positive and gram-negative bacteria species. The enhanced surface area and bactericidal properties of functionalized HNTs could be beneficial for employing of the prepared material as low cost filtration media for water treatment applications. Molecular dynamics (FPMD) were performed to obtain insights about possible physiochemical mechanisms for chemical adsorption and on the HNT thermal stability.

Tetracycline removal enhancement with Fe-saturated nanoporous montmorillonite in a tripartite adsorption/desorption/photo-Fenton degradation process

The adsorption and photo-Fenton degradation of tetracycline (TC) over Fe-saturated nanoporous montmorillonite was analyzed. The synthesized samples were characterized using XRD, FTIR, SEM, and XRF analysis, and the adsorption and desorption of TC onto these samples, as well as the antimicrobial activity of TC during these processes, were analyzed at different pH. Initially, a set of adsorption/desorption experiments was conducted, and surprisingly, up to 50% of TC adsorbed was released from Mt structure. Moreover, the desorbed TC had strong antibacterial activity. Then, an acid treatment (for the creation of nanoporous layers) and Fe saturation of the montmorillonite were applied to improve its adsorption and photocatalytic degradation properties over TC. Surprisingly, the desorption of TC from modified montmorillonite was still high up to 40% of adsorbed TC. However, simultaneous adsorption and photodegradation of TC were detected and almost no antimicrobial activity was detected after 180 min of visible light irradiation, which could be due to the photo-Fenton degradation of TC on the modified montmorillonite surface. In the porous structures of modified montmorillonite high, ˙OH radicals were created in the photo-Fenton reaction and were measured using the Coumarin technique. The ˙OH radicals help the degradation of TC as proposed in an oxidation process. Surprisingly, more than 90% of antimicrobial activity of the TC decreased under visible light (after 180 min) when desorbed from nanoporous Fe-saturated montmorillonite compared to natural montmorillonite. To the best of our knowledge, this is the first time that such a high TC desorption rate from an adsorbent with the least residual antimicrobial activity is reported which makes nanoporous Fe-saturated montmorillonite a perfect separation substance of TC from the environment.

Preparation of 2D supramolecular material doping with TiO2 for degradation of tetracycline

Anatase TiO₂ photocatalyst supported on [BMPP]₂[2D-Mo₁₈O₅₆] (BMPP = 1, 3-bis(4-methylpyridine) propane dibromide) was successfully prepared by hydrothermal method. The composites were characterized by field emission scanning electron microscopy (SEM), X-ray diffractometer (XRD), infrared spectroscopy (IR) and energy-dispersive X-ray spectrometer (EDS). The results show that the high content anatase nanoparticles are uniformly loaded on the polyacid supramolecules to form the composite material. The photocatalytic activity of TiO₂/Mo₉O₂₈-BMPP towards the tetracyclines (TCs), a model pollutant, has been investigated. The results show that under a 500W high-pressure xenon lamp, 0.15 g TiO₂/MoB can degrade 97% of 20 mL (25 mg/L) Tc after 115 min, showing high catalytic activity. In addition, 0.15-TiO₂/MoB can be easily separated from the reaction system by centrifugation, and the catalyst still maintains high photocatalytic activity after 3 cycles of tests under the same conditions. This shows that it has the potential for recycling. This research provides a new way for the development of new supported catalysts.

The Antimicrobial Properties of Modified Pharmaceutical Bentonite with Zinc and Copper

Pharmaceutical grade bentonite, containing a high amount of montmorillonite, enriched with zinc (Zn) or copper (Cu) (ZnBent and CuBent, respectively) was used as the main component for the creation of formulations for cutaneous use and tested for their antimicrobial capacity. Bentonite (Bent) with added phenoxyethanol (PH) as a preservative and unmodified bentonite were used as control groups. The mineralogical composition, structural state, and physical or chemical properties, before and after the modification of the samples, were characterized utilizing X-ray Diffraction Analysis (XRD), Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray Fluorescence (XRF) techniques, and Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM, SEM-EDS) analyses. In addition, the profile of zinc and copper concentration from two types of surfaces ZnBent and CuBent, and into Phosphate-Buffered Saline (PBS) are discussed. Finally, the formulations in the form of basic pastes were challenged against bacteria, molds, and yeasts, and their performance was evaluated based on the European Pharmacopeia criteria. The Cu-modified bentonite performed excellently against bacteria and yeasts, while the Zn-modified bentonite only showed great results against yeasts. Therefore, Cu-modified bentonite formulations could offer antimicrobial protection without the use of preservatives.

Electrospun Functional Nanofiber Membrane for Antibiotic Removal in Water: Review

As a new kind of water pollutant, antibiotics have encouraged researchers to develop new treatment technologies. Electrospun fiber membrane shows excellent benefits in antibiotic removal in water due to its advantages of large specific surface area, high porosity, good connectivity, easy surface modification and new functions. This review introduces the four aspects of electrospinning technology, namely, initial development history, working principle, influencing factors and process types. The preparation technologies of electrospun functional fiber membranes are then summarized. Finally, recent studies about antibiotic removal by electrospun functional fiber membrane are reviewed from three aspects, namely, adsorption, photocatalysis and biodegradation. Future research demand is also recommended.

The removal of tetracycline from water using biochar produced from agricultural discarded material

An issue of significant importance worldwide is the contamination of water with antibiotics giving rise to antibiotic resistance in the environment. Antibiotics such as tetracycline are widely used in agriculture, as such they can pollute water courses, providing a means by which environmental bacteria can evolve antibiotic resistance genes. Biochar can form part of a solution as it is a well-known adsorbent. This material can be efficient in the adsorption of a wide range of pollutants and is inexpensive. An innovative heat pipe reactor was used to produce biochar from excess food and garden materials. This biochar was characterised using scanning electron microscopy with energy dispersive X-ray analyser (SEM-EDAX), Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy. The biochar produced had an adsorption capacity between 2.98 mg/g and 8.23 mg/g for initial tetracycline concentrations of 20 mg/l and 100 mg/l, respectively. The Freundlich isotherm provided the best fit to the experimental data. Kinetics examination revealed a rapid adsorption of tetracycline during the initial stages. The Elovich equation fitted the experimental data well. This adsorbent could therefore be produced at the site of an agricultural enterprise through the pyrolysis of agriculture waste and then used to reduce the infiltration of antibiotics into the environment.

Nanocellulose–organic montmorillonite nanocomposite adsorbent for diuron removal from aqueous solution: optimization using response surface methodology

Herbicides have been ubiquitous in water environments in recent years, and so it is an appealing proposition to develop an efficient adsorbent for the adsorption of diuron. Therefore, the present study investigated a cellulose nanocrystal/organic montmorillonite nanocomposite adsorbent (CNC/CTM) and its adsorption properties towards diuron present in water. The structure and characteristics of the adsorbent used in this study were characterized by various characterization methods. The optimal diuron adsorption conditions for the CNC/CTM nanocomposite were analyzed based on the response surface methodology (RSM). The adsorption isotherms and kinetics of diuron adsorption were investigated. The results indicated that the adsorption process is the result of hydrogen bonding and the hydrophobicity of the alkyl chain. Under the optimal adsorption conditions, 0.07 g L⁻¹ CNC/CTM adsorbed 5.86 mg L⁻¹ diuron in less than 318.68 min and an efficiency of 82.32% could be achieved. The simulation results showed that the adsorption capacity of CNC/CTM for diuron removal followed the Sips model most closely. The maximum adsorption capacity was approximately 69.04 mg g⁻¹ at 288 K. The experimental data was described best by a pseudo-second-order kinetic equation, signifying a chemical adsorption process. The adsorbent can be reused at least five times after simple solvent washing. This study provides a theoretical basis for understanding the adsorption process of diuron present in water.

CNCs and CTM were combined to obtain a nanocomposite used to remove diuron in water. The adsorption of the nanocomposite was analyzed using response surface methodology, isothermal adsorption model and adsorption kinetics.