Reusability Properties Research Articles

Immobilization of laccase on Fe3O4@SiO2 core@shell magnetic nanoparticles for methylene blue biodegradation

Here we report the preparation and characterization of novel enzyme supports based on silica-coated Fe3O4 magnetic nanoparticles. These nanomaterials were modified at their outer silica surface with isocyanate, trimethylammonium and β-cyclodextrin moieties to immobilize laccase from Trametes versicolor through covalent, electrostatic and supramolecular interactions, respectively, with protein immobilization yields ranging from 21.7% to 53.5%. The effect of the immobilization approach on the activity, optimal working conditions, stability and reusability of the resulting biocatalysts were studied. Best results were achieved for native and adamantane-modified laccase supramolecularly immobilized on β-cyclodextrin bearing supports in terms of their catalytic properties, showing 18.0 U and 14.0 U of immobilized laccase activity per gram of support. However, high thermal stability was observed for the enzyme covalently immobilized on isocyanate-modified nanoparticles, with 14.8-fold increase in the half-life time at 65ºC in comparison with native laccase. Best reusability properties were also achieved by covalent immobilization, retaining over 88% of the initial catalytic activity after 13 cycles of magnetic reuses. All enzyme derivatives were evaluated for the catalytic degradation of methylene blue as pollutant model, showing significant reduction of the dye. In special, a 68-fold increase in the removal efficacy was observed for covalently immobilized enzyme compared to the free laccase. These results suggest high potential application of these biocatalysts in wastewater treatment.

Enhancing the oil/water separation efficiency of polylactic acid fiber membrane via polydimethylsiloxane-polycaprolactone copolymer

Membrane technology is one of the important methods of treating oily wastewater due to low energy consumption. How to design the membrane with high efficiency, biodegradable, reusable and good mechanical properties has attracted increasing interest. In this work, a polydimethylsiloxane-polycaprolactone (PDMS- PCL) was synthesized to endow polylactic acid (PLA) fiber membrane with superhydrophobicity and superoleophilicity via electrospinning without secondary processing. When the blend ratio of PDMS-PCL/PLA is 15wt%, the water contact angle of the fiber membrane is 155.1 ± 3°, and the oil contact angle is almost zero. The tensile strength and elongation at break are 2.05 ± 0.16MPa and 37.9 ± 2.3%, respectively. The fiber membrane exhibited high oil/water separation performance and quick adsorption of oil drop underwater. The permeate flux and separation efficiency for n-hexane are 3550 ± 50L·m-2·h-1 and 99.3 ± 0.2%, separately. It also has excellent self-cleaning and durable properties. The fiber membrane maintains high oil flux, separation efficiency, and mechanical properties after more than 10 rounds of separation. The fiber membrane can resist the external environment variation such as to some extent. The water contact angle of the fiber membrane undergoing friction and heating at 100 °C stably remains at about 150°. The weight loss is little in salt solution. Then this simple efficient method is suitable large-scale production and will promote membrane technologies in application of oil/water separation.

Constructing SDBS-intercalated MoS2 nanosheets confined and near-vertically grown on network biochar adsorbent: Insights into highly efficient co-adsorption of ciprofloxacin and lead ions

To overcome the problems of the weak adsorption ability of biochar to heavy metal ions (HMIs) and competitive adsorption between HMIs and antibiotics during co-adsorption, the adsorbent material in which 2D sodium dodecylbenzenesulfonate-intercalated molybdenum disulfide nanosheets confined and growing near-vertically on 3D network biochar (SDBS-MoS2/BC) was synthesized. The SDBS-MoS2/BC demonstrated good adsorption ability for ciprofloxacin (CIP) and lead ions (Pb2+). Notably, the adsorption capacity of SDBS-MoS2/BC for the target in the binary system remains higher than in the single system, even at elevated concentrations of the competing target (Qmax,CIP = 393.701 mg g−1, Pb2+: 100 mg/L; Qmax,Pb = 264.550 mg g−1, CIP: 100 mg/L). This may be due to the improvement in the utilization of edge/interlayer adsorption sites by the near-vertical SDBS interlayer expansion of MoS2 as a heavy metal ion anchor. Furthermore, the spatial difference between the upper edge site of near-vertical SDBS-MoS2 and the BC plane, that is, the “longitudinal steric effect”, can separate the CIP and Pb2+ adsorptions in a different horizontal plane to avoid competitive adsorption. The underlying adsorption mechanism was elucidated through a series of experiments and the analysis of characterization results. Furthermore, the load of the SDBS-MoS2/BC sponge-packed column can continuously remove contaminants from water. The rapid, anti-interference, multifunctional and reusable properties make SDBS-MoS2/BC promising for excellent environmental treatment.

Flexible X-ray Imaging and Stable Information Storage of SrF2:Eu Based on Radio-Photoluminescence.

X-ray imaging has garnered widespread interest in biomedical diagnosis and nondestructive detection. The exploration of radio-photoluminescence has hastened the advancement of X-ray information storage. However, significant challenges persist in achieving the prolonged imaging of curved objects without attenuation. Here, europium-doped strontium fluoride (SrF2:Eu) is meticulously created to exhibit a linear response to an extensive range of X-ray doses (maximum dose > 5000 Gy), showcasing excellent X-ray information reading/erasing reusability properties (10 cycles). This is accompanied by a red-to-blue emission transition under UV excitation, sustaining for 150 days without attenuation. To elucidate the phenomena of irradiated photoluminescent discoloration and the reversible X-ray storage of SrF2:Eu, we propose an electron-vacancy trap (valence conversion) mechanism, information stably retained by the SrF2:Eu-based device under ambient conditions due to high energy barriers. The time-lapse readout capability is further demonstrated for three-dimensional imaging of curved objects (10 lp mm-1) based on SrF2:Eu embedded within a polydimethylsiloxane (SrF2:Eu@PDMS). The SrF2:Eu demonstrates time-lapse imaging, reversible radio-photoluminescence, and recoverable X-ray storage, offering a promising avenue for optical information encryption and anticounterfeiting applications.

Ultrapure gold recovery from electronic waste as nanoparticles immobilized in hydrogel matrix

Solid-supported gold nanoparticles possess significant value as economical and eco-friendly catalysts due to their durability and reusability. Conventional methods to synthesize heterogeneous catalysts require the use of expensive gold precursors, diminishing their economic viability. Recovering gold directly as nanoparticles immobilized in a solid matrix from electronic waste (e-waste) provides a promising economic solution. However, the greater abundance of other metal ions in e-waste solutions makes this task challenging, demanding more selective approaches. This study presents a cost-effective one-pot synthesis of gold nanoparticles immobilized in a hydrogel matrix from e-waste solutions, circumventing the need for gold precursors. The fabricated hydrogel exhibits exceptionally selective gold reduction, producing well-distributed and highly pure (23.78 K) gold nanoparticles inside the hydrogel matrix. The fine control in nanoparticle diameters from 22 to 35 nm was achieved by tuning the monomer compositions of the hydrogel. These hydrogel-supported gold nanoparticles demonstrate reusable catalytic properties, indicating their potential sustainability and industrial compatibility. This approach addresses the economic challenges of synthesizing solid-supported gold nanoparticles and offers a sustainable pathway.

Reusable and non-invasive TiO2-based photodynamic transdermal patch (RPT) for treating MDR-negative bacteria strain and promote wound healing through a synergistic approach of ROS-induced RNS

Wound healing is delayed due to the infection and biofilm formation of antibiotic-resistant species of gram-negative bacteria especially Pseudomonas aeruginosa and Escherichia coli. Antibacterial photodynamic therapy provides an efficient therapeutic strategy for overcoming drug resistance by producing reactive oxygen species (ROS) and reactive nitrogen species (RNS). Here, we have designed a low-cost light emitting diode (LED) based reusable and non-invasive titanium dioxide nanoparticles patch which is sandwiched between the thin polymer layers. The light-induced pore formation in the polymeric film due to the free radical, in turn, passes through the system and kills the bacteria rather than nanoparticles entering the system resulting in the reusability nature of the patch. The patch's in vitro antibacterial and antibiofilm activity and their mechanism (synergic ROS-induced RNS) were studied. In addition, the reusable antibacterial properties, biocompatibility and wound-healing properties of the patch were also successfully elucidated.

Fabrication of CoTiO3/MgIn2S4 S–scheme heterojunctions with efficient charge separation to enhance the photocatalytic activities of hydrogen generation and formaldehyde removal

The efficient separation of photoinduced charge carriers is a primary factor in the catalytic performance of photocatalysts. Constructing S-scheme heterojunctions is a prospective strategy to efficiently and spatially separate photoinduced charges while retaining strong oxidation and reduction capacities of the catalyst system. Herein, CoTiO3/MgIn2S4 (abbreviated x% CTO/MIS, where x% represents the mass ratio of CTO-to-MIS; x = 5, 10, 15, 20, and 25) heterojunctions were successfully synthesized using a hydrothermal method. These heterojunctions exhibited highly efficient and reusable visible-light photocatalytic properties for hydrogen (H2) generation and formaldehyde (HCHO) degradation. Notably, the 15 % CTO/MIS demonstrated an admirable H2 evolution activity of 631.77 μmol·g−1·h−1, with AQE = 2.25 % at λ = 420 nm, and an HCHO degradation rate of 67.18 %. The intermediate products generated during HCHO removal were identified applying in situ diffuse reflectance infrared Fourier transform spectroscopy. The exceptional catalytic performance of the synthesized materials was attributed to the boosted light absorption and utilization, rapidly separation, and transfer of photoproduced charge carriers, which resulted from the internal electric field of the S-scheme mechanism. Moreover, the S-scheme electron transfer pathway for the CTO/MIS catalyst system during the photocatalytic process was confirmed using electron spin resonance spectroscopy, free-radical capturing tests, density functional theory calculations, in situ X-ray photoelectron spectroscopy, and semiconductor energy band theory. The study offers an innovative perspective for establishing S-scheme heterojunctions with highly efficient and stable photocatalytic activity for H2 generation and HCHO removal.

ZnO Impregnated Graphene Silica Composite to Enhance Cr(VI) Adsorption: Batch Studies

Abstract Hexavalent chromium [Cr(VI)] is a profoundly poisonous heavy metal due to its significant mobility across cell membranes as HCrO4 − and CrO4 2- ions. There is a limited amount of research on the effectiveness of metal oxide impregnated graphene silica composite (GSC) as adsorbents for treating [Cr(VI)]. However, the existing studies indicate that these composites are very efficient. The project involved synthesizing a new type of adsorbent by impregnating zinc oxide (ZnO) particles onto a composite material of graphene and silica. This was achieved using the co-precipitation method. The findings revealed that the highest level of Cr (VI) removal (97%) is achieved at basic, a contact period of 45 minutes. The Langmuir isotherm had the highest degree of fit, suggesting a uniform and chemical adsorption process with the highest possible adsorption capacity of 142 mg/g. The application of ZnO on GSC improves the motion of Cr(VI) in the composite, resulting in an increase in both the adsorption capacity and adsorption kinetics. The findings of this investigation show that the ZnO/GSC composite is a very effective and versatile adsorbent for treating wastewater, highlighting its new and reusable properties.

Enhanced Hydrophobicity and Oleophilicity of Modified Activated Carbons Derived from Agro-Wastes Biomass for the Removal of Crude Oil from Aqueous Medium

Crude oil spillage has tremendous environmental impacts and poses severe pollution problems worldwide due to the continuous activities and operations in the oil and gas sector. This has resulted in the urgent need for clean-up techniques such as the use of natural adsorbents which is considered a relatively low-cost, readily-available, efficient, eco-friendly, and easy-to-deploy mode of addressing oil spillage due to its high oil sorption capacity/efficiency, high oil selectivity, oleophilic, enduring, reusability and biodegradable properties. Empty palm fruit bunch and coconut coir were used as precursors to produce activated carbons for oil spill remediation. The influence of varying parameters was investigated using a batch experimental procedure resulting in the crude oil adsorption capacity increasing with a corresponding increase in contact time, initial oil concentration, temperature, agitation speed, and particle size but decreasing in adsorbent dosage. The combination of surface morphological modification and hydrophobicity enhancement resulted in significantly improved adsorption capacity for crude oil removal (2710.0 mg/g and 4859.5 mg/g for EPFBAC<SUB>LA</SUB> and CCAC<SUB>L.A</SUB> respectively), as evidenced by both FTIR and SEM analyses. The experimental isotherm data were analysed using various isotherm models and the best-fitted isotherm model was the Freundlich model with a correlation coefficient (R<sup>2 </sup>= 0.991 and R<sup>2 </sup>= 0.999) for EPFB<SUB>L.A</SUB> and CCAC<SUB>L.A</SUB> respectively. The kinetic behaviour of the adsorption process was best described by pseudo-second order with R<sup>2</sup> values of 0.970 and 0.999 for EPFBAC<SUB>LA</SUB> and CCAC<SUB>L.A</SUB> respectively while Boyd model revealed that the adsorption was controlled by an internal transport mechanism and film diffusion was the rate-limiting step. The crude oil adsorption was chemisorption and endothermic owing to the positive enthalpy values (ΔH<sup>o</sup> = 183.890 KJ/mol for EPFBAC<SUB>L.A </SUB>and ΔH<sup>o</sup> = 69.656 KJ/mol for CCAC<SUB>L.A</SUB>), the positive value of entropy suggested that the adsorption process was accompanied by an increase in the degree of randomness or disorder at the interface between the adsorbent and the adsorbate. A temperature rise led to a decline in Gibbs energy (ΔG<sup>o</sup>), suggesting that adsorption became more feasible and spontaneous at higher temperatures and the significant activation energies indicated the existence of a substantial energy barrier that must be overcome to initiate the reaction. The results showed the significant capability of the prepared adsorbents to be used as a low-cost, re-generable and eco-friendly adsorbent in oil spill clean-up and is recommended to exploit its usage on a large scale.

Impact of titanium dioxide/graphene in polyvinylidene fluoride nanocomposite membrane to intensify methylene blue dye removal, antifouling performance, and reusability

AbstractThe development of efficient water purification technologies is a critical research focus driven by the crucial role of clean water sources for ecological sustainability. This study explores the strategic incorporation of nanoparticles within polyvinylidene fluoride (PVDF) membranes as a promising approach to enhance membrane performance for wastewater remediation. PVDF membranes containing varying ratios of graphene (GR) and titanium dioxide (TiO2) nanocomposites were fabricated via phase inversion method. Characterization techniques including XRD, FTIR, and FESEM‐EDX revealed that the 80% GR nanocomposite membrane exhibited desirable structural and functional properties with pronounced sponge‐like morphology and homogenous nanoparticle distribution. Fourier‐transform infrared spectroscopy and x‐ray diffraction analysis confirmed the 80% GR membrane retained PVDF crystallinity while uniquely eliminating TiO2 crystallinity. Subsequently, performance testing demonstrated the 80% GR nanocomposite membrane had the highest water flux and methylene blue dye rejection rates compared to other ratios and the pristine PVDF membrane. Both fabricated membranes exhibited sufficient reusability and antifouling properties. However, 80% GR ratio exhibited superior antifouling properties, indicating its potential as an optimal material for improving membrane hydrophilicity and overall water purification technologies. These findings underscore the strategic utility of GR‐TiO2 nanocomposites for enhancing PVDF membrane performance in sustainable wastewater treatment applications.

Circular economy approach for thermal regeneration of graphene-encapsulated magnetic nanoparticles as an efficient adsorbent for sustainable wastewater management

High-performing nanostructured magnetic adsorbents, featuring enhanced dye adsorption from wastewater at various conditions of pH, and separability through the application of magnetic fields, offer significant technical advantages for streamlined water purification processes. Moreover, the efficient regeneration of exhausted magnetic adsorbents provides additional benefits in terms of the sustainability of adsorption process and promoting circular economy principles. Here, we explore the performance of the graphene encapsulated magnetic adsorbent Ni0.4Fe2.6O4/(Fe,Ni)@graphene (GMA) for decolorization of wastewater containing crystal violet (CV), and its reusability properties through thermal regeneration of the exhausted adsorbent at temperatures ranging from 200 to 600 °C. The graphene layer around GMA provides an enhanced adsorption capacity and stability for the agent. Meanwhile, the application of a straightforward and potentially low-cost thermal treatment offers a rapid regeneration strategy, facilitating efficient recycling of the adsorbent. While maintaining structural and morphological stability up to 400 °C, samples regenerated at this temperature exhibit a BET surface area and pore volume of 207.46 m²/g and 0.44 cm³/g, respectively, closely resembling those of the original adsorbent. The regenerated sample recovers over 92 % of the original adsorption capacity. At the same time, approximately 86 % of the saturation magnetization (Ms) of the sample can also be restored through the thermal regeneration, with magnetic remanence and coercivity remaining nearly unchanged compared to the original adsorbent, ensuring the functionality of the regenerated adsorbent.

Management of trihalomethanes in water by ZnO@kaolinite composite: integrated experimental and modeling studies.

The adsorption of trihalomethanes (THMs) from drinking water was investigated in the current study through comparison studies of kaolinite and ZnO@kaolinite nanocomposites. The clay structural network's successful immobilization on the zincite hexagonal structure of ZnO nanoparticles' lattice layers was verified by the SEM/EDX analysis. Under the optimum conditions, the maximum removal of THMs was achieved by kaolinite and ZnO@kaolinite nanocomposites after 60 min. The adsorption performance of the ZnO@kaolinite nanocomposites was greater than that of kaolinite because the former had a larger surface area than the latter. The Freundlich isotherm model best matched the adsorption experimental data, which also reveals the existence of multilayer adsorption on a diverse surface with the greatest correlation (R2 = 0.956 and 0.954, respectively) for both nanoadsorbents using the pseudo-first-order (PFO), pseudo-second-order (PSO), mixed 1, 2-order (MFSO), and intraparticle diffusion (IPD) models. The mechanism by which THMs in drinking water adsorb onto nanoadsorbents was examined. This revealed that both intraparticle and film diffusion were involved in the adsorption process. Kaolinite and ZnO@kaolinite nanocomposites can be used in water treatment to remove THMs due to their great recyclable and reusable properties, even after six cycles.

Recent Advances in Magnetic Feˣ⁺/TiO₂ Microfibers for Wastewater Treatment as Climate Change Mitigation

Chemical dyeing and finishing processes used in the clothing and textile industries are among the main contributors that can increase the impact of climate change. Photocatalysis using nanosized titanium dioxide (TiO2) has been continuously developed as a promising technology for purifying dye wastewater into simpler and environmentally friendly components. In addition, the decoration of iron cations (Fe2+) and (Fe3+) increases the reusability of the photocatalyst due to their magnetic properties, which are easy to collect for the recycling process. Magnetic Fex+/TiO2 microfibers have been successfully prepared using a hydrothermal method using titanium dioxide in an alkaline solution. Cations were added into the solution with the different molar ratios of Ti/Fex+ to produce Fe2+/TNW and Fe3+/TNW, respectively. Photocatalysis activity test using magnetic Fex+/TNW was carried out using methylene blue in a reactor equipped with an incandescent bulb lamp representing solar light. The results showed that adding the cations resulted in a new shape of palm tree leaves, like titanate microfibers. Controlling the cation’s molar ratio produces the magnetic Fex+/TNW with a 50-150 µm length. SEM images of each material presented the uniformly elongated shape and aggregated on one side morphology. In addition, paramagnetic properties indicate that magnetic Fex+/TNW can be easily separated from the dispersion in less than 1 minute using an external magnet. A photocatalysis activity test of magnetic Fex+/TNW was performed by calculating the percent degradation of methylene blue with variations in irradiation time in visible light conditions. The result showed the effectiveness of photodegradation of methylene blue was significantly increased in materials with 3.3 molar ratios of both Ti/Fe2+ and Ti/Fe3+ with a percent degradation reaching 79% and 70%, respectively, in 5 hours. In conclusion, magnetic Fex+/TNW is introduced as an alternative dye wastewater treatment technology that has reusable properties and works well on sustainable energy sources of solar light.

Adsorption of ionic contaminants from complex water matrices by versatile chitosan-based beads

Most adsorbents are currently restricted by their single function in pollutant removal from complex wastewater. Herein, we constructed a versatile chitosan-based adsorbent (MC-DA) by grafting amphoteric copolymers with high pH-responsiveness property, aiming at the removal of multiple ionic contaminants. Specifically, the surface charge and hydrophobicity/hydrophilicity of MC-DA can be finely tuned under different pH conditions. As a result, the effective adsorption of cationic methylene blue (MB) and anionic Acid Orange 7 (AO7) with capacities of 627.4 mg/g and 1146.8 mg/g were achieved respectively, superior to most reported materials. Regarding the characterization results, the adsorption mechanisms for MB adsorption were electrostatic and hydrophobic interactions, while the electrostatic attraction was the main driving force for AO7 adsorption. Apart from the versatile adsorption performance, high acid resistance (pH ≥ 2.0), good reusability and rapid separation property under an external magnetic field suggested MC-DA’s promising environmental benefits and practical application potential in water remediation.

A novel thermosensitive porous imprinted polymer for selectively separating ReO4− based on Pickering‐like emulsion polymerization

AbstractIn this study, we combined the imprinting technique, temperature‐sensitive polymer, and Pickering emulsion polymerization to prepare a temperature‐sensitive porous imprinted polymer. First, the temperature‐sensitive block polymer PDEA‐b‐P (DEA‐co‐AM) was prepared by reversible‐addition fragmentation chain transfer polymerization, and then a temperature‐sensitive porous ReO4− imprinted polymer (ReO4−‐TPIP) was prepared using the Pickering‐like polymerization technique, which was introduced to the preparation of the imprinted polymer. The structure and morphology of the polymer were characterized by FTIR, SEM‐EDS, and BET. The adsorption experiments showed that the maximum adsorption (Q), separation (R), and desorption (D) of ReO4−‐TPIP were 0.1568 mmol/g, 3.41, and 85.22%, respectively, and the adsorption equilibrium could be reached after 120 min, which decreased to 0.1212 mmol/g, 1.23, and 70.01% after repeated use for 11 times. These results indicate that ReO4−‐TPIP has good adsorption and reusability properties. The adsorption studies showed that ReO4−‐TPIP conformed to the zero‐level kinetic model in the pre‐adsorption stage, the quasi‐one‐level kinetic model in the late stage, and the isothermal adsorption process conformed more to the Langmuir model. In addition, in the secondary leach solution of high‐temperature alloys, the purity of rhenium in the solution increased from 35.4119% to 53.4812% after one adsorption/desorption cycle. The prepared ReO4−‐TPIP provides a new material and strategy for the selective separation and purification of rhenium in complex rhenium‐containing solutions for the industry.

High adsorption of Cu(II) in novel thiacalix[4]arene/acrylic polymer/diatomite fast fabricated by electron beam irradiation: Controllable microstructures, adsorption performance and mechanism

Chemical grafting of calix[4]arene is a common method to prepare high-performance calix[4]arene adsorbents for heavy metals, however, the chemical grafting process consumes much time and a large amount of heating energy due to the tedious steps. Herein, a thiacalix[4]arene/acrylic polymer/diatomite (TC4A/PAA/diatomite) adsorbent was fast fabricated by electron beam irradiation induced grafting, polymerization and crosslinking technique only in one-pot for the removal of Cu(II) as an important form of heavy metal pollution. Characterization by Fourier transform infrared (FTIR) spectra, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), diffuse reflectance UV–visible spectra and positron annihilation lifetime spectra (PALS) disclosed that the eco-friendly and low-cost TC4A/PAA/diatomite irradiated at 90 kGy namely TC4A/PAA/diatomite (90 kGy) with strong complexing ability owing to many functional groups such as carboxyl, hydroxyl etc in it. The effects of electron beam irradiation dose, initial solution pH, and initial concentration of Cu(II) on the adsorption performance of TC4A/PAA/diatomite were investigated. The isotherm adsorption data of Cu(II) in TC4A/PAA/diatomite (90 kGy) are more suitable for the Langmuir model with the maximum adsorption capacity of 123.30 mg/g. In addition, the bifunctional TC4A/PAA/diatomite (90 k Gy) can efficiently remove Cu(II) and display excellent reusability properties. The adsorption mechanism was further analyzed by FTIR, SEM, X-ray photoelelctron spectroscopy (XPS), diffuse reflectance UV–visible spectra and PALS. This study provides a fast, efficient and eco-friendly synthesis method of calix[4]arene adsorbent, conducing to the design of material innovation. Meanwhile, TC4A/PAA/diatomite (90 kGy) has potential application prospects in the treatment of practical Cu(II) contaminated wastewater.

Melamine-based hyper-cross-linked resin for efficient removal of total petroleum hydrocarbons (C10-C32) from aqueous solutions.

Petroleum hydrocarbons (PHCs) are produced from industrial discharges, storage leakages, accidental spills, and operational failures. The hazardous nature of PHCs causes serious health risks and threatens the entire aquatic habitat. In this research work, the investigation of the removal of total petroleum hydrocarbons (TPHs) from the contaminated water is carried out utilizing a novel hypercross-linked resin, MAICY, which is generated by condensation of commercially available precursors. The chemical structures of MAICY have been examined extensively by FESEM, FT-IR, solid (CP-MAS) 13C-NMR, and TGA. A comprehensive analysis for adsorption parameters of TPHs has been performed, and different models such as Langmuir and Freundlich isotherms have been employed where the Freundlich isotherm was found to be the best fit for removal of THPs (R2= 0.9991). The results revealed that the performance of MAICY for the adsorption of TPHs from contaminated water gives a maximum adsorption capacity (qe) of 146 mg.g-1. The results of various parameters hinted that the contact time (0.25-4 h), the dosage of adsorbent (0.17 g/L), pH (7), and concentration of TPHs (26.5 mg/L) have controlled the overall adsorptive performance. Moreover, the kinetic data of qe(expt.) and qe(calc.) for adsorption of TPHs disclosed the regression values (R2) for pseudo-first order (R2= 0.9921) and pseudo-second order (R2= 0.9891). Additionally, based on CHI factor (X2) error estimations, the data was shown to be more consistent with pseudo-first-order kinetics. Moreover, MAICY demonstrated excellent reusability and recycling properties for up to four consecutive adsorption-desorption cycles.

Visible-Light-Responsive Novel Ru(II)-Metallo-Antibiotics with Potential Antibiofilm and Antibacterial Activity.

Growing challenges with antibiotic resistance pose immense challenges in combating microbial infections and biofilm prevention on medical devices. Lately, antibacterial photodynamic therapy (aPDT) is now emerging as an alternative therapy to overcome this problem. Herein, we synthesized and characterized four Ru(II)-complexes, viz., [Ru(ph-tpy)(bpy)Cl]PF6 (Ru1), [Ru(ph-tpy)(dpq)Cl]PF6 (Ru2), [Ru(ph-tpy)(dppz)Cl]PF6 (Ru3), and [Ru(ph-tpy)(dppn)Cl]PF6 (Ru4) (where 4'-phenyl-2,2':6',2″-terpyridine = ph-tpy; 2,2'-bipyridine = bpy; dipyrido[3,2-f:2',3'-h]quinoxaline = dpq; dipyrido[3,2-a:2',3'-c]phenazine = dppz; and Benzo[I]dipyrido[3,2-a:2',3'-c]phenazine = dppn), among which Ru2-Ru4 are novel. Octahedral geometry of the complexes with a RuN5Cl core was evident from the crystal structure of Ru2. Ru1-Ru4 showed an MLCT absorption band in the 450-600 nm region, useful for aPDT performances. Further, optimum triplet excited state energy and excellent photostability of Ru1-Ru4 made them good photosensitizers for aPDT. Ru1-Ru4 demonstrated enhanced antimicrobial activity on visible-light exposure (400-700 nm, 10 J cm-2), confirmed using different antibacterial assays. Mechanistic studies revealed that inhibition of bacterial growth was due to the generation of oxidative stress (via NADH oxidation and ROS generation) upon treatment with Ru2-Ru4, resulting in destruction of the bacterial wall. Ru2 performed best killing performance against both Gram-negative (Escherichia coli) and Gram-positive (Bacillus subtilis) bacteria when exposed to light. Ru2-Ru4, when coated on a polydimethylsiloxane (PDMS) disk, showed long-term reusability and durable antibiofilm properties. Molecular docking confirmed the efficient interaction of Ru2-Ru4 with FabH (regulates fatty acid biosynthesis of E. coli) and PgaB (gives structural stability and helps biofilm formation of E. coli), resulting in probable downregulation. In vivo studies with healthy Wistar rats confirmed the biocompatibility of Ru2. This study shows that these lead complexes (Ru2-Ru4) can be used as potent alternative antimicrobial agents in low concentrations toward bacterial eradication with photodynamic therapy (PDT).

Adsorption and catalytic degradation of tetracycline hydrochloride by HCNTs /MnFe2O4

Developing efficient, stable and selective materials is essential for removing antibiotics from aquatic systems. In this study, one composite is prepared via loading of magnetic MnFe2O4 onto hydroxylated multi-walled carbon nanotubes (HCNTs) through co-precipitation, named as HCNTs/MnFe2O4. The characterization of materials was performed using various methods, such as Vibrating Sample Magnetometer (VSM), Electron Paramagnetic Resonance (EPR), etc. There are larger surface and good magnetic property, which are useful to bind adsorbate and easy separation from mixtures. The as-synthesized composite exhibited excellent adsorption capacity and ability to activate potassium persulfate (KPS) for the efficient removal of Tetracycline hydrochloride (TC) from solution. The results showed that the adsorption capacity of HCNTs/MnFe2O4 towards TC was 341 mg·g–1 at 303 K. The kinetic process can be elucidated using pseudo-second-order kinetic model while the adsorption equilibrium can be fitted by Freundlich model. The mechanism of adsorption may include electrostatic attraction, complexation, π-π stacking, etc. To initiate Fenton-like heterogeneous catalytic degradation, KPS was added to the adsorption system to degrade and remove TC from solution. The experimental results showed that HCNTs/MnFe2O4 as a catalyst could achieve up to 89 % degradation of TC in the range of pH=3–8 due to its ability to generate active species such as ‧OH, SO4‧-, ‧O2- and 1O2 as confirmed from radical capturing experiments and EPR analysis. The removal efficiency after three adsorption regeneration or degradation cycles could reach up to 56 %, confirming its good reusability properties. There are good prospects of HCNTs/MnFe2O4 for the practical removal of antibiotics from aqueous solutions.

Removal of arsenic from water by silver nanoparticles and Fe-Ce mixed oxide supported on polymeric anion exchanger

By encapsulating nanoscale particles of goethite (α-FeO(OH)), hydrous ceric oxide (CeO2·H2O, HCO) and silver nanoparticles (AgNPs) in the pores of polystyrene anion exchanger D201, a novel nanocomposite FeO(OH)-HCO-Ag-D201 was prepared for the effective removal of arsenic from water. The isotherm study shows that FeO(OH)-HCO-Ag-D201 has excellent adsorption performance for As(III) and As(V), with an increased adsorption capacity of As(III) to 40.12 mg/g compared to that of 22.03 mg/g by the composite adsorbent without AgNPs (FeO(OH)-HCO-D201). The adsorption kinetics data showed that the sorption rate of FeO(OH)-HCO-Ag-D201 for As(III) is less than that for As(V), and the adsorption of As(III) and As(V) were consistent with the pseudo-second-order model and the pseudo-first-order model, respectively. Neutral or basic conditions are favored for the adsorption of As(III/V) by FeO(OH)-HCO-Ag-D201. Compared with nitrate/chloride/bicarbonate, sulfate/silicate/phosphate showed more remarkable inhibition of arsenic removal by FeO(OH)-HCO-Ag-D201, whereas natural organic matter showed no interference to the arsenic removal. The As(V) adsorption involved different interactions such as electrostatic attraction and surface complexation, while the adsorption of As(III) involved the part oxidization of As(III) to As(V) and the simultaneous adsorption of As(III) and As(V). In addition to the Ce(IV) in CeO2·H2O acted as an oxidant, the synergistic effect of α-FeO(OH) and AgNPs also contributed to the oxidization of As(III) to As(V). Moreover, the reusable property suggested that this FeO(OH)-HCO-Ag-D201 nanocomposite has great potential for arsenic-contaminated water purification.