•Properties and mechanisms of Cr(VI) adsorption onto LDH-based materials reviewed.•Such materials: high anion exchange capacity and positively charged external surface.•Identified mechanism: anion ...exchange, adsorption-coupled reduction, electrostatic attraction.•Adsorption-coupled reduction: identified by some advanced techniques from 2016.•Thermodynamic parameters: ΔG° <0, ΔH° >0, and ΔS° >0 in the most observation cases.
An attempt has been made in this review to provide some insights into the possible adsorption mechanisms of hexavalent chromium onto layered double hydroxides-based adsorbents by critically examining the past and present literature. Layered double hydroxides (LDH) nanomaterials are typical dual-electronic adsorbents because they exhibit positively charged external surfaces and abundant interlayer anions. A high positive zeta potential value indicates that LDH has a high affinity to Cr(VI) anions in solution through electrostatic attraction. The host interlayer anions (i.e., Cl−, NO3−, SO42−, and CO32−) provide a high anion exchange capacity (53–520 meq/100 g) which is expected to have an excellent exchangeable capacity to Cr(VI) oxyanions in water. Regarding the adsorption-coupled reduction mechanism, when Cr(VI) anions make contact with the electron-donor groups in the LDH, they are partly reduced to Cr(III) cations. The reduced Cr(III) cations are then adsorbed by LDH via numerous interactions, such as isomorphic substitution and complexation. Nonetheless, the adsorption-coupled reduction mechanism is greatly dependent on: (1) the nature of divalent and trivalent salts utilized in LDH preparation, and the types of interlayer anions (i.e., guest intercalated organic anions), and (3) the adsorption experiment conditions. The low Brunauer–Emmett–Teller specific surface area of LDH (1.80–179 m2/g) suggests that pore filling played an insignificant role in Cr(VI) adsorption. The Langmuir maximum adsorption capacity of LDH (Qomax) toward Cr(VI) was significantly affected by the natures of used inorganic salts and synthetic methods of LDH. The Qomax values range from 16.3 mg/g to 726 mg/g. Almost all adsorption processes of Cr(VI) by LDH-based adsorbent occur spontaneously (ΔG° <0) and endothermically (ΔH° >0) and increase the randomness (ΔS° >0) in the system. Thus, LDH has much potential as a promising material that can effectively remove anion pollutants, especially Cr(VI) anions in industrial wastewater.
Gold nanoparticles (AuNPs) decorated CNTs are promising materials for photocatalytics and biosensors. However, the synthesis of AuNPs chemically linked to the walls of MWCNTs is challenging and toxic ...products such as thionylchloride (SOCl
) or 1-ethyl-3(dimethyl-amino) propyl carbodiimide hydrochloride (EDAC) need to be used. This work reports a new approach to prepare gold nanoparticles decorated multiwalled carbon nanotubes (MWCNTs) by using cysteaminium chloride via the formation of a Zwitterionic acide-base bond. The grafting process consists of 3 mains steps: oxidation, thiolation and decoration of AuNPs on the surface of MWCNTs. The completion of each step has been verified out by both spectroscopic (Raman, UV-Vis, FT-IR) and Scanning Electron Miscroscopy (SEM). The chemical bonding states of synthesized products have been proven by X-ray photoelectron spectroscopy (XPS).
This work aims to clarify the photocatalytic degradation mechanism and heat reflectance recovery performance of waterborne acrylic polymer/ZnO nanocomposite coating. To fabricate the nanocomposite ...coating, ZnO nanoparticles (nano‐ZnO) were dispersed into acrylic polymer matrix at the various concentrations from 1 to 6% (by total weight of resin solids). The photocatalytic degradation of nanocomposite coating under ultraviolet (UV) light irradiation has been investigated by monitoring its weight loss and chemical/microstructural/morphological changes. As the topcoat layer, its heat reflectance recovery has been evaluated under UV/condensation exposure by using an artificial dirty mixture of 85 wt% nanoclay, 10 wt% silica particles (1–5 μm), 1 wt% carbon black, and 2 wt% engine oil. After 108‐cycle UV/condensation exposure, infrared spectra and weight loss analysis indicated that the maximal degradation for nanocomposite coating is observed at 1 wt% nano‐ZnO. On the other hand, after 96 hr of UV light exposure, the nanocomposite coating with1 wt% nano‐ZnO could restore effectively the reflective index of solar‐heat reflectance coating (from 58.45 to 80.78%). Finally, the photodegradation mechanism of this waterborne acrylic polymer coating has been proposed as the UV‐induced formation of CCCO conjugated double bonds. As a result, its self‐cleaning phenomenon can be achieved as the recovery of heat reflectance.
An hybrid system of combined plasma with photocatalysis for treatment of hospital indoor air.
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•A possible way for treatment of air from hospitals and swimming pools is proposed.•The ...destruction of CVOC in air by photocatalysis and plasma and coupling is studied.•The synergistic effect of the combined system is observed.•The effects of operating parameters on the performance of each process are tested.•TiO2 + UV showed high performance in the mineralization and ozone elimination.
The purpose of this study is to evaluate the efficiency of non-thermal plasma and heterogeneous photocatalysis processes for indoor air treatment using cylindrical continuous reactor at pilot scale and high flow rates. Trichloromethane (CHCl3) also called chloroform was chosen as a model pollutant representing hospital indoor air. This pollutant is considered as carcinogenic, mutagenic and reprotoxic agent. The effect of several parameters such as inlet pollutant concentrations (25–300 mg m−3), flow rates (2–8 m3 h−1), relative humidity of the effluent (5, 30, 50 and 90%) as well as input of the plasma discharge (9–21 kV) on the photodegradation of trichloromethane is investigated.
Our findings show that the increase of flow rate leads to a reduction of degradation efficiency, while the humidity promotes the degradation in the case of photocatalysis process due to the formation of OH radicals.
Moreover, the addition of a photocatalyst under UV radiation in the discharge zone enhances the reduction of ozone and CO gases compared to plasma process alone.
The combination of plasma DBD and photocatalysis enhances the removal efficiency with a synergetic effect, leading to removal efficiency higher than 10% if we consider the sum of the contribution of each process separately.
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•UV-curable acrylic urethane/Fe3O4-Ag nanocomposite coating was successfully prepared.•The addition of Fe3O4-Ag nanohybrids is found not effect on the photocrosslinking.•Abrasion ...resistance of coating increased with the presence of the nanohybrids.•Antimicrobial activity was inversely proportional to crosslinking density of coating.
In this paper, an antibacterial nanocomposite coating has been prepared by a green method based on photocroslinking with the addition of new synthesized Fe3O4-Ag nanohybrids. Fe3O4-Ag hybrid nanoparticles (0.1 wt.%) were dispersed in UV-curable acrylate resin stystem (BGDM and HDDA). The kinetic of UV-curing reaction of the nanocomposite was studited by measuring the coversion of acrylate double bonds, the variation of relative hardness, gel fraction and swelling degree of the coating. The structural morphology, mechanical and antibacterial properties of the nanocomposite were characterized. The analysis data demonstrated that the addition of 0.1 wt.% of Fe3O4-Ag hybrid nanoparticles into the coating affected insignificantly to its crosslinking process; the UV-exposure time to achieve a full crosslinking coating was about 4.8 s; the hybrid nanoparticles were homogeneously dispersed in network polymer matrix. The addition of the nanohybrids into the UV curing coating improved its its abrasion resistance from 98.24 to 126.54 lite/mil. The antibacterial testing indicated that the antimicrobial activity of the nanocomposite against E. coli was inversely proportional to its crosslinking density. Adding the nanocomposite in the culture, the growth rate of culture reduced about 3–5 % compared to that of the pure culture, after 5 h of cultivation while no antibacterial activity was observed for the neat coating.
The crystallization and segregation behavior of immiscible polycaprolactone/poly(ethylene glycol) PCL/PEG (50/50) blends was investigated using mainly resonance-enhanced atomic force microcopy ...coupled with infrared spectroscopy (AFM-IR) which allows a spatial resolution of the order of 30–50 nm. Chemical infrared images of the blends at different scales highlight their island-like spherulitic structures. The nanoscale IR spectra on both sides of the spherulitic interfaces are different. The polymer segregation mechanism of the blend in the spherulitic structure is also investigated in which PEG is rejected outside of PCL spherulites at low crystallization temperature (30 °C) while it is rejected in the form of small nodules with a dimension in the order of few micrometers, inside of PCL spherulites at higher crystallization temperature (40 °C) due to the presence of an upper critical solution temperature (UCST).
Abstract This study investigates the effects of molecular weight and crystallinity of polylactic acid (PLA) on the morphology and crystallization behavior of polyhydroxybutyrate (PHB)/PLA blends. ...Utilizing a solution casting method, we discovered that the molecular characteristics of PLA significantly influence the thermal and structural properties of the blends. The lower molecular weight and amorphous PLA notably broadened the temperature range for PHB's banded spherulite formation, indicating enhanced miscibility. In contrast, semicrystalline PLA variants produced smaller spherulites within large PHB matrices. The high molecular weight PLA had an unusual, relatively low melting point which led to a competition between the molecular weight effect and the supercooling effect regarding the isothermal crystallization kinetics. The blend morphology was observed in thin films in which the usual crystal formation of PHB was severely hindered in the presence of crystalline PLA but could form thin lamellae when the PLA was amorphous. At ultra‐thin thickness, where crystallization is impossible, the amorphous co‐continuous structure of the blends was revealed by melting the film. Our research contributes to the development of advanced biodegradable materials for environmental sustainability, emphasizing the intricate interplay between polymer blend components that can be tuned for specific applications. Highlights The study explores the blend morphology and crystallization of PLA/PHB. The temperature range for PHB's spherulite formation broadens with PLA. PLA's partial miscibility with PHB shifted T g and caused delayed T m of PHB. Usual PHB crystal formation is hindered with crystalline PLA. Thin PHB lamellae formed within amorphous PLA and observed via AFM.
•Antibacterial ZnO nanoparticles for edible surface coatings were successfully fabricated.•Incorporation of ZnO nanoparticles in a chitosan/gum arabic edible coating was evaluated.•Effects of ZnO ...nanoparticles on the performance of the edible coating for banana preservation were investigated.•Properties of the edible coating and changes in the physical chemical properties of the banana were investigated.•The developed edible coating composite can be applied for banana preservation.
ZnO nanoparticles are nontoxic inorganic oxides that have been extensively used as a supplement for zinc nutrients and antibacterial agents in the food industry, especially in edible coatings to protect food from deterioration by viruses, fungi, and bacteria. In this work, ZnO nanoparticles were fabricated by a hydrothermal method and characterized by scanning electron microscopy and X-ray diffraction. The prepared ZnO nanoparticles exhibited good antibacterial properties against several bacteria, including Staphylococcus aureus, Escherichia coli, and Bacillus subtilis. The ZnO nanoparticles as an antibacterial agent were incorporated into a chitosan/gum arabic (CH/GA) edible coating, and the protective performance for the preservation of bananas was investigated. The obtained CH/GA/ZnO coating significantly improved the quality and shelf life of bananas at a temperature of 35 °C and relative humidity (RH) of 54 %. The banana surface treated with the CH/GA/ZnO coating was relatively smooth with a CH/GA/ZnO film thickness of approximately 50 μm. The utilization of the resultant coating enabled the maintenance of banana quality, including fruit firmness, weight loss, reducing sugar, and titratable acidity, for a remarkably longer period. The banana coated with the CH/GA/ZnO system was demonstrated to maintain freshness for more than 17 d in comparison with the less than 13 d for the control banana at 35 °C and 54 % RH.
Developing advanced materials with antibacterial and antifouling activities offers an adequate protection solution against surface bacterial contamination—a common cause of infection threatening ...human health. The current work reports the preparation of polyhydroxybutyrate (PHB) microfiber membranes decorated with photoactive Ag‐TiO2 nanoparticles using electrospinning coupled with dip‐coating methods. The decoration of Ag‐TiO2 nanoparticles strongly enhances the antibacterial properties of prepared membranes, particularly under light illumination, thanks to their photocatalytic activity. The best‐performing sample exhibits potent antibacterial efficiency exceeding 99% against Escherichia coli and Staphylococcus epidermidis after 3 and 1 h of exposure to low‐power commercial LED light, respectively. The prepared samples also display excellent reusability with an insignificant antibacterial activity decrease after three cycles (<2% loss in antibacterial efficiency). Furthermore, these samples effectively prevent bacterial fouling due to their potent antibacterial properties. Notably, despite the strong antibacterial effect, decorated Ag‐TiO2 nanoparticles promote the adhesion of microorganisms, accelerating the biodegradation of PHB microfibers. As a result, the prepared microfiber membranes with nanoparticle decoration exhibit biodegradability comparable to the non‐decorated membrane, with the soil degradation rates reaching almost 99% after only 6 weeks.
Light‐enhancement of Antibacterial Properties and Biodegradability of PHB‐Ag@T membrane.
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