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.
•The SDS-modified α-Al2O3 particles behaved as high-performance adsorbents.•The optimal conditions were pH 4, NaCl 1 mM, and the α-Al2O3 dosage of 25 mg. mL−1.•The high TCs removal efficiencies were significantly enhanced by greater than 88%.•The transformation rate was in the order of CTC > TC > OTC.•The TCs transformations and activations were strongly affected by the adsorption.
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•A new polycation PVBTAC-modified ZnO/SiO2 nanocomposite based on rice husk was successfully fabricated.•The optimum conditions for DCF removal using PVBTAC-modified ZnO/SiO2 were ...contact time 90 min, pH 8 and dosage 10 mg/mL.•The maximum adsorption capacity of DCF was 66 mg/g and the removal efficiency was 91.8%.•After four regenerations, the DCF removal using PVBTAC modified ZnO/SiO2 was still greater than 84%.•The E.coli removal was greater than 88 % that was controlled by electrostatic and non-electrostatic interactions.
The present study investigated the adsorptive removal of non-steroidal medication diclofenac (DCF) using polycation, PVBTAC modified zinc oxide/silica nanocomposite (ZnO/SiO2). The ZnO/SiO2 which was fabricated based on nanosilica rice, was examined by XRD, FT-IR, TEM, EDX, and zeta potential measurements. Surface of ZnO/SiO2 was modified by PVBTAC adsorption at pH 9 and 100 mM KCl to reverse the high charge of material. The optimum parameters for DCF removal using PVBTAC-modified ZnO/SiO2 were contact time 90 min, pH 8 and adsorbent dosage 10 mg/mL. The maximum adsorption capacity and the removal efficiency of DCF were found to be 66 mg/g and 91.8%, respectively, while the bacteria Escherichiacoli(E.coli) removal reached greater than 88 %. Adsorption of DCF on PVBTAC-modified ZnO/SiO2 was mainly controlled by electrostatic attraction between anionic DCF molecules and positively charged PVBTAC-modified ZnO/SiO2 surface whereas the E.coli removal was controlled by both electrostatic and non-electrostatic interactions. Adsorption isotherms of DCF on PVBTAC-modified ZnO/SiO2 at different ionic strengths were reasonably represented by a two-step model while adsorption kinetics fitted well with the pseudo-second-order model. After four regenerations of PVBTAC modified ZnO/SiO2, the DCF removal still exceeded 84%. Our materialis agreat performance adsorbent to remove pharmaceutical and bacteria.
In this study, the zinc oxide-decorated graphitic carbon nitride composite (ZnO/gC3N4 – ZCN) was synthesized for photocatalytic degradation of organic dyes in aqueous media. Particularly, ZnO was ...fabricated by the calcination method with the assistance of Garcinia mangostana pericarp extract as a stabilizer and reducing agent, while graphitic carbon nitride (gC3N4 – CN) was prepared by the calcination method and exfoliated using a strong oxidizer mixture. Characterization results showed ZnO possesses a spherical shape with an average diameter of 30–80 nm and is distributed evenly on the CN sheets. Subsequently, ZCN was subjected to photodegradation towards methylene blue (MB), which indicated that under optimal conditions of 50 mg of catalyst, pH 9, and 10 mg/L of MB concentration, the overall efficiency reached up to 99.16 % after 180 min of visible irradiation. Additionally, ZCN also possesses the degradation ability for other organic dyes, for instance, malachite green (MG) and methyl orange (MO) with an overall efficiency of 96.42 and 57.57 %, respectively. Moreover, the radical scavenging experiments elucidated that the major responsible component for the photodegradation was the photogenerated holes, while other radicals also facilitated the process. Besides, the reusability of the material was excellent as only 10 % of the yield decreased after five cycles. The aforementioned findings reveal the notable potential applications of the ZCN material in the environmental remedial field.
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•The ZnO/gC3N4 composite was biosynthesized with the aid of sonication.•The spherical ZnO distributed evenly on the gC3N4 exfoliation sheet.•The composite exhibited great methylene blue photodegradation under visible light.
In this study, the bio-zeolite (BZ) was successfully fabricated by solvothermal method from the rice husk. The fabricated BZ was thoroughly characterized by SEM, XRD, XRF, BET, and FT-IR. The BZ ...characteristics were demonstrated with a homogenous, porous, and crystal structure, a uniform round edge shape, a SiO2/Al2O3 ratio of about 2.65, a specific surface area of 3.31 m2 g−1, and specific linkages of Si–O–Al, Si–O–Si, and Si–OH. Subsequently, the BZ particles were modified by the adsorption of a cationic surfactant CTAB. Then CTAB@BZ was applied as an effective adsorbent to remove the herbicide glyphosate (GP) from aqueous solutions. The GP removal variables were optimized at 10 mM CTAB, pH 5, free ionic strength, 1 mg mL−1 BZ dosage, and 60 min contact time. The GP removal efficiency was more significantly enhanced by greater than 90 % with the surface modification. The GP adsorption isotherm was accorded to the pseudo-second-order model with multiple-adsorbed layer formation. The GP adsorption mechanisms were the main surface adsorption due to the major CTAB-GP electrostatic attractions.
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•Zeolite (BZ) fabricated from rice husk was modified by cationic surfactant CTAB.•Optimal variables to remove the GP were found at pH 5, free ionic strength.•GP multiple layers were formed based on mainly CTAB-GP electrostatic attractions.•GP adsorption isotherm was well-followed to the pseudo-second-order model.
Purpose
This study aims to investigate specific professional competencies of teachers to implement education for sustainable development (ESD) in the contexts of Vietnam.
Design/methodology/approach
...The authors carried out a Delphi study with eight ESD experts in Vietnam to collect their expertise viewpoints regarding teachers’ ESD professional competencies.
Findings
In total, 13 competencies related to three dimensions (content knowledge/cognitive, pedagogical and pedagogical content knowledge, motivation and volition) were highlighted by ESD experts.
Research limitations/implications
The proposed teachers’ competencies were based on the ideas of a small group of experts, and the results need to be tested, refined and confirmed by further work. Besides, in this study, we have not defined the levels of achievement for each competency as well as developed assessment tools.
Practical implications
The specific professional competencies for teachers can be considered as a foundation for developing educational offers focusing on promoting the specific teachers’ professional competencies in basic ESD training.
Originality/value
Studies on educators’ professional competencies for ESD mostly were conducted in western countries. However, competencies do not exist independently; instead, they should be considered in specific contexts of teaching, school, culture and society. This research is among one of the first studies that contextualizes teachers’ competencies in a non-western context.
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•Temporal change of δH and EPM of PSL particle coated with oppositely charged polyelectrolyte after over dosage incubation was monitored.•Charge density of polyelectrolyte chain is ...confirmed to have significant influences on the morphological relaxation of adsorbed polyelectrolytes.•Effects of the diameter of particle and ionic strength were clarified.
Temporal change of hydrodynamic layer thickness (δH) and electrophoretic mobility (EPM) of polystyrene sulfate latex (PSL) particles adsorbed by oppositely charged polyelectrolytes were monitored herein to clarify the relaxation behavior after overshooting. Two linear polyelectrolytes with nominal molecular weight of 5 million differing in chain charge density, σ = 100 % (PTMA5M) and σ = 4 % (PTMC5M), and PSL particles of different diameters were used in the experiment. With the former polyelectrolyte, a remarkably thick layer that is formed at the incubation decays with the time scale of several tens of minutes and the EPM remains constant. The value of δH decreases with the increase of particle size, whereas with the latter polyelectrolyte, the initial value of δH is several times smaller than that of the former. There is a case wherein the EPM decreases with time, although δH remains constant. The initial δH is independent of the particle size. Ascribing the reason for the relaxation phenomena to desorption of overshot polyelectrolytes attached with meta-stable conformation in the initial stage, we have obtained an approximate picture of the conformational change for the chain of different charge density.
The temporal behavior of adsorbed polymers is important in the analysis of colloid–polymer systems. The single-particle-tracking method provides a reliable approach to acquiring information on the ...adsorbed polymer layer on a spherical particle. Imaging, tracking, and analysis of the Brownian motion of a single colloidal particle with/without adsorbed polymers provided the trajectory of the Brownian motion and the layer thickness of adsorbed polymers. The temporal decrease in the thickness of an adsorbed polyelectrolyte layer was monitored within 2 h. A polyelectrolyte with a high charge density formed a thick layer on the particle surface and the layer thickness rapidly decreased. A polyelectrolyte with a low charge density formed a thinner layer, and its thickness decreased slightly. The transient adsorption behavior in a system undergoing flocculation can be used for the analysis of adsorption and flocculation in colloid–polymer systems.
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•Temporal changes of polymer layer were estimated by single-particle tracking method.•A decrease of polymer layer was apparently observed within 2 h.•The thick layer of high-charge-density polymer decreases rapidly as a function of time.•The thin layer of low-charge-density polymer decreases only slightly.
In recent years, the applications of nanomaterials are getting more common in commercial products. Amongst them, silver nanoparticles (AgNPs) are the most well‐known nanomaterials for their ...outstanding antibacterial properties and potential applications in the biomedical field. The agglomeration of AgNPs due to their high surface energy has diminished the actual antibacterial applications of these plasmonic nanoparticles. To tackle this problem, the AgNPs are grafted onto graphene oxide (GO) sheets (Ag/GO) to minimize the agglomeration of AgNPs and enhance the extraordinary antibacterial characteristics of AgNPs thanks to several outstanding features of GO. Ag/GO composite also exhibits other properties such as good optical sensitivity to trace heavy metal ions, adsorption affinity, and catalytic activity for the removal of organic compounds. With all the possibilities, Ag/GO can be considered a multifunctional nanocomposite that can be applied in various fields such as biomedical treatment and environmental remedy.
Titanium dioxide/graphene aerogel (TiO2/GA) was synthesized via a one-pot hydrothermal method and characterized by various spectroscopic techniques, including X-ray diffraction, Fourier transform ...infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscopy, Raman spectroscopy, and UV-Vis spectroscopy. The influences of pH and TiO2/GA dose on the photocatalytic performance were investigated against positive dye methylene blue (MB) under UV light control. The characterization of TiO2/GA revealed that the synthesized TiO2 nanosize of 12–22.5 nm was uniformly distributed onto the graphene layers. The bandgap of the as-prepared nanocomposite was 2.63 eV, lower than that of pure TiO2 (3.2 eV). The kinetic studies exhibited that the adsorption–desorption equilibrium was achieved after 60 min following the pseudo-second-order. Meanwhile, 99.9% of MB was eliminated after 120 min at pH 9 with a 20 mg catalyst. The degradation data were well fitted to the pseudo-first-order kinetic model. Accordingly, applying TiO2/GA as an efficient photocatalyst indicates a potential pathway for the degradation of organic contaminants in wastewater treatment.
Effects of ionic strength on the adsorption of highly charged polycationic ((2-dimethylamino)ethyl methacrylate) methyl chloride quaternary salt (PTMA5M) individually as well as in a binary mixture ...with polyanionic acrylic acid (PAA) onto polystyrene sulfate latex (PSL) particles with negative charges were investigated by means of Brownian movement particle tracking and measurement of electrophoretic mobility. In addition, the adsorption mechanism was confirmed by Fourier transform infrared (FT-IR) and energy-dispersive X-ray (EDX) spectroscopic methods. The hydrodynamic thickness of the adsorbed polyelectrolyte layer (δH) and electrophoretic mobility (EPM) of particles as a function of concentration ratios of the two polyelectrolytes were measured to clarify the effect of negatively charged molecules on the structure of the positively charged adsorbed layer at various ionic strengths. Extremely thick δH was confirmed for the case of excess dosage of polycations. The δH decreased more significantly with the addition of PAA than increasing ionic strength. Interestingly, in the presence of PAA, the adsorbed layer thickness increased more at lower ionic strength than at higher ionic strength. In addition, the initial δH decreases remarkably after a time lapse of 1 h. Contrary to the decrease of the δH, almost all EPM either remained unchanged or increased over time depending on the concentration ratio of the two polyelectrolytes. Constant charge density, desorption of polyanions, and then reconformation of the adsorbed polycationic layer are proposed model components.
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