In this study, the biosorption mechanisms of methylene blue (MB) and Cr(
iii
) onto pomelo peel collected from our local fruits are investigated by combining experimental analysis with
ab initio
...simulations. Factors that affect the adsorption such as pH, adsorption time, adsorbent dosage and initial adsorbate concentration, are fully considered. Five isotherm models-Langmuir, Freundlich, Sips, Temkin, and Dubinin-Radushkevich-are employed to estimate the capacity of pomelo peel adsorption, whereas four kinetic models-pseudo-first-order, pseudo-second-order, Elovich and intra-diffusion models-are also used to investigate the mechanisms of the uptake of MB and Cr(
iii
) onto the pomelo fruit peel. The maximum biosorption capacities calculated from the Langmuir models for MB and Cr(
iii
) at 303 K are, 218.5 mg g
−1
and 11.3 mg g
−1
, respectively. In particular, by combining, for the first time, the experimental FT-IR spectra with those obtained from
ab initio
calculations, we are able to demonstrate that the primary adsorption mechanisms of the uptake of MB onto pomelo fruit peel are electrostatic attraction and hydrogen-bond formations, whereas the adsorption mechanisms for Cr(
iii
) are electrostatic attraction and n-d interactions.
In this study, the biosorption mechanisms of methylene blue (MB) and Cr(
iii
) onto pomelo peel collected from our local fruits are investigated by combining experimental analysis with
ab initio
simulations.
The morphology and elemental compositions at the surface of poly(styrene sulfonic acid) (PSSA) grafted poly(ethylene‐co‐tetrafluoroethylene) polymer electrolyte membranes (ETFE‐PEMs) in a grafting ...degree (GD) range of 0%–127% are investigated by using FE‐SEM and XPS analyses. The concentrations of elemental components at the surface are not a linear function of GDs, resulting from different grafting speeds at the surface and bulk. In addition, low accumulation of PSSA grafts on the surface of ETFE‐PEMs in the low GDs of 0%–19%, as well as their homogeneous distribution through the membranes at least at a GD of 19% are observed. At higher GDs of 19%–127%, the PSSA accumulation on the surface is relatively limited, indicating the presence of more PSSA grafts inside the bulk than on the surface. The surface signatures of ETFE‐PEMs over the entire GD range can be determined based on the grafting process. These interesting observations suggest the significant advantages of interfacial properties of ETFE‐PEMs for fuel cell applications.
The ETFE‐PEMs within the GDs of 0%–127% reflected the significant advantages in fuel cell applications because the low accumulation on the surface (0%–19%) and the presence of more grafts inside the bulk in the entire GD range.
The effect of high‐energy radiation in poly(ethylene‐co‐tetrafluoroethylene) (ETFE) films has been extensively investigated. However, the microstructure and molecular changes of the film under ...different irradiation conditions are less well‐understood. In this study, microstructure and molecular changes in ETFE films induced by gamma and electron irradiation with doses of 0–800 kGy are investigated using FTIR, UV–Vis, XRD, contact angle, SEM, and AFM measurements. The irradiated ETFE films show a linear dose–response relation in the dose range of 50–400 kGy. In particular, in the low doses of 50–150 kGy, the crystallization in the irradiated amorphous regions and the partial degradation of inherent crystalline layers are observed. In the irradiation doses higher than 150 kGy, the degradation of newly generated crystalline areas and the recrystallization of disordering regions take place. Moreover, the microstructure alterations occur within the bulk and at the surface of the irradiated films. The 2‐year shelf‐aged films exhibit the partial preservation of chemical structures with the low oxidation effects, plus the features of linear dose–response with doses of 50–400 kGy. The obtained results provide a further understanding of radiation‐induced effects in the ETFE films, which is the basic to extend their applications, especially in radiation resistance and dosimetry.
In this report, the adsorption of Cr(VI) onto MnO2/CS nanocomposite material from aqueous solution is investigated. All the factors, which affect the adsorption, such as pH, adsorption time, Cr(VI) ...initial concentration and adsorbent dosage, are also examined. The results obtained show that the Cr(VI) uptake is strongly affected by pH and ion strength. Analysis within the nonlinear isotherm models indicates that the Sips isotherm combining with the Langmuir and Freundlich models offer the best fit to the experimental data due to the obtained highest R2 and smallest RMSE and χ2 values. The calculated Langmuir monolayer adsorption capacity is 61.56 mg g−1 at pH of 2.0 and adsorption time of 120 min. Moreover, the mechanism studies by combining theoretical models with analytical spectroscopies reveal that the electrostatic attraction plays the important role to the uptake of Cr(VI) onto MnO2/CS nanocomposite. Therefore, the present nanocomposite material can be applied to remove total Cr from wastewater produced by the galvanized manufacturing factory with a relatively high efficiency.
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•MnO2/CS nanocomposite was used as an adsorbent to remove Cr(VI) from aqueous solution.•The Langmuir monolayer adsorption capacity is 61.56 mg g−1.•The primary mechanism of the uptake of Cr(VI) onto MnO2/CS was proposed.•MnO2/CS was applied to remove total Cr in effluent with the high removal of 94.21%.
TiO2 is a well-known semiconductor used widely in the photocatalyst field, but its photocatalytic applications are hampered by a fast electron–hole recombination rate and low visible light absorption ...due to a wide-band-gap energy. Herein, we present a simple, low cost, and green approach to obtain carbon dots from microalgae, namely microalgae-based carbon dots (MCDs), using an unprecedented microwave-assisted treatment. The MCDs were successfully decorated on the surface of TiO2 nanoparticles. The as-prepared composite exhibited a superior photodegradation of methylene blue, compared with pristine TiO2 (83% and 27%, respectively) under visible light irradiation. The MCDs in TiO2-MCDs serve as electron reservoirs to trap photoinduced electrons and as photosensitizers for the improvement of visible light absorption; both factors play an important role in the improvement of the TiO2 photocatalytic activity. Furthermore, the as-prepared composite photocatalyst also exhibits high photostability and recyclability during the photodegradation of methylene blue. Therefore, this work provides an original approach to the development of environmentally friendly and highly effective photocatalysts for the treatment of various organic pollutants, which can go a long way toward ensuring a safe and sustainable environment.
•Preparation of microalgae-based carbon dots (MCDs) by microwave-assisted treatment.•Decoration and stabilization of MCDs on the TiO2 surface to obtain the TiO2-MCDs catalyst.•Enhanced photocatalytic activity of TiO2-MCDs under visible light irradiation.•High performance of TiO2-MCDs in photodegradation of methylene blue.
Manganese dioxide nanoparticles are loaded onto the surface of chitosan (CS) in order to enhance their adsorption properties. Various theoretical models and spectroscopic analytical methods are used ...to investigate the equilibrium isotherm, kinetics, and mechanisms of the removal of lead(II) from the aqueous solution. The kinetic studies based on a pseudo-second-order model show that the uptake of lead(II) occurs via three stages depending on the reaction time. The experimental data are fitted using four nonlinear isotherm models, namely the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models. The results obtained within the Langmuir model gave the highest R2, the smallest root-mean-squared error (RMSE), and the best nonlinear chi-square test (χ2) values, indicating that this model is the most appropriate approach for describing the adsorption of lead(II) onto the MnO2/CS nanomaterials. It is also found that the maximum monolayer adsorption capacity is 126.1 mg/g, which is higher than most of the values obtained from other materials. In addition, the results of the heat of the sorption process and the mean free energy calculated from the Fourier transform infrared spectroscopy (FTIR) suggested that the adsorption indeed follows a physical process. By using the Positron Lifetime Spectroscopy, which is used for the first time to investigate the “ions-holes” mechanism of the removal of lead(II) by CS loaded MnO2 nanoparticles, we found that the “ions-holes” mechanism in fact occurs at the micropores of MnO2 crystals in the MnO2/CS nanomaterials. This result is significant as it will be a reference for the use of the spectroscopic analytical methods for investigating the adsorption mechanism.
•MnO2 nanoparticles are loaded onto the surface of Chitosan in order to enhance its adsorption capacity.•The removal of lead (II) from the aqueous solution using MnO2/CS is found to be better than the use of other materials.•The Positron Lifetime Spectroscopy is used for the first time to investigate the “ions-holes” mechanism.
Red mud modified by chitosan (RM/CS) was utilized as an adsorbent to effectively remove Pb(II) from aqueous solution. The surface area of RM/CS was found to significantly increase by more than 50% ...compared to that of original red mud. Different factors that affected the Pb(II) removal on this material, such as initial Pb(II) concentration, pH, and contact time, were investigated. The pseudo-first-order, pseudo-second-order, and intra-diffusion models were used to fit the experimental data to investigate the Pb(II)'s removal kinetics. The Pb(II) removal followed the intra-diffusion model. Additionally, the non-zero C value obtained from this model indicates that the removal was controlled by many different mechanisms. We also found that the interaction of Pb(II) and carbonate group on the material's surface played a primary role once the adsorption equilibrium was reached. Finally, the maximum adsorptive capacity was found to be about 209 mg/g. This obtained value is higher than those obtained for some other materials. Therefore, the present RM/CS should be a potential material for removing Pb(II) from aqueous solution.
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•Red mud modified by chitosan (RM/CS), a novel adsorbent, was used to remove Pb(II).•Characteristics of RM/CS were investigated by XRD, SEM, BET, FT-IR, and TGA-DSC.•The adsorption capacity is 208.48 mg g−1 higher than some other materials.•Several different mechanisms of the uptake of Pb(II) onto RM/CS were proposed.
The present work investigates the primary adsorption mechanisms of lead (II) and cadmium (II) cations onto pomelo fruit peel (PFP) from aqueous solution. pH, adsorption time, ion strength, and ...initial metal cation concentrations, which are factors affecting the uptake of these cations, are investigated. Results show that pH and ion strengths strongly affect the removal of these cations from aqueous solution. Different isotherm adsorption models, such as Langmuir, Freundlich, and Sips, are utilized to fit the experimental data in order to determine the adsorption in nature. The Langmuir monolayer adsorption capacities are found to be 47.18 mg/g for lead (II) and 13.35 mg/g for cadmium (II). Kinetic and thermodynamic studies based on a combination of FT-IR and TG-DSC spectroscopies demonstrate that electrostatic attraction plays a primary adsorption mechanism of lead (II) and cadmium (II) cations onto pomelo fruit peel.
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