Materials coming from renewable resources have drawn recently an increased attention in various applications as an eco-friendly alternative in the synthesis of novel functional materials. ...Polysaccharides, with their prominent representative – chitosan (CS), are well-known for their sorption properties, being able to remove metal ions from dilute solutions either by electrostatic interactions or chelation. In this context, we proposed here a comparative study on Cu2+, Zn2+, Ni2+, Fe3+, and Cr3+ metal ions removal from industrial wastewaters by CS-based composite cryogels using batch technique. The composite cryogels consisting of CS embedding a natural zeolite, namely clinoptilolite, were synthesized by cryogelation, and their sorption performance were compared to those of CS cryogels and of acid-activated zeolite. A deeper analysis of thermodynamics and kinetics sorption data was performed to get insights into the sorption mechanism of all metal ions onto sorbents. Based on the optimized sorption conditions, the removal of the above-mentioned ions from aqueous solutions by the composite sorbent using dynamic technique was also evaluated.
A viable option for dehumidification of air stream moisture in closed environments is the use of super adsorbent materials with high capacity for water retention. Selective transport of water ...molecules across porous materials makes it possible to reduce the humidity of an air stream. The use of such materials has advantage over many commercially available desiccants because they allow an independent control of humidity, being nontoxic materials that adsorb water molecules. It is critical to design new super adsorbent materials for air dehumidification. For instance, a technical solution proposed in this work refers to the development of a specific super adsorbent matrix based on polymer-molecular sieves composites. The polymers are deposited on the rigid structure of different molecular sieves providing a composite structured network with synergistic properties. Theoretical screening indicates that these composites can be used for water retention as efficient desiccants alternative to other available adsorbents and were proved by water adsorption experiments. These polymer-inorganic composites are critical for controlling air dehumidification process.
•The modification of the mesoporous materials surface is proposed.•The aminofunctionalization seems to be successful.•Polymer coating was associated with moisture sorption.•High water adsorption capacity has been reached.
The aim of this study was to synthesize a CoFe2O4@HaP nanocomposite (HaP-Hydroxyapatite) through the coprecipitation method in aqueous solution, with the purpose of using it in adsorption processes ...for the removal of Congo Red dye from aqueous solutions. Fourier Transform Infrared Spectroscopy (FT-IR) was used to characterize the synthesized material, identifying absorption bands specific to the functional groups of cobalt ferrite (Fe-O and Co-O at 603 and 472 cm−1) and hydroxyapatite PO43− at 1035, 962, 603 and 565 cm−1. Powder X-ray diffraction confirmed the cubic spinel structure of cobalt ferrite (S.G Fd-3m) and the hexagonal structure of hydroxyapatite (S.G P63/m). The nanocomposite’s crystallite size was calculated to be 57.88 nm. Nitrogen adsorption/desorption isotherms and BET specific surface area measurements were used to monitor textural parameters, revealing an increase in specific BET surface area when cobalt ferrite nanoparticles (15 m2/g) were introduced into the hydroxyapatite heterostructure (34 m2/g). Magnetic properties were investigated by interpreting hysteresis curves in the ±10 kOe range, with the nanocomposite showing a saturation magnetization of 34.83 emu/g and a coercivity value of 0.03 kOe. The adsorption capacity of the CoFe2O4@HaP nanocomposite is up to 15.25 mg/g and the pseudo-second-order kinetic model (Type 1) fits the data with a high correlation coefficient of 0.9984, indicating that the chemical adsorption determines the rate-determining step of the process. The obtained nanocomposite is confirmed by the analyses, and the absorption measurements demonstrate that it can be utilized to degrade Congo Red dye.
Indium is an extremely important element for industry that is distributed in the Earth's crust at very low concentrations. The recovery of indium by silica SBA-15 and titanosilicate ETS-10 was ...investigated at different pH levels, temperatures, times of contact and indium concentrations. A maximum removal of indium by ETS-10 was achieved at pH 3.0, while by SBA-15 it was within the pH range of 5.0-6.0. By studying kinetics, the applicability of the Elovich model for the description of indium adsorption on silica SBA-15 was shown, while its sorption on titanosilicate ETS-10 fitted well with the pseudo-first-order model. Langmuir and Freundlich adsorption isotherms were used to explain the equanimity of the sorption process. The Langmuir model showed its applicability for the explanation of the equilibrium data obtained for both sorbents, the maximum sorption capacity obtained using the model constituted 366 mg/g for titanosilicate ETS-10 at pH 3.0, temperature 22 °C and contact time 60 min, and 2036 mg/g for silica SBA-15 at pH 6.0, temperature 22 °C and contact time 60 min. Indium recovery was not dependent on the temperature and the sorption process was spontaneous in nature. The interactions between the indium sulfate structure and surfaces of adsorbents were investigated theoretically using the ORCA quantum chemistry program package. The spent SBA-15 and ETS-10 could be easily regenerated by using 0.01 M HCl and reused with up to 6 cycles of adsorption/desorption with a decrease in the removal efficiency between 4% and 10% for SBA-15 and 5% and 10% for ETS-10, respectively.
In this paper, we present the synthesis of new polymeric adsorbents derived from macroporous chloromethylated styrene-divinylbenzene (DVB) copolymers with different cross-linking degrees ...functionalized with the following aminobenzoic groups: styrene-6.7% DVB (PAB1), styrene-10% DVB (PAB2), and styrene-15% DVB (PAB3). The new polymeric products, PAB1, PAB2, and PAB3, were characterized by FTIR spectroscopy, thermogravimetric analysis, and EDX, SEM, and BET analysis, respectively. The evolution of the functionalization reaction was followed by FTIR spectroscopy, which revealed a decrease in the intensity of the γCH
Cl band at 1260 cm
, and, simultaneously, the appearance of C=O carboxylic bands from 1685-1695 cm
and at 1748 cm
. The thermal stability increased with the increase in the cross-linking degree. The data obtained from the EDX analysis of the novel cross-linked copolymers confirmed the functionalization with aminobenzoic groups through the presence and content of nitrogen, as follows: PAB1: N% = 0.47; PAB2: N% = 0.85; and PAB3: N% = 1.30. The adsorption performances of the novel polymeric adsorbents, PAB1, PAB2, and PAB3, were tested in the adsorption of three antibiotics, tetracycline, sulfamethoxazole, and amoxicillin, from aqueous solutions, by using extensive kinetic, equilibrium, and thermodynamic studies. The best adsorption capacity was demonstrated by the tetracycline. Amoxicillin adsorption was also attempted, but it did not show positive results.
In this work we have presented the results obtained in the adsorption behavior of hydroxyapatite with different treatment towards aluminium ions from synthetic wastewaters. Experiments were performed ...in batch technique at different pH values, temperatures, sorbent dosage, contact time and initial aluminium concentration. The thermodynamic studies on the adsorption process of aluminium onto hydroxyapatite indicated that the process is spontaneous and endothermic. The Langmuir, Freundlich, Flory-Huggins, Dubinin-Radushkevich and Temkin equilibrium models were applied to the description of experimental data. The adsorption of aluminium follows the Langmuir adsorption isotherm. The kinetics of adsorption was evaluated using the pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models. The rate of aluminium adsorption was successfully described by a pseudo-second-order kinetic model. The obtained results indicated that hydroxyapatite treated with Pluronic P123 surfactant has a higher sorption capacity toward aluminium ions (117.65 mg g-1) than hydroxyapatite treated with Pluronic F127 surfactant (109.89 mg g-1) while untreated hydroxyapatite exhibited the lowest one (104.17 mg g-1).
Recently, the ultrasound-assisted sol-gel synthesis procedure of mesoporous titania (TiO2) photocatalysts caught the researcher’s attention, due to the physicochemical properties enhancement of the ...resulting titania nanomaterials. Thus, by varying different synthesis parameters particular characteristics could be obtained. In the present study, the ultrasound pulse on/off ratio has been considered and the effect of the envisaged parameter on the textural, morphological, and optical features of titania nanomaterial has been investigated. Therefore, X-ray Diffraction (XRD), Fourier-Transform Infrared spectroscopy (FTIR), N2-sorption measurements, SEM imaging, and UV-Vis Diffuse Reflectance spectroscopy (UVDR) have been used. And further, the photocatalytic activity of the prepared TiO2 materials was evaluated by the features developed about the applied ultrasound pulse on/off ratio as 1/1, 2/1, 3/1, 4/1, 1/3 and 2/2. It was found that the ultrasound pulse on/off ratio considered in the synthesis procedure of titania leads to TiO2 materials with different textural (SBET = 98–156 m2/g), morphological, and optical (Eg = 3.1–3.2 eV) characteristics. For this reason, TiO2 nanomaterials prepared were found to exhibit suitable features for photocatalytic applications. Thus, the TiO2 4.1 sample prepared at 4/1 ultrasound pulse on/off ratio revealed the highest photodegradation efficiency of Congo Red dye (98.28%) as the results of photocatalytic tests show. More than that, a possible reaction mechanism of the CR photodegradation process through the contribution of reactive oxygen species (·HO, ·O2−), holes (h+), and electrons (e−) of developed titania photocatalyst was proposed.
Up to now, the use of TiO2 has been considered a promising advanced technology for organic pollutants removal from air or water, since it has high biological and chemical stability, high ...photoactivity, low toxicity, and low-cost production. However, there are issues to be addressed in enhancing TiO2 performance, and one of the current key issues is redesigning UV-active photocatalysts and making them active in the visible region of the electromagnetic spectrum. This way, solar light absorption will be insured, and thus, a more efficient photocatalyst could be obtained. For this reason, conjugated polymers and their derivatives are considered to act as photosensitizers, being able to shift the TiO2 activity from the UV to the visible region. Therefore, this study focuses on the synthesis of TiO2/conjugated polymer systems, which was accomplished by the deposition of poly-3,4-ethylene-dioxy-thiophene (PEDOT -C6H4O2S-n), a low-band semiconductor with an excellent stability due to its extending π-conjugated electron system, on titania nanoarchitecture. First of all, a TiO2 nanoarchitecture was synthesized by an ultrasound-assisted sol–gel method. Then, TiO2/PEDOT systems were obtained and characterized by using different techniques such as X-ray diffraction, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, UV–Vis diffuse reflectance, and N2 sorption measurements. The synthesized composites confirmed their mesoporosity and lower band gap values compared to bare titania, which clearly shows the ability to work as photocatalysts under visible-light activity. Further, we demonstrated that an organic pollutant, Congo Red dye, used as a model molecule could be photodegraded with the synthesized TiO2/PEDOT systems, with efficiencies of up to 95% in the case of TconvPEDOT under UV light and up to 99% for TconvPEDOT under visible-light irradiation, accomplishing in this way a successful synthesis of visible-light-activated titania photocatalyst.
Due to their structural, morphological, and behavioral characteristics (e.g., large volume and adjustable pore size, wide functionalization possibilities, excellent biocompatibility, stability, and ...controlled biodegradation, the ability to protect cargoes against premature release and unwanted degradation), mesoporous silica particles (MSPs) are emerging as a promising diagnostic and delivery platform with a key role in the development of next-generation theranostics, nanovaccines, and formulations. In this study, MSPs with customized characteristics in-lab prepared were fully characterized and used as carriers for doxorubicin (DOX). The drug loading capacity and the release profile were evaluated in media with different pH values, mimicking the body conditions. The release data were fitted to Higuchi, Korsmeyer–Peppas, and Peppas–Sahlin kinetic models to evaluate the release constant and the mechanism. The in vitro behavior of functionalized silica particles showed an enhanced cytotoxicity on human breast cancer (MCF-7) cells. Bio- and mucoadhesion on different substrates (synthetic cellulose membrane and porcine tissue mucosa)) and antimicrobial activity were successfully assessed, proving the ability of the OH- or the organically modified MSPs to act as antimicrobial and mucoadhesive platforms for drug delivery systems with synergistic effects.
The paper reports on the performances of cross-linked amidoxime hosted into mesoporous silica (AMOX) in the removal of As(III) and As(V). The optimum pH for sorption of As(III) and As(V) was pH 8 ...and pH 5, respectively. The PFO kinetic model and the Sips isotherm fitted the best the experimental data. The thermodynamic parameters were evaluated using the equilibrium constant values given by the Sips isotherm at different temperatures and found that the adsorption process of As(III) and As(V) was spontaneous and endothermic on all AMOX sorbents. The spent AMOX sorbents could be easily regenerated with 0.2 mol/L HCl solution and reused up to five sorption/desorption cycles with an average decrease of the adsorption capacity of 18%. The adverse effect of the co-existing inorganic anions on the adsorption of As(III) and As(V) onto the sorbent with the highest sorption capacity (AMOX3) was arranged in the following order: H2PO4 – > HCO3 – > NO3 – > SO4 2–.
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