Surface-bound humic acid increased rhodamine B adsorption on nanosized hydroxyapatite

A modified approach towards facile and green conversion of cement kiln dust wastes to efficient hydroxyapatite-carbon nanocomposite water adsorbents

A new modified approach was used to synthesize hydroxyapatite-carbon nanocomposite (HAP-C) by utilizing cement kiln dust (CKD), which is an industrial waste product, as a source of calcium. Calcium from CKD was first chelated using citric acid, and the chelate was transformed into calcium carbonate and carbon by calcination at 450 °C for 1 h, then reacted with ortho-phosphoric acid using a precipitation method, thus serving as a precursor for the formation of HAP-C. Then, HAP-C was calcined at various temperatures for 2 h after it reached the desired temperature at a heating rate of 10 °C/min. By characterizing the adsorbent, the composite was mesoporous, with a negatively charged surface at the operating pH, and an average diameter and length of 10 ± 3.6 nm and 8 ± 2.9 nm, respectively. Quantile regression analysis showed that the removal varies directly with time and dose, and inversely with initial concentration. Removal efficiency reached about 95% and about 80% at 10 ppm initial concentration, 10 min contact time, and a dose of 3.8 g/L, at pH 7 for RB and pH 4 for LV, respectively. Adsorption isotherms followed Sips model as inferred from linear and non-linear regression analysis. Adopting this novel approach in synthesizing HAP-C using a single precursor and a waste raw material reduces the environmental impact and incurred costs associated with the conventional synthesis route, while following the principles of circular economy in converting wastes to value-added products.

Interfacial-assembly engineering of asymmetric magnetic-mesoporous organosilica nanocomposites with tunable architectures

The asymmetric morphology of nanomaterials plays a crucial role in regulating their physical and chemical properties, which can be tuned by two key factors: (i) interfacial interaction between seed particles and growth materials (anisotropic island nucleation) and (ii) reaction kinetics of the growth material (growth approach). However, controllable preparation of asymmetric nanoarchitectures is a daunting challenge because it is difficult to tune the interfacial energy profile of a nanoparticle. Here, we report an interfacial-assembly strategy that makes use of different surfactant/organosilica-oligomer micelles to actively regulate interfacial energy profiles, thus enabling controllable preparation of well-defined asymmetric nanoarchitectures (i.e., organosilica nano-tails) on magnetic Fe₃O₄ nanoparticles. For our magnetic nanocomposite system, the assembly structure of surfactant/organosilica-oligomer micelles and the interfacial electrostatic interaction are found to play critical roles in controlling the nucleation and architectures of asymmetric magnetic-mesoporous organosilica nanocomposite particles (AMMO-NCPs). Surfactant/organosilica-oligomer micelles with a one-dimensional wormlike linear structure could strengthen the interfacial assembly behavior between seed particles and growth materials, and thus achieved the longest tail length (25 μm) exceeding the previously reported highest recorded value (2.5 μm) of one order of magnitude. In addition, clickable AMMO-NCPs can employ a thiol-ene click reaction to modify their surface with a broad range of functional groups, such as amines, carboxyls, and even long alkyl chains, which allows for expanding functionalities. We demonstrate that C18 alkyl-grafted AMMO-NCPs can self-assemble into self-standing membranes with robust superhydrophobicity. In addition, carboxyl-modified AMMO-NCPs exhibit excellent adsorption capacity for cationic compounds. This study paves the way for designing and synthesizing asymmetric nanomaterials, which possess immense potential for future engineering applications in nanomaterial assembly, nanoreactors, biosensing, drug delivery, and beyond.

Synthesis of Hydroxyapatite/Iron Oxide Composite and Comparison of Selected Structural, Surface, and Electrochemical Properties

The paper presents the synthesis of a hydroxyapatite/iron oxide composite utilizing the wet chemical method, as well as the comparison of several selected material characteristics. As follows from the literature reports, hydroxyapatite is a common mineral possessing numerous significant properties. Nowadays, there is an increase in the amount of research on possible modifications of this compound. The promising way to improve hydroxyapatite features is its combination with iron oxide. Particularly, there can be two forms that are distinguished, namely Fe₃O₄ and γ-Fe₂O₃. These oxides exhibit valuable properties, particularly magnetism. A combination of the mentioned materials leads to multifunctional composite formation with many potential applications, as follows from several studies. However, this area of science is not fully developed. There are still many aspects to be examined. The synthesized composite and its components were analyzed by employing the following methods. The X-ray diffraction analysis revealed formation of hydroxyapatite and Fe₂O₃ crystalline phases. Moreover, porosimetry proved a larger specific area for the composite sample in comparison with other materials. The results obtained using the SEM method confirmed an external layer of hydroxyapatite and spherical shapes of internal Fe₂O₃ particles. Furthermore, the X-ray photoelectron spectroscopy data presented characteristic peaks of Fe, Ca, P, and O atoms in all samples. The Fourier Transform Infrared spectra displayed all the specific vibrations typical of the analyzed materials. What is more, the Vibrating Sample Magnetometer method confirmed the paramagnetic nature of the samples. It could be concluded that the synthesized composite has intermediate properties between the components used in the formation process. The results suggest that these composites are superparamagnetic. This type of material architecture would be well suited for biomedical applications.

Inorganic Porous Bulk Discs as a Matrix for Thin-Layer Chromatography and Translucent Hard Composite Materials

Magnesium-stabilized amorphous calcium carbonate (Mg-ACC), amorphous magnesium calcium silicate hydrate (MCSH), and hydroxyapatite (HAp) are prepared by a precipitation method. By cold-pressing these particles, it is possible to produce porous bulk discs with a narrow pore size distribution. These porous inorganic discs (Mg-ACC, MCSH, and HAp) are investigated as stationary phases to study the chromatographic behavior and adsorption ability of rhodamine B, methylene blue, and ribonuclease. The adsorption affinities of different biomolecules can be easily observed and evaluated through this method. Furthermore, by infiltrating fabricated opaque porous discs with benzyl ether, which has a similar refractive index as the used inorganic particles (Mg-ACC, MCSH, and HAp), their optical properties significantly change and the discs become translucent. Moreover, by infiltrating the MCSH discs with a light-curing polymer, translucent composites with good surface hardness are fabricated. By doping particles with ions such as Ni²⁺, Co²⁺, Fe³⁺, and Eu³⁺, the color and UV-visible spectrum of the bulk discs can be adjusted. Typically, by using iron-doped MCSH particles as the inorganic matrix, nanocomposites, which show a steep UV-absorption edge at 400 nm, are fabricated. Our work provides a simple and economical method to evaluate the affinity of biomolecules to inorganic materials and a novel way to fabricate translucent hard composite materials. The fabricated nanocomposite discs show a great UV shielding effect and superior surface hardness compared to polymethyl methacrylate and commercial sunglasses, suggesting their potential as new sunglass materials.

Adsorption and photo-Fenton catalytic degradation of organic dyes over crystalline LaFeO3-doped porous silica

LaFeO₃ (LFO)-doped mesoporous silica (HPS) (HPS-xLFO with theoretical LFO/silica molar ratio x = 0.075, 0.15, 0.3) was successfully prepared via impregnation of metal ions into the porous silica HPS-0LFO support and subsequent calcination. The characterization studies suggest that increasing the doping of LFO, which exhibited a particle size of ∼10–15 nm, in the silica support led to a reduction in surface area and bandgap of the resulting catalyst. The use of HPS-0.15LFO yielded a superior removal rate (98.9%) of Rhodamine B (RhB), thanks to the effective dark adsorption and visible light-induced photo-Fenton degradation, both of which were greater than those of pure LFO crystals. This enhancement could be explained by the unique properties of the mesoporous silica support. In particular, the wide-opening mesopores created a large surface area to dope LFO as active sites and minimize diffusion of RhB into pores during the photo-Fenton reaction. The photo-Fenton catalytic degradation of RhB could reach 98.6% within 90 min exposure to visible light irradiation under optimized conditions: RhB concentration = 10 mg L⁻¹, catalyst dosage = 1 g L⁻¹, pH = 6 and H₂O₂ = 15 mM. Moreover, the recycle and reuse test proved the good stability and repetitive use of HPS-0.15LFO for high performance RhB removal.

LFO-doped mesoporous silica yielded high removal rate of dye, due to the dark adsorption and visible light-induced photo-Fenton degradation.