Ewa Mijowska

Equilibrium and kinetic studies on acid dye Acid Red 88 adsorption by magnetic ZnFe2O4 spinel ferrite nanoparticles.

A magnetic ZnFe2O4 (MNZnFe) was synthesized by microwave assisted hydrothermal method and was used as an adsorbent for the removal of acid dye Acid Red 88 (AR88) from aqueous solution. The effects of various parameters such as initial AR88 concentration (10-56 mg L(-1)), pH solution (3.2-10.7), and temperature (20-60°C) were investigated. Prepared magnetic ZnFe2O4 was characterized by XRD, SEM, HRTEM, ICP-AES, BET, FTIR, and measurements of the magnetic susceptibility. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. Equilibrium data fitted well with the Langmuir model. Pseudo-first-order and pseudo-second-order kinetic models and intraparticle diffusion model were used to examine the adsorption kinetic data. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. Thermodynamics parameters, ΔG°, ΔH° and ΔS°, indicate that the adsorption of AR88 onto MNZnFe was spontaneous and exothermic in nature.

Adsorption of anionic azo-dyes from aqueous solutions onto graphene oxide: Equilibrium, kinetic and thermodynamic studies

In the present study, graphene oxide (GO) was used for the adsorption of anionic azo-dyes such as Acid Orange 8 (AO8) and Direct Red 23 (DR23) from aqueous solutions. GO was characterized by Fourier Transform-Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), Thermogravimetric Analysis (TGA), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), High-Resolution Transmission Electron Microscopy (HRTEM) and zeta potential measurements. The influence of dye initial concentration, temperature and pH on AO8 and DR23 adsorption onto GO was investigated. Equilibrium data were analyzed by model equations such as Langmuir Freundlich, Temkin, Dubinin-Radushkevich and Redlich-Peterson isotherms and were best represented by Langmuir and Redlich-Peterson isotherm model. Kinetic adsorption data were analyzed using the pseudo-first-order kinetic model, the pseudo-second-order kinetic model and the intraparticle diffusion model. The adsorption kinetics well fitted using a pseudo-second-order kinetic model. Thermodynamics parameters, ΔG°, ΔH° and ΔS°, were calculated, indicating that the adsorption of AO8 and DR23 onto GO was spontaneous process. The adsorption process of AO8 onto GO was exothermic, while the adsorption of DR23 onto GO was endothermic in nature.

Converting real-world mixed waste plastics into porous carbon nanosheets with excellent performance in the adsorption of an organic dye from wastewater

Waste plastic utilization and wastewater treatment are the two most serious challenges on the path to urbanization and industrialization, due to the limited fossil fuel resources, ever-increasing energy demands, and severe environmental pollution. The conversion of waste plastics into high value-added carbon nanomaterials has become a promising way to utilize waste plastics; however, most current studies are limited to single component waste plastic; besides, little attention has been paid to porous carbon nanosheets (PCNSs). Herein, a facile approach was established to prepare PCNSs by the carbonization of real-world mixed waste plastics on organically-modified montmorillonite and subsequent KOH activation. The morphology, microstructure, textural property, phase structure, surface element composition, and thermal stability of the PCNSs were investigated. The PCNSs showed high specific surface area (2315 m2 g−1) and large pore volume (3.319 cm3 g−1) with high purity (>99.6%). More importantly, the PCNSs exhibited fast adsorption (about 95% of methylene blue (MB) was removed during the first 10 min of adsorption), an unprecedented adsorption capacity of 769.2 mg g−1 (higher than most of reported adsorbents), and excellent recyclability (after ten cycles, an adsorption capacity of 692.0 mg g−1 remained and 90 wt% of the PCNS was reclaimed) for MB from wastewater. This was attributed to the high specific surface area and large pore volume of the PCNS, and due to multiple adsorption mechanisms, including pore filling, hydrogen bonding, and π–π and electrostatic interactions between MB and the PCNS. It is believed that this work not only provides a novel potential way to utilize waste plastics, but also presents a facile sustainable approach to synthesize PCNSs, which will be an ideal candidate for various applications.

Striking influence of Fe2O3 on the “catalytic carbonization” of chlorinated poly(vinyl chloride) into carbon microspheres with high performance in the photo-degradation of Congo red

A one-pot approach was demonstrated to effectively synthesize carbon microspheres through “catalytic carbonization” of commercial chlorinated poly(vinyl chloride) (CPVC) microspheres by Fe2O3 at 700 °C. Without Fe2O3, a “sponge-like” carbon lump was obtained. However, after adding Fe2O3 (even 0.5 g per 100 g CPVC) into CPVC, carbon microspheres with octahedral Fe3O4 microcrystals uniformly embedded on the surface (Fe/CMS) were synthesized. The influence of Fe2O3 on the carbonization of CPVC microspheres was investigated. It was found that Fe2O3 significantly accelerated the dehydrochlorination of CPVC into polyene before the melting of the CPVC microsphere surface. As a result, the microspheres of raw CPVC showed a “shape-duplicate” carbonization behaviour. The resultant Fe/CMS showed high photo-degradation efficiency of Congo red under UV irradiation via a heterogeneous photo-Fenton process with high recyclablity, reusability and long-term stability. This indicated that the resultant Fe/CMS has a potential application in wastewater treatment. Therefore, the initial catalytic substance could be effectively used as a catalyst twice in the carbonization of CPVC microspheres and in the subsequent application of Fe/CMS. More importantly, the strategy of “catalytic carbonization” offers a new potential way to largely convert charring polymers into functional carbon and carbon-based materials with various morphologies.

A facile approach to prepare porous cup-stacked carbon nanotube with high performance in adsorption of methylene blue

Novel porous cup-stacked carbon nanotube (P-CSCNT) with special stacked morphology consisting of many truncated conical graphene layers was synthesized by KOH activating CSCNT from polypropylene. The morphology, microstructure, textural property, phase structure, surface element composition and thermal stability of P-CSCNT were investigated by field-emission scanning electron microscope, transmission electron microscope (TEM), high-resolution TEM, N2 sorption, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and thermal gravimetric analysis. A part of oblique graphitic layers were etched by KOH, and many holes with a diameter of several to a doze of nanometers connecting inner tube with outside were formed, which endowed P-CSCNT with high specific surface area (558.7 m(2)/g), large pore volume (1.993 cm(3)/g) and abundant surface functional groups. Subsequently, P-CSCNT was used for adsorption of methylene blue (MB) from wastewater. Langmuir model closely fitted the adsorption results, and the maximum adsorption capacity of P-CSCNT was as high as 319.1mg/g. This was ascribed to multiple adsorption mechanisms including pore filling, hydrogen bonding, π-π and electrostatic interactions. Pseudo second-order kinetic model was more valid to describe the adsorption behavior. Besides, P-CSCNT showed good recyclablity and reusability. These results demonstrated that P-CSCNT had potential application in wastewater treatment.

One-pot synthesis of core/shell Co@C spheres by catalytic carbonization of mixed plastics and their application in the photo-degradation of Congo red

Much attention has been paid to the synthesis of core/shell metal@carbon composites, but many of the proposed methods are limited by sophisticated procedure and expensive precursors. Herein, a facile one-pot approach is established to prepare magnetic core/shell Co@C spheres through catalytic carbonization of mixed plastics (consisting of polypropylene, polyethylene and polystyrene) by Co3O4 at 700 °C. The yield, composition, morphology, phase structure, textural property, surface element composition, thermal stability and magnetic property of core/shell Co@C spheres are investigated. The core/shell Co@C spheres have a distinct ordered and curved graphitic structure, and their main diameters are in the range of 110–130 nm. Besides, they show a ferromagnetic behavior with high saturation magnetization (85.6–101.6 emu g−1). Furthermore, it was observed that Co3O4 was uniformly distributed in mixed plastics and formed a network structure, which provided a precondition for the carbonization of mixed plastics into core/shell Co@C spheres with uniform sizes. Finally, the core/shell Co@C spheres were found to show high performance in photo-degradation of Congo red (CR) with good recyclablity, reusability and long-term stability. It was demonstrated that the outer carbon shell promoted the degradation of CR and served as a protective layer for cobalt core to improve acid resistance, while the inner cobalt core accelerated the decomposition of H2O2 into radicals, which catalyzed the degradation of CR. More importantly, this simple approach offers a potential way to prepare magnetic core/shell metal@carbon composites from cheap waste plastics.

Template method synthesis of mesoporous carbon spheres and its applications as supercapacitors

Mesoporous carbon spheres (MCS) have been fabricated from structured mesoporous silica sphere using chemical vapor deposition (CVD) with ethylene as a carbon feedstock. The mesoporous carbon spheres have a high specific surface area of 666.8 m2/g and good electrochemical properties. The mechanism of formation mesoporous carbon spheres (carbon spheres) is investigated. The important thing is a surfactant hexadecyl trimethyl ammonium bromide (CTAB), which accelerates the process of carbon deposition. An additional advantage of this surfactant is an increase the yield of product. These mesoporous carbon spheres, which have good electrochemical properties is suitable for supercapacitors.

Beaded structured CNTs-Fe3O4@C with low Fe3O4 content as anode materials with extra enhanced performances in lithium ion batteries

The present paper reports a facile method to synthesize CNT-Fe2O3 and CNTs-Fe3O4@C beaded structures by deposition of Fe2O3 and carbon layers on CNTs, which integrate both electronic conductivity and buffering matrix design strategies. The CNT-Fe2O3 and CNTs-Fe3O4@C were tested as anode materials for lithium-ion batteries, CNT-Fe2O3 showed excellent cycling performance, the reversible capacity retention after 80 cycles is stable at 410 mA h g−1. However, CNTs-Fe3O4@C exhibited improved reversible capacity and better cycling performance when compared to CNT and CNTs-Fe2O3. The highly improved reversible capacities are attributed to the combination of (a) the network structured CNTs, which improve the matrix electrical conductivity, (b) the mesopores created by the carbon coating on Fe3O4 nanoparticles and CNTs, which increases lithium-ion mobility and storage, and (c) the Fe3O4 nanoparticles attached to the CNTs facilitate the transport of electrons and shorten the distance for Li+ diffusion. This study provides a cost-effective, highly efficient method to fabricate nanomaterials which combines carbon nanotubes with iron oxide nanoparticles for the development of lithium ion batteries with high-performance.

Striking influence of NiO catalyst diameter on the carbonization of polypropylene into carbon nanomaterials and their high performance in the adsorption of oils

Recently, there has been intense interest in the conversion of plastics into high value-added carbon nanomaterials (CNMs), however, the effect of catalyst diameter on the formation of CNMs is still ambiguous. Herein, uniform NiO catalysts with different diameter (18–227 nm) were firstly prepared by a sol–gel combustion synthesis method and calcination at different temperatures. Subsequently, the combined organically-modified montmorillonite (OMMT)/NiO catalyst was used to catalyze carbonization of polypropylene (PP, selected as an example of plastics) into CNMs at 700 °C. The effect of NiO catalyst diameter on the yield, morphology, microstructure, phase structure, thermal stability and texture properties of CNMs including sponge-like cup-stacked carbon nanotubes (CS-CNTs) and carbon fibers were investigated by scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, X-ray diffraction, Raman spectroscopy, thermal gravimetric analysis and N2 sorption. Besides, the effects of NiO catalyst diameter on the coalescence and reconstruction of NiO particles were explored. It was demonstrated that NiO catalysts with small diameter were more susceptible to coalescence and reconstruction into rhombic shape, which facilitated the growth of long, straight CS-CNTs. Finally, the obtained sponge-like CS-CNTs were found to show high performance in the adsorption of diesel, vegetable oil, kerosene and mineral oil with good recycling performance. It is believed that this work will contribute to the conversion of waste plastics into high value-added CNMs.

Characterization of Mechanical and Bactericidal Properties of Cement Mortars Containing Waste Glass Aggregate and Nanomaterials

The recycling of waste glass is a major problem for municipalities worldwide. The problem concerns especially colored waste glass which, due to its low recycling rate as result of high level of impurity, has mostly been dumped into landfills. In recent years, a new use was found for it: instead of creating waste, it can be recycled as an additive in building materials. The aim of the study was to evaluate the possibility of manufacturing sustainable and self-cleaning cement mortars with use of commercially available nanomaterials and brown soda-lime waste glass. Mechanical and bactericidal properties of cement mortars containing brown soda-lime waste glass and commercially available nanomaterials (amorphous nanosilica and cement containing nanocrystalline titanium dioxide) were analyzed in terms of waste glass content and the effectiveness of nanomaterials. Quartz sand is replaced with brown waste glass at ratios of 25%, 50%, 75% and 100% by weight. Study has shown that waste glass can act as a successful replacement for sand (up to 100%) to produce cement mortars while nanosilica is incorporated. Additionally, a positive effect of waste glass aggregate for bactericidal properties of cement mortars was observed.