Preparation and Characterization of a Novel Amidoxime-Modified Polyacrylonitrile/Fly Ash Composite Adsorbent and Its Application to Metal Wastewater Treatment

The polyacrylonitrile/fly ash composite was synthesized through solution polymerization and was modified with NH2OH·HCl. The amidoxime-modified polyacrylonitrile/fly ash composite demonstrated excellent adsorption capacity for Zn2+ in an aqueous medium. Fourier transform-Infrared spectroscopy, thermogravimetric analysis, nitrogen adsorption, X-ray diffraction, and scanning electron microscopy were used to characterize the prepared materials. The results showed that the resulting amidoxime-modified polyacrylonitrile/fly ash composite was able to effectively remove Zn2+ at pH 4–6. Adsorption of Zn2+ was hindered by the coexisting cations. The adsorption kinetics of Zn2+ by Zn2+ followed the pseudo-second order kinetic model. The adsorption process also satisfactorily fit the Langmuir model, and the adsorption process was mainly single layer. The Gibbs free energy ΔG0, ΔH0, and ΔS0 were negative, indicating the adsorption was a spontaneous, exothermic, and high degree of order in solution system.

Textural and Thermal Properties of the Novel Fucoidan/Nano-Oxides Hybrid Materials with Cosmetic, Pharmaceutical and Environmental Potential

The main purpose of the research was to obtain and study hybrid materials based on three different nano-oxides commonly used in the cosmetic and pharmaceutical industries: Al2O3, TiO2, and ZnO, with the natural bioactive polysaccharide fucoidan. Since the mentioned oxides are largely utilized by industry, there is no doubt that the presented studies are important from an environmental point of view. On the basis of the textural studies (dynamic light scattering DLS, low temperature nitrogen adsorption, X-ray diffraction analysis XRD, scanning electron microscopy SEM) it was proved that the properties of the hybrid materials differ from the pure components of the system. Moreover, the advanced thermal analysis (TG-DTG-DSC) combined with the evolved gas analysis using Fourier transformed infrared spectroscopy (FTIR) and mass spectrometry were applied to describe the thermal decomposition of fucoidan, oxides and hybrid materials. It was found that the interactions between the polymer and the oxides results in the formation of the hybrid materials due to the functionalization of the nanoparticles surface, and that their thermal stability increased when compared to the pure substrates. Such findings definitely fill the literature void regarding the fucoidan based hybrid materials and help the industrial formulators in the preparation of new products.

The impregnation of ZnO onto ZSM-5 derived from red mud for photocatalytic degradation of methylene blue

Photocatalytic degradation of Methylene Blue (MB) by zinc oxide/zeolite socony mobile-5 (ZnO/ZSM-5) composites was investigated. The ZSM-5 material was synthesized from red mud by a two-step hydrothermal method to which ZnO loadings at different mass ratios were subsequently performed. Characterizations using X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and scanning electron microscopy were carried out to identify the formation of ZSM-5 and ZnO/ZSM-5. ZSM-5 and ZnO/ZSM-5 have cubic microcrystallite morphologies. ZnO loading in the ZnO/ZSM-5 composites was successfully performed and confirmed by the appearance of wurtzite peaks in the XRD spectra that matched the Joint Committee on Powder Diffraction Standards data. The presence of ZnO in ZSM-5 leading resulted in a decrease in the surface area and pore size as confirming by nitrogen adsorption-desorption isotherm experiments. The band gap of the samples was measured using UV-Vis diffuse reflectance spectroscopy. The optimum photocatalytic degradation of MB was observed at a ZnO loading of 34% w/w dubbed 34-ZnO/ZSM-5. The influence of the initial concentration of MB was also investigated at 80, 90, and 100 mg L− 1 using 34-ZnO/ZSM-5 and ZSM-5. Liquid chromatography–mass spectrometry characterization was performed to analyze the degradation products.

Enhancement of Visible Light-Responsive Photocatalytic Efficiency by Using a Laccaic Acid-Modified Titanium Dioxide Photocatalyst

In this study, a laccaic acid-modified TiO2 photocatalyst (Lac-TiO2) was prepared via an impregnation method with 0.50, 1.00, 2.50, and 5.00 wt.% laccaic acid. The products’ physical properties were examined through X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoemission spectroscopy (XPS), UV-Vis diffused reflectance spectroscopy (DRS), Fourier-transform infrared spectroscopy (FTIR), nitrogen adsorption/desorption, and photoluminescence (PL) spectroscopy. A possible photocatalytic mechanism was also proposed. XRD patterns revealed the anatase phase of TiO2 and Lac-TiO2 samples. High-magnification FE-SEM images showed that the TiO2 and Lac-TiO2 samples exhibited spherical-like structures. XPS results complementarily confirmed the presence of Ti, O, and C as the main elements of the Lac-TiO2 samples. Interestingly, the DRS spectra of the Lac-TiO2 samples extended into the visible region. FTIR spectra presented the characteristic bands of TiO2 and hydroxyl groups on the TiO2 surface. Instead of hydroxyl groups, the characteristic bands of laccaic acid were observed on the surface of the Lac-TiO2 samples. The photocatalytic properties of the Lac-TiO2 samples were evaluated in terms of methyl orange degradation under visible light irradiation. The Lac-TiO2 samples showed higher photocatalytic performance than the TiO2 sample.

Influence of the Process of Synthesis of Zeolites from Volcanic Ash in Its Synergistic Action as a Flame-Retardant for Polypropylene Composites

In this research, the influence of natural zeolites obtained from the volcanic ash of the Ubinas volcano has been studied as synergistic agents in a flame-retardant system (composed of ammonium polyphosphate, pentaerythritol, and polypropylene). Four zeolites were synthesized from volcanic ash, including those that had been calcined and those that had not. These were then placed in an alkaline solution at three synthesis temperatures. Zeolites were characterized through X-ray diffraction, specific surface area by nitrogen adsorption analysis (Brunauer–Emmett–Teller) and scanning electron microscopy. Polypropylene matrix composites were prepared with ammonium polyphosphate, pentaerythritol and zeolites at 1, 5 and 9%. Its thermal stability and fire resistance were evaluated by thermogravimetric analysis, limiting oxygen index, vertical burning test and cone calorimeter and its morphological structure by scanning electron microscopy. It was determined that the synthesis temperature and the use of calcined and without calcined volcanic ash have an influence on the characteristics of the zeolites and on its synergistic action.

Porous SiC and SiC/Cf Ceramic Microspheres Derived from Polyhydromethylsiloxane by Carbothermal Reduction

A simple and inexpensive method for the preparation of porous SiC microspheres is presented. Polysiloxane microspheres derived from polyhydromethylsiloxane (PHMS) cross-linked with divinylbenzene (DVB) were ceramized under conditions leading to the removal of oxygen from the material. The content of free carbon (Cf) in highly crystalline silicon carbide (SiC) particles can be controlled by using various proportions of DVB in the synthesis of the pre-ceramic material. The chemical structure of the ceramic microspheres was studied by elemental analysis for carbon and oxygen, 29Si MAS NMR, 13C MAS NMR, SEM/EDS, XRD and Raman spectroscopies, and their morphology by SEM, nitrogen adsorption and mercury intrusion porosimetries. The gaseous products of the thermal reduction processes formed during ceramization created a porous structure of the microspheres. In the SiC/Cf microspheres, meso/micro pores were formed, while in carbon-free SiC, microspheres macroporosity dominated.

Genesis of Coalbed Methane and Its Storage and Seepage Space in Baode Block, Eastern Ordos Basin

The Baode block on the eastern margin of the Ordos Basin is a key area for the development of low-rank coalbed methane (CBM) in China. In order to find out the genesis of CBM and its storage and seepage space in Baode block, the isotopic testing of gas samples was carried out to reveal the origin of CH4 and CO2, as well, mercury intrusion porosimetry, low temperature nitrogen adsorption, and X-ray CT tests were performed to characterize the pores and fractures in No. 4 + 5 and No. 8 + 9 coal seams. The results showed that the average volume fraction of CH4, N2, and CO2 is 88.31%, 4.73%, and 6.36%, respectively. No. 4 + 5 and No. 8 + 9 coal seams both have biogenic gas and thermogenic methane. Meanwhile, No. 4 + 5 and No. 8 + 9 coal seams both contain CO2 generated by coal pyrolysis, which belongs to organic genetic gas, while shallow CO2 is greatly affected by the action of microorganisms and belongs to biogenic gas. The average proportion of micropores, transition pores, mesopores, and macropores is 56.61%, 28.22%, 5.10%, and 10.07%, respectively. Samples collected from No. 4 + 5 coal seams have developed more sorption pores. Meanwhile, samples collected from No. 8 + 9 coal seams exhibited a relatively low degree of hysteresis (Hg retention), suggesting good pore connectivity and relatively high seepage ability, which is conducive to gas migration. The connected porosity of coal samples varies greatly, mainly depending on the relative mineral content and the proportion of connected pores.

Preparation of Sodalite and Faujasite Clay Composite Membranes and Their Utilization in the Decontamination of Dye Effluents

The present work describes the deposition of two zeolite films, sodalite and faujasite, by the hydrothermal method to tune the mesopores of clay support, which are prepared from a widely available clay depot from the central region of Morocco (Midelt). The clay supports were prepared by a powder metallurgy method from different granulometries with activated carbon as a porosity agent, using uniaxial compression followed by a sintering process. The 160 µm ≤ Φ ≤ 250 µm support showed the highest water flux compared to the supports made from smaller granulometries with a minimum water flux of 1405 L.m−2·h−1 after a working time of 2 h and 90 min. This support was chosen for the deposition of sodalite (SOM) and faujasite (FAM) zeolite membranes. The X-ray diffraction of sodalite and faujasite showed that they were well crystallized, and the obtained spectra corresponded well with the sought phases. Such findings were confirmed by the SEM analysis, which showed that SOM was crystalized as fine particles while the FAM micrographs showed the existence of crystals with an average size ranging from 0.53 µm to 1.8 µm with a bipyramidal shape and a square or Cubo octahedral base. Nitrogen adsorption analysis showed that the pore sizes of the supports got narrowed to 2.28 nm after deposition of sodalite and faujasite. The efficiencies of SOM and FAM membranes were evaluated by filtration tests of solutions containing methyl orange (MO) using a flow loop, which were developed for dead-end filtration. The retention of methylene orange (MO) followed the order: SOM > FAM > 160 µm ≤ Φ ≤ 250 µm clay support with 55%, 48% and 35%, respectively. Size exclusion was the predominant mechanism of filtration of MO through SOM, FAM, and the support. However, the charge repulsion between the surface of the membrane and the negatively charged MO have not been ruled out. The point of zero charge (pzc) of the clay support, SOM and FAM membrane were pHpzc = 9.4, pHpzc = 10.6, and pHpzc = 11.4, respectively. Filtrations of MO were carried out between pH = 5.5 and pH = 6.5, which indicated that the surface of the membranes was positively charged while MO was negatively charged. The interaction of MO with the membranes might have happened through its vertical geometry.

Experimental and Theoretical Study For Removal of Trimethoprim (TMP) From Wastewater Using Organically Modified Silica With Pyrazole-3-Carbaldehyde Bridged To Copper Ions

BackgroundHuman and veterinary antibiotics are typically discharged as parent chemicals in urine or feces and are known to be released into the environment via wastewater treatment plants (WWTPs). Several research investigations have recently been conducted on the removal and bioremediation of pharmaceutical and personal care products (PPCPs) disposed in wastewater. ResultsSiNP-Cu, a chelating matrix, was produced by delaying and slowing 1.5-dimethyl-1H-pyrazole-3-carbaldehyde on silica gel from functionalized with 3-aminopropyltrimethoxysilane. The prepared sorbent material was characterized using several techniques including BET surface area, FT-IR spectroscopy, Scanning electron microscopy (SEM), Thermogravimetric analysis (TGA), and nitrogen adsorption-desorption isotherm. The pseudo-second-order model provided the best correlation due to the big match between the experimental and theoretical of different adsorption coefficients. The Langmuir and Freundlich adsorption models were used and the study showed better match with Fruendlich model. The removal capacity was depending on pH and increased by increasing pH The adsorbent demonstrated a high percentage removal of TMP, reaching more than 94 %. The sample was simply regenerated by soaking it for a few minutes in 1N HCl and drying it. The sorbent was repeated five times with no discernible decrease in removal capacity. Thermodynamic study also showed endothermic, increasing randomness and not spontaneous in nature. The findings of the DFT B3LYP/6-31+g (d,p) local reactivity descriptors revealed that nitrogen atoms and p-electrons of the benzene and pyrimidine rings in the TMP are responsible for the adsorption process with the SiNP surface. The negative values of the adsorption energies obtained by molecular dynamic simulation indicated the spontaneity of the adsorption process. ConclusionThe global reactivity indics prove that TMP is stable and it can be removed from wastewater using SiNP surface. The results of the local reactivity indices concluded that the active centers for the adsorption process are the nitrogen atoms and the p-electrons of the pyrimidine and benzene rings. Furthermore, the positive value of the maximum charge transfer number (DN) proves that TMP has a great tendency to donate electrons to SiNP surface during the process of adsorption.