Concentrated Nitrate Solutions Research Articles

Crystal structure of ZnO nanocrystals synthesized by the spray pyrolysis method

The paper discusses the issues related to the influence of technological conditions of synthesis by ultrasonic spray pyrolysis on the size and lattice parameters of ZnO:Mn nanocrystals. It is found that, depending on the concentration of zinc nitrate in the base solution from 5% to 10%, the synthesized nanocrystals have sizes ranging from 36÷40 nm for small solution droplets and 51÷55 nm for large droplets, respectively. Based on the X-ray diffraction data, it is found that the nanocrystals of small sizes have a more perfect crystal structure with a small number of intrinsic defects compared to the nanocrystals of larger sizes.

Study on the Reaction Parameters on Transesterification of Rubber Seed Oil Using MgO/zeolite-A Catalyst

In this research, transesterification of rubber seed oil (RSO) with methanol in the presence of MgO/zeolite-A composites with different MgO loads as catalysts was investigated. In addition, the effect of different reaction parameters including oil to methanol ratio, the amount of catalyst, and transesterification time were also investigated. Zeolite-A was prepared from rice husk silica (RHS) and food-grade aluminum foil and confirmed using XRD and SEM/EDS techniques. The MgO/zeolite-A composites with different MgO loads were prepared by impregnating the zeolite with Mg (NO3)2 solution of different concentrations. The composites were then characterized using XRF, XRD, and SEM, and finally applied as a catalyst in transesterification of RSO at varied experimental conditions. The XRF results indicated that the zeolite has been successfully impregnated, and the content of MgO varied depending on the concentration of magnesium nitrate solution used for impregnation process. Zeolite-A and also MgO/zeolite-A composites were confirmed by XRD investigations, supported by SEM analysis with indicated the shape of cubic particle, a characteristic feature of zeolite-A, and rod like structure which is most likely the MgO particle. The results of transesterification experiments revealed the appreciable activities of the composites and the effect of reaction parameters on the conversion of the RSO, with the highest conversion of 89 % achieved using 12.5 % catalyst relative to the mass of RSO, with MgO 4.43 %/zeolite-A catalyst, oil to methanol ratio of 1:10, and a transesterification time of 6.0 h. Analysis of the transesterification products using GC-MS confirmed that fatty acids composing the RSO were converted into corresponding methyl esters. HIGHLIGHTS Zeolite A was prepared from rice husk silica and food grade aluminum foil MgO/Zeolite A composites with different MgO load were prepared using impregnation method MgO/Zeolite A composites were used as catalyst for transesterification of rubber seed oil GRAPHICAL ABSTRACT

OBTAINING AND PROPERTIES OF THE IMPLANT FILM MADE WITH CARBOXYMETHYLCELLULOSE CONTAINING SILVER NANOPARTICLES USED FOR TREATMENT OF BURN WOUNDS

This article studies feasibilities of making an implant-film for treatment of burn wound, based on silver nanoparticles (AgNPs) stabilized by sodiumcarboxymethylcellulose (Na-CMC) with degrees of substitution (DS) 0.65-0.90 and polymerization (DP) 200-600 synthesized using a photochemical method. The structural, physical and chemical, and physicalmechanical, burn wound healing properties as well as antimicrobial effects of implant-films containing the Na-CMC and AgNPs have been investigated. The shape, quantity, and size of the AgNPs embedded into the Na-CMC films were determined by UV-Vis spectroscopy, dynamic light scattering (DLS), atomic force microscopy (AFM) and transmission electron microscopy (TEM). It was found that the increase of silver nitrate concentration in solution of Na-CMC followed by photoirradiation leads to changes of AgNPs size and shape. It was found out that Na-CMC films containing AgNPs in the size ranging from 5 to 35 nm had enhanced the microbicide effects and burn wound healing properties within 14 days.

Impact of the urea nitrate content in the leaching solution on the granite weight decrease and the fluoride ion concentration

The paper presents the results of the study on the impact of the initial concentration of urea nitrate and fluoride ion in the leaching solution on the weight decrease of granite mined at Prydniprovsk Specialized Quarry and the change in the fluoride ion concentration in the solution during intermittent and continuous agitation. During the experiments, we used urea nitrate with weight fraction of nitrate acid 41.5%, urea - 44.3%, water - 14.2%, and ammonium fluoride-bifluoride (fluorine content was 61.2%). Fluoride ion concentration was measured using a fluoride-selective electrode relatively a saturated silver chloride half-cell while the acidity of solutions was measured by titrimetry. Weight decrease was studied for a granite sample, grain fraction -2.0 + 1.0 mm, during intermittent stirring depending on the initial concentration of urea nitrate 0.25 g/dm3, 0.5 g/dm3, and 1.0 g/dm3 and fluoride ion 2.81×10-2 g/dm3 to 3.20×10-1 g/dm3 with intermittent stirring at a temperature of 20±2 °C for 7 days. The data on the change in sample weight depending on the initial concentration of fluoride ion and addition of urea nitrate were received. It was revealed that the decrease in the fluoride ion concentration ambiguously depended on the initial concentration of both urea nitrate and fluoride ion. In our opinion, the fluoride ion concentration decrease occurred with adding urea nitrate due to the fact that nitric acid urea could form adducts with both sulfuric and fluoric acids resulting in the decrease of their reactivity. We have studied the decrease of the granite sample weight and the change in the fluoride ion concentration under continuous stirring and at a temperature of 30±2 °C for 4 days. It was found that the change in the sample weight and concentration of fluoride ion during continuous stirring differed from the similar data obtained during intermittent stirring due to more intensive formation of urea nitrate adducts with sulfuric and fluoride acids. The initial dissolution rate was calculated for a granite sample, its value was 2.384×10-7 s-1 after adding urea nitrate and 2.299×10-7 s-1 without its addition.

Deposition of inorganic nanoparticles on the RO membrane surface via a simple and environmentally friendly approach based on surface mineralization

Different modification techniques are employed by researchers to alter surface characteristics of thin film composite (TFC) membrane, but these techniques are typically associated with drawbacks such as multiple fabrication steps and requirement of organic solvents. In this work, a simple, rapid and environmentally friendly approach based on surface mineralization was employed, aiming to simultaneously improve membrane water flux and antifouling properties without compromising rejection. Lead sulphate (PbSO4) was deposited atop polyamide layer of reverse osmosis (RO) membrane via electrostatic interaction by varying concentration (0.05–0.2 M) of lead nitrate and sodium sulphate in aqueous solution. Our findings indicated that precipitation of PbSO4 nanoparticles from 0.05-M Pb source onto the membrane surface was sufficient to achieve desired characteristics including hydrophilicity, surface charge and homogenous nanoparticles distribution, leading to 48 % higher flux and 2.3 % higher NaCl rejection compared to the control membrane. Our results also revealed that the surface-mineralized membrane demonstrated extraordinary fouling resistances against sodium alginate and dyes. Most importantly, Pb ions leaching from the membrane could be negligible as it was below the detection limits of ICP-MS (<1.0 ppb). In conclusion, the PbSO4-mineralized membrane developed in this work is able to show great potential for RO application.

Evaluation of Nitrate Soil Probes for a More Sustainable Agriculture

Synthetic nitrogen (N) fertilizers and their increased production and utilization have played a great role in increasing crop yield and in meeting the food demands resulting from population growth. Nitrate (NO3-) is the common form of nitrogen absorbed by plants. It has high water solubility and low retention by soil particles, making it prone to leaching and mobilization by surface water, which can seriously contaminate biological environments and affect human health. Few methods exist to measure nitrate in the soil. The development of ion selective sensors provides knowledge about the dynamics of nitrate in the soil in real time, which can be very useful for nitrate management. The objective of this study is to analyze the performance of three commercial probes (Nutrisens, RIKA and JXCT) under the same conditions. The performance was analyzed with respect to electrical conductivity (EC) (0-50 mS/cm) and nitrate concentration in aqueous solution and in sand (0-180 ppm NO3-) at 35% volumetric soil moisture. Differences were shown among probes when studying their response to variations of the EC and, notably, only the Nutrisens probe provided coherent accurate measurements. In the evaluation of nitrate concentration in liquid solution, all probes proved to be highly sensitive. Finally, in the evaluation of all probes' response to modifications in nitrate concentration in sand, the sensitivity decreased for all probes, with the Nutrisens probe the most sensitive and the other two probes almost insensitive.

Ni(NO3)2-induced high electrocatalytic hydrogen evolution performance of self-supported fold-like WC coating on carbon fiber paper prepared through molten salt method

Exploring high-performance and inexpensive electrocatalysts for hydrogen evolution reaction to substitute Pt-based compounds is important to sustain hydrogen production. Herein, WC based self-supported catalysts doped with different concentration of nickel nitrate solution (Ni(NO3)2) were synthesized on carbon fiber paper (CFP) by one-step molten salt method (abbreviated as x Ni-WC@CFP). With the increasing of Ni(NO3)2 concentration, fold-like structures were formed on the catalysts, which was conducive to active sites exposure. As Ni(NO3)2 concentration increased from 1M to 5M, the catalytic performance of the electrocatalyst showed a trend of increasing first and then decreasing. The optimal 4M Ni-WC@CFP showed comparable catalytic ability in 0.5M H2SO4 with a low overpotential of 73 mV at 10 mA cm−2 and Tafel slope of 66.4 mV dec−1. However, excessive nickel doping would inhibit HER performance. The density functional theory calculation further verified the experimental results. The adsorption energy of hydrogen showed a decreasing trend with the rising amount of Ni doped in, while the W-H binding energy would change in an opposite direction as over doped Ni. This work provided an insight for the preparation of high-efficiency self-supported W-based electrocatalysts and expounded the influence trend of Ni doping concentration on the performance of electrocatalysts.

Self-supporting NiCoP for hydrogen generation via hydrolysis of ammonia borane

Ammonia borane (NH3BH3) is being widely used as a hydrogen (H2) storage material. Hydrogen storage content of NH3BH3 is suitable to produce H2 at room temperature in the presence of an efficient catalyst. Herein, cobalt doped nickel phosphide catalyst is developed to improve NH3BH3 hydrolysis by two steps. In first step, cobalt doped nickel hydroxide nanosheets are developed on the surface of nickel foam (NF) by immersing the NF in different concentrations of cobalt nitrate solution. In second step, self-supported cobalt doped nickel phosphide on NF is prepared by phosphidation at 300 °C. The partial positive charge of Ni and partial negative charge of P produce the charged polarization at the surface of NF. The catalyst optimization shows that 4-NiCoP/NF (0.01 M concentration of cobalt nitrate solution) produces the highest H2 production among all prepared samples. Same procedure is adopted to produce FeNiP/NF to determine the authenticity of the method. The reaction kinetics are calculated for both 4-NiCoP/NF and 4-FeNiP/NF best catalysts. The energy of activations 58.95 kJ·mol−1 for NiCoP/NF and 60.26 kJ·mol−1 NiFeP/NF are calculated via Arrhenius Equation. High activation energy of NiFeP/NF reveals that NiCoP/NF is better for H2 production. The on/off characteristics of the catalyst is unique for H2 evolution.

HIGH-SPEED ANODIC DISSOLUTION OF CHROMIUM-NICKEL STEEL IN A NITRATE SOLUTION WITH THERMOKINETIC INSTABILITY OF THE OXIDE FILM

It is shown that high-speed anodic dissolution of Kh18Ni10 chromium-nickel steel (Cr18Ni10) in a concentrated nitrate solution occurs through an anode oxide film (AOP), the for-mation of which is carried out as a result of charge transfer, and the dissolution is chemically. The condition of constant film thickness is achieved due to the equality of the rates of these two pro-cesses (electrochemical formation of the film and its chemical dissolution) and is realized under pulsed conditions until the boiling point of the electrolyte is reached at the film-solution interface. When thermokinetic instability of the anodic oxide film occurs at the film-solution interface at surface temperatures exceeding the boiling point of the electrolyte, the interaction of the dissolving surface of the alloy free of the film with the solution (electrolyte) is observed. The dissolution rate in this case may exceed the Faraday rate (anomalous anodic dissolution) as a result of the destruc-tion of the film, for the formation of which the leaked charge was spent. The presence of a barrier film at the metal-film interface is the reason that the change in the surface temperature and disso-lution rate is achieved only by changing the heat transfer conditions of the metal surface.The porous part of the film in contact with the solution is a “heat seal” (limits the heat removal towards the electrolyte), as a result of which a change in the electrolyte flow rate does not affect the surface temperature. Based on the results of calculating heat fluxes, the influence of the temperature of the metal surface in contact with air (the outer part of the surface of the dissolving metal) on the heat transfer coefficient during natural convection and rotation at a speed of 1000 rpm of the elec-trode was estimated, as well as the ratio of the corresponding heat fluxes. An increase in convective heat removal during rotation leads to a decrease in temperature in the anode treatment zone and, as a consequence, to a decrease in the dissolution rate.

Efficiency definition of the deposition process of electrochromic Ni(OH)2-PVA films formed on a metal substrate from concentrated solutions

Electrochemical devices based on nickel hydroxide electrodes are used in different areas. The main ones are chemical current sources, variable transparency “smart” windows, devices for carrying out electrocatalytic reactions, sensors for determining various substances. In this regard, methods of nickel hydroxide synthesis are of great interest, especially those that allow forming nickel hydroxide directly on the surface of electrodes. One of these methods is electrochemical deposition with cathodic current polarization. The available information on nickel hydroxide synthesis from nickel solutions was considered. It was shown that the available data mainly covered information on dilute solutions from 0.01 to 0.25 mol/L Ni(NO3)2. In addition, no comparison was found in the literature for the efficiency of the cathodic formation of Ni(OH)2 at different concentrations of nickel nitrate. To eliminate the lack of information, the dependence of the current efficiency on the concentration of nickel nitrate in the electrodeposition solution was determined at a constant cathode current density of 0.625 mA/cm2. The resulting dependence decreased nonlinearly with increasing concentration. The nickel hydroxide deposit formed in this case had an X-ray amorphous structure, and it depended little on the Ni(NO3)2 concentration. In addition, the current efficiency reached zero at concentrations of 1.5 mol/L Ni(NO3)2 and higher. However, with polyvinyl alcohol in the solution and at Ni(NO3)2 concentrations of 1.5 and 2 mol/L, electrochemically and electrochromically active Ni(OH)2 films were deposited. The current efficiency calculated indirectly for 1.5 and 2 mol/L Ni(NO3)2 solutions was 3.2 and 2.3 %, respectively. Thus, it was concluded that polyvinyl alcohol affected the mechanism of nickel hydroxide electrodeposition from aqueous solutions of nickel nitrate.

Tailoring growth of MOF199 on hierarchical surface of bamboo and its antibacterial property

Bamboo, as a fast-grown forest resource, can be functionalized by metal–organic frameworks (MOFs) with various potential applications. However, the stability of MOFs immobilized on bamboo surface remains to be improved. In this work, MOF199, as known as HKUST-1, was in situ anchoring on moso bamboo via regulating pretreatment of bamboo and a green two-step synthesis route. The two-step synthesis route was completed under room temperature and both precursor solutions can be reused. The results indicated that, with the collaboration of delignification and carboxymethylation pretreatment of bamboo, a dense and well-dispersed MOF coating was successfully synthesized, the adhesion between MOF199 and bamboo surface was also improved. Besides, the quantity and size of MOF199 on bamboo can be tailored by tunning the carboxyl groups of pretreated bamboo and the concentration of copper nitrate solution. More importantly, results show that the formation of carboxyl-copper (II) complex served as nucleation sites for the growth of MOF199 crystals, which was essential to prepare uniform MOF layers. The growth of MOF199 endowed bamboo with good antibacterial activity against Escherichia coli. This method provides a facile and practical strategy for designing MOF coated woody materials.

Effect of Bacillus spp. on Lettuce Growth and Root Associated Bacterial Community in a Small-Scale Aquaponics System

The integration of probiotics in aquaponics systems is a strategy for mitigating environmental impacts and for promoting sustainable agriculture. In order to understand the role of probiotics, we investigated the effect of a commercial probiotic mixture of Bacillus subtilis and B. licheniformis on the growth of lettuce (Lactuca sativa L.) under deep-water culture integrated with Mozambique tilapia (Oreochromis mossambicus). We determined plant growth, water quality parameters, and leaf mineral analysis, and assessed the influence of a probiotic mixture on the microbiota. Bacterial communities were analyzed by high-throughput 16S rRNA gene sequencing. Compared to the control systems, the addition of the probiotic Bacillus significantly increased the concentration of nitrate and phosphate in deep water culture solution, which contributed to improved lettuce growth. In both the growth trials, the Fv/Fm, the mean shoot dry weight, and the mean fresh weight of the harvested shoots from the Bacillus treatment were significantly higher than those observed for the control plants. Higher concentrations of phosphorus, potassium, and zinc in the lettuce leaves were found in systems that received the Bacillus. Although differences were observed at the phylum level, Proteobacteria and Bacteroidetes were predominant in both the Bacillus-treatment and the control systems. At the genus level, however, the communities present in the two types of systems were heterogeneous with Bacillus-treated systems, containing significantly higher numbers of Chryseobacterium, Bacillus, Nitrospira, Polynucleobacter, and Thermomonas. The results indicate that Bacillus supplementation can effectively alleviate nutrient deficiencies, improve water quality, and modify the composition of bacterial communities in aquaponics systems.

Investigating the Possibility of Green Synthesis of Silver Nanoparticles Using Vaccinium arctostaphlyos Extract and Evaluating Its Antibacterial Properties.

Objective Vaccinium genus plants have medicinal value, of which Vaccinium arctostaphylos (Caucasian whortleberry or Qare-Qat in the local language) is the only available species in Iran. Public tendency to use herbal remedies and natural products such as synthesized nanoparticles is increasing due to the proof of the destructive side effects of chemical drugs. Nanosilver products have been effective against more than 650 microbe types. This study was aimed at assessing the possibility of green synthesis of silver nanoparticles using Vaccinium arctostaphylos aqueous extract and at evaluating its antibacterial properties, as well. Materials and Methods In order to synthesize silver nanoparticles, different volumes of Vaccinium arctostaphylos aqueous extract (3, 5, 10, 15, and 30 ml) were assessed with different silver nitrate solution concentrations (0.5, 1, 3, 5, and 10 mM) and different reaction time durations (1, 3, 5, 10, and 20 minutes) at room temperature using a rotary shaker with a speed of 150 rpm. Ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction analysis (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) were carried out. The antibacterial activity of the aqueous extract and the synthesized nanoparticles was evaluated, as well. Results Silver nanoparticle formation process was confirmed with XRD analysis, transmission electron microscopy (TEM), and FTIR spectroscopy. The UV-Vis spectroscopy of silver colloidal nanoparticles showed a surface plasmon resonance peak at 443 nm under optimal conditions (3 ml aqueous extract volume, 1 mM silver nitrate solution concentration, and 3 min reaction time under sunlight exposure). The reduction of silver ions to silver nanoparticles in solution was confirmed, as well. Based on X-ray diffraction analysis, the size of silver nanoparticles was in the range of 7-16 nm. TEM images showed an even distribution of silver nanoparticles, with a spherical shape. FTIR spectroscopy demonstrated the presence of different functional groups of oxygenated compounds such as carboxyl, hydroxyl, and nitrogenous groups. The antibacterial properties of the synthesized nanoparticles were confirmed. Conclusion The synthesized nanoparticles showed more antibacterial properties against gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) than gram-negative ones (Escherichia coli and Salmonella enteritidis).

Improved modification of clinoptilolite with silver using ultrasonic radiation

The modification of natural clinoptilolite with silver ions using ultrasound has been investigated in the current work. The modification process was performed using clinoptilolite of different fractions (0–3.0 mm) over the temperature range of 25–55 °C, ultrasonic power range of 8.0–12.5 W and AgNO3 concentration range of 0.01–0.1 M. The zeolite modification was performed in the presence of sonication and mechanical stirring in separate runs for comparison. Fundamental analysis demonstrated that the use of ultrasound ensures desorption of air from clinoptilolite particles and accelerates the diffusion of Ag+ ions and subsequent ion exchange. Increasing the particle size of clinoptilolite led to a natural decrease in its sorption capacity. A slight increase in the sorption capacity with an increase in the equivalent particle diameter from 0.081 to 0.35 mm was seen due to changes in the structure of clinoptilolite particles during mechanical grinding. The calculated temperature coefficient of the sorption process of Ag+ ions as <1.47 means that the modification takes place with dominant control in the intradiffusion region. Increasing the power of ultrasonic irradiation did not provide a monotonous change in the sorption capacity of clinoptilolite. Increasing the concentration of argentum nitrate solution provided an increase in the content of silver ions in clinoptilolite. In general, the advantage of using ultrasonic vibrations to modify the natural clinoptilolite of different fractions with Ag+ ions was demonstrated in terms of achieving higher sorption capacity, also elucidating the effect of different operating conditions.

Nitrogen-defective g-C3N4 with enhanced photocatalytic performance fabrication by destructing C[dbnd]N[sbnd]C bond via H2O2

The g-C3N4 nanosheets with N-defects were fabricated by a sample oxidative reaction via H2O2, which can generate hydroxyl radical (•OH) to destruct the bonds of g-C3N4. The existence of •OH was confirmed by PL (photoluminescence spectroscopy) and HPIC (high-pressure ion chromatography). The N-defects were confirmed by the concentration of nitrate in solution increasing from 1.04 to 4.65 mg/L. Further, the source of N-defects was speculated as the destruction of CNC due to its lower bond-energy and decreasing ratio of CNC (CASTEP, XPS). As a result, the obtained N-defective g-C3N4 improved the photocatalytic degradation efficiency to Methylene blue (MB) from 53.1% (g-C3N4) to 100.0% under visible light. This result was ascribed by the N-defect narrowed the bandgap from 2.71 to 2.67 eV, accelerated the separation and transfer of photo-generated carriers. This work provides a new strategy to construct defects in a catalyst improving photocatalytic performance.

Physicochemical properties and antimicrobial activity of nanocomposite films based on carboxymethylcellulose and silver nanoparticles

AbstractSilver nanoparticles (AgNPs) stabilized by sodium carboxymethylcellulose (Na‐CMC) with degree of substitution (DS) 0.65‐0.90 and degree of polymerization (DP) 200‐600 were synthesized by photochemical method. The structural, physico‐chemical, and physico‐mechanical properties as well as antimicrobial activity of polymer films containing the Na‐CMC and AgNPs were studied. The shape, quantity, and size of the AgNPs embedded into the Na‐CMC films were determined by UV‐Vis spectroscopy, ZETASIZER Nano ZS, atomic force microscopy and transmission electron microscopy. It was found that the increase of silver nitrate concentration in solution of Na‐CMC followed by photoirradiation leads to the change of size and shape of AgNPs. The AgNPs in the range of size from 5 to 35 nm were found to enhance the microbicidal activities of the Na‐CMC films.

Simulation of nitrate and potassium concentrations in soil solution using parametric models and Hydrus-2D

This study estimated the nitrate and potassium concentration in the soil solution of drainage lysimeter using the mathematical models developed by Vogeler et al. (1996) and Muñoz-Carpena et al. (2005) and the computational model Hydrus-2D, while comparing the simulated and observed data using statistical parameters. The cultivar used for the study was ‘Prata Gorutuba’. The experimental plots were six lysimeters of drainage. Fertigation was performed weekly. The mathematical models developed by Vogeler et al. (1996) and Muñoz-Carpena et al. (2005) were used to determine the specific concentration of a given ion (Ci). The Hydrus software was used to simulate the dynamics of nutrients. The concentrations of nitrate and potassium in the soil solution were estimated by the model of Vogeler et al. (1996), adapted to the linear type CEw-Ci ratio and simulated by the Hydrus model, resulting in an acceptable characterization of the distribution of these nutrients.

Reduction of Nitrate Content in Water by the Use of Banana Peels Biochar

The intensification of agricultural, domestic and industrial activities leads to the increasing contamination of groundwater and surface water by nitrates. Indeed, agricultural runoff, septic tank effluents, landfill leachates or wastewater treatment plant effluents contribute to this nitrification, yet drinking water containing high nitrate content can cause health problems. The study examines the improvement of nitrate removal in synthetic water solution by adsorption on banana peel’s activated carbon (BPAC). Different effects of physicochemical parameters, such as the optimal contact time of BPAC in solution, the pH of the nitrate solution, the initial concentration of nitrate solution, the BPAC mass, and the temperature were evaluated. The study revealed that BPAC has a low nitrate adsorption capacity under normal laboratory conditions. However, this adsorption capacity of BPAC increases with increasing of temperature and initial content of nitrate, while it decreases with increasing BPAC mass. For a content of 100 mg/L nitrate solution, the maximum adsorption capacity was 0, 687 mg/g for an equilibrium time of 180 min. Nitrate adsorption is optimal in acidic media (pH=3). The application of kinetic models to the experimental data showed that the mechanism of nitrate adsorption on BPAC obeys pseudo-first order kinetics. The Freundlich isotherm perfectly describes the mechanism of nitrate adsorption on BPAC.

Ion exchange capacity of zeolite A with zinc nitrate and its antimicrobial activity

Abstract Various type of zeolites has been produced based on kaolinite and this study likewise utilized kaolin clay as raw material to synthesis zeolite A. Kaolin was in inactive state, therefore it was transformed to metakaolin through dehydroxylation at 800 °C for 4 h. The metakaolin as a source of silica and alumina was then utilized in the synthesis of zeolite A. After hydrothermal synthesis, the zeolite A was exchanged with different concentration of zinc nitrate solution. Zinc content in ion-exchanged zeolite A, ZnA was determined through AAS to calculate the ion exchange capacity. Higher concentration of zinc nitrate had higher zinc content and higher ion exchange capacity. Zeolite A and zinc-exchanged zeolite A were characterized under SEM, XRD and FTIR. Finally, zeolite A and zinc-exchanged zeolite A was used to investigate the antimicrobial properties against gram-negative bacteria, Escherichia coli and gram-positive bacteria Staphylococcus aureus. There was no antimicrobial activity for zeolite A yet zinc-ion–exchanged zeolite A showed inhibition zones around the samples for both the microorganisms.

Effect of Zr Incorporation on Mordenite Catalyzed Dimethyl Ether Carbonylation

Zr-mordenite catalysts were prepared by post-treatment method and H-mordenite catalyst was synthesized by hydrothermal method for the dimethyl ether carbonylation reaction. XRD, N2 adsorption/desorption, ICP-OES, SEM, TEM, UV–Vis, XPS, Raman, CO-TPD, NH3-TPD, 27Al MAS NMR, FTIR and Py-IR were employed to characterize the catalysts. The results demonstrated that part of Zr atoms existed in a tetrahedral coordination state after incorporating into the mordenite framework. Zirconium Lewis acid sites with the ability to absorb CO molecules were formed during this process although the amount of Bronsted acid sites in 8-member ring channels decreased upon the incorporation of zirconium. During the concentration of zirconium nitrate solution increased from 0.02 to 0.08 mol/L, the Zr-mordenite catalyst through post-treatment with 0.04 mol/L zirconium nitrate solution exhibited the best catalytic performance at 473 K and 1 MPa. Dimethyl ether conversion and methyl acetate selectivity increased to 78% and 96% respectively compared with H-mordenite catalyst. Schematic of Zr incorporating MOR framework