Adsorption of carbon dioxide using activated carbon impregnated with Cu promoted by zinc

In the present study, modified activated carbon (AC) was used in a fixed-bed column for CO2 adsorption of gaseous mixtures. The adsorbents were prepared by impregnation two metals Cu and Zn on the surface of the acid modified AC using a two-stage modification. At the first stage, the samples of AC were pretreated by oxidizing agent (nitric acid) to increase the amount of oxygen surface groups and at the second stage, the acid modified AC were impregnated by two metal salts Cu and Zn on the surface to produce a superior CO2 adsorbent. Metal-loaded acid modified AC was prepared by using different ratios of Cu/Zn ranging from 4 to 20%. The CO2 adsorbed have been measured over the temperature range of (30–50 °C), pressure (100–200 kPa) and CO2 concentrations from 5 to 50%. An increase of 49% CO2 adsorbed was resulted by using modified activated carbon. The breakthrough curves indicated that the breakthrough time increased with increasing the operating pressure, and decreased with increasing the temperature from 30 to 50 °C and CO2 concentration from 5 to 50%. The deactivation model was successfully applied to analyze the breakthrough curves under various operating conditions

Synthesis, characterization and performance evaluation of three-layered photoanodes by introducing a blend of WO3 and Fe2O3 for dye degradation

A three-layered photoanode has been synthesized by the introduction of an additional layer of mixed WO3 and Fe2O3. A total of nine differently-packaged films were prepared by sol-gel method. The fabricated photoanodes were then successfully characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). A comparative study was also done to differentiate the films fabricated with WO3, Fe2O3 and their mixture. Compact, columnar tree and shallow patterns were observed on the cross cleavage of the synthesized layers. These distinct patterns were associated with the growth of layers which consequently led to unique surface morphologies. An increase in photocurrent density was observed on the bicomponent film which has been linked to a high degree of surface roughness as well as improved internal porosity. Three-layered photoanodes, modified with an additional bicomponent layer of WO3:Fe2O3 established much higher photocurrent outputs compared to that of nanostructured WO3 or Fe2O3, regardless of the bicomponent layer arrangement. However, with the bicomponent layer on top and middle, the measured photocurrent soared more than three times as much compared to a slight increase observed when the bicomponent was placed on the bottom

Effect of intermediate layer in photocurrent improvement of three-layer photoanodes using WO3 and Fe2O3

Sol–gel method was applied to synthesize WO3/Fe2O3 three-layer films in order to improve the generated photocurrent under UV–vis light irradiation. The films were deposited on FTO glass substrates through doctor bladding method. The samples were then calcined at 500 °C. The photocurrents of the synthesized photoanodes were evaluated by measuring the electric current and voltage under UV–vis light at room temperature. Scanning electron microscopy (SEM) revealed unique surface morphologies owing to the presence of the intermediate layers. At an applied potential of 1300 mV, the WO3\Fe2O3\WO3 and Fe2O3\WO3\Fe2O3 photoanodes exhibited photocurrent densities up to 0.1 mA/cm2 and 0.6 mA/cm2, respectively. It was found that porous films with easy accessibility to the inner surface reveal high photocurrents. The intermediate layer of WO3 demonstrated higher values of photocurrent due to roughness enhancement on the upper surface with columnar tree-growth particles. However, a compact state was observed on the cross section of Fe2O3 growth. A comparison was also drawn between the two and three-layer photoanodes using Fe2O3 andWO3. The films were characterized by XRD, SEM/EDX, and UV–vis irradiation to determine the photocurrent densities

Development of coating technology using rotary pan for production of slow-release urea

Urea fertilizer has been used for many years to supplement nutrients in growing media. Urea has the advantages of low cost and easy availability, thus touts as the most popular nitrogenous fertilizer. However, the major disadvantage of urea is its high solubility in water and its susceptibility to nitrogen losses through various pathways like leaching, ammonia volatilization, nitrification and denitrification. This adds extra cost for fertilizers manufacturer and higher concentration of urea in the soil. Currently,the use of slow-release fertilizer is a trend to reduce fertilizer consumption and to minimize environmental pollution. Slow-release nitrogenous-based fertilizer is often linked to positive characteristics such as regular release of nitrogen over a long period, reductions in nitrate leaching and reduced volatilization. However, slow-release nitrogen sources tend to be more expensive compared to other products and may lead to nitrogen release mismatch. The coating process of urea has been performed using different techniques and various materials to delay urea release. In this study, a low cost rotary pan coating technology running at room temperature was used as the coating process for urea. In the first experiment, a fractional factorial design of experiment was utilized to screen the operational parameters of rotary pan including urea particle size, proportion of coating,amount of spray water, rotation speed, pan inclination, pan loading and spray flow rate. In the second experiment; the most effective coating parameters were analyzed and optimized using a central composite design of experiments. The results of the optimized process correlated well with a second-order polynomial model with percentage of variation, R2 at 95.12%. In the next experiment, the effects of different coating formulations on the efficiency,crushing strength and morphology of the coated urea were examined. Urea fertilizer was coated using six different materials, namely, gypsum, sulfur, ground magnesium lime, kaolin clay, rice husk ash and zeolite based on the “optimal‟ parameters of rotary pan. A mixture of 25% of gypsum, 25% of sulfur and 50% zeolite gave the lowest rate of urea release with acceptable crushing strength. Six different models namely, zeroth order, first order, second order, Higuchi and Ritger & Peppas and Kopcha model were examined to understand better the relationship between coating layer and urea release mechanism. By comparing coefficient of determination (R2) of models, the Ritger & Peppas model provided the highest R2 value (≈ 0.93) for final coating formulation. The efficiency of gypsum-sulfur-zeolite (25/25/50%) coated urea was improved further where microcrystalline wax and polyol was experimented as a sealant. The efficiency of gypsum-sulfur-zeolite coated urea sealed by 3% of microcrystalline wax improved to around 56% while the efficiency of commercial sulfur coated urea is about 65%. This indicates the potential of gypsum-sulfur-zeolite coated urea produced in a room temperature process to be commercialized and used as a slow released nitrogen fertilizer

Electrochemical investigation of amino acids Parkia seeds using the composite electrode based on Copper/Carbon nanotube/Nanodiamond

An electrochemical biosensor comprising copper, nano-diamond (ND) and carbon nanotube (CNT) has been fabricated to detect the amino acids of Parkia speciosa (PS) seeds. Parkia speciosa (stink bean), a Southeast Asian legume, is composed of medicinal chemicals which exhibit biological activities. The electro-catalytic activity of three electrodes Cu/CNT/ND, Zn/CNT/ND and NiO/CNT/ND was studied using 5 mM potassium ferrocyanide in 0.1 MKCl. The Zn/CNT/ND electrode exhibited irreversible reaction free oxidation with reduction peaks at -1 V, whereas, a pair redox peaks was observed for Cu/CNT/ND electrode. The immobilization of l-amino acid oxidase on the Cu/CNT/ND electrode was carried out to catalyze the amino acids detection. It was observed that the anodic and cathodic peak currents increased linearly with both the square root of the scan rate (ν1/2) and scan rate (ν) over the studied scan range of 0.01-0.1 V/s with high correlation coefficients and following both the adsorption and the diffusion-controlled mechanisms. The developed biosensor displayed a very good electro-catalytic activity toward the oxidation of the amino acid to release H2O2 and NH3 as a result of the reaction between the active sites and the Parkia speciosa component. This was also confirmed by a drop in the pH value from 6.8 to 6.5 and a change in the color of the solution from green to yellow (releasing H2S). The impedance results indicated an inductance behavior due to the co-formation of the hydrogen peroxide (H2O2) and the water via the adsorption on the electrode surface.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

3D Bioprinting of Lignocellulosic Biomaterials

The interest in bioprinting of sustainable biomaterials is rapidly growing, and lignocellulosic biomaterials have a unique role in this development. Lignocellulosic materials are biocompatible and possess tunable mechanical properties, and therefore promising for use in the field of 3D-printed biomaterials. This review aims to spotlight the recent progress on the application of different lignocellulosic materials (cellulose, hemicellulose, and lignin) from various sources (wood, bacteria, and fungi) in different forms (including nanocrystals and nanofibers in 3D bioprinting). Their crystallinity, leading to water insolubility and the presence of suspended nanostructures, makes these polymers stand out among hydrogel-forming biomaterials. These unique structures give rise to favorable properties such as high ink viscosity and strength and toughness of the final hydrogel, even when used at low concentrations. In this review, the application of lignocellulosic polymers with other components in inks is reported for 3D bioprinting and identified supercritical CO2 as a potential sterilization method for 3D-printed cellulosic materials. This review also focuses on the areas of potential development by highlighting the opportunities and unmet challenges such as the need for standardization of the production, biocompatibility, and biodegradability of the cellulosic materials that underscore the direction of future research into the 3D biofabrication of cellulose-based biomaterials.SCOPUS: re.jinfo:eu-repo/semantics/publishe

New coating formulation for the slow release of urea using a mixture of gypsum and dolomitic limestone

The use of urea and urea-based fertilizers has increased considerably over the past 15 years. They currently account for approximately 51% of the world's agricultural nitrogen consumption. However, about 20–70% of the applied urea fertilizer is lost to the environment, causing serious pollution and increasing costs. These losses come from leaching, decomposition, and ammonium volatilization in the soil during handling and storage. Controlled release by coating can be used to increase urea fertilizer efficiency. We studied the use of gypsum, sulfur, and ground magnesium lime as cost-effective coating materials. All these coating materials contain nutrients required by plants. The effects of the coating composition and proportion of sealant on the rate of urea release and the crushing strength of the coated urea were investigated. We found that coated urea with the same proportion of gypsum–ground magnesium lime (GML) exhibited low urea release and high crushing strength. The performance was enhanced when using polyols as a sealant on the surface of the coated urea. A surface morphology analysis indicated a uniform and smooth surface on the coated film. The efficiency of the coated urea improved by 34.2% when using gypsum–GML (1:1 ratio) containing 1.1% polyols

Effect of catalyst and substrate on growth characteristics of carbon nanofiber onto honeycomb monolith

Carbon nanofiber coated monolith with a homogeneous and consistent layer was prepared by catalytic decomposition of benzene on iron catalyst. A comparative study was carried out on carbon nanofiber growth onto bare monolith, acid modified monolith and wash-coat alumina monolith. The catalyst was prepared by dip-coating the monolith into an iron-salt solution with different concentrations (0.1-0.3 g/mL), dried, and calcined at 500 °C. It was found that the concentration of catalyst controlled Fe particles dispersion, which in turn was responsible for the catalytic activity. Lower iron concentration loaded monolith showed higher bulk density of nanofibers growth compared with higher concentration of iron solution used. The results demonstrated that after treatment with nitric acid, the surface area of cordierite monoliths could be increased to values as high as 30.6 m2/g. Intertwined bundles of carbon nanofibers grown by this pre-treatment formed of a wide range of diameter sizes with tree like morphology. In addition, wash-coat materials such as alumina, utilized to increase the specific surface area and to distribute the catalyst on the surface of the monolith. The deposition of alumina wash-coat layer caused the iron (Fe) to appear more homogeneously distributed after drying and calcination, indicating Fe-0.2-Al2O3/monolith to be a superior support to grow CNFs compared to other substrates

Biosorption of azoimide on almond integument: Kinetics, isotherm and thermodynamics studies

Hospital effluents are a serious problem in waterways due to azoimide that provides physical and health hazards. The removal of azoimide using powdered almond integument was studied in batch mode. Hydroxyl, carbonyl and carboxyl on the biosorbent surface were measured by titration method. The biosorption of azoimide was found to depend on the initial concentrations, pH and contact time. The equilibrium data was analyzed by using a non-linear form of Langmuir, Freundlich, Toth and Redlich-Peterson isotherm models. The fitness of data was evaluated using three error functions and correlation coefficient value (R 2). The error analysis showed three parameters models described the best biosorption in comparison of two parameters models such as Langmuir and Freundlich. The pseudo-first order, pseudo-second order and Elovich kinetic models were applied to study the kinetic behavior, and revealed applicability of the pseudo-second order model. The evaluation of thermodynamic parameters showed that biosorption process was endothermic and spontaneous. © 2013 Elsevier Ltd. All rights reserved.info:eu-repo/semantics/publishe