Showing papers on "Ammonium hydroxide published in 2021"

Influence of Ammonia Stripping Parameters on the Efficiency and Mass Transfer Rate of Ammonia Removal

Abstract: This study analyzed the influence of different ammonia stripping parameters on ammonia removal efficiency and mass transfer rate. Ammonia stripping was performed on two devices, a column and a packed tower, with artificial ammonium hydroxide wastewater. First, ammonia concentration and pH were varied in a column without liquid circulation. At the same pH, the removal efficiency and mass transfer rate were constant, irrespective of initial ammonia concentration. When pH was increased, the ammonia fraction also increased, resulting in higher removal efficiency and mass transfer rate. Second, the effects of stripping were assessed using a packed tower with fluid circulation. The ammonium hydroxide concentration did not affect the removal efficiency or mass transfer rate. Furthermore, at apparatus liquid-gas ratios of 26.8–107.2 L/m3, a lower liquid-gas ratio led to increased ammonia removal efficiency and mass transfer rate. Conversely, the lower the liquid-gas ratio, the greater the air consumption. In conclusion, considering the removal rate and volume of air supply, the range of optimal liquid-gas ratio was determined as 26.8–53.6 L/m3. In particular, the 26.8 L/m3 condition achieved the best ammonia removal rate of 63.0% through only 6 h of stripping at 70 °C and pH 8.5.

Significant improvement in antibacterial property of ZIF-8 decorated graphene oxide by post-synthetic modification process

Abstract: The effects of different ammonium hydroxide loadings towards morphological and antibacterial properties of ZGO composites in a straightforward post synthetic-modification were comprehensively investigated. Fourier Transform Infrared Spectroscopy (FTIR) result indicated a successful modification of ZGO with amine due to the existence of the N–H group, with minor changes in their crystal structure. Antibacterial activities were tested using Escherichia coli and Staphylococcus aureus as model strains of Gram-negative and Gram-positive bacteria, respectively, using disc diffusion (DDT) and minimum inhibitory concentration (MIC) test. The modified sample showed significant improvement against both bacteria. The best antibacterial activity was observed in ZGO-NH 20 with MIC values of 5 and 25 times lower than those of ZIF-8 and ZGO, respectively. Different mechanisms of bacterial death were proposed based on the FESEM images of the two bacteria after contact with the synthesized nanocomposites.The functionalization of ZGO with ammonium hydroxide significantly improved the antibacterial effect of the modified sample, depending on the loading volume of ammonium hydroxide used during modification. Overall, the synergistic effects of amine groups and metal zinc (Zn) in the ZGO-NH composites developed in this work may have tremendous potential as a beneficial antibacterial agent in the areas of water purification and biological applications.

Evaluation of Na-13X zeolites activity in the catalytic pyrolysis of rapeseed oil cake to produce bio-oil

Abstract: Zeolite with cavities (Na-13XCAV) was obtained by treating of a commercially Na-13X zeolite with tetrapropyl ammonium hydroxide aqueous solution (TPAOH, 03 mol/L) In addition, to generate secondary mesopores in the zeolite network (Na-13XCAV-SM), the Na-13X zeolite was treated with a mixture solution of TPAOH/NaOH (ratio 1:1) The charaterization of the zeolites was performed by N2 sorption, X-ray diffraction spectroscopy and scanning electron microscopy Na-13XCAV-SM showed a higher selectivity and was effective for increasing the hydrocarbon content in bio-oil, it was obtained a hydrocarbon yield of 68 wt %, which was over three times bigger than that resulted with Na-13 × The properties of bio-oil produced were determined and a comparison of the properties depending on the catalyst used was made In the presence of secondary mesopores,the diffusion of intermediates compounds became faster and their re-polymerization reactions were slowed down, thus, the resulting amount of coke was reduced and bio-oil fraction increased

Chemical synthesis of orthorhombic Ag8SnS6/zinc oxide nanorods photoanodes for photoelectrochemical salt-water splitting

Abstract: Orthorhombic Ag8SnS6/ZnO nanorods grown onto indium-tin-oxide conductive glass substrates were prepared using a simple chemical synthesis method for the application in photoelectrochemical salt-water splitting. For the deposition of ZnO nanorods on substrates, the concentrations of ammonium hydroxide in the solution bath were changed to obtain the pristine ZnO nanorods with good morphology for the growth of silver-tin-sulfide layer. Pristine ZnO nanorods prepared with concentration of 5.5 M for ammonium hydroxide in the reaction solution has the highest intensity of (0 0 2) crystal plane, which indicates that pristine ZnO nanorods sample has good morphology for the preparation of the Ag8SnS6 core/shell photoanode. From the results of X-ray diffraction patterns and energy-dispersive X-ray spectroscopy analysis for samples, with decreasing [Ag]/[Ag + Sn] molar ratio in the reaction solution, crystal phases of samples changed from Ag2S/SnS/ZnO, orthorhombic Ag8SnS6/ZnO to Ag8SnS6/SnS/ZnO mixing phases. The values of sample’s energy band gap were located in the range of 1.36 ~ 1.79 eV. At the [Ag]/[Ag + Sn] molar ratio of 0.4 in the reaction solution, the maximum photoelectrochemical activity of 0.79 mA cm−2 for samples was obtained with the external bias set at + 1.5 V vs. an Ag/AgCl electrode in 0.5 M NaCl aqueous solution. The photoelectrochemical activity of sample could remain at least 2000 s without any decay in the salt-water solution.

Synthesis of magnetic core-shell amino adsorbent by using uniform design and response surface analysis (RSM) and its application for the removal of Cu 2+ , Zn 2+ , and Pb 2+

Abstract: The magnetic Fe3O4 was synthesized by using a one-step solvothermal method. Then, anhydrous ethanol as a solvent, tetramethyl ammonium hydroxide (TMAOH) as an auxiliary agent, tetraethyl orthosilicate (TEOS) as a silicon source, and (3-aminopropyl) triethoxysilane (APTES) as amino source were used to prepare Fe3O4@mSiO2-NH2 by using the sol-gel method. Uniform design U14*(145) and the response surface method (RSM) were used to optimize the synthesis ratio. According to the results of TEM, SEM, N2 adsorption–desorption test, VSM, and XRD, it found that the best coating effect obtained when the relative molar ratio of TMAOH:TEOS:APTES:Fe3O4 was 5:4:6:0.45. The results of EDS and elemental analysis confirmed the success of amino group coating; VSM magnetization after surface modification was 32 emu/g; BET results show that specific surface area is 236 m2/g, size 5 nm, and the pore volume is 0.126 cm3/g. The removal of Cu2+, Zn2+, and Pb2+ by Fe3O4@mSiO2-NH2 was studied at the optimal initial pH value 6 of the adsorption test system. The isothermal adsorption results show that the Langmuir model and Redlich–Peterson model are more suitable than the Freundlich model to describe the adsorption behavior, and Cu2+, Zn2+, and Pb2+ adsorption is mainly single molecular layer. The maximum adsorption capacity qm of the Langmuir model for Cu2+, Zn2+, and Pb2+ removal was 48.04 mg/g, 41.31 mg/g, and 62.17 mg/g, respectively. The adsorption kinetic rates of Cu2+, Zn2+, and Pb2+ on Fe3O4@mSiO2-NH2 relatively more suitable for pseudo-second-order kinetic model, i.e., R2, were ranged between 0.995 and 0.999, and the suitable reaction time was 60 min. These results proved that Fe3O4@m-SiO2-NH2 prepared by using this method is easy to synthesize, has easy recovery, is ecofriendly, and can be potential adsorbent for Cu2+, Zn2+, and Pb2+ removal.

Exploitation of ammonia-inducible promoters for enzyme overexpression in Bacillus licheniformis.

Abstract: Ammonium hydroxide is conventionally used as an alkaline reagent and cost-effective nitrogen source in enzyme manufacturing processes. However, few ammonia-inducible enzyme expression systems have been described thus far. In this study, genomic-wide transcriptional changes in Bacillus licheniformis CBBD302 cultivated in media supplemented with ammonia were analyzed, resulting in identification of 1443 differently expressed genes, of which 859 genes were upregulated and 584 downregulated. Subsequently, the nucleotide sequences of ammonia-inducible promoters were analyzed and their functionally-mediated expression of amyL, encoding an α-amylase, was shown. TRNA_RS39005 (copA), TRNA_RS41250 (sacA), TRNA_RS23130 (pdpX), TRNA_RS42535 (ald), TRNA_RS31535 (plp), and TRNA_RS23240 (dfp) were selected out of the 859 upregulated genes and each showed higher transcription levels (FPKM values) in the presence of ammonia and glucose than that of the control. The promoters, PcopA from copA, PsacA from sacA, PpdpX from pdpX, Pald from ald, and Pplp from plp, except Pdfp from dfp, were able to mediate amyL expression and were significantly induced by ammonia. The highest enzyme expression level was mediated by Pplp and represented 23% more α-amylase activity after induction by ammonia in a 5-L fermenter. In conclusion, B. licheniformis possesses glucose-independent ammonia-inducible promoters, which can be used to mediate enzyme expression and therefore enhance the enzyme yield in fermentations conventionally fed with ammonia for pH adjustment and nitrogen supply.

A New Process for the Recovery of Ammonia from Ammoniated High-Salinity Brine

Abstract: This paper describes a new method for the recovery of high-concentration ammonia from water in the form of ammonium chloride, ammonium hydroxide and ammonium carbonate. The method was applied to the Solvay process, in which sodium bicarbonate is produced through the reaction of ammoniated brine and CO2 gas. The Solvay effluent contains ammonia in the form of soluble ammonium chloride. The proposed method is based on the recovery of ammonia using a high-alkalinity reactant, calcium oxide (CaO), in a closed electrocoagulation cell operating at a specific current density. The recovered ammonia is collected as a gas within a closed cell containing deionized (DI) water at room temperature. Afterwards, the collected solution (DI water–NH3 gas) is concentrated through a separate process, and is then reused in the Solvay process and other applications. The electrocoagulation process is applied to the treatment cell using aluminum electrodes and a current density of 5–15 mA/cm2. After 7 h of treatment using the electrocoagulation cell, a high reduction of the ammonia concentration—99%—was realized after ~9 h of the electrochemical treatment. The initial ammonia concentration in a Solvay effluent of 13,700 mg/L N was decreased to 190 mg/L N. Furthermore, an ammonia recovery of 77.1% in the form of ammonium hydroxide was achieved. Generally, this process, which starts at room temperature, can result in an energy reduction of 80%—from 7.8 to 2.3 kWh/kg NH3—compared to conventional processes, which entail heating the Solvay effluents to 160 °C. The proposed system and method were found to be suitable for the recovery of ammonia from ammoniated water, and can be utilized for the treatment of landfill leachate, and municipal and industrial wastewater.

Conversion of CO2 into cyclic carbonate catalyzed by an N-doped mesoporous carbon catalyst

Abstract: N-Doped mesoporous carbon spheres (N-MCSs) had been synthesized through a dissolve–reassemble pathway using ammonium hydroxide as both the nitrogen source and base catalyst. The BET surface area and pore volume of the N-MCSs were measured to be 1341 m2 g−1 and 1.47 cm3 g−1, respectively. The analysis results of XPS and CO2-TPD indicated that the N element was successfully doped in the carbon matrix and provided basic sites to the N-MCSs. It was an effective, mono-component, halogen- and metal-free catalyst for the cycloaddition of CO2 with epichlorohydrin, and the TOF could reach 236 h−1. The high catalytic activity of N-MCS800 was ascribed to the synergistic effect of the specific surface area and pyridine nitrogen. More importantly, N-MCS materials had good stability and reusability.

Purification of thorium by precipitation

Abstract: A precipitation method was applied to produce high-purity thorium product from industrial grade Th(NO3)4·4H2O. The conditions of pH in the thorium solution, the contents of hydrogen peroxide, calcination temperature were investigated as well as calcination time. The hydrogen peroxide of 30% (v:v) was added into the thorium solution and was continually stirred. The concentration of hydrogen peroxide was exceeded over 0.1–0.5 mol/L after suitable reaction between Th(NO3)4·4H2O and hydrogen peroxide. The pH of the solution was maintained at 2 through adding ammonium hydroxide. The precipitation obtained in the form of Th2O7·4H2O. The high-purity thorium product was prepared after calcination for 2 h at 700 °C. The purity of the purified thorium product was above 99.8%.

The effect tetra butyl ammonium hydroxide and tween on the kinetics of carbon dioxide hydrate formation

Abstract: In this research, the kinetics of CO2 hydrate formation in the presence and absence of TBAOH as a thermodynamic additive and tween as a kinetic additive is investigated. A high-pressure autoclave e...

Gradual Replacement of Ca2+ with Mg2+ Ions in Brushite for the Production of Ca1−xMgxHPO4·nH2O Materials

Abstract: The present study investigates the gradual replacement of Ca2+ with Mg2+ ions in brushite (CaHPO4·2H2O). To date, this approach has not been systematically explored and may prove beneficial for the production of Ca1−xMgxHPO4·nH2O materials with tailored properties which are suitable for environmental and medical applications. For their production, solutions of sodium dihydrogen orthophosphate dehydrate, NaH2PO4·2H2O, calcium nitrate tetrahydrate, Ca(NO3)2·4H2O, magnesium nitrate hexahydrate, Mg(NO3)2·6H2O and ammonium hydroxide solution, NH4OH, were used. At low Mg/Ca molar ratios (up to 0.25) in the starting solution, partial replacement of Ca with Mg takes place (Mg doping) but no struvite is produced as discrete phase. When the Mg/Ca molar ratio increases gradually to 1.5, in addition to Mg-doped brushite, struvite, NH4MgPO4·6H2O, precipitates. The microstructure of the materials produced for different degrees of Ca replacement with Mg has been analyzed in depth with the use of powdered XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy), thermogravimetric (TG) analysis and SEM (scanning electron microscopy). The results of this study prove that the Mg/Ca ratio in the starting solution can be monitored in such a way that materials with tailored composition are obtained.

The Comparison between Magnetite Nanoparticles Co-Precipitated by Different Bases and Their Effects on Human Cells

Abstract: The superparamagnetic magnetite nanoparticles were synthesized through co-precipitation method by using a strong base such as sodium hydroxide or a weak base such as ammonium hydroxide. The magneti...

A new polymorph of HMTD

Abstract: While exploring the synthesis pathway of HMTD, an unexpected new route for preparing HMTD was found through the reaction of formaldehyde, hydrogen peroxide, and ammonium hydroxide. The recovered HM...

Fabrication and characterization of robust zirconia-kaolin hollow fiber membrane: Alkaline dissolution study in ammonia solution

Abstract: Kaolin has been found to be a more economical alternative in ceramic hollow membrane fabrication compared to alumina, silica, and zirconia despite having similar properties. However, it was discovered that apart from having high mechanical strength and the ability to withstand high operational temperature, the kaolin membrane has the tendency to dissolve in a high alkaline solution. Hence, in this study, zirconia (ZrO2) was imposed to kaolin suspension as co-starting material due to its stable hexagonal properties with kaolin to overcome this drawback. To study the dissolution property of the modified kaolin-based membrane, a phase inversion technique was used to fabricate zirconia-kaolin hollow fiber membrane (ZKHFM) followed by immersion in ammonium hydroxide (NH4OH) as an alkaline solution. Ammonia was aptly chosen for it being considered as one of the pollutants to be removed from wastewater. The mechanism, morphology and properties of the membrane were investigated in terms of sintering temperature, morphology, mechanical strength, pore size and porosity The results showed that ZKHFM with 10 wt% (ZK-10) with sintering temperature of 1,200 °C had the best performance in terms of having high mechanical strength (21MPa), excellent permeation flux (∼1,600 Lm2/h) and lowest dissolution (0.01 g dissolute) at pH 13, indicating the ability of ZKHFM to be used in alkaline solution.

Investigating the Effects of Surface Adsorbates on Gold and Palladium Deposition on Carbon

Abstract: Surface functional groups have a strong influence on the deposition and final state of nanoparticles adsorbed on to the surface, a role discussed by Professor Spencer in his work. This tribute to Spencer explores the formation of hydroxyls, thiosulfates, sulfites and sulfur atoms on carbon (HOPG) surfaces and their effect on the deposition of gold and palladium from aqueous solutions. Hydroxyls formed from ammonium hydroxide treatment have identical behaviour to those formed by acid treatment, and gold adsorption from Au3+ solutions gives Au0 initially, with Au3+ formed at higher concentrations on these surfaces. In contrast, palladium adsorption is hindered by the presence of the hydroxyls and there is no indication of any reduction to the metallic state. Ammonium thiosulfate adsorbs dissociatively from aqueous solutions on HOPG if the surface is pre-activated by the presence of surface hydroxyls. At low concentrations of ammonium thiosulfate, adsorbed sulfite and sulfur are formed in equimolar concentrations whereas adsorption of high concentrations of ammonium thiosulfate gives some degree of molecular adsorption, with evidence in XP spectra for an ammonium ion and a sulfur 2p peak at 282.9 eV attributed to the undissociated thiosulfate ion. Both sulfur and the sulfite are stable at the surface in neutral solutions but the sulfite desorbs when treated with acidified solutions (~ pH ≤ 6). These two groups are also stable at 373 K but begin to desorb by 473 K. Exposure to a weak chloroauric acid solution causes the desorption of the sulfite and formation of a gold species with an XP binding energy of 84.6 eV; we cannot determine from the present data whether this peak is due to a Au(I) state or very small nanoparticles of Au(0).

Investigation of surfactant effect during synthesis of magnesium oxide nanoparticles from bittern using ultrasonic destruction process

Abstract: Magnesium oxide (MgO) nanoparticles have been widely used in a variety of applications because of their good surface reactivity. Magnesium oxide from bittern has a larger surface area compared to magnesium oxide from calcined magnesite and magnesium ions precipitation from bittern using sodium hydroxide has higher purity than using calcium hydroxide or ammonium hydroxide. In this research, sodium hydroxide was added to a bittern solution obtaining magnesium hydroxide precipitate, followed by the calcination process to produce magnesium oxide. Nano magnesium oxide was synthesized by the ultrasonic destruction process using ethanol and 2-propanol as media. In this study, sonication time and particle concentration effect on the ultrasonic destruction process were investigated. During the process, the sonication time was varied between 8, 16, 32, 64, and 128 minutes while the magnesium oxide concentration was varied between 1 %, 2 %, and 3 %. Increasing sonication time and particle concentration will decrease the particle size. The previous study shows that particles with very small sizes tend to have an agglomeration effect. The aim of this work is to optimize nano magnesium oxide production from bittern. Surfactant addition was also studied to prevent agglomeration between particles. Four types of surfactant namely anionic (sodium lauryl sulfate), cationic (cetyl tri-methyl-ammonium bromide), amphoteric (fatty acid amido alkyl betaine), and non-ionic (nonylphenol 10 ethoxylated) with a concentration of 1 % and a volume of 0.125 ml were added during the second ultrasonic destruction process. All types of surfactants have a positive effect to prevent agglomeration during the ultrasonic destruction process, with the amphoteric surfactant having the highest performance