Stoichiometric Molar Ratio Research Articles

Inorganic Salts as Chemical Foam Suppressors

Can the foamability of surfactant aqueous solutions be controlled chemically? Well-known antifoams can prevent foaming by inducing the coalescence of the bubbles, but can the surfactants be deactivated chemically? If yes, how does this affect the surface tension of their aqueous solutions and their foaming capacity? To shed a light on these fundamental questions, we chose a well-known surfactant containing in its molecule a sulfate group (Sodium dodecyl sulfate, SDS) and mixed it with BaCl2, (the solubility of BaSO4 is 0.245 mg/100 mL water, T = 20 °C), Pb(NO3)2 (the solubility of PbSO4 is 40.4 mg/100 mL water, T = 25 °C) and FeCl3 (the solubility of Fe2(SO4)3 is 25.6 g/100 mL water, T = 20 °C) at different molar ratios (MXn/SDS): 1/2, 1/1, 2/1, 4/1. The results were surprising: in the case of BaCl2, despite being in stoichiometric molar ratio with SDS (BaCl2 + 2SDS -> Ba(DS)2 + 2 NaCl), or in excess of BaCl2, which should convert the whole amount of SDS into a sediment, the surface tension value remained significantly lower than that of the single surfactant. At the same time, foamability was either low or absent. It therefore appears that all of the surfactants should be converted into a sediment with very small solubility, but the low surface tension indicates the opposite. The lack of foamability indicated the opposite of that opposite. With Pb(NO3)2 and FeCl3, the results are even stranger. The surface tension values are substantially smaller than those of the single surfactants, and at the same time, low foamability or lack of foamability was observed. It appears that the surfactant exists and at the same time does not exist in the aqueous solution. Where is the truth? Future studies will shed a light.

CeO2-conjugated CoFe layered double oxides as efficient non-noble metal catalysts for NH3-decomposition enabling carbon-free hydrogen production

CeO2-conjugated Co1.5Fe1.5 LDOs were synthesized through a one-pot co-precipitation method of Ce-introduced Co1.5Fe1.5 LDHs and their thermal treatment. By manipulating the stoichiometric molar ratio of Ce/(Co + Fe), a series of Cex-Co1.5Fe1.5 LDOs (x = 0.05, 0.1. 0.2, 0.5, and 1, corresponding to the molar ratio for the sum of Co and Fe) was comprehensively characterized to investigate the intricate interplay among factors such as spinel mixed metal oxides, LDH-derived LDOs, and the introduced Ce to achieve high catalytic performance in NH3 decomposition. Notably, Ce0.2-Co1.5Fe1.5 LDOs exhibited remarkable activity, achieving an NH3 conversion of 81.9 % at 450 °C and a WHSV of 6,000 mLNH3 gcat-1h−1, and maintained excellent NH3-conversion with a negligible decrease over 80 h of continuous operation at 550 °C and high WHSV of 30,000 mLNH3 gcat-1h−1. The synergistic interaction between the incorporated CeO2 and Co1.5Fe1.5 LDOs induced modifications of structural properties including the distribution of Co and Fe within the spinel crystal structure, as well as affecting the lattice parameters and electronic properties. These modifications play a pivotal role in ultimately altering metal-N binding energy, which facilitates the efficient activation of absorbed NH3 at the lowest temperature and minimizes the delay in recombinative N2-desorption. Hence, this study aims to highlight a new concept and demonstrate its feasibility for fabricating cost-effective and high-performing catalysts at mild temperatures to meet the growing demand for NH3 as a hydrogen carrier.

Synergy of Rh Nanoparticles With Fe3O4 for Efficient Selective Catalytic Transfer Hydrogenation of Nitrostyrenes Using Stoichiometric Hydrazine Hydrate

ABSTRACTHydrazine hydrate as a hydrogen source has a good effect on nitro reduction, but overuse has environmental toxicity and is prone to over‐hydrogenation, resulting in low selectivity. Herein, we report a magnetically separable Rh/Fe3O4 (1.26 wt%) catalyst containing an optimal Rh content that can completely convert 3‐nitrostyrene to 3‐vinylaniline (> 99% selectivity) using a stoichiometric molar ratio of hydrazine hydrate (‐NO2:N2H4·H2O = 1:1.5). This is due to the synergy between Rh and Fe3O4 and the natural selectivity of N2H4·H2O for nitro. The synergy can reduce the activation energy of the reaction (36.6 kJ/mol), increasing the reduction rate of nitro group and avoiding the combination of active hydrogen species (H*) to H2 as well as the hydrogenation of N2H4 to NH3. Moreover, the active H* produced by N2H4·H2O is different from that produced by H2, and excess dose of N2H4 will inevitably yield H2 thus decline the selectivity.

In situ arsenic immobilization by natural iron (oxyhydr)oxide precipitates in As–contaminated groundwater irrigation canals

Arsenic-contaminated groundwater is widely used in agriculture. To meet the increasing demand for safe water in agriculture, an efficient and cost-effective method for As removal from groundwater is urgently needed. We hypothesized that Fe (oxyhydr)oxide (FeOOH) minerals precipitated in situ from indigenous Fe in groundwater may immobilize As, providing a solution for safely using As-contaminated groundwater in irrigation. To confirm this hypothesis and identify the controlling mechanisms, we comprehensively evaluated the transport, speciation changes, and immobilization of As and Fe in agricultural canals irrigated using As-contaminated groundwater. The efficiently removed As and Fe in the canals accumulated in shallow sediment rather than subsurface sediment. Linear combination fitting (LCF) analysis of X–ray absorption near edge spectroscopy (XANES) indicated that As(V) was the dominant As species, followed by As(III), and there was no FeAsO4 precipitate. Sequential extraction revealed higher contents of amorphous FeOOH and associated As in shallower sediment than in the subsurface layer. Stoichiometric molar ratio calculations, SEM‒EDS, FTIR, and fluorescence spectroscopy collectively demonstrated that the microbial reductive dissolution of amorphous FeOOH proceeded via reactive dissolved organic matter (DOM) consumption in subsurface anoxic porewater environment facilitating high labile As, whereas in surface sediment, the in situ-generated amorphous FeOOH was stable and strongly inhibited As release via adsorption. In summary, groundwater Fe2+ can efficiently precipitate in benthic surface sediment as abundant amorphous FeOOH, which immobilizes most of the dissolved As, protecting agricultural soil from contamination. This field research supports the critical roles of the phase and reactivity of in situ-generated FeOOH in As immobilization and provides new insight into the sustainable use of contaminated water.

Investigation of iron oxide supported on activated coke for catalytic reduction of sulfur dioxide by carbon monoxide

In view of the low utilization rate of by-product in limestone-gypsum wet flue gas desulfurization process, a method of catalytic reduction of SO2 to elemental sulfur was proposed. In this work, supported iron catalyst using activated coke as supporter was prepared and characterized. Moreover, the performance of SO2 reduction using CO as reducing agent at various Fe loadings, temperatures, gaseous hourly space velocities and CO/SO2 molar ratios was studied. Research shows that, compared with other metals, the highest catalytic activity is achieved over Fe-based catalyst. The iron sulfide is the main active component during the catalytic reduction reaction, hence the catalyst needs to be presulfided before use. The micropores of activated coke become more abundant after loading Fe, whereas excessive increase of Fe loading may bloke the mesopores and weaken the catalytic activity. Higher reaction temperature, lower GHSV and a stoichiometric molar ratio are conducive to the improvement of SO2 conversion and S yield. The catalytic performance at lower temperatures was further improved by loading Co. When the Co loading is 4 wt%, the SO2 conversion rate reaches 90.9% at 400 °C because loading Co enhances the redox performance of the catalyst surface. The findings are instructive for the development of cost-effective carbon-based catalysts for resource recovery of sulfur.

Development of lipid-based SEDDS using digestion products of long-chain triglyceride for high drug solubility: Formulation and dispersion testing

A self-emulsifying drug delivery system (SEDDS) containing long chain lipid digestion products (LDP) and surfactants was developed to increase solubility of two model weakly basic drugs, cinnarizine and ritonavir, in the formulation. A 1:1.2 w/w mixture of glyceryl monooleate (Capmul GMO-50; Abitec) and oleic acid was used as the digestion product, and a 1:1 w/w mixture of Tween 80 and Cremophor EL was the surfactant used. The ratio between LDP and surfactant was 1:1 w/w. Since the commercially available Capmul GMO-50 is not pure monoglyceride and contained di-and-triglycerides, the digestion product used would provide 1:2 stoichiometric molar ratio of monoglyceride and fatty acid after complete digestion in gastrointestinal fluid. Both cinnarizine and ritonavir had much higher solubility in oleic acid (536 and 72 mg/g, respectively) than that in glyceryl monooleate and glyceryl trioleate. Therefore, by incorporating oleic acid in place of glyceryl trioleate in the formulation, the solubility of cinnarizine and ritonavir could be increased by 5-fold and 3.5-fold, respectively, as compared to a formulation without the fatty acid. The formulation dispersed readily in aqueous media, and adding 3 mM sodium taurocholate, which is generally present in GI fluid, remarkably improved the dispersibility of SEDDS and reduced particle size of dispersions. Thus, the use of digestion products of long-chain triglycerides as components of SEDDS can enhance the drug loading of weakly basic compounds and increase dispersibility in GI fluids.

Mechanochemical Synthesis of Dolomite-Related Carbonates—Insight into the Effects of Various Parameters

The low-temperature formation of dolomite (CaMg(CO3)2) is undoubtedly a long and interesting geological problem, which has troubled many researchers for centuries to explore the formation of dolomite. Recently, efforts have been made by synthesizing dolomite analogues such as norsethite (BaMg(CO3)2), PbMg(CO3)2, with Ba and Pb to replace Ca and investigating their reaction pathways. In this study, we reported our efforts to synthesize dolomite-related complex carbonates by using the mechanical ball milling method as a new approach to control the solid–water ratio compared to the commonly used solution method. Two analogues of norsethite and PbMg(CO3)2 have been simply obtained even at stoichiometric molar ratio of Ba/Mg = 1:1 and Pb/Mg = 1:1 with various parameters examined; and product properties including morphology and phase compositions were investigated by a range of techniques, including XRD, SEM-EDS, and FTIR. Finally, we attempted to synthesize dolomite and compared the differences from the synthesis of analogues. In conclusion, we have synthesized norsethite and PbMg(CO3)2 in one step by the ball milling method, which greatly reduces the reaction time compared with the conventional solution method and may provide other choices for the formation of dolomite.

Thermal stability of ReB2‐type transition metal diborides

AbstractThe thermal stability of metastable ReB2‐type transition metal diborides (TMB2), which are considered as new type of superhard material, is of vital importance to obtain bulk samples. In the present work, thermal stability of four kinds of ReB2‐type TMB2 powders, ReB2, OsB2, Os1–xRexB2, and Os1‐xWxB2, were synthesized with varied transition metal (TM)‐to‐B molar ratio by mechanochemical methods and the subsequent annealing was compared. The as‐synthesized powders were then consolidated using a pressureless sintering technique. The results showed that the B content required to obtain the pure hexagonal ReB2‐type Os1–x(TM)xB2 phase varied, which indicated different thermal stabilities, such as OsB2 < Os0.1W0.1B2 < Os0.9Re0.1B2 < Os0.8W0.2B2 < ReB2 < Os0.6W0.4B2 and Os0.5W0.5B2. Among them, Os0.6W0.4B2 and Os0.5W0.5B2 were found to be relatively thermally stable and could be synthesized with a stoichiometric molar ratio of (Os + W):B = 1:2. It was also found that the thermal stability of TMB2 with a hexagonal ReB2 structure could be mainly governed by the length of lattice constant c. The results have guiding significance for the design and preparation of new type of TM borides. In addition, the hardness of TMB2 can be increased by tailoring the B content in the raw materials more precisely.

Comparative Study of Sorbents for Spray Dry Scrubbing of SO2 from Flue Gases.

This study presents the findings of an investigation involving the absorption of SO2 from flue gases, using three different sorbents, in a spray dryer. Experimentation involved the evaluation of three sorbents, i.e., hydrated lime (Ca[OH]2), limestone (CaCO3), and trona (Na2CO3·NaHCO3·2H2O), and their relevant properties, for flue gas desulfurization by spray dry scrubbing. Experiments were conducted to explore the effects of spray characteristics in the spray drying scrubber on SO2 removal efficiency using the selected sorbents. The ranges of various operating parameters were considered, including the stoichiometric molar ratio of (1.0-2.5), the inlet gas phase temperature of (120-180 °C), and an inlet SO2 concentration of 1000 ppm. The use of trona gave better SO2 removal characteristics; a high SO2 removal efficiency of 94% was recorded at an inlet gas phase temperature of 120 °C and a stoichiometric molar ratio of 1.5. Under the same operating conditions, Ca[OH]2 and CaCO3 gave 82 and 76% SO2 removal efficiency, respectively. Analysis of the desulfurization products by X-ray fluorescence (XRF) and Fourier transform infrared (FTIR) spectroscopy revealed the presence of CaSO3/Na2SO3, a product of the semidry desulfurization reaction. A significant proportion of unreacted sorbent was observed when Ca[OH]2 and CaCO3 sorbents were used at a stoichiometric ratio of 2.0. Trona also gave the highest degree of conversion (96%) at a stoichiometric molar ratio of 1.0. Ca[OH]2 and CaCO3 gave 63 and 59%, respectively, under the same operating conditions.

Removal of Cl([sbnd]I) from zinc sulfate electrolyte by the porous Bi2O3 rich in OVs: Efficiency and mechanism

During the zinc electrolysis, the concentration of Cl(I) impurity in the zinc sulfate electrolyte needs to be controlled below 100 mg/L. In the promising approach for Cl(I) removal from the zinc sulfate electrolyte by bismuth oxide (Bi2O3), the low efficiency and high reagent dosage, arising from the limited solubility of Bi2O3, are the major technical bottleneck to be solved. In this study, an improved approach for the removal of Cl(I) from zinc sulfate electrolyte by the porous Bi2O3 rich in oxygen vacancies (OVs) was explored. For the common zinc sulfate electrolyte, a high efficiency above 90 % was always obtained under the stoichiometric mole ratio of reagent to Cl(I) under room temperature, when the Bi2O3 being irradiated for 300 min under ultraviolet (UV) was utilized. 98.9 % of the employed Bi2O3 was regenerated after the treatment using sodium hydroxide (NaOH) solution, and thus, Cl(I) was finally transferred from the zinc sulfate electrolyte to the concentrate. Thanks to the improved Bi2O3 dissolution caused by the porous surface and the adsorption of Cl(I) on OVs, the transformation process of inner Bi2O3 to BiOCl can be effectively improved, leading to the significant enhancement in Cl(I) removal efficiency and decrease in reagent dosage.

Efficient removal of p-arsanilic acid and arsenite by Fe(II)/peracetic acid (Fe(II)/PAA) and PAA processes

The widespread occurrence of p-arsanilic acid (p-ASA) in natural environments poses big threats to the biosphere due to the generation of toxic inorganic arsenic (i.e., As(III) and As(V), especially As(III) with higher toxicity and mobility). Oxidation of p-ASA or As(III) to As(V) followed by precipitation of total arsenic using Fe-based advanced oxidation processes demonstrated to be a promising approach for the treatment of arsenic contamination. This study for the first time investigated the efficiency and inherent mechanism of p-ASA and As(III) oxidation by Fe(II)/peracetic acid (Fe(II)/PAA) and PAA processes. p-ASA was rapidly degraded by the Fe(II)/PAA process within 20 s at neutral to acidic pHs under different conditions, while it was insignificantly degraded by PAA oxidation alone. Lines of evidence suggested that hydroxyl radicals and organic radicals generated from the homolytic OO bond cleavage of PAA contributed to the degradation of p-ASA in the Fe(II)/PAA process. p-ASA was mainly oxidized to As (V), NH4+, and p-aminophenol by the Fe(II)/PAA process, wherein the aniline group and its para position were the most vulnerable sites. As(III) of concern was likely generated as an intermediate during p-ASA oxidation and it could be readily oxidized to As(V) by the Fe(II)/PAA process as well as PAA alone. The in-depth investigation demonstrated that PAA alone was effective in the oxidation of As(III) under varied conditions with a stoichiometric molar ratio of 1:1. Efficient removal (> 80%) of total arsenic during p-ASA oxidation by Fe(II)/PAA process or during As(III) oxidation by PAA process with additional Fe(III) in synthetic or real waters were observed, mainly due to the adsorptive interactions of amorphous ferric (oxy)hydroxide precipitates. This study systematically investigates the oxidation of p-ASA and As(III) by the Fe(II)/PAA and PAA processes, which is instructive for the future development of arsenic remediation technology.

Improving Co(II) separation from Ni(II) by solvent extraction using phosphonium-based ionic liquids

The solvent extraction of Co(II) from its aqueous solutions free of acids or chloride salts at high concentration by the ionic liquids trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate ([P66614][C272]) and trihexyl(tetradecyl)phosphonium thiocyanate ([P66614][SCN]) was characterised at saturation of the organic phase with Co(II) using toluene as diluent. The ionic liquids’ cation participated in the formation of two ion-pairs in the organic phase, i.e., one with the complex anion containing cobalt, and the other with the cobalt counter anion, thus preserving electroneutrality in both the organic and aqueous phases. This was considered to be an example of bifurcated extraction.UV–visible spectral studies of the intensively blue organic phase after Co(II) extraction demonstrated that the Co(II) coordination sphere geometry in the case of both extractants was tetrahedral. The Co(II) extraction stoichiometry was experimentally determined for the first time by saturating the organic phase with Co(II). The [P66614][C272] to Co(II) stoichiometric mole ratio in the extracted adduct was found to be 2.8:1, suggesting that eight phosphinate anions acted as bridging ligands around three cobalt centres. For the [P66614][SCN], the stoichiometric mole ratio was found to be 2.5:1 with the Co(II)-thiocyanate adduct consisting of two Co(II)-thiocyanate tetrahedra linked by a bridging thiocyanate ion.The Co(II) extraction was enhanced when the aqueous phase contained an anion with high lipophilicity (e.g., nitrate, thiocyanate). [P66614][SCN] did not extract Ni(II) from nitrate or chloride solutions, thus demonstrating its potential for the separation of Co(II) from Ni(II) without requiring the addition of high concentrations of acids or chloride salts to the aqueous phase.

Nitrate as an alternative electron acceptor destabilizes the mineral associated organic carbon in moisturized deep soil depths.

Numerous studies have investigated the effects of nitrogen (N) addition on soil organic carbon (SOC) decomposition. However, most studies have focused on the shallow top soils <0.2 m (surface soil), with a few studies also examining the deeper soil depths of 0.5-1.0 m (subsoil). Studies investigating the effects of N addition on SOC decomposition in soil >1.0 m deep (deep soil) are rare. Here, we investigated the effects and the underlying mechanisms of nitrate addition on SOC stability in soil depths deeper than 1.0 m. The results showed that nitrate addition promoted deep soil respiration if the stoichiometric mole ratio of nitrate to O2 exceeded the threshold of 6:1, at which nitrate can be used as an alternative acceptor to O2 for microbial respiration. In addition, the mole ratio of the produced CO2 to N2O was 2.57:1, which is close to the theoretical ratio of 2:1 expected when nitrate is used as an electron acceptor for microbial respiration. These results demonstrated that nitrate, as an alternative acceptor to O2, promoted microbial carbon decomposition in deep soil. Furthermore, our results showed that nitrate addition increased the abundance of SOC decomposers and the expressions of their functional genes, and concurrently decreased MAOC, and the ratio of MAOC/SOC decreased from 20% before incubation to 4% at the end of incubation. Thus, nitrate can destabilize the MAOC in deep soils by stimulating microbial utilization of MAOC. Our results imply a new mechanism on how above-ground anthropogenic N inputs affect MAOC stability in deep soil. Mitigation of nitrate leaching is expected to benefit the conservation of MAOC in deep soil depths.

Experimental evaluation of lime spray drying for SO&lt;sub&gt;2&lt;/sub&gt; absorption

&lt;abstract&gt; &lt;p&gt;This paper presents the findings of an experimental investigation on the performance of a laboratory-scale spray dryer involving flue gas desulfurization. Using commercial hydrated lime as a sorbent, a systematic set of experiments were performed to evaluate SO&lt;sub&gt;2&lt;/sub&gt; absorption capacity of the spray dryer. The experimentation involved accurate measurement of the spray drying characteristics, such as temperature and SO&lt;sub&gt;2&lt;/sub&gt; concentration along the spray chamber, by varying the input and output variables. Tests were done to investigate the effects of spray characteristics, i.e., inlet gas phase temperature (120–180 ℃) and calcium-to-sulfur ratio (1–2.5), on SO&lt;sub&gt;2&lt;/sub&gt; removal efficiency. The performance of the spray dryer was further evaluated based on the degree of conversion of calcium (sorbent utilization) after SO&lt;sub&gt;2&lt;/sub&gt; absorption. Results indicated an increase in SO&lt;sub&gt;2&lt;/sub&gt; removal efficiency by increasing the stoichiometric ratio and decreasing the temperature. Absorption efficiency of SO&lt;sub&gt;2&lt;/sub&gt; beyond 90% was achieved at a stoichiometric ratio of 2.5. A high degree of conversion of calcium was realized at low stoichiometric ratios, with a maximum utilization of 94% obtained at a stoichiometric ratio of 1.5. The analysis of the final desulfurization product revealed the presence of sulfite with better conversion achieved at a stoichiometric molar ratio of 1.5. A significant amount of unreacted sorbent (63.43%) was observed at a stoichiometric ratio of 2, while samples collected at a stoichiometric ratio of 1.5 had the lowest concentration of unreacted Ca[OH]&lt;sub&gt;2&lt;/sub&gt; (41.23%).&lt;/p&gt; &lt;/abstract&gt;

RE(III) 3-Furoate Complexes: Synthesis, Structure, and Corrosion Inhibiting Properties.

In this study, two types of Rare Earth (RE) 3-furoate complexes were synthesized by metathesis reactions between RE chlorides or nitrates and preformed sodium 3-furoate. Two different structural motifs were identified as Type 1RE and Type 2RE. The Type 1RE monometallic complexes form 2D polymeric networks with the composition [RE(3fur)3(H2O)2]n (1RE = 1La, 1Ce, 1Pr, 1Nd, 1Gd, 1Dy, 1Ho, 1Y; 3furH = 3-furoic acid) while Type 2RE bimetallic complexes form 3D polymeric systems [NaRE(3fur)4]n (2RE = 2Ho, 2Y, 2Er, 2Yb, 2Lu). The stoichiometric mole ratio used (RE: Na(3fur) = 1:3 or 1:4) in the metathesis reaction determines whether 1RE or 2RE (RE = Ho or Y) is formed, but 2RE (RE = Er, Yb, Lu) were obtained regardless of the ratio. The corrosion inhibition behaviour of the compounds has been examined using immersion studies and electrochemical measurements on AS1020 mild steel surfaces by a 0.01 M NaCl medium. Immersion test results revealed that [Y(3fur)3(H2O)2]n has the highest corrosion inhibition capability with 90% resistance after 168 h of immersion. Potentiodynamic polarisation (PP) measurements also indicate the dominant behaviour of the 1Y compound, and the PP curves show that these rare earth carboxylate compounds act predominantly as anodic inhibitors.

Optimization of effective parameters in arsenite oxidation process with Cl2, H2O2, and O3 using response surface methodology

This study explores a comprehensive study on the effective parameters in As(III) oxidation process with the high initial concentration of 5 mg/L by using of H2O2, O3, and Cl2 oxidants. For this purpose, As(III) oxidation process was successfully optimized using a Box–Behnken design with response surface methodology (RSM). A three-level-four-variable design was applied with three numerical factors including oxidant dosing (1, 2 and 3 times the stoichiometric molar ratio), pH (6, 7 and 8), time (1, 5 and 10 min), and oxidant type (H2O2, O3, and Cl2). Oxidation results showed the highest percentage of As(III) oxidation at zero levels of oxidant dosing, pH, and time variables were achieved by Cl2 oxidant compared to O3 and H2O2 oxidants. According to factors F-values, time, oxidant type, and oxidant dosing factors are the most effective factors on As(III) oxidation efficiency, respectively and pH factor and its interactions indicated the slight effects. The optimal oxidation conditions were oxidant dosing of 1.89 ratio, pH= 7.75, t=4.06 min by Cl2 oxidant causing complete As(III) oxidation. Finally, validation of the proposed optimal conditions for As(III) oxidation was investigated by conducting the oxidation process under the optimal conditions with real well water sample with a specific As(III) concentration of 5 mg/L, yielding an oxidation efficiency of 99.8% and 99.5%, respectively. The findings provide new insight into superior efficiency of Cl2 compared to H2O2 and O3 oxidants in oxidation of As(III) as an effective approach to solve the low removal efficiency problem of As(III).

Effects of p-sulfonatocalixarene and p-sulfonatocalixarene/sulfobetaine surfactant complex on the activities of bromelain and polyphenol oxidase

Calixarene is a third-generation supra-molecular compound and has broad application prospects in clinical disease diagnosis and intervention treatment. Calixarene/surfactant systems have received increasing attention recently because the properties of these systems can be customized. However, very little is currently known about the binding of calixarene and calixarene/surfactant systems to proteins and the effects of calixarene and calixarene/surfactant systems on protein activity. In this study, we studied the binding of sulfonatocalix[n]arene (SC[n], n = 4, 6 and 8) with bromelain (BM) and polyphenol oxidase (PPO) both in the absence and presence of sulfobetaine surfactant (N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SDDAB)) using various techniques, including protein activity measurements, molecular simulation, and fluorescence, UV–Vis, 1H NMR, and circular dichroism spectroscopies. We found that SC[n] entered the docking pocket of the proteins in a stoichiometric molar ratio of 1:1, whereas the proteins did not enter the cavity of SC[n]. In addition, SC[n] formed a stronger bond with BM than with PPO. SC[n] decreased the activities of the proteins, where the activity of BM was inhibited to a greater extent than that of PPO. SC[n] and SDDAB formed complexes. The proteins did not destroy the binding between SC[n] and SDDAB but bonded with the SC[n]/SDDAB complex instead by interacting with SDDAB. Moreover, the protein activities could be controlled by the molar ratio of SC[n] to the surfactant: a lower ratio corresponded to higher activity.

Mo2N as a high-efficiency catalyst for transfer hydrogenation of nitrobenzene using stoichiometric hydrazine hydrate

A straightforward and commonly-used approach of direct pyrolysis for the preparation of molybdenum nitride (Mo2N) is conducted via reduction of MoO3 under ammonia atmosphere. The as-synthesized Mo2N catalyst demonstrated high activity for transfer hydrogenation of nitrobenzene, giving a 99% aniline yield at near-room temperature of 30 °C within only 50 min. More significantly, the amount of the hydrogen donor hydrazine monohydrate (N2H4·H2O) can be limited to stoichiometric molar ratio (-NO2: N2H4·H2O = 1: 1.5), preventing the possible generation of hazardous NH3, which is seldom reported in previous protocols. Through various characterizations and control experiments, conclusively, the remarkable catalytic performance of Mo2N catalyst should be credited to the large quantity of Lewis-acidic Mo sites. This research might provide a practical approach to aromatic amines production.

Purification of zinc sulfate solutions from chloride ions using bismuth hydroxosulfate

ABSTRACT An efficient, simple and lowcost method for purification of zinc sulfate solutions from chloride ions by precipitation with bismuth hydroxosulfate BiOHSO4∙H2O was proposed. Chemical analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to characterize the solid obtained. The studied parameters were reaction temperature, pH, concentrations of zinc sulfate and chloride, and the molar ratio between BiOHSO4∙H2O and chloride. Under optimal conditions, the chloride removal efficiency reached 94.5–95.8% and the residual concentration of Cl− in the purified solution was 65–85 mg/L, which meets the requirements for zinc electrolysis and allows the production of special high-grade zinc. Compared with the commonly used approaches, the method proposed has the advantages such as a higher degree of purification of zinc electrolyte, the short period of time required for the BiOCl precipitation (1 hour) and good filterability. Apart from that, the consumption of the precipitant is close to the stoichiometric molar ratio, which makes the purification process cost-effective.

Efficient Conversion of Ethanol to Hydrogen in a Hybrid Plasma-Catalytic Reactor

The present work describes highly efficient hydrogen production from ethanol in a plasma-catalytic reactor depending on the discharge power and catalyst bed temperature. Hydrogen production increased as the power increased from 15 to 25 W. A further power increase to 35 W did not increase hydrogen production. The catalyst was already active at a temperature of 250 °C, and its activity increased with increasing temperature to 450 °C. The further temperature increase did not increase the activity of the cobalt catalyst. The most important advantage of using the catalyst was the increased ethanol conversion to CO2 instead of CO production. As a result, the hydrogen yield was very high and reached 4.1 mol(H2)/mol(C2H5OH). This result was obtained with a stoichiometric molar ratio of water to ethanol of 3.