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We present a joint experimental and computational study on the geometric and electronic structures of deprotonated sulfamic acid (SA) clusters [(SA)n–H]− (n = 1, 2) employing negative ion photoelectron spectroscopy and high-level ab initio calculations. The photoelectron spectra provide the vertical/adiabatic detachment energy (VDE/ADE) of the sulfamate anion (SM−) H2N●SO3− at 4.85 ± 0.05 and 4.58 ± 0.08 eV, respectively, and the VDE and ADE of the SM−●SA dimer at 6.41 ± 0.05 and 5.87 ± 0.08 eV, respectively. The significantly increased electron binding energies of the dimer confirm the enhanced electronic stability upon the addition of one SA molecule. The CCSD(T)-predicted VDEs/ADEs agree excellently with the experimental data, confirming the identified structures as the most stable ones. Two types of dimer isomers possessing different hydrogen bonding (HB) motifs are identified, corresponding to SM− binding to a zwitterionic SA (SM−●SAz) and a canonical SA (SM−●SAc), respectively. Two N–H⋯O HBs and one superior O–H⋯O HB are formed in the lowest-lying SM−●SAc, while SM−●SAz has three moderate N–H⋯O HBs, with the former being 4.71 kcal/mol more stable. Further theoretical analyses reveal that the binding strength advantage of SM−●SAc over SM−●SAz arises from its significant contributions of orbital interactions between fragments, illustrating that sulfamate strongly interacts with its parent SA acid and preferably chooses the canonical SA in the subsequent cluster formations. Given the prominent presence of SA, this study provides the first evidence that the canonical dimer model of sulfamic acid should exist as a superior configuration during cluster growth. [ABSTRACT FROM AUTHOR]

The nitrogen (N) and oxygen (O) stable isotope analysis of dissolved nitrous oxide (N2O) can provide important constraints on the sources and cycling of N2O in aquatic environments. The isotopic composition of aqueous N2O, both in field (natural abundance) or experimental (15N‐labeling) samples, however, may be altered by abiotic reactions involving nitrite (NO2−) or hydroxylamine (NH2OH) and microbial activity during sample storage, if samples are not adequately preserved. Here we tested five different preservatives, mercuric chloride (HgCl2), copper sulfate (CuSO4), zinc chloride (ZnCl2), hydrochloric acid (HCl) mixed with sulfamic acid (SFA), and sodium hydroxide (NaOH), for fixing natural water samples from an estuary and a lake with different NO2− concentrations over a range of different storage times for N2O analyses. ZnCl2 and CuSO4 decreased the pH, and led to abiotic N2O production from 15NO2−, shifting the N2O isotopic composition significantly. Removal of NO2− with a mixture of SFA and HCl did not always prevent the alteration of the original N and O isotope composition of N2O, confirming the requirement for complete NO2− removal, and underscoring the biasing effects of NO2− at very low pH, even at trace levels. At low NO2− background, HgCl2 preservation led to robust and accurate results. However, in light of its toxicity and bioaccumulation potential in food webs, this fixative should be avoided. The addition of NaOH reduced abiotic side reactions involving NO2−, and yielded the most reliable and reproducible results for N2O concentration and isotope ratio measurements across tested settings and storage times. [ABSTRACT FROM AUTHOR]

The valorization of massive strandings of holopelagic Sargassum spp. is strongly limited by high levels of inorganic arsenic (Asi) that are potentially above the limit of current regulations. Monitoring Asi in algal biomass is currently achieved using standard chromatographic separation followed by spectroscopic detection. Here, we propose an alternative simpler procedure based on the extraction of Asi from the freeze-dried algal powder in deionized water and the electroanalytical detection of the diluted extract at a gold-microwire electrode. The protocol was optimized both in terms of extraction (powder/water ratio, extraction time, temperature) and electrolyte used for the voltammetric detection. Two electrolytes were tested: one composed of citric acid, sulfamic acid and KCl (pH 2.0) and another composed of an acetate buffer (pH 4.7) and NaCl. We demonstrate here that Asi determination is possible with the first electrolyte but it is necessary to deal with a relative unstable signal. Measurement of Asi was best achieved with the second electrolyte (acetate buffer and NaCl) with the following optimized electrochemical conditions: deposition potential of −1.2 V, deposition time of 30 seconds and linear scan voltammetry. Voltammetric results were then compared to a reference method (HPLC-ICP-MS) using different morphotypes of holopelagic Sargassum spp. (S. natans VIII, S. natans I and S. fluitans III), using commercial extracts of brown seaweeds and using a Hijiki certified reference material. Very good agreement was obtained between our novel method and HPLC-ICP-MS. Both methods show that inorganic arsenic is almost entirely present as As(V) in Sargassum spp. extracts. [ABSTRACT FROM AUTHOR]

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The present study examines the process of biomethanization of cow manure in an anaerobic environment, in the presence of small amounts of Bi(III) complex of sulfamic acid. Since this complex has good antimicrobial activity, the purpose of adding the complex is to determine its effect on biogas and methane production. The reference samples (cow manure only) and mixtures of cow manure + 10 mg and cow manure + 20 mg of bismuth complex with a composition [Bi6O4(OH)4](NH2SO3)6 are subjected to biodegradation under the following conditions -- duration of 33 days, nitrogen atmosphere and temperature of 34.5 ± 1°C. During the process, the volume of biogas and the percentage content of methane in biogas are measured in 2 - 3 days as well. The analyses performed reveal that until the 10th day, the amount of biogas produced increases constantly and is comparable both for the control samples and for the mixtures. Further, until the end of the experiment, a significant and constant increase in the volume of biogas produced by the mixtures is observed compared to the control samples. Regarding the percentage of methane produced by the reference samples and the mixtures, comparable relative amounts are found by the 7th day. From the 8th day to the 33rd day, the percentage of methane released by the mixtures is visibly greater than that by the reference samples. [ABSTRACT FROM AUTHOR]

Heavy metal ions and dyes in wastewater pose a severe hazard to ecological system and human health. This study used sulfamic acid (SA) to modify cellulose for adsorbent material preparation. The results from the structural characterization indicated that cellulose was successfully modified by introducing sulfonic acid groups to obtain sulfamic acid modified cellulose (SAMC). Subsequently, SAMC was prepared into spheres via being dissolved in ionic liquid and obtaining in antisolvent. The adsorption performance of SAMC aerogel spheres was investigated using methylene blue (MB) and lead ions (Pb2+). The maximum absorption capacity of SAMC aerogel spheres to MB and Pb2+ achieved 14.53 mg/g and 112.15 mg/g, respectively. The adsorption process conformed to the pseudo-second-order (PSO) model and Langmuir model. The adsorption mainly involved chemical action via coordination interaction between -SO32− and MB/Pb2+. Thermodynamic experiments confirmed that the adsorption process in the experiment was a spontaneous endothermic process. Therefore, this study provided a simple adsorbent production method for wastewater treatment. [ABSTRACT FROM AUTHOR]

Covalently bonded sulfamic acid on the titanate nanotubes (TNTs-N(SO3H)-(CH2)2-NHSO3H) was designed and successfully fabricated by the post-synthesis modification method. The as-prepared catalyst was characterized by a variety of characterization techniques such as FT-IR, TEM, XRD, XPS, and TG-DTG. The catalytic activity of TNTs-N(SO3H)-(CH2)2-NHSO3H was evaluated for the synthesis of n-butyl levulinate (BL) from levulinic acid (LA). It was found that the tube-like structure of the TNTs still maintained during the modification process, and Brønsted and Lewis acid sites can be efficiently immobilized on the TNTs. The effects of reaction factors such as reaction time, reaction temperature, and catalyst dosage on the esterification of LA were systematically studied. Under the optimal reaction conditions, a relatively high yield of BL (95.3%) was achieved for esterification of levulinic acid owing to the strong Brønsted acidic sites. Furthermore, the hybrid catalyst TNTs-N(SO3H)-(CH2)2-NHSO3H was used at least five times without significant decrease in activity, and no leaching of the active species in hot filtration test was observed. [ABSTRACT FROM AUTHOR]

Silver (Ag) nanowires, as an important one-dimensional (1D) nanomaterial, have garnered wide attention, owing to their applications in electronics, optoelectronics, sensors, and other fields. In this study, an alternative hydrothermal route was developed to synthesize Ag nanowires via modified reduction of Ag+. Silver sulfamate plays an important role in the formation of Ag nanowires via controlled release of free Ag+. Results of controlled experiments and characterizations such as UV–vis spectroscopy, FTIR, XPS, and 1H NMR revealed that sulfamic acid does not function as a reductant, supporting by the generation of free Ag+ instead of Ag nanostructures in hydrothermally treated silver sulfamate solution. The initial reduction of Ag+ was induced by the combination of poly (vinylpyrrolidone) (PVP) end group and degradation products. This phenomenon was supported by abundant free Ag+ in the mixed preheated silver sulfamatic and preheated PVP aqueous solutions, indicating a second and distinct Ag+ autocatalytic reduction. Thus, the roles of different reagents and Ag+ reduction must be studied for nanomaterial syntheses. [ABSTRACT FROM AUTHOR]

In this study, sulfated cellulose pulps (SCPs), synthesized via environmentally friendly methods by supporting sulfamic acid and urea on wood-derived cellulose pulps (CPs), were used to prepare completely dispersed cellulose nanofibers (CNs). CP is a sustainable natural polymer that is biodegradable, nontoxic, and relatively inexpensive. Additionally, cellulose nanofibers prepared from CPs have attracted attention as promising natural nanofibers with various useful properties. Therefore, sulfation of CP with sulfamic acid and urea was investigated as a method for preparing completely dispersed CNs. The SCPs were synthesized in high yields through the sulfamic acid ≥ urea (molar ratio) reaction system at 393 K for 30 min. The SCPs contained sulfate groups with 0.79–1.33 mmol g−1 at hydroxy groups of C6, and C2 and/or C3 positions of cellulose, maintained long fibers and exhibited a 429–880 degree of polymerization (DP), retaining 60% more DP than the original CP. Some SCPs attained a maximum water retention value of approximately 3000%, suggesting a swollen fiber structure. Completely dispersed sulfated CNs with a fiber diameter of approximately 3–4 nm could be prepared by defibrating these SCPs. The swollen fiber structure observed in the SCPs reduced the defibrated energy and time required to achieve complete dispersion. [ABSTRACT FROM AUTHOR]

We used to consider native cellulose to be composed of microfibrils continuously crystalline along the chain direction with constant lateral dimension. To sulfate the surface of cellulose microfibrils, we activated cotton fibers by pre-swelling in water or DMF followed by immersion in an excess amount of sulfamic acid in dimethylformamide (DMF) in heterogeneous conditions. The degree of sulfation was followed by elemental analysis and conductometric titration, while the structural changes associated with the sulfation and the homogenization were investigated by infrared spectroscopy, solid-state NMR, and X-ray diffraction. The initial sulfation of the cellulose surface was well described as a first order reaction with a kinetic constant of 2 × 10 - 3 s - 1 at 80 °C using 3.6% sulfamic, indicating that about half of the available hydroxy groups were sulfated within the first 5 min. A water pre-swelling step, followed by solvent exchange with DMF, increased the amount of available hydroxy groups by up to a factor of two. At long reaction times, there was a gradual increase in the degree of sulfation beyond the initially available surface by up to 20% during the two hours reaction investigated. FTIR and solid-state NMR spectra both suggest the reaction of surface primary hydroxy groups with sulfamic acid. While the apparent lateral crystallite size of cotton is unaffected by sulfation treatment, X-ray diffraction suggested that homogenization resulted in cellulose nanofibers (CNFs) with a crystallite width below 3 nm, much smaller than the initial cellulose microfibrils (6–7 nm). This apparent crystallite splitting during homogenization suggests that cotton microfibrils have an intertwined polycrystalline structure, rather than being monocrystalline along the whole length. [ABSTRACT FROM AUTHOR]

Burning corncob for energy requirements caused a huge waste of biomass resources and serious environment pollution. Herein, this study provided a high-value utilization strategy for corncob. Corncob was first pretreated by hydrothermal process. The collected hydrolysates were converted into furfural by a recyclable solid acid with a yield of 52.35%. The pretreated solid was disintegrated into fibers by disc grinding. When corncob fiber addition is below 15%, the ring crush index, tear index, and tensile strength index of the prepared handsheets increased by 1.43 N·m/g, 0.43 mN·m2/g, and 4.66 N·m/g, respectively, compared with that using pure softwood fibers. Besides, corncob fibers were hydrophilically modified with aminosulfonic acid. Water retention value of paper with the modified fiber addition increased by 48.35%. Therefore, this study provided a method of corncob utilization toward two purposes: furfural production and papermaking. [ABSTRACT FROM AUTHOR]

The article titled "Making the Complicated Simple: A Minimizing Carrier Strategy on Innovative Nanopesticides" by Shangguan et al. in Nano-Micro Letters has been published with errors. Specifically, there were mistakes in the structural formulas and captions of the three acyl chlorides in Figure 3A. The authors have reviewed the article and made corrections to ensure the accuracy of the scientific information. The revised figure and caption have been provided in the correction notice. [Extracted from the article]

Xylan sulfation using a Deep Eutectic Solvent (DES), formed by sulfamic acid and urea (1:2 molar ratio), was investigated with different reagent dosages (xylan/sulfamic acid molar ratio 1:10 and 1:5) and time (30 and 60 min). The effect of xylan/reagent ratio on the degree of substitution (DS) was higher than time, varying from 0.4 to 1.1. NMR spectra confirmed that the sulfate group was introduced into the C-2 and C-3 of the xylose moieties. Polyelectrolyte complex suspensions were prepared using the different sulfated xylan (SXyl) and chitosan (Ch) (mass ratio 55 SXyl/45 Ch) and deeply characterized. It was found that a precipitate was obtained for moderate conditions of sulfation; however for the others, stable suspensions were formed. Hydrogels with acceptable dry and wet mechanical properties (up to 45 MPa and 6 MPa of resistance, and 10% and 90% of elongation, respectively), and thermal properties were produced. Differences in crystallinity as well as in water uptake at 75% RH, depending on the SXyl used, were found. Promising results for potential use in drug delivery were the swelling capacity, which reached a maximum of 384% and was directly related to the degree of substitution of xylan, and the high water-resistant. [ABSTRACT FROM AUTHOR]

The reaction of hydrazine hydrate, N2H4 ⋅ H2O, and SO3 leads to hydrazine sulfonic acid (Pca21, a=849.59(4) pm, b=482.18(2) pm, c=832.17(4) pm). Structure elucidation reveals the zwitter‐anionic nature of the compound according to NH3NH(SO3). With the barium salt Ba[NH2NH(SO3)]2(H2O), a first salt of hydrazine sulfonic acid has been prepared (P1‾ $\bar 1$ , a=489.75(5) pm, b=737.52(7) pm, c=1317.4(1) pm, α=88.238(4)°, β=84.761(4)°, γ=79.701(4)°). The compounds were characterized by vibrational spectroscopy, DFT calculations and thermal analyses. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have low cost and high photoelectric conversion efficiency (PCE), but their performance still needs to be improved. This paper analyzed the electrochemical performance of PSCs by additives. First, PSCs with sulfamic acid (SA) and fumaric acid (FMAC) as additives were prepared; then, the electrochemical properties to be measured were briefly introduced. It was found that the electrochemical properties of both SA-PSCs and FMAC-PSCs were effectively improved compared with the standard samples, their photovoltaic conversion efficiency (PCE) was 18.46% and 19.48%, respectively, and they showed better stability. After aging experiments, the PCE of SA-PSCs and FMAC-PSCs was 74.7% and 76.8% of that before the experiments; after light experiments, the PCE of SA-PSCs and FMAC-PSCs was 52.4% and 54.6% of the pre-experimental ones, which were superior to the standard PSC samples. The experimental results verify the optimization effect of additives on PSCs, which is beneficial to further improving PSCs performance. [ABSTRACT FROM AUTHOR]

The structure of the surfactant was characterized by infrared spectroscopy, and its low-temperature solubility, surface properties, emulsification properties and dispersion properties were measured by turbidity, drop volume, water splitting time and dispersion index methods. The effects of reaction temperature, reaction time, catalyst dosage and raw material ratio on the content of active substances in the products were investigated by the single-factor experimental method, and the optimum synthesis reaction conditions were determined. The results showed that under the conditions of reaction temperature of 100 °C, reaction time of 3 h, catalyst dosage of 1% of the total mass of the reactants and re(block polyether) : re(sulfamic acid) = 1:1.5, the content of active substances in the products reached 96.49%. [ABSTRACT FROM AUTHOR]

Sulfated polysaccharides are important promising biologically active substances with anticoagulant properties. Biological activity is affected by the method of preparation, as well as the type of the polysaccharide and its molecular structure. In this work, we have considered various methods for the synthesis of promising anticoagulants – polysaccharide sulfates using the example of obtaining agarose sulfate. We compared various sulfating agents: chlorosulfonic acid, sulfamic acid, with various activators, and a deep eutectic solvent mixture of sulfamic acid with urea (in the melt). It has been shown that when urea is used as an activator of the process of sulfation of agarose with sulfamic acid in 1,4-dioxane, agarose sulfate with a high sulfur content (up to 14.5 wt%) is formed, which is close to the use of chlorosulfonic acid as a sulfating agent (with the production of agarose sulfate with 15.0 wt% sulfur). The use of solid catalysts in the process of sulfation of agarose with sulfamic acid leads to the production of agarose sulfate with a sulfur content of up to 14.1 wt% (for a catalyst based on the oxidized carbonaceous material Sibunit-4®). Sulfation of agarose in a deep eutectic solvent – a mixture of sulfamic acid with urea – leads to the production of agarose sulfate with a sulfur content of up to 13.7 wt%. The resulting agarose sulfates were characterized by FTIR spectroscopy, X-ray diffraction, elemental analysis, atomic force microscopy and DFT. [ABSTRACT FROM AUTHOR]

In this paper, starch was first liquefied using sulfamic acid as catalyst, and then the starch-based polyurethane coating was prepared. The optimum ratio between the hydroxyl group of liquefied starch and isocyanate group of PM200 was determined to be 1:1.3. Differential scanning calorimetry was used to study the curing reaction kinetics of starch-based polyurethane, and the result showed that the initial temperature (Ti), peak temperature (Tp) and end temperature (Tf) of thermostatic curing reaction were 23.31 °C, 83.15 ℃ and 199.75 ℃, respectively. According to the Kissinger model, the calculated activation energy and preexponential factor of the curing reaction system were 44.34 kJ mol−1 and 7.36 × 103 s−1, respectively. Meanwhile, the Crane model indicated that the order of curing reaction was 0.88. The curing kinetic equation was also established to provide a theoretical basis for the actual curing process of starch-based polyurethane materials. [ABSTRACT FROM AUTHOR]

Sulfamic acid functionalized polyvinyl chloride catalysts (PVC-N-SO3H, N = EDA, DTA, TTA, TPA, PHA) were prepared as efficient heterogeneous solid acid catalysts via two-step treatment processes. The prepared catalysts were characterized by X-ray diffraction analysis (XRD), TG thermograms/derivative thermogravimetric (TG/DTG), transmission electron microscope (TEM), elemental mappings and energy-dispersive spectroscopy analyses (STEM-EDS), and FTIR measurements (FTIR) as well as acid–base back-titration. The acetalization of aldehydes (ketones) and alcohols to acetal (ketal) was selected to evaluate the acid catalytic performance of PVC-N-SO3H. The results showed that PVC-EDA-SO3H exhibit excellent activity and reusability due to its highly exposed sulfonic acid sites, high surface acid density (2.28 mmol g−1) for the conversion of aldehydes (ketones) to acetal (ketal). This new solid acid has obvious advantages in reusability and catalytic activity over traditional homogeneous concentrated sulfuric acid and heterogeneous sulfonated resin catalysts. Furthermore, PVC-EDA-SO3H exhibited an excellent catalytic performance in the synthesis of 12 acetals (ketals) as well as a good compatibility in the hydroxyalkylation of phenol with formaldehyde to bisphenol F (BPF) and the esterification reaction of oleic acid and methanol to biodiesel. More importantly, it could also be recovered easily and used repeatedly at least nine times without an obvious decrease in the activity. [ABSTRACT FROM AUTHOR]

The application of thin film pretreatment technology in automobile painting was introduced. The cause of "crop circle" defect occurring during electrocoating after thin film pretreatment was analyzed. Some solutions were discussed. The problem was solved by improving the spray cleaning before and after electrocoating, increasing the concentration of sulfamic acid in electrocoating tank, and optimizing the production line running speed in electrocoating section. [ABSTRACT FROM AUTHOR]

A three-dimensional reduced graphene oxide aerogel modified by sulfamic acid and ethylenediamine was prepared via one-step reduction self-assembly under atmospheric pressure within 90 °C heating constantly. The adsorption efficiency of palladium (II) was ~ 97.0% at pH 11 within 50 min by the prepared composite. While the composite exhibited adsorption for platinum (IV) at acid condition, giving a rising to an adsorption efficiency was 61.7% at pH 5. Only 25.8% adsorption efficiency of platinum (IV) was found at pH 11, and 17.0% adsorption efficiency of palladium (II) was obtained at pH 5. The adsorption capacity of the composite for palladium (II) was 80 μg mg−1 above, and the adsorption capacity of the composite for platinum (IV) was ~ 160 μg mg−1. The obtained palladium (II) and platinum (IV) can be eluted by urea and surfactant from the surface of the composite, respectively. Understanding the mechanism of the adsorption/desorption between palladium (II)/platinum (IV) and the composite, explored a promising way for recycling and enrichment of noble metal at a low concentration. [ABSTRACT FROM AUTHOR]

Different problems may occur during acid treatment of oil reservoirs because of the incompatibility of acid with rocks and fluids. One of the issues is the formation of acid-in-oil emulsions, which block pore throats and hinder acid removal. The standard "bottle-test" method does not fully characterize such emulsions and allows only quick reagent selection. This article presents a new methodology that enables the evaluation of emulsion formation and the possible risk for acid treatment. This methodology includes visual control and measurement of viscosity, interfacial tension, and voltage stability. We found that HCl-based emulsions are generally more viscous, finer, and stable, but the high strength of the acid may lead to emulsion breakdown. We also established that emulsions that are stable under static conditions may break down after applying mechanical stress, which is a characteristic of sulfamic acid-based emulsions. Although it may not be possible to separate emulsions visually, a water content gradient may be observed in an emulsion column. Our results demonstrate that the acid and oil parameters are interconnected in emulsion formation issues. This methodology and the obtained results may be applied for quick and proper reagent selection for better acid treatment results. [ABSTRACT FROM AUTHOR]

The aim of this work was to study the systemic antinociceptive and anti-inflammatory effects and to evaluate the gastropathic effects of L-proline and L-tryptophan sulfamide derivatives on experimental models in rodents as compared to diclofenac. The target compounds were synthesized by the reaction of 4-(tert-butyl)-benzenesulfonyl chloride, which was previously obtained from tert-butylbenzene and chlorosulfonic acid, with the amino acids L-tryptophan and L-proline in aqueous NaOH solution. The target sulfamic acids were obtained in high yields and did not require further purification. The acids were converted to water-soluble sodium salts for subsequent pharmacological tests. The investigational compounds and diclofenac were administered intragastrically in doses of 10 mg/kg of body weight. The L-tryptophan sulfamide derivative demonstrated an antinociceptive effect close to that of diclofenac in the acetic acid-induced writhing test in mice. The number of writhings in each group decreased by 97% as compared with the control (p = 0.03 for diclofenac; p > 0.05 for the tryptophan derivative). The anti-inflammatory activity of the L-tryptophan sulfamide derivative on a formalin-induced paw edema model in rats exceeded that of diclofenac by 78% (p = 0.02). The L-proline sulfamide derivative did not exhibit antinociceptive and anti-inflammatory activity in the studied dose. In addition, L-proline and especially L-tryptophan sulfamide derivatives administered for 14 d had significantly lower ulcerogenic effects in rats as compared to diclofenac when assessing the degree of gastric ulceration and the percentage of rats that developed gastric ulcers. The L-tryptophan sulfamide derivative appears to be a promising compound from the viewpoint of balancing the analgesic and anti-inflammatory activities and gastrointestinal safety. [ABSTRACT FROM AUTHOR]

Xylan is a polysaccharide found in plant cell walls. It is considered to be a biodegradable polymer, which does not affect negatively the environment. Sulfated xylan derivatives exhibit valuable bioactive properties, in particular, anticoagulant and hypolipidemic. We report on the development of a new method for sulfation of birch wood xylan. Activators of the sulfation reaction with sulfamic acid have been evaluated. Numerical methods have been used to establish the optimum process parameters that ensure the maximum sulfur content in the reaction product. The incorporation of a sulfate group has been confirmed by infrared and nuclear magnetic resonance spectroscopy, and elemental analysis. The initial and sulfated xylans have been comprehensively studied by theoretical methods and the most favorable conformations of the initial xylan and its sulfate have been established. [ABSTRACT FROM AUTHOR]

The retrosynthetic strategy employed for the synthesis of the alkyl 2-(pyrrolo[1,2- I a i ]quinoxaline-4-carbonyl)benzoate ( B 11 b ) and alkyl 2-(indolo[1,2- I a i ]quinoxaline-6-carbonyl)benzoate ( B 12 b ) derivatives is depicted in Scheme 1. We explored the possibility of a simple, iodine-catalyzed approach for the synthesis of tetracyclic and pentacyclic pyrrolo/indolo[1,2- I a i ]quinoxaline derivatives with 2-(1 I H i -pyrrol-1-yl)aniline ( B 7 b )/2-(1 I H i -indol-1-yl)aniline ( B 9 b ), ninhydrin ( B 8 b ), and an alcohol ( B 10 b ) via a multicomponent reaction strategy. Keywords: Pictet-Spengler reaction; spirocyclic ring opening; quinoxalines; cascade coupling; multicomponent synthesis EN Pictet-Spengler reaction spirocyclic ring opening quinoxalines cascade coupling multicomponent synthesis 1616 1620 5 07/31/23 20230815 NES 230815 Graph The pyrrolo[1,2- I a i ]quinoxaline skeleton is found in a large number of natural products, as well as in several molecules undergoing clinical trials (Figure 1). [Extracted from the article]

A few metal–organic frameworks (MOFs), which typically use strong acids as proton sources, display superprotonic conductivity (≈10−1 S cm−1); however, they are rare due to the instability of MOFs in highly acidic conditions. For the first time, we report superprotonic conductivity using a moderately acidic guest, zwitterionic sulfamic acid (HSA), which is encapsulated in MOF‐808 and MIL‐101. HSA acts not only as a proton source but also as a proton‐conducting medium due to its extensive hydrogen bonding ability and zwitterion effect. A new sustained concentration gradient method results in higher HSA encapsulation compared to conventional methods, producing 10HSA@MOF‐808‐(bSA)2 and 8HSA@MIL‐101. These MOFs show impressive superprotonic conductivity of 2.47×10−1 and 3.06×10−1 S cm−1, respectively, at 85 °C and 98 % relative humidity, and maintain stability for 7 days. [ABSTRACT FROM AUTHOR]

In green chemistry, the most notable objectives include atom economy, the use of non-hazardous catalysts and solvents, and the reduction of by-products, energy costs, and waste. Initially, the reaction between I i -naphthol (2.0 mmol) and benzaldehyde (1.0 mmol) for the preparation of B 5e b was studied in various solvents and temperatures in the presence of different concentrations of supramolecular I i -cyclodextrin. In this context we now report the use of supramolecular I i -cyclodextrin in the synthesis of 12-aryl-tetrahydrobenzo[ I i ]xanthene-11-ones and 14-aryl-14 I H i -dibenzo[ I ,j i ]xanthenes in an aqueous medium. 14-Aryl-14H-dibenzo[ ,j]xanthenes derivatives (5) A mixture of I i -naphthol ( B 1 b , 2.0 mmol), the appropriate aromatic aldehyde ( B 2 b , 1.0 mmol), I i -CD (15 mol %) and 5 mL H SB 2 sb O was reacted at 80 °C (Scheme 2). [Extracted from the article]

This work deals with the study of the anticorrosion behavior of a biopolymer, namely Guar Gum (GG) and its composite on mild steel (MS) in sulfamic acid (SA) solution using electrochemical techniques. GG was found to be a potential inhibitor relatively at its higher concentration and showed maximum inhibition efficiency (IE) of 74% at 3 g/L (3000 ppm). To improve its IE, exfoliated graphite oxide (xGO)/GG polymer composite was prepared, and its inhibition property was assessed in 1 M SA solution at different temperatures by weight loss method (WL). The chemical structure of xGO/GG polymer composite was examined by FT-IR, and the morphology was inspected by optical microscopy, scanning electron microscopy study, and energy dispersive spectroscopy technique. xGO/GG polymer composite emerged as an efficient corrosion inhibitor for MS as marked from the outcomes of the electrochemical investigations and showed improved IE of 93% at 0.6 g/L (600 ppm) when compared to GG. Experimental results found by WL measurements are used to evaluate the thermodynamic parameters at various temperatures. Further, a Box-Behnken composite design with three factors and three levels has been used to minimize the experimental conditions. The IE was enhanced with the increase in the inhibitor concentration as observed from the main effect plot. The maximum IE of 84.21% was projected by the response surface method (RSM) with temperature (A = 30 °C), inhibitor concentration (B = 600 ppm), and time (C = 1 h). [ABSTRACT FROM AUTHOR]

Experimentation under dynamic shocked conditions has attained the status of one of the appealing classes of methods for identifying the functional materials whose degree of long-range order is significantly altered. In the present work, we have systematically investigated the dynamic impact of shock waves on the technologically important single crystal of sulfamic acid at various numbers of shocks exposed and the results have been analyzed by X-ray diffraction and Raman spectroscopic profiles. Based on the obtained results, the shocked phase profile with respect to the number of shock pulses is of the sequential order (Pbca)–disorder–order (Pbca)–disorder–order (Pbca) for the 0, 1, 2, 3 and 4 shocks, respectively. The observed switchable phase transitions of the titled crystal after shocked conditions might be due to the rotational order–disorder transformation that is followed by the molecular symmetry changes of NH3 and SO3 trigonal units for which the possible macroscopic mechanism is provided. The observed switchable phase transitions occurring between order and disorder states may be an interesting asset for molecular electronic devices such as the molecular switches. [ABSTRACT FROM AUTHOR]

Fluorescent carbon quantum dots are a new type of nano‐fluorescent probe material, which overcomes some deficiencies of organic fluorescent materials and semiconductor quantum dots. In addition, they also have excellent optical properties, biocompatibility, and good application potential in environmental detection and other fields. To realize the special functions of carbon quantum dots, various functionalized composite carbon quantum dots have also been gradually developed. Lignin is a kind of natural polymer material rich in aromatic ring structure, which has abundant π electrons and a large number of easily functionalized active groups. Therefore, lignin is gradually used as a fluorescent probe material. In this article, sulfadiazine, p‐aminobenzenesulfonic acid, ammonium sulfamate as the amination reagents were used to modify lignin, and then citric acid was used as raw material to prepare carbon quantum dots (CQDs), and finally sulfadiazine lignin composite carbon quantum dots (PSA‐L‐CQDs), sulfamic acid lignin composite carbon quantum dots (BSA‐L‐CQDs), and sulfamate amine lignin composite carbon quantum dots (ASA‐L‐CQD) were prepared. Their structure and fluorescence characteristics were analyzed. The selectivity and sensitivity of PSA‐L‐CQDs to metal ions were tested by fluorescence spectroscopy. The experimental results show that PSA‐L‐CQDs have good selectivity and high sensitivity to Fe3+. The detection limit of Fe3+ was 29.5634 nmol/L. The composite carbon quantum dots have the advantages of low cost, simple manufacture, high selectivity, and high sensitivity. [ABSTRACT FROM AUTHOR]

A common problem associated with conventional gel breakers is that they can cause a premature reduction in gel viscosity at high temperatures. To address this, a urea-formaldehyde (UF) resin and sulfamic acid (SA) encapsulated polymer gel breaker was prepared via in situ polymerization with UF as the capsule coat and SA as the capsule core; this breaker was able to withstand temperatures of up to 120–140 °C. The encapsulated breaker was characterized using scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), and thermogravimetric (TG) analysis. Meanwhile, the dispersing effects of various emulsifiers on the capsule core, and the encapsulation rate and electrical conductivity of the encapsulated breaker were tested. The gel-breaking performance of the encapsulated breaker was evaluated at different temperatures and dose conditions via simulated core experiments. The results confirm the successful encapsulation of SA in UF and also highlight the slow-release properties of the encapsulated breaker. From experimentation, the optimal preparation conditions were determined to be a molar ratio between urea and formaldehyde (nurea:nformaldehyde) of 1:1.8 for the capsule coat, a pH of 8, a temperature of 75 °C, and the utilization of Span 80/SDBS as the compound emulsifier; the resulting encapsulated breaker exhibited significantly improved gel-breaking performance (gel breaking delayed for 9 days at 130 °C). The optimum preparation conditions determined in the study can be used in industrial production, and there are no potential safety and environmental concerns. [ABSTRACT FROM AUTHOR]

The design of reactors based on high performance photocatalysts is an important research in catalytic hydrogenation. In this work, modification of titanium dioxide nanoparticles (TiO2 NPs) was achieved by preparation of Pt/TiO2 nanocomposites (NCs) through photo-deposition method. Both nanocatalysts were used for the photocatalytic removal of SOx from the flue gas at room temperature in the presence of hydrogen peroxide, water, and nitroacetanilide derivatives under visible light irradiation. In this approach, chemical deSOx was achieved along with protection of the nanocatalyst from sulfur poising through the interaction of the released SOx from SOx-Pt/TiO2 surface with p-nitroacetanilide derivatives to produce simultaneous aromatic sulfonic acids. Pt/TiO2 NCs have a bandgap of 2.64 eV in visible light range, which is lower than the bandgap of TiO2 NPs, whereas TiO2 NPs have a mean size of 4 nm and a high specific surface area of 226 m2/g. Pt/TiO2 NCs showed high photocatalytic sulfonation of some phenolic compounds using SO2 as a sulfonating agent along with the existence of p-nitroactanilide derivatives. The conversion of p-nitroacetanilide followed the combination processes of adsorption and catalytic oxidation–reduction reactions. Construction of an online continuous flow reactor–high-resolution time-of-flight mass spectrometry system had been investigated, realizing real-time and automatic monitoring of completion the reaction. 4-nitroacetanilide derivatives (1a-1e) was converted to its corresponding sulfamic acid derivatives (2a–2e) in 93–99% isolated yields of within 60 s. It is expected to offer a great opportunity for ultrafast detection of pharmacophores. [ABSTRACT FROM AUTHOR]

The P(CS-CO-EGDE) was synthesized with cysteamine hydrochloride, glycol diglycidyl ether as raw materials. The structure was characterized by infrared spectrometer. And the corrosion behaviours of Q235 carbon steel in sulfamic acid with the P(CS-CO-EGDE) were studied by means of corrosion weight-loss measurement, polarization curve measurement and electrochemical impedance spectroscopy. The results showed that the poly(CS-CO-EGDE) was a hybrid inhibit with the same performance as heptadie- nylamine ethyl imidazoline quaternary ammonium salt. When the dosing concentration of synthetic product was 40 mg/L,the corrosion rate of Q235 carbon steel was 0.8155g/(m²·h),which was lower than the control index requirement of GB/T 25146—2010 that the laboratory verification result of carbon steel cor- rosion rate had to be lower than 2g/(m²·h). [ABSTRACT FROM AUTHOR]

Cellulose as a moisture sensing material had been successfully used in preparation of fiber optic relative humidity sensors (FORHSs) to monitor the humidity of external environment. However, the sensitivity of cellulose to humidity response needs to be further improved. Based on it, sulfamic acid esterified cellulose (SAEC) was fabricated to be a moisture sensitive material for FORHS preparation. The produced SAEC exhibited a good hygroscopicity and dehumidification stability (the standard deviation of weight changes, σ = 0.0035) and high moisture absorption (121% of its own weight). After coating the SAEC hydrogel on the end face of optical fiber, a FORHS was fabricated and its humidity response performance and stability were measured. The results showed that the FORHS displayed a relatively high humidity response (the interference fringe contrast, 3.84 dB), small humidity hysteresis error (rH = ± 0.07%), high sensitivity (0.16 dB/%RH), and a good stability (R2 = 0.9642, the confidence factor) within a relative humidity (RH) range from 45 to 80% and a temperature range between 25 and 45 °C. Therefore, this study provided a new preparation method of FORHS based on biomass material. [ABSTRACT FROM AUTHOR]

The study was to use a memory-free hydride generation atomic fluorometer to determine mercury content in feed. The joint developed atomic fluorescence spectrometer breaks through the problem of serious memory effect in determination of trace mercury by spectrometry, and established a method for determination of mercury in feed by atomic fluorescence spectrometry with water as carrier current without memory effect hydride. HNO3-H2O2 (1:1) was selected from the four mixed acids as the digestion system, and 2 mL 220 g/L sulfamic acid solution was selected to eliminate interference of nitrogen oxides. The established method had good linearity in concentration range of 0.2~1.0 µg/L, the correlation coefficient r=0.999 6, the detection limit (n=11) was 0.003 1 µg/L, the relative standard deviation (n=7) was 2.28%, and the recovery rate was between 93%~99%. The study indicates that the method has the advantages of high sensitivity, accuracy and efficiency, which can realize the rapid detection of mercury content in feed. [ABSTRACT FROM AUTHOR]

Cellulose sulfates are important biologically active substances with a wide range of useful properties. The development of new methods for the production of cellulose sulfates is an urgent task. In this work, we investigated ion-exchange resins as catalysts for the sulfation of cellulose with sulfamic acid. It has been shown that water-insoluble sulfated reaction products are formed in high yield in the presence of anion exchangers, while water-soluble products are formed in the presence of cation exchangers. The most effective catalyst is Amberlite IR 120. According to gel permeation chromatography, it was shown that the samples sulfated in the presence of the catalysts KU-2-8, Purolit s390 plus, and AN-31 SO42− underwent the greatest degradation. The molecular weight destribution profiles of these samples are noticeably shifted to the left towards low-molecular-weight compounds with an increase in fractions in the regions Mw ~2.100 g/mol and ~3.500 g/mol, indicating the growth of microcrystalline cellulose depolymerization products. The introduction of a sulfate group into the cellulose molecule is confirmed using FTIR spectroscopy by the appearance of absorption bands at 1245–1252 cm−1 and 800–809 cm−1, which correspond to the vibrations of the sulfate group. According to X-ray diffraction data, amorphization of the crystalline structure of cellulose is observed during sulfation. Thermal analysis has shown that with an increase in the content of sulfate groups in cellulose derivatives, thermal stability decreases. [ABSTRACT FROM AUTHOR]

In this work, we report the synthesis and identification of ZnFe2O4@SiO2–SO3H as a novel and green nanomagnetic solid acid catalyst, which is containing the sulfuric acid catalytic sites on the surface of ZnFe2O4 magnetic nanoparticles as the catalytic support. The as-synthesized ZnFe2O4@SiO2–SO3H MNPs were characterized with accuracy by different physicochemical methods; including, X-ray powder diffraction, energy-dispersive spectroscopy, Scanning electron microscopy, Fourier transform infrared, X-ray elemental mapping, Thermogravimetric analysis, and Vibrating Sample Magnetometer analyses. The catalytic activity of this nanomagnetic material is considered for the synthesis of the diversely substituted tetrahydrobenzo[b]pyran and DHQZ (2,3-dihydroquinazolin-4(1H)-ones) in ethanol solvent, which affording excellent yields (86–97%). The heterogeneous nature of the catalyst was confirmed via the hot filtration experiment. Furthermore, the activity of the recycled nanocatalyst was examined for at least five cycles with a negligible loss of its activity (97–92%). Also, the amount of sulfamic acid function in the ZnFe2O4@SiO2–SO3H was calculated from back titration. [ABSTRACT FROM AUTHOR]

The inner wall of the thrust chamber in hydrogen-oxygen rocket engines is preferentially constructed from Narloy-Z, an aging-strengthened Ag–Cu–Zr alloy, which should be corroded to expose fresh and clean surface prior to outer wall electroforming and thus achieve strong adhesion between the outer and inner walls. However, the high resistance of Narloy-Z to chemical corrosion necessitates the use of alternative techniques (e.g., electrochemical dissolution). Herein, we investigate the electrochemical dissolution behavior of Narloy-Z in H2SO4 and NH2SO3H solutions, study the polarization behavior, and probe its surface composition and structure by instrumental analyses. Passivation and activation behaviors are observed in H2SO4 and NH2SO3H, respectively, and dissolution behavior is found to be influenced by the formation of electrochemical dissolution products (e.g., CuO, Ag2O) on the specimen surface. The passivation and activation mechanisms are analyzed in detail, and further experiments reveal that fresh and clean surface can be exposed in NH2SO3H at current densities of ≥ 6 A cm−2. Finally, qualitative models for the observed electrochemical dissolution behavior are proposed. Thus, this study deepens our mechanistic understanding of electrochemical Narloy-Z dissolution in acidic solutions and provides guidance for the pretreatment of this alloy prior to the electroforming of the outer wall of the thrust chamber. [ABSTRACT FROM AUTHOR]

Extensive chemical data for the corrosion of zinc in hydrochloric acid, sulphuric acid, sodium hydroxide and sodium chloride are available in the respective literature. However, studies of the corrosion of zinc in sulfamic acid are minimal. The present paper highlights the work on the corrosion behavior of zinc in sulfamic acid, which can be used as a pickling agent. Studies were carried out with three different acid concentrations: 0.1, 0.25, and 0.5 M at a temperature range of 303–323 K. The measurements were done by potentiodynamic polarization and electrochemical impedance spectroscopy techniques. In addition, scanning electron microscopy, energy dispersive X-ray, and atomic force microscopy techniques were applied for the surface studies. Spectroscopic techniques like X-ray diffraction analysis and atomic absorption spectroscopy were used to substantiate the corrosion process. Studies showed that the corrosion rate increased with an increase in the acid concentration and temperature. Surface morphology studies and spectroscopic studies confirmed enhanced deterioration of zinc at higher acid concentrations. [ABSTRACT FROM AUTHOR]

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Microbial manganese (Mn) oxidation plays a critical role in Mn(III/IV) oxide formation in modern day environmental systems. These oxidation processes and resulting biominerals are sensitive to aqueous conditions, such as pH and dissolved constituent concentrations. With Mn and sulfur (S) biogeochemical cycling closely linked in many environmental systems, and dissolved organic sulfur comprising a substantial pool of total sulfur in several environments, the impact of dissolved organic sulfur compounds on Mn redox processes is important to consider. Sulfonic acids, environmentally ubiquitous organosulfur compounds, play substantial roles in S cycling in many natural and contaminated systems. Research to assess the effects of these abundant sulfonic acids on Mn biogeochemical cycling, microbial Mn oxidation processes, and Mn biominerals is needed for understanding and predicting the impact of coupled S and Mn biogeochemical cycles, particularly in environments with dynamic redox gradients or in anthropogenically contaminated systems. Further, with research on microbial and abiotic Mn oxidation processes often using aminosulfonic acids to control pH, understanding the impact of such sulfonic acids on microbial Mn oxidation processes is critical. Several recent studies found that commonly used zwitterionic N substituted aminosulfonic acids, known as Good's buffers, such as HEPES and MES, can alter abiotic birnessite sheet structures. Here we investigate the impact of two sulfonic acids with broad applications to natural and contaminated sites as well as laboratory settings (HEPES and MES) on fungal Mn oxidation relative to a carbonate buffer and a buffer-free control by three Ascomycete fungi known to oxidize Mn(II): Stagonospora sp. SRC1lsM3a, Paraphaeosphaeria sporulosa AP3s5–JAC2a, and Plectosphaerella cucumerina DS2psM2a2. Structural analyses of the products show that sulfonic acids promote Mn oxidation by P. cucumerina , producing hexagonally symmetric phyllomanganates analogous to hexagonal birnessite or c–disordered H+ birnessite [(Ca,Na,K)(Mn4+,Mn3+,□)O 2 n H 2 O], with solid–associated Mn(II) bound to vacancy sites and biomass, while in their absence almost all Mn remains as either aqueous Mn(II) or solid–associated Mn(II) bound to biomass. In contrast, sulfonic acids exert the opposite effect on Mn oxidation by P. sporulosa , with their presence suppressing Mn(II) oxidation to Mn(IV), likely leading to the formation of mycogenic bixbyite (Mn3+ 2 O 3) while the buffer–free control forms a poorly crystalline phyllo- or tectomanganate. Meanwhile, all treatments exert a minimal effect on Mn(II) uptake from solution and Mn oxidation with Stagonospora sp., with all experimental systems and controls forming poorly crystalline, hexagonally symmetric phyllomanganates. The fact that the sulfonic acids here studied exert similar effects on Mn oxidation, but substantially different effects for each fungus, suggests they affect Mn oxidation via mechanistically similar pathways that are likely dependent on interactions with fungal exudates (which vary from species to species) or specific fungal Mn oxidation processes. Interestingly, for all fungi, MES increases Mn(III) in the resulting biominerals, while the carbonate buffer consistently decreases Mn(III). These results clearly demonstrate that sulfonic acids not only alter Mn oxide structures, as has been previously noted in abiotic studies, but can interfere with Mn oxidation reactions themselves, highlighting the incredible sensitivity of both Mn oxide structures and the Mn oxidation process to the aqueous environment. [ABSTRACT FROM AUTHOR]

We examine the protective properties of imidazoline corrosion inhibitors with added thiourea and potassium iodide. A model of reservoir water saturated with carbon dioxide as well as hydrochloric and sulfamic acids were taken as aggressive media. The corrosion inhibition efficiency was evaluated using a gravimetric method under dynamic and static conditions in the carbon dioxide‑rich and acidic environments, respectively. The effect of individual compounds on the inhibition mechanism for metal was determined experimentally in media with different properties. [ABSTRACT FROM AUTHOR]

We examine the protective properties of imidazoline corrosion inhibitors with added thiourea and potassium iodide. A model of reservoir water saturated with carbon dioxide as well as hydrochloric and sulfamic acids were taken as aggressive media. The corrosion inhibition efficiency was evaluated using a gravimetric method under dynamic and static conditions in the carbon dioxide‑rich and acidic environments, respectively. The effect of individual compounds on the inhibition mechanism for metal was determined experimentally in media with different properties. [ABSTRACT FROM AUTHOR]

Polysaccharides are important structural components of all plant species. Gel-like polysaccharides have found wide application in various fields, including medicine, construction, and the food industry. In the present work, galactomannan and galactoglucomannan gel-like polysaccharides were modified with sulfate groups and their anticoagulant activity was studied. Sulfation with chlorosulfonic acid in pyridine and with sulfamic acid in pyridine and a sulfamic acid–urea deep eutectic solvent were used as synthesis routes. The resulting gel-like polysaccharide sulfates were studied by elemental analysis, Fourier-transform infrared spectroscopy, and gel permeation chromatography. It was established that the anticoagulant effect of sulfated galactoglucomannan (SGGM) and galactomannan (SGM-1 and SGM-2) is related to an independent antithrombin-independent decrease in the amidolytic activity of thrombin and factor Xa. It is shown that the inhibitory activity of SGGM and SGM-2 against the collagen-induced platelet aggregation can be an additional factor in selecting compounds that are most promising for modifying polymer surfaces to ensure resistance to blood clotting. [ABSTRACT FROM AUTHOR]

The profitability and sustainability of future biorefineries are dependent on efficient feedstock use. Therefore, it is essential to improve the lignocellulosic utilization efficiency when using lignocellulosic biomass. In this research, a novel corn stover (CS) pretreatment process was established and the effectiveness was verified via d-lactic acid fermentation. The results indicated that after pretreatment with 4% sulfamic acid and 3% sodium chloride solutions (SA/NaCl) at 80 °C for 60 min, and enzymatic hydrolysis with 20 FPU/g cellulase for 72 h, the glucose concentration was14.57 g/L, the cellulose transformation rate was 97.56%, and 56.93% of the solid recovery rate. The concentration of d-lactic acid reached 45 g/L after fermentation for 72 h at 42 °C. In conclusion, SA/NaCl was a safe to use, easy to transport, and more promising CS pretreatment catalyst than sulfuric acid and hydrochloric acid. [ABSTRACT FROM AUTHOR]

Diosgenin is an important intermediate of drugs, the special structure similar to hormone determines its important position in drug synthesis. Diosgenin was generally obtained by sulfuric acid hydrolysis of dioscorea, which produced too much acid wastewater, and caused environmental issues. A new solid acid based on TiO2 was designed and synthesized through the sulfonation of the prepared TiO2, the structure was fully characterized by FTIR, SEM, EDX, XPS and XRD. Under the optimized conditions, the yield of diosgenin reached 30.75%, the value was much higher than that of H2SO4 of the same quality. To explore the factors that affect the yield, the usage amount of the solid acid, the temperature, the solvent volume and the extraction time were taken into the analysis, and the results of the recycling experiments indicated that the prepared solid acid can be used for three time and maintain its high activity. A highly efficient solid acid catalyst for diosgenin extraction from saponins was successfully synthesized, and the extraction method was environmentally friendly. [ABSTRACT FROM AUTHOR]

Diosgenin is an important intermediate of drugs, the special structure similar to hormone determines its important position in drug synthesis. Diosgenin was generally obtained by sulfuric acid hydrolysis of dioscorea, which produced too much acid wastewater, and caused environmental issues. A new solid acid based on TiO2 was designed and synthesized through the sulfonation of the prepared TiO2, the structure was fully characterized by FTIR, SEM, EDX, XPS and XRD. Under the optimized conditions, the yield of diosgenin reached 30.75%, the value was much higher than that of H2SO4 of the same quality. To explore the factors that affect the yield, the usage amount of the solid acid, the temperature, the solvent volume and the extraction time were taken into the analysis, and the results of the recycling experiments indicated that the prepared solid acid can be used for three time and maintain its high activity. A highly efficient solid acid catalyst for diosgenin extraction from saponins was successfully synthesized, and the extraction method was environmentally friendly. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel 2-step method for efficient & selective nitrate to nitrogen conversion. • Ag NWs electrode enable > 99 % selective electrocatalytic nitrate-to-nitrite reduction. • Ag NWs electrodes can be easily used in static and flow electrolytic cells. • Chemical reduction of nitrite to N 2 using sulfamic acid: ∼100 % selectivity. • Electrocatalysis + chemical reduction: up to 99.44 % nitrate-to-nitrogen selectivity. Nitrate pollution in natural water bodies poses a severe threat to human health and the environment. Developing efficient and environmentally friendly nitrate removal methods has become a global need. Electrochemical techniques offer a cost-effective strategy for nitrate remediation; however, the complexity of the reaction and the formation of multiple by-products make the selective production of harmless nitrogen a challenging task. This study proposes a novel two-step strategy to achieve high efficiency and selectivity in converting nitrate into nitrogen. First, a membrane electrode consisting of silver nanowires (Ag NWs) is used to electrochemically reduce nitrate to nitrite through a direct electron transfer pathway. Whether in a static electrolytic cell or a flow cell, the process has very high nitrite selectivity and Faraday efficiencies, with Faraday efficiency up to 98.40 % and selectivity up to 99.90 % at −1.0 V vs Ag/AgCl. Subsequently, the nitrite is converted into nitrogen through a specific reaction with sulfamic acid with near 100 % conversion and selectivity. By coupling these two reactions, the selectivity for converting nitrate to nitrogen can reach more than 99 %. In addition, the membrane electrode can be readily used in a flow-through electrolytic cell to treat nitrates at a maximum rate of 150 L h−1 m−2. When operated at 50 L h−1 m−2, the membrane electrode demonstrates relatively stable performance for 100 h, reducing nitrates at 1.61 mM to below 0.81 mM (50 ppm), as recommended by the World Health Organization for drinking water. This novel synergistic approach not only enhances nitrogen selectivity but also simplifies the process of electrocatalytic nitrate reduction, making it a promising method for nitrate removal. [ABSTRACT FROM AUTHOR]