Neutral Reagents Research Articles

A sustainable black liquor-based carbon scavenger to promote urea formaldehyde as green wood adhesive with low formaldehyde emission

The current study focuses on finding an ecological method to dispose of black liquors (BLs), containing lignin macromolecules, which are produced as byproducts of rice straw-based paper production. In addition to maximizing their value as precursors in the preparation of novel formaldehyde scavengers to avoid the environmental risks associated with using urea formaldehyde in agro-wood composites. To optimize the route, various black liquors are prepared from pulping of rice straw by different pulping agents (alkali, neutral, acidic and kraft reagents) used as additions or precursors for carbon compounds. Elemental analysis, thermogravimetric analysis [TGA], Fourier transform infrared [FTIR] and scanning electron microscope (SEM), are the techniques used to characterize the BLs; while the gel time, bond strength, and differential scanning calorimetry (DSC) methodologies are applied to determine the impact of black liquor (BL) and black liquor‑carbon nanostructures (BL-CNSs) on performance of urea formaldehyde (UF) adhesive. The behavior of the investigated BL-CNSs as HCHO-scavengers is assessed from their affinity to capture the HCHO, and reduction of free-HCHO in UF-palm fibers agro-composites. BL-CNSs, as novel scavengers, exhibit promising properties where the bonding strength of BL-CNSs-UF adhesives increased to 19.7 MPa even though the UF was only 8.4 MPa. Moreover, the formaldehyde adsorption capacity ranges from 35.4 to 63.6 mg/g as well as lowering the gel time. It is interesting to note that the investigated scavengers not only reduced the free-HCHO of composites by about 40–91 %, but also enhancement in their mechanical and water resistance properties; where the modulus of rupture (MOR), internal bond (IB) and reduction in thickness swelling improved to about 50 % and 83.3 %, and 38.8 %, respectively. According to the American National Standards Institute (ANSI) standard these new scavengers, especially from BL of neutral pulping, permit the production of an eco-board (E1) with static bending exceeding the H-3 class.

The long-term transformation of FeIII-AsV coprecipitates at room temperature under oxic conditions: New insights for the fate and the speciation of As

The long-term stability of FeIII-AsV coprecipitates, a typically hydrometallurgical or naturally produced As-bearing wastes in tailings or in other environments, is critical to evaluating the As risk caused by them. A wide pH range, different Fe/As molar ratios, reaction media, and neutralization reagents were considered in order to find the mechanisms controlling the fate of As during the 1640 days of transformation at 25 °C. The results indicated that at pH 4 and 12, As continuously released from the solid phase. The components and their proportions determined the fate of As at pH 4. However, at pH 12, crystalline calcium carbonates (CCA) formed due to the CO2 in the air and this combined with the adsorption capacity of As on the 2-line ferrihydrite controlling the fate of As. If pH changed to 8 and 10, yukonite formed after the release of As. The CCA also appeared in the presence of Ca. Therefore, these two processes controlled the fate of As at this pH range. These findings are important for understanding and predicting the transport of As under various environmental conditions. The technology chosen for As remediation in soils and As removal from waste waters will also be benefit from these results.

Mechanistic insight into the kinetic fragmentation of norpinonic acid in the gas phase: an experimental and density functional theory (DFT) study

Abstract. Norpinonic acid has been known as an important α-pinene atmospheric secondary organic aerosol (SOA) component. It is formed in the reaction of α-pinene, β-pinene or verbenone with atmospheric oxidizing reagents. In the presented study, tandem mass spectrometry techniques were used to determine the exact norpinonic acid fragmentation pathway in the gas phase. The precursor anion – deprotonated norpinonic acid (m/z 169), generated in an electrospray (ESI) source – was introduced into the collision cell of the mass spectrometer and fragmented using the energy-resolved collision-induced dissociation (ER-CID) technique. The experimental energy values of degradation processes were determined via analysis of the breakdown curves. Quantum chemical calculations of the reaction models were also constructed, including calculation of all transition states. Comparison between the experimental and the theoretical threshold energies calculated at a ωB97XD/6-311+G(2d,p) theoretical level has shown a good correlation. Two basic pathways of the fragmentation of the parent anion [M-H]− (m/z 169) were observed. Firstly this leads to the decarboxylation product (m/z 125) and secondly to the loss of a neutral molecule (C4H6O), together with the formation of the anion m/z 99. On the other hand, the breakdown of the anion m/z 125 gives rise to the m/z 69, 57 and 55 ions. To confirm structures formed during ER-CID experiments, the gas-phase proton transfer reactions were examined of all norpinonic acid anionic fragments with a series of neutral reagents, characterized by proton affinity (PA) values. Based on PA difference analysis, the most possible chemical structures were proposed for the observed fragment anions.

Evaluation of the Potential of Boiler Ash from Palm Oil Mill as an Alternative Material for the Improvement of Acid Coal Main Drainage

The study aimed to evaluate the potential of boiler ash from palm oil mills to improve the quality of acid mine drainage (AMD). The experiment was conducted using boiler ash with five doses of 0, 3, 6, 9, 12, and 15 mg. Quicklime was used as a comparison material with doses of 0, 0.02, 0.03, 0.05, 0.1, and 0.3 mg. Boiler ash and quicklime were added to each 500 mL AMD. The parameters of the AMD quality measured were pH, dissolved iron (Fe) and manganese (Mn), and the precipitates of Fe and Mn. The results showed that the addition of boiler ash and quicklime into AMD increased the pH and decreased the concentration of dissolved Fe and Mn and increased the precipitate of Fe and Mn. The pH value of AMD increased with increasing doses of boiler ash and quicklime. An increase in the pH value was followed by a decrease in the dissolved Fe and Mn and anincrease in the Fe and Mn precipitate. The highest pH values, Fe and Mn precipitates, and the lowest dissolved Fe and Mn were obtained by the treatment of 15 mg/L boiler ash and 0.3 mg/L quicklime. The boiler ash showed promising potential as an alternative neutralizing reagent to improve AMD even though the amount of boiler ash needed to repair AMD was more than quicklime.

Synergistic valorization of rice straw and red brick demolition in development performance of lightweight cement mortars

This work deals with upgrading the undesirable agro- and industrial wastes, such as rice straw (RS), red brick demolition (RBP), and polystyrene foam (PSF), for construction purposes, as an excellent strategy to protect the environment. In this respect, the RS and its pulp fibers are modified by PSF, followed by their incorporating individually or in hybrid with RBP, in cement mortar formulation. As a substitute for fine aggregates. Six rice straw pulps used in this study were prepared from alkali, neutral, acidic, and kraft pulping agents. The effective performance of this investigated route is assessed from the mechanical properties, density, moisture resistance (thickness swelling and water absorption), measurements of the resulting mortar composites, as well as how the investigated treatment effects on behavior of RS fibers. The finding results show that the modified RS fibers, especially those results from KOH–NH4OH and neutral RS-pulping reagents, in hybrid with red brick waste provide motors with better mechanical and water resistance properties. These treated fibers have a synergistic role for including the RBP in mortar formulation to 30 %. The produced mortar has compressive strength 6.2 MPa and flexural strength 4.4 MPa, which is convenient to apply as load-bearing wall. Moreover, they provide improvement in resistance to thickness swelling and water absorption after 24-h exposure to water. The reduction in thickness swelling and water resistance reached 36.7 and 52.8 %, respectively. From the TGA measurements and SEM, it is interesting to notice that the investigated route accepts the RS fibers thermal stability and hydrophobic surface character.

Dual Nickel/Photoredox‐Catalyzed Asymmetric Carbamoylation of Benzylic C(sp3)−H Bonds

AbstractRadical‐mediated Hydrogen Atom Abstraction of Csp3−H bonds has become a powerful tool for the asymmetric functionalization of organic feedstocks. Here, we present an asymmetric synthesis of α‐aryl amides via carbamoylation of alkylarenes with isocyanates as electrophiles. The synergistic combination of a photoredox and a chiral nickel‐catalyst, enables the use of readily available and neutral reagents under mild reaction conditions and provides straightforward access to pharmacologically relevant motifs in enantiomerically pure form.

Dual Nickel/Photoredox-Catalyzed Asymmetric Carbamoylation of Benzylic C(sp3 )-H Bonds.

Radical-mediated Hydrogen Atom Abstraction of Csp3 -H bonds has become a powerful tool for the asymmetric functionalization of organic feedstocks. Here, we present an asymmetric synthesis of α-aryl amides via carbamoylation of alkylarenes with isocyanates as electrophiles. The synergistic combination of a photoredox and a chiral nickel-catalyst, enables the use of readily available and neutral reagents under mild reaction conditions and provides straightforward access to pharmacologically relevant motifs in enantiomerically pure form.

A fixed-charge model of the N-protomer of 4-aminobenzoic acid to facilitate the study of the unimolecular and bimolecular chemistry of its "neutral" carboxylic acid group.

There are a growing number of examples of protomers formed via electrospray ionization (ESI) that do not fragment under mobile proton conditions, giving rise to distinct tandem mass spectra. To model the N-protomer of 4-aminobenzoic acid, here we study the gas-phase unimolecular and bimolecular chemistry of the 4-(carboxyphenyl)trimethylammonium ion. 4-(Carboxyphenyl)trimethylammonium iodide was synthesized, purified via recrystallization and transferred to the gas phase via ESI. 4-(Carboxyphenyl)trimethylammonium ion, 7, was mass selected and subjected to collision-induced dissociation and ion-molecule reactions in a linear ion trap mass spectrometer. The major fragmentation channel for the fixed-charge cation 7 is methyl radical loss, whereas loss of trimethylamine and CO2 represents minor pathways. The free carboxylic acid functional group of 7 is unreactive toward a number of neutral reagents (methanol, acetone, acetonitrile, and N,N'-diisopropylcarbodiimide). 7 reacts very slowly with trimethylborate via addition-elimination, consistent with density functional theory (DFT) calculations that show this reaction is slightly endothermic. The deuterated cation 7(D) undergoes slow D/H exchange with ethanol, and DFT calculations reveal that a flip-flop mechanism operates. The free carboxylic group of 7 is not very reactive toward neutral reagents in the gas phase.

Toward pulping process for enhancing the RS-black liquors as precursor of activated carbons for aqueous adsorbent purposes

This work deals with providing a green pulping process of rice straw with zero waste discharged, via valorization of its by-product as a promising precursor for production of carbon nanostructures. The carbon nanostructures (BL-CNSs) from rice straw pulping liquors (BLs) are prepared in one step with phosphoric acid activation. The carbon nanostructures (BL-CNSs) from rice straw pulping liquors (BLs) are prepared in one step with phosphoric acid activation. The optimal pulping approach for achieving effective adsorbent (BL-CNSs) of cationic and anionic dyes is recommended from using different BLs precursors resulting from different reagents (alkaline, neutral, and acidic reagents). The carbon precursors are characterized by elemental, thermal (TGA and DTG) and ATR FTIR analyses. While the impact of pulping route on performance of CNSs is evaluated by their adsorption of iodine, cationic dye and anionic dye, as well as ATR-FTIR, textural characterization, and SEM. The data of elemental analysis displayed a high Carbon content ranges from 57.85 to 66.69% suitable for CNSs preparation, while the TGA showed that Sulphur-containing BLs (Kraft, neutral sulfite and acidic sulfite) have higher degradation temperature and activation energies as compared with other BLs. The optimum BL-CNSs adsorbent is prepared from the disposed neutral sulfite black liquor, with the following characteristics: cationic dye adsorption capacity 163.9 mg/g, iodine value 336.9 mg/g and SBET 310.6 m2/g. While the Kraft-CNSs provided highest anionic adsorption (70.52 mg/g). The studies of equilibrium and kinetic adsorption of dyes showed that the adsorption equilibrium of all investigated BL-CNSs toward MB follow the Langmuir and mainly Freundlich models for BB adoption. Their adsorption kinetics are a good fit with the pseudo-second-order model. The textural characterization and SEM revealed the CNSs exhibit a mixture of mesoporous and microporous structure.

Intermolecular interactions and the weakly bound precursor states of elementary physicochemical processes

This study concerns the importance of the precursor (or pre-reactive) state of elementary physicochemical processes whose basic features, as structure, stability, and trapping effect of reagents, are controlled by the balance of intermolecular forces that arise at long range and operate at intermediate and short separation distances. The detailed formulation of such forces, determining formation probability and dynamical evolution of the precursor state, is of relevance in molecular science and difficult to be treated by quantum chemistry. Such a problem has been tackled by us exploiting the phenomenological approach, which employs semi-empirical and empirical formulas to represent strength, range and angular dependence of the leading interaction components involved. In addition to the study of transport phenomena, part of the attention is addressed to chemi-ionization (or Penning ionization) reactions for which neutral reagents lead to atomic and/or molecular ions plus electrons as products. Chemi-ionizations are bimolecular processes occurring in several environments of interest, where a reagent is a species, formed in excited-metastable electronic states by collisions with energetic electrons or cosmic rays. For such reactions all crucial electronic rearrangements, affecting stability and evolution of the weakly bound precursor state, here coincident with the reaction transition state, are characterized with a high detail. The results of the present study are of interest for many other processes, whose precursor states and their relevant features are difficult to characterize, often masked by several other effects.Graphical abstract

Structural and Morphological Features of Anisotropic Chitosan Hydrogels Obtained by Ion-Induced Neutralization in a Triethanolamine Medium.

For the first time, anisotropic hydrogel material with a highly oriented structure was obtained by the chemical reaction of polymer-analogous transformation of chitosan glycolate-chitosan base using triethanolamine (TEA) as a neutralizing reagent. Tangential bands or concentric rings, depending on the reaction conditions, represent the structural anisotropy of the hydrogel. The formation kinetics and the ratio of the positions of these periodic structures are described by the Liesegang regularities. Detailed information about the bands is given (formation time, coordinate, width, height, and formation rate). The supramolecular ordering anisotropy of the resulting material was evaluated both by the number of Liesegang bands (up to 16) and by the average values of the TEA diffusion coefficient ((15-153) × 10-10 and (4-33) × 10-10 m2/s), corresponding to the initial and final phase of the experiment, respectively. The minimum chitosan concentration required to form a spatial gel network and, accordingly, a layered anisotropic structure was estimated as 1.5 g/dL. Morphological features of the structural anisotropic ordering of chitosan Liesegang structures are visualized by scanning electron microscopy. The hemocompatibility of the material obtained was tested, and its high sorption-desorption properties were evaluated using the example of loading-release of cholecalciferol (loading degree ~35-45%, 100% desorption within 25-28 h), which was observed for a hydrophobic substance inside a chitosan-based material for the first time.

Combining a Lipophilic Phenanthroline Carboxamide and a Hydrophilic Diglycolamide to Increase the Separation Factors of Adjacent Light Lanthanides

ABSTRACT The combination of two neutral CHON reagents, a lipophilic phenanthroline dicarboxamide and a hydrophilic diglycolamide, resulted in a synergistic separation of adjacent light lanthanides in nitrate medium as the ligands present a reversed lanthanide selectivity. Separation factors higher than 7 were obtained for the pair Pr/Nd, which is one of the highest values reported in the literature.

Bis(1-Methyl-ortho-Carboranyl)Borane.

The Lewis superacid, bis(1-methyl-ortho-carboranyl)borane, is rapidly accessed in two steps. It is a very effective hydroboration reagent capable of B-H addition to alkenes, alkynes, and cyclopropanes. To date, this is the first identified Lewis superacidic secondary borane and most reactive neutral hydroboration reagent.

Bis(1‐Methyl‐ortho‐Carboranyl)Borane

AbstractThe Lewis superacid, bis(1‐methyl‐ortho‐carboranyl)borane, is rapidly accessed in two steps. It is a very effective hydroboration reagent capable of B−H addition to alkenes, alkynes, and cyclopropanes. To date, this is the first identified Lewis superacidic secondary borane and most reactive neutral hydroboration reagent.

Separation of neptunium and plutonium with neutral phosphorus ligands: A theoretical perspective

Effective treatment of the transuranic neptunium and plutonium from nuclear waste is of great importance and remains a challenge for developing advanced nuclear fuel cycles. Currently, novel ligands for efficient separation of actinides need to be designed urgently. Neutral extractants containing phosphorus have shown great potential for actinides separation. In this paper, we systematically explored the extraction and separation performances of neptunium(IV,V,VI) and plutonium(IV) by three phosphorus derivatives, di(1-methyl-heptyl) methyl phosphonate (P350), tri-iso-amyl phosphate (TiAP), and tributyl phosphate (TBP) by density functional theory (DFT). The outcomes showed that these neutral phosphorus reagents act as monodentate ligands through the PO group for all the extraction complexes. According to bonding nature analysis, the P350 ligand has the strongest complexing ability to the studied actinide cations. In addition, these ligands show a preference to coordination with Pu4+ and NpO22+ over Np4+ and NpO2+, respectively. As expected, the thermodynamic analysis demonstrated the potential application of these neutral extractants in Np and Pu separation, among which the P350 ligand is more promising than TBP and TiAP in acid solution system. This work can help to further understand the separation mechanism of Np/Pu with neutral phosphorus reagents and provide insight into the development of highly efficient extractants in recovery of Np and Pu.

Abiotic Synthetic Antibody Inhibitor with Broad-Spectrum Neutralization and Antiviral Efficacy against Escaping SARS-CoV-2 Variants.

The rapid emergence and spread of vaccine/antibody-escaping variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has posed serious challenges to our efforts in combating corona virus disease 2019 (COVID-19) pandemic. A potent and broad-spectrum neutralizing reagent against these escaping mutants is extremely important for the development of strategies for the prevention and treatment of SARS-CoV-2 infection. We herein report an abiotic synthetic antibody inhibitor as a potential anti-SARS-CoV-2 therapeutic agent. The inhibitor, Aphe-NP14, was selected from a synthetic hydrogel polymer nanoparticle library created by incorporating monomers with functionalities complementary to key residues of the SARS-CoV-2 spike glycoprotein receptor binding domain (RBD) involved in human angiotensin-converting enzyme 2 (ACE2) binding. It has high capacity, fast adsorption kinetics, strong affinity, and broad specificity in biologically relevant conditions to both the wild type and the current variants of concern, including Beta, Delta, and Omicron spike RBD. The Aphe-NP14 uptake of spike RBD results in strong blockage of spike RBD-ACE2 interaction and thus potent neutralization efficacy against these escaping spike protein variant pseudotyped viruses. It also inhibits live SARS-CoV-2 virus recognition, entry, replication, and infection in vitro and in vivo. The Aphe-NP14 intranasal administration is found to be safe due to its low in vitro and in vivo toxicity. These results establish a potential application of abiotic synthetic antibody inhibitors in the prevention and treatment of the infection of emerging or possibly future SARS-CoV-2 variants.

Regio- and Enantioselective Allylic Cyanomethylation by Synergistic Rhodium and Silane Catalysis.

Rh/silane-cocatalyzed regio- and enantioselctive allylic cyanomethylation with inert acetonitrile directly has been developed. Addition of a catalytic amount neutral silane reagent as an acetonitrile anion carrier is essential for the success of this reaction. The synthesis of mono- and bis-allylation products can be switched by adjusting the size of substituents on the silane, ligands, and temperature. Chiral homoallylic nitriles could be synthesized in above 20:1 branch/linear ratio, up to 98% yield and >99% ee.

Interaction of the anion [2-B<sub>10</sub>H<sub>9</sub>O(CH<sub>2</sub>)<sub>4</sub>O]− with secondary amines

Objectives. One of the most promising methods of treating malignant tumors is 10B-neutron capture therapy. While compounds based on cluster boron anions [BnHn]2− (n = 10, 12) are often used as boron-containing agents due to the very high specific concentration of boron atoms per particle, the use of such compounds is associated with the need to develop new methods for the functionalization of boron clusters associated with the production of boron-containing derivatives containing biologically active functional groups. One of the most convenient methods of modification of [BnHn]2− (n = 10, 12) anions is the interaction of their derivatives containing cyclic oxonium-type substituents with negatively charged or neutral nucleophilic reagents. The disclosure of substituents of this type leads to the formation of closo-borates with functional groups separated from the cluster by an alkoxyl spacer chain. The purpose of this study is to develop methods for the synthesis of derivatives of the closo-decaborate anion [B10H10]2− with pendant nitrogen-containing groups.Methods. The general control of the reactions of the disclosure of cyclic substituents was carried out on the basis of 11B nuclear magnetic resonance (NMR) spectroscopy data. The structure of the obtained derivatives, including the nature of the attached functional groups, was determined using 1H, 13C attached proton test (APT) NMR and infrared (IR) spectroscopy data. The molecular weight of the synthesized compounds was confirmed by electrospray ionization mass-spectrometry (ESI–MS).Results. The interaction of the anion [2-B10H9O(CH2)4O]− with secondary amines (dimethylamine, dipropylamine, diallylamine, dibutylamine, diisobutylamine, morpholine, di-sec-butylamine) in an ethanol environment is investigated. As a result of the reactions, a cyclic substituent is shown to expand with the addition of a nucleophilic reagent. Seven new derivatives of the closodecaborate anion with pendant nitrogen-containing groups have been synthesized.Conclusions. A developed method for obtaining closo-decaborates with ammonium groups separated from the boron cluster by an alkoxyl spacer group is presented. It is shown that the use of amines of various structures does not fundamentally affect the course of the reactions, allowing the composition and structure of the target derivatives to be effectively regulated. The resulting compounds can be involved in further modification reactions due to a reactive pendant group, as well as being suitable for use as effective polydentate ligands. Closo-decaborates with pendant nitrogen-containing groups and their derivatives are of considerable interest in the synthesis of compounds for use in 10B-neutron capture therapy of malignant tumors.

Recovery of arsenic oxide, harmless gypsum residue and clean water by lime neutralization and precipitation

The nonferrous metal smelting industry-an influential industry in China- produces a large quantity of arsenic-containing acidic wastewater (ACAW) that seriously hinders the development of the industry. In this study, low-cost and effective methods for treating acidic wastewater were systematically examined. Lime neutralization and compound salt precipitation were used to remove arsenic (As) from acidic wastewater. The residues produced during neutralization and compound salt precipitation were treated harmlessly by H2SO4 leaching, and As2O3 was recovered from the sulfuric acid leach solution (ALS). The results showed that the appropriate pH for the neutralization process was 3. The arsenic concentration in the solution after compound salt precipitation was <0.5 mg/L at pH 8.5 and suitable molar ratios (Cu/As: 0.45 to 2.3, Fe/As: 1.20 to 6.0, and Zn/As: 1.20 to 6.0). After acid leaching of residues obtained during neutralization and compound salt precipitation, the content of CaSO4 in the leach residue reached the specified value (CaSO4 ≥ 75 wt%) of industrial byproduct gypsum (GB/T 21371–2019 of China), and the concentration of arsenic in the toxicity leaching experiment was <5 mg/L. The ALS was reduced by SO2 to recover arsenic trioxide, and the recovery of arsenic reached 96.5%. Compared to the NaOH neutralization reagent, the lime treatment process is cost-effective and produces non-hazardous solid waste.

Oyster shell waste as potential co-substrate for enhancing methanogenesis of starch wastewater at low inoculation ratio

This study evaluated the effect of oyster shells on the methanogenesis of starch wastewater subjected to over-acidification (pH < 4.5) at low inoculum/substrate ratios, and revealed that oyster shells could be used as co-substrates for methane production. The methane yield was improved by approximate 86-folds with optimal dose when compared with that in control. Oyster shells conditioning synchronously improved the acidogenesis and hydrogenotrophic methanogenesis steps, resulting in high methane production. These improvements were attributed to the fact that the oyster shells served as the neutralizing reagent and buffered the sharp pH drop. Carbon dioxide was also released during this process, which was subsequently converted into methane and contributed 17% of the total methane yield. Furthermore, some spheroid and rod microcolonies were observed on the surfaces of the oyster shells. Along with the remarkable enrichment of acetotrophic and methylotrophic methanogens, these microbes benefitted the successful methanogenesis of starch wastewater.