P-toluenesulfonic Acid Research Articles

Formation of Bis‐indolylmethanes from Symmetrical Triarylmethanes via Brønsted Acid Catalyzed C−C Bond Breaking Reaction

AbstractAn alternative approach to synthesize bis‐indolylmethanes (BIMs) via a unique p‐toluenesulfonic acid (PTSA) catalyzed dual Csp3−Csp2 bond‐breaking reaction has been reported here. In the reported protocol, 1,3,5‐trimethoxybenzene (TMB), an electron‐rich and sterically bulky arene, acts as a carbon‐based leaving group which can be recovered after the completion of the reaction. In this process, several BIMs of various indole derivatives can be synthesized from symmetrical triarylmethanes (TRAMs) containing bis‐TMB motifs. By modifying the reaction conditions, we could control the sequential bond cleavage of two Csp3−Csp2 bonds in starting TRAM.

Method for Synthesis of 4-(4-Hydroxyphenyl)cycloalkanedicarboxylic Acids Based on SEAr Alkylation

A study was carried out on the alkylation reaction of anisole with cycloalkenedicarboxylic acids in the presence of various catalytic systems. It was found that the reaction proceeds with high yields in the presence of aluminum chloride, ferric chloride, and p-toluenesulfonic acid. The possibility of further cleavage of the ether bond to obtain 4-(4-hydroxyphenyl)cycloalkanedicarboxylic acids was demonstrated. The resulting compounds are potential biologically active compounds.

Electrocatalytic Hydrogen Evolution Reaction of Cobalt Triaryl Corrole Bearing Nitro Group

The use of non–precious metals for electrocatalytic hydrogen reaction (HER) is particularly important for energy conservation and environmental protection. In this work, three new cobalt corroles containing o−, m−, and p−nitrobenzyl (1, 2, 3) at the meso 10−position of the corrole macrocycle were synthesized, and their electrocatalytic hydrogen evolution reaction in organic and neutral aqueous systems was also investigated. The results show that these three cobalt corroles have significant catalytic HER activity in both systems, and the catalytic efficiency follows 1 > 3 > 2, which indicates that the position of the nitro group can affect the catalytic property of the complexes. In the organic phase, when using trifluoroacetic acid or p−toluenesulfonic acid as the proton source, the electrocatalytic HER may undergo an EECC (E: electron transfer, C: proton coupling) pathway. In a neutral aqueous system, the HER turnover frequency value of 1 is up to 137.4 h−1 at 938 mV overpotential.

Unsymmetric Co-Facial "Salixpyrrole" Hydrogen Evolution Catalysts: Two Metals are Better than One.

Designing ligand architectures that can mimic enzyme active sites is a promising approach for developing efficient small molecule activation catalysts for sustainable energy applications. Some key design features include chemically distinct binding pockets for multiple metal centers and a three-dimensional structure that controls the positioning of catalytic sites. With these principles in mind, mono- and bimetallic unsymmetric cofacial palladium complexes, 2 and 3, respectively, bearing ligands with calixpyrrole and salen coordination sites, or "salixpyrrole" ligands, are reported. These species were accessed in a straightforward Schiff-base reaction with appreciable yields. In addition, both 2 and 3 were found to be active hydrogen evolution electrocatalysts using para-toluenesulfonic acid monohydrate as the proton source. The two salixpyrrole species displayed different mechanisms of action, with 2 showing a second-order dependence on acid concentration, whereas 3 exhibited a first-order dependence. Moreover, the bimetallic catalyst was significantly more efficient, with higher turnover frequencies, 4640 s-1 vs 1680 s-1 for 2, and lower overpotentials, 0.39 V vs 0.69 V for 2. The results reported herein provide proof-of-concept that bimetallic catalysts with chemically distinct binding sites demonstrate enhanced catalytic properties in comparison to monometallic or symmetric analogues.

Precision detection of cyanide, fluoride, and hydroxide ions using a new tetraseleno-BODIPY fluorescent sensor

A new chemosensor based on Seleno-BODIPY (4) was designed and synthesized for the rapid and sensitive detection of CN–, F−, and OH– ions in THF, exhibiting ultra-low detection limits of 26.26 nM, 43.05 nM, and 8.64 nM, respectively, through a turn-on fluorescent process. The seleno-funcionalization step was based on a novel methodology developed by our group, allowing direct functionalization of the BODIPY core. This procedure involves a quick reaction utilizing Ph2Se2 as a selenium source, BPO (benzoyl peroxide), and p-TSA (p-toluenesulfonic acid) in acetonitrile, enabling the production of the corresponding chalcogenated BODIPYs containing one to four selenium groups, demonstrating its versatility. The structure of BODIPY 4 was confirmed by HRMS, 1H, 13C, 77Se NMR, and IR spectra, and its photophysical properties were also evaluated. BODIPY 4 was applied to detect CN–, F−, and OH– ions in dual-mode detection (UV–Vis and fluorescence spectra), displaying a ratiometric response. The new probe exhibited a fast response time, visual color change from blue to fluorescent yellow, and high sensitivity and selectivity for these analytes over other selected anions. Mechanistic investigation through mass analysis revealed that the detection of these anions by BODIPY 4 occurs via an Aromatic Nucleophilic Substitution reaction with phenylselenide as the leaving group.

Enhancing structural diversity through chemical engineering of Ambrosia tenuifolia extract for novel anti-glioblastoma compounds

Natural products are an unsurpassed source of leading structures in drug discovery. The biosynthetic machinery of the producing organism offers an important source for modifying complex natural products, leading to analogs that are unattainable by chemical semisynthesis or total synthesis. In this report, through the combination of natural products chemistry and diversity-oriented synthesis, a diversity-enhanced extracts approach is proposed using chemical reactions that remodel molecular scaffolds directly on extracts of natural resources. This method was applied to subextract enriched in sesquiterpene lactones from Ambrosia tenuifolia (Fam. Asteraceae) using acid media conditions (p-toluenesulfonic acid) to change molecular skeletons. The chemically modified extract was then fractionated by a bioguided approach to obtain the pure compounds responsible for the anti-glioblastoma (GBM) activity in T98G cell cultures. Indeed, with the best candidate, chronobiological experiments were performed to evaluate temporal susceptibility to the treatment on GBM cell cultures to define the best time to apply the therapy. Finally, bioinformatics tools were used to supply qualitative and quantitative information on the physicochemical properties, chemical space, and structural similarity of the compound library obtained. As a result, natural products derivatives containing new molecular skeletons were obtained, with possible applications as chemotherapeutic agents against human GBM T98G cell cultures.

Enhancing Optical and Thermal Stability of Blue-Emitting Perovskite Nanocrystals through Surface Passivation with Sulfonate or Sulfonic Acid Ligands.

This study aims to enhance the optical and thermal properties of cesium-based perovskite nanocrystals (NCs) through surface passivation with organic sulfonate (or sulfonic acid) ligands. Four different phenylated ligands, including sodium β-styrenesulfonate (SbSS), sodium benzenesulfonate (SBS), sodium p-toluenesulfonate (SPTS), and 4-dodecylbenzenesulfonic acid (DBSA), were employed to modify blue-emitting CsPbBr1.5Cl1.5 perovskite NCs, resulting in improved size uniformity and surface functionalization. Transmission electron microscopy and X-ray photoelectron spectroscopy confirmed the successful anchoring of sulfonate or sulfonic acid ligands on the surface of perovskite NCs. Moreover, the photoluminescence quantum yield increased from 32% of the original perovskite NCs to 63% of the SPTS-modified ones due to effective surface passivation. Time-resolved photoluminescence decay measurements revealed extended PL lifetimes for ligand-modified NCs, indicative of reduced nonradiative recombination. Thermal stability studies demonstrated that the SPTS-modified NCs retained nearly 80% of the initial PL intensity when heated at 60 °C for 10 min, surpassing the performance of the original NCs. These findings emphasize the optical and thermal stability enhancement of cesium-based perovskite NCs through surface passivation with suitable sulfonate ligands.

Deprotonation-induced changes in π-electron systems of iridium(III) and rhodium(III) complexes with azophenine

N,N′,N′′,N′′′-Tetraphenyl-2,5-diamino-1,4-benzoquinonediimines (RAp·H2) are used as unique bridging ligands containing localized π-electron systems at each of the two NCCCNH moieties, which are susceptible to changes on coordination of the N atoms to Lewis acid(s). In this contribution, we disclose deprotonation-induced changes in the π-electron systems, spectroscopic properties, and electronic state of cationic cyclometalated iridium(III) and rhodium(III) complexes with 4-EtAp·H2, i.e., [M(ppy)2(4-EtAp·H2)]Cl (ppy: 2-phenylpyridinate; M: Ir(III) (1·H2+) and Rh(III) (2·H2+)). The cationic complexes possessed localized π-electron systems, but the NCCCNH moieties were isomerized from those in free 4-EtAp·H2. Although 4-EtAp·H2 showed no responsiveness to tetrabutylammonium hydroxide (TBAOH) as a base, the reaction of 1·H2+ and 2·H2+ with TBAOH afforded monodeprotonated neutral complexes [M(ppy)2(4-EtAp·H)] (M: Ir(III) (1·H) and Rh(III) (2·H)). UV–vis absorption spectral titrations of 1·H2+ and 2·H2+ with TBAOH revealed the occurrence of monodeprotonation even in the presence of 4 equivalents of TBAOH. The cationic complexes were regenerated from 1·H and 2·H upon addition of p-toluenesulfonic acid. X-ray crystallography of 2·H showed that the complex has localized and delocalized π-electron systems at the NCCCNH and NCCCN moieties, respectively. The UV–vis absorption spectra of 1·H2+ and 2·H2+ in CH2Cl2 present intense bands around 500 nm, and those of 1·H and 2·H exhibit intense bands around 450 nm and broad bands around 700 nm. Density functional theory (DFT), time-dependent DFT, and natural transition orbital calculations suggest that the intense bands of all complexes and the broad bands of 1·H and 2·H stem from π–π* transitions in the localized and delocalized π-electron systems, respectively, with MLCT transition.

Design and Development of p-toluenesulfonic acid Functionalized Dual-functional Fe-MOF@SBC Heterogeneous Catalyst for Efficient Biodiesel Production and Photocatalytic Degradation of Metronidazole

Design and Development of p-toluenesulfonic acid Functionalized Dual-functional Fe-MOF@SBC Heterogeneous Catalyst for Efficient Biodiesel Production and Photocatalytic Degradation of Metronidazole

Ethyl Cyanoacetate Reactions

Ethyl cyanoacetate is a chemical intermediate that has been frequently used. The esterification of cyanoacetic acid and absolute ethanol with a mixed catalyst yielded ethyl cyanoacetate (the same proportion of silicotungstic and p-toluene sulfonic acid as catalyst). The influence factors of the amount of catalyst, n (cyanoacetic acid): n (absolute ethanol), reaction time and reaction temperature on the esterification rate was investigated by orthogonal experiment of four factors and three levels. The product was analyzed by gas chromatography to determine the optimum reaction conditions

Characterization and optimization of ultrasound assisted oxidative desulfurization of a model fuel using a novel magnetic deep eutectic solvent

ABSTRACT In various studies, researchers have utilised different solvents to extract sulfur compounds from the fuels. This paper introduces a novel magnetic deep eutectic solvent employed in the ultrasound-assisted oxidative desulfurisation of dibenzothiophene within a model fuel. The solvent, synthesised at 85°C by combining choline chloride, p-toluene sulfonic acid, and FeCl₃, underwent characterisation through Fourier transform-infrared, Vibrating-sample magnetometer, and Raman spectrometry. Exploration of the key parameters, including oxidant to model fuel volumetric fraction percentage (0.2–0.3), Iron (III) chloride to choline chloride mole fraction (0.1–0.3), and Magnetic deep eutectic solvent to model fuel volumetric fraction (0.2–0.3), was conducted to assess their impact on dibenzothiophene conversion rates. Employing response surface methodology based on central composite experimental design, optimal operational parameters for the ultrasound-assisted oxidative desulfurisation process were identified, resulting in a sulfur removal rate of 98.7%. The findings highlight the solvent sustained efficiency even at higher dibenzothiophene concentrations. Additionally, the solvent paramagnetic properties facilitated an expedited separation from the fuel, leading to the significantly reduced process times.

Novel catalyst-solvent system for high molecular weight polylactic acid synthesis via azeotropic solution polycondensation method

ABSTRACT Polycondensation for PLA synthesis is widely used due to its cost-effectiveness, but it often leads to low molecular weight PLA. To address this limitation, researchers have explored different catalysts, with the stannous chloride and p-toluene sulfonic acid combination being a popular choice. However, this method typically yields PLA with a MW of no more than 35000 g/mol, which is unsuitable for commercial applications. In contrast, ring-opening polymerization is considered the most effective method for synthesizing high MW PLA, despite its complexity and cost. Industrial-scale production predominantly employs ROP due to its capability to produce high MW PLA. The use of stannous octoate as a catalyst for ROP has shown promise in synthesizing higher MW PLA. However, its sensitivity to water limits its use in polycondensation, where stannous chloride is commonly employed but is not capable of synthesizing high MW PLA. This study explores the use of stannous octoate for the synthesis of high MW PLA with higher yield.

Experimental and dynamic molecular study of zinc extraction from sphalerite concentrate in ternary deep eutectic solvent

The utilization of deep eutectic solvents (DESs) as a novel class of solvents in metal production offers a promising alternative to aqueous solutions due to their biocompatibility and non-aqueous nature. This study investigated the leaching of sphalerite concentrate using a ternary stable DES composed of choline chloride (ChCl), p-toluene sulfonic acid (PTSA), and ethylene glycol (EG) (at a molar ratio of 1:1:1). The effects of time, temperature, and milling time on zinc recovery were examined within specific ranges (20–1440 min, 40–100 °C, and 0–24 h, respectively). The study revealed the significant influence of time and temperature on zinc dissolution efficiency within ChCl:PTSA:EG. Higher temperatures and longer leaching times were found to improve efficiency substantially. The research emphasized the crucial role of milling time, demonstrating that longer durations enhanced zinc efficiency by introducing more defects on the sphalerite surface and reducing particle size. Under optimized conditions, including a temperature of 100 °C, 24 h of ball milling, and 1440 min of leaching, a zinc recovery of 99.7% was achieved. Infrared analysis confirmed the chemical stability of the solvents during the leaching process. The sphalerite leaching process involved the formation of zinc chloride ion complexes and evolution H2S gas. An unexpected finding is the presence of lead sulfate in the leach residue, which may be attributed to sulfide oxidation to sulfate species. The Avrami kinetic model provided an excellent fit with the sphalerite dissolution data in ChCl:PTSA:EG DES, indicating that the rate-controlling step was primarily influenced by the diffusion process. R2 values for kinetics fitting data were in the range of 0.87–0.97 for temperature of 40–100 °C. The molecular dynamic (MD) simulation findings indicated robust electrostatic interactions between the metal ions Zn2+ and Fe2+ and the Cl− ions of the ChCl molecules. Additionally, the MD calculations showed that the metal ions formed complexes with some O-S-O atoms within the PTSA molecule.

Preparation of single crystals of palmatine-sulfophenyl acids pharmaceutical salts by substituting Cl− in palmatine chloride to improve hygroscopic stability and antibacterial activity of palmatine and to preserve its solubility

To enhance the hygroscopic stability of palmatine chloride (PMTCl) while maintaining its solubility, several unexplored pharmaceutical salts of palmatine (PMT) were synthesised using benzenesulfonic acid (PMT-BSA), p-toluenesulfonic acid (PMT-PTSA), and aminobenzenesulfonic acid (PMT-SUL). These novel salts were thoroughly characterized using techniques such as single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), infrared spectroscopy (IR), and Hirshfeld surface analysis to determine their structural properties. Surprisingly, it was discovered that these salts exhibited improved antibacterial activity in addition to their enhanced hygroscopic stability. As anticipated, all three pharmaceutical salts demonstrated improved hygroscopic stability. This improvement might be attributed, to some extent, to the introduction of safe, stable, and less electronegative anions (BSA, PTSA, and SUL) to replace the more electronegative chloride (Cl−) in PMTCl. The replacement of Cl− hindered the binding of the pharmaceutical with external water molecules, thus increasing its resistance to moisture. Moreover, the interaction between PMT and the anions from the benzenesulfonic acid group via hydrogen bonding might have played a role in the improved hygroscopic stability. The crystal structure formed by the PMT molecules exhibited long-range order, while the benzenesulfonic acid anions cleverly avoided potential binding sites for water molecules. Additionally, the antibacterial activities of all three pharmaceutical salts were enhanced. This improvement can be attributed to the alteration of electron cloud density (ρe) in the isoquinoline group of PMT upon the introduction of benzenesulfonate anions to form the pharmaceutical salts. This hypothesis was supported by analyzing the molecular electrostatic potential, electron cloud density, and Hirshfeld surface. The successful outcome of this study suggests that modifying the ρe of the isoquinoline group in protoberberines through the introduction of benzenesulfonic acid anions to form pharmaceutical salts can potentially alter their physicochemical properties and biological activities. This finding paves the way for future research on improving the physicochemical properties of protoberberines-based pharmaceuticals.

Preparation and characterization of MnIIMnIII complexes with relevance to class Ib ribonucleotide reductases

The Mn2 complex [MnII2(TPDP)(O2CPh)2](BPh4) (1, TPDP = 1,3-bis(bis(pyridin-2-ylmethyl)amino)propan-2-ol, Ph =phenyl) was prepared and subsequently characterized via single-crystal X-ray diffraction, X-ray absorption, electronic absorption, and infrared spectroscopies, and mass spectrometry. 1 was prepared in order to explore its properties as a structural and functional mimic of class Ib ribonucleotide reductases (RNRs). 1 reacted with superoxide anion (O2•–) to generate a peroxido-MnIIMnIII complex, 2. The electronic absorption and electron paramagnetic resonance (EPR) spectra of 2 were similar to previously published peroxido-MnIIMnIII species. Furthermore, X-ray near edge absorption structure (XANES) studies indicated the conversion of a MnII2 core in 1 to a MnIIMnIII state in 2. Treatment of 2 with para-toluenesulfonic acid (p-TsOH) resulted in the conversion to a new MnIIMnIII species, 3, rather than causing O—O bond scission, as previously encountered. 3 was characterized using electronic absorption, EPR, and X-ray absorption spectroscopies. Unlike other reported peroxido-MnIIMnIII species, 3 was capable of oxidative O—H activation, mirroring the generation of tyrosyl radical in class Ib RNRs, however without accessing the MnIIIMnIV state.

Evolution of morphology, structure, and performance of the COF membranes with monomer concentrations: Enabling effective desalination and kinetics analysis

Fabricating crystalline covalent organic framework (COF) membrane with sub-nanopores for desalination remains challenging. Monomer (p-phenylenediamine (Pa) and 1,3,5-triformylphloroglucinol (Tp)) concentration was crucial to tailor the diffusion-reaction process in the p-toluenesulfonic acid (PTSA)-mediated interfacial catalytic polymerization process for crystalline TpPa-COF membrane fabrication. By increasing monomer concentration, membrane surface color evolved from light yellow to dark orange. TpPa-COF layers with adjustable thickness (90.47–436 nm) transformed from amorphous to crystalline with crystalline and cross-linking degree increasing from 16.47 % to 73.90 %, and 66.40 % to 87.60 %, respectively. Pore size decreased from 1.69 to 0.17 nm, while Na2SO4 rejection significantly increased from 26.7 % to 90.4 %. A 3-day filtration test for RO concentrate demonstrated the stability and robust desalination performance with SO42− rejection ratio of 74.3 ± 1.08 % and Mg2+ rejection ratio of 65.6 ± 1.33 %. Diffusion behavior experiments demonstrated that diffusion coefficient for Pa-PTSA complex (6.49 × 10−5–8.87 × 10−5 cm2 s−1, Pa > 0.05 wt%) higher than Tp (3.53 × 10−6–6.39 × 10−6 cm2 s−1, Tp > 0.006 wt%) by one order of magnitude promoted structural crystallinity and regulated assembly at the interface, resulting in TpPa-COF layer with sub-nanopores. This study highlighted the importance of monomer concentration on the COF membrane formation, providing valuable insights for the highly crystalline COF membrane fabrication.

Crystal structures, Hirshfeld surface analysis, thermogravimetric, and spectroscopic properties of three Zn(Ⅱ) complexes bridged by 4,4′-bipy with organic sulfonate anions as counterions

Three Zn(Ⅱ) sulfonate compounds: {[Zn3(Ac)4(4,4′-bipy)4]·2(3-pySO3)·H2O}n (1), {[Zn(4,4′-bipy)(H2O)4]·2(Me-phSO3)}n (2), and {[Zn(4,4′-bipy)(H2O)4]·2(NH2-phSO3)}n (3), were synthesized through solvent diffusion method at room temperature (3-pySO3H = Pyridine-3-Sulfonic acid; Me-phSO3H = P-Toluene Sulfonic acid; NH2-phSO3H = Sulfanilic acid). Single-crystal X-ray diffractions reveal that the crystal structure of compound 1 contains a 2D cationic layer with pseudo-square grid motifs formed by trinuclear Zn(II) units which connected by 4,4′-bipy ligands. Water molecule forms hydrogen bonds with free 3-PySO3− anions which are located in the voids of the cationic grids. Compounds 2 and 3 show isostructural 1D [Zn(4,4′-bipy)(H2O)4]2+ chains with sulfonate anions connected to the chain via hydrogen bonding. The weak interactions in the structures of the three compounds have been assessed using Hirshfeld surface analyses and 2D fingerprint plots. The Hirshfeld surface shows that the most important contributions for the crystal packing are from H···H and H··O/O··H interactions, which indicate dominant van der Waals interactions. In addition, the compounds were investigated by powder X-ray diffraction (PXRD), elemental analyses, UV–vis, FT-IR, solid-state fluorescence spectroscopy, and thermal analyses (TG-DSC).

Innovative deep decontamination of radioactive solid surfaces using microemulsions of deep eutectic solvents in supercritical carbon dioxide

Radioactive solid wastes resulting from the application of nuclear energy pose a risk to the environment, yet traditional decontamination methods generate many secondary wastes. Thus, sustainability-driven innovations are receiving increasing attention to achieve eco-friendly decontamination methods characterized by minimizing secondary waste generation. Here, we proposed a sustainable and pioneering approach to decontaminate radioactive solid wastes using microemulsions of deep eutectic solvents (DESs) in supercritical carbon dioxide (SC-CO2). We also determined the optimal ratios of the additives as follows: prepared DESs with a molar ratio of choline chloride (ChCl) to p-toluenesulfonic acid monohydrate (ptsa) of 1:2, and nonyl phenol polyoxyethylene ether (NP-10) to ChCl:ptsa DESs in a molar ratio of 0.8. Remarkably, after optimization of the decontamination process in terms of pressure, temperature and cleaning time, the radioactivity on the sample surface can be reduced to a level that is reusable in the nuclear field. Detailed analyses provided insights into the intermolecular interactions within the DESs. And the decontamination mechanisms involved the spontaneous evolution of microemulsions with ChCl:ptsa as the core to facilitate the solvation and removal of radioactive contaminants. Additionally, repeated cleaning was proved to be effective for ultra-deep decontamination, with the radioactivity on the sample surface reaching a clearance level and a decontamination efficiency of 99.8%. The DESs-in-CO2 systems successfully decontaminated various materials and simulated radionuclides, even real radioactive metal wastes from the nuclear industry. It was notable that the DESs-in-CO2 systems achieved decontamination efficiencies of more than 95.0% for radioactive contaminants on these solid surfaces. Overall, this innovative approach provided a green alternative to conventional radioactive solids decontamination, meeting the need for sustainable development of nuclear energy.

Integrated Preparation of Hollow Lignin Nanoparticles as a Drug Carrier and Levulinic Acid from the Poplar Wood Prehydrolysis Liquor.

Prehydrolysis liquid (PHL) from dissolving pulp and biorefinery industries is rich in saccharides and lignin, being considered as a potential source of value-added materials and platform molecules. This study proposed an environmentally friendly and simple method to prepare morphologically controllable hollow lignin nanoparticles (LNPs) and levulinic acid (LA) from PHL. In the first step, after hydrothermal treatment of PHL with p-toluenesulfonic acid (p-TsOH), lignin with a uniform molecular weight was obtained to prepare LNPs. The prepared LNPs have an obvious hollow structure, with an average size of 490-660 nm, and exhibit good stability during 30 days of storage. When the as-obtained LNPs were used as a sustained-release agent for amikacin sulfate, the encapsulation efficiency reached over 70% and the release efficiency within 40 h reached 69.2% in a pH 5.5 buffer. Subsequently, the remaining PHL that contains saccharides was directly used for LA production under the catalysis of p-TsOH. At 150 °C for 1.5 h, the LA yield reached 58.4% and remained at 56% after 5 cycles of p-TsOH. It is worth noting that only p-TsOH was used as a reactive reagent throughout the entire preparation process. Overall, this study provided a novel pathway for the integrated utilization of PHL and showed the immense potential of the preparation and application of LNPs.

Lignin nanoparticles as a highly efficient adsorbent for the removal of methylene blue from aqueous media

This work demonstrated enhanced adsorption capabilities of lignin nanoparticles (LNPs) synthesized via a straightforward hydrotropic method compared to pristine lignin (PL) powder for removing methylene blue dye from aqueous solutions. Kraft lignin was used as a precursor and p-toluenesulfonic acid as the hydrotrope to produce spherical LNPs with ~ 200 nm diameter. Extensive characterization by SEM, AFM, DLS, zeta potential, and BET verified successful fabrication of microporous LNPs with fourfold higher specific surface area (14.9 m2/g) compared to PL (3.4 m2/g). Significantly reduced particle agglomeration and rearranged surface chemistry (zeta potential of −13.3 mV) arising from the self-assembly of lignin fractions under hydrotropic conditions enabled the application of LNPs and superior adsorbents compared to PL. Batch adsorption experiments exhibited up to 14 times higher methylene blue removal capacity, from 20.74 for PL to 127.91 mg/g for LNPs, and ultrafast equilibrium uptake within 3 min for LNPs compared to 10 min for PL. Kinetic modeling based on pseudo-first-order and pseudo-second-order equations revealed chemisorption as the predominant mechanism, with a rate constant of 0.032825 g/mg·h for LNPs—over an order of magnitude higher than PL (0.07125 g/mg·h). Isotherm modeling indicated Langmuir monolayer adsorption behavior on relatively uniform lignin surface functional groups. The substantially augmented adsorption performance of LNPs arose from the increased surface area and abundance of surface functional groups, providing greater accessibility of chemically active binding sites for rapid dye uptake. Overall, this work demonstrates that tailoring lignin nanoparticle structure and surface chemistry via scalable hydrotropic synthesis is a simple and sustainable approach for producing highly efficient lignin-based nano-adsorbents for organic dye removal from industrial wastewater.