Oligomeric Products Research Articles

Polyphenols and Their Biogenic Nano-Formulations Targeting BACE1 as Anti-Amyloid Therapies; Meeting the Challenges of Bioavailability, Safety, and Specificity for the Treatment of Alzheimer's Disease.

Alzheimer's disease (AD), a progressiveneurodegenerative condition is marked by extensive damage in the brain and dementia. Among the pathological hallmarks of AD is beta-amyloid (Aβ). Production of toxic Aβ oligomers production and accumulation in the brain is among the characteristic features of the disease. The abnormal accumulation Aβ is initiated by the catalytic degradation of Amyloid Precursor Proteins (APP) by Beta Amyloid Cleaving Enzyme 1 (BACE1) to generate insoluble amyloid plaques. The abnormal proteins are mitochondrial poison which disrupt the energy production and liberate excessive free radicals causing neuronal damage and mutations. Consequently, targeting Aβ-associated pathways has become a focus in the pursuit of developing effective AD treatments. An obstacle faced by many medications used to treat neurodegenerative diseases (NDs) is the restricted permeability across the blood-brain barrier (BBB). Unfortunately, no anti-amyloid drug is clinically approved till now. Recent advancements in nanotechnology have provided a possible solution for delivering medications to specific targets. By integrating natural products with nano-medicinal approaches, it is possible to develop novel and highly efficient therapeutic strategies for the treatment of AD.

Evaluation of Physicochemical and Biological Properties of Chitosan Hydrolysate Produced by Microwave-Assisted Cellulase Hydrolysis

AbstractThis work estimated the biochemical nature of the enzymatic chitosan hydrolysate (CH) as oligomeric chitooligosaccharide products resulting from microwave-aided cellulase hydrolysis of chitosan from shrimp and crab as well as their biological effects and potential preservative application. The microwave irradiation was conducted at 125 W for 15 min simultaneously during the cellulase degradation of shrimp and crab chitosan, previously prepared by a 30-min microwave-aided deacetylation (86.7% and 82.7% degree of deacetylation), producing shrimp chitosan hydrolysate (SCH) and crab chitosan hydrolysate (CCH), respectively. The products SCH and CCH were tested for their solubility in distilled water, viscosity, molecular weight (Mw), FTIR, mass spectra, antioxidant, and antibacterial activities. The obtained SCH and CCH were incorporated into two food systems (yogurt and orange juice) at proportions of 0.08–0.12 g/100 mL as potential preservatives. The average Mw of SCH and CCH was 14.79 and 13.18 kDa, respectively, coupled in each case with 1–6° of polymerization (DP), strong antibacterial and antioxidant activities, and the capacity to dissolve in water in all proportions, becoming more soluble as weight decreased. The chemical, microbiological, and sensory changes in orange juice and yogurt were investigated at 0, 15, and 30 days of cold storage after being enriched with these ingredients. Over the 30-day storage period, the orange juice and yogurt showed enhanced physicochemical, microbiological, and sensory characteristics based on the content of chitosan hydrolysate. The study provided potentially a new and safe preservation technology for food systems.

Online Mass Spectrometric Characterization of Oligomeric Products in High-Pressure Liquid-Phase Lignin Depolymerization Reactions

Online Mass Spectrometric Characterization of Oligomeric Products in High-Pressure Liquid-Phase Lignin Depolymerization Reactions

Influence of anti-fibrillation TNGQ peptide and rutin combination on β-cell cytoprotective effects against IAPP-induced cell death and oxidative stress

Type 2 diabetes development has been associated with islet amyloid polypeptide (IAPP) fibrillation. IAPP fibrils have various deleterious effects, such as oxidative stress and disruption of cellular membrane integrity, resulting in pancreatic β-cell toxicity. Rutin, a plant polyphenol, possesses promising cytoprotective effects as a fibrillation inhibitor. Similarly, bioactive peptides have been identified as potential inhibitors to IAPP fibrillation. In this study, the effect of peptide/polyphenol mixtures consisting of rutin and each peptide, TNGQ, MANT, and YMSV, on anti-fibrillation activity and cellular response was elucidated. Results indicated a 54.7–75.1 % decrease in thioflavin T fluorescence, confirming anti-fibrillation activity. The combination decreased the average particle diameters of IAPP more than the single inhibitors, suggesting a combined effect of peptide/rutin mixtures in enhancing anti-fibrillation activity. IAPP fibrillation-induced rat insulinoma RIN-m cell death was minimized in the presence of the peptide/rutin mixture, but the activity was lower relative to rutin alone, suggesting a non-additive effect of the mixtures. Transmission electron microscopy showed a near-complete inhibition of IAPP fibrillation by TNGQ/rutin mixtures, which translated to a decreased production of membrane-bound IAPP oligomers in RIN-m cells based on immunofluorescence staining. Additionally, TNGQ/rutin mixtures significantly decreased reactive oxygen species production by 30 %, higher than the effects of single inhibitors, but no effect was observed on glucose-stimulated insulin secretion. The results demonstrate the potential of multifunctional compounds as dual inhibitor systems in controlling IAPP fibrillation and provide insight into the implications of peptide/polyphenol mixtures towards the rational development of novel anti-diabetic nutraceutical combinations.

Biodegradable Polyurethane Foams Based on Polyols Obtained from Cellulose and Its Hydroxypropyl Derivative.

Three methods of cellulose-derived polyol synthesis were elaborated. The suitable substrates were (hydroxypropyl)cellulose or cellulose, which were hydroxyalkylated in reactions with glycidol and ethylene carbonate in triethylene glycol or in water. The products were characterized by IR, 1H NMR, and MALDI ToF spectroscopies. For all polyols, IR spectra showed strong bands at 1060 cm-1 from the ether group formed upon the ring opening of GL and EC. The polyol obtained from (hydroxypropyl)cellulose in the triethylene glycol solvent was accompanied by oligomeric products of glycol hydroxyalkylation and oligomeric glycidol. The polyol obtained by the hydroxyalkylation of cellulose with glycidol and ethylene carbonate in the water contained units of hydroxyalkylated cellulose and products of hydroxyalkylation of water. The physical properties of the obtained polyols, like density, viscosity, and surface tension, were determined. The polyols were then used to obtain rigid polyurethane foams. The foams have apparent density, water uptake, and polymerization shrinkage similar to classic rigid PUFs. The foams showed advantageous thermal resistance in comparison with classic ones. After thermal exposure, their compressive strength improved. The biodegradation of the obtained materials was tested by a respirometric method in standard soil conditions by the measurement of biological oxygen demand and also using the cellulases or the enzymes responsible for cellulose degradation. It has been found that polyols are totally biodegradable within one month of exposure, while the foams obtained thereof are at least 50% biodegraded in the same conditions. The enzymatic biodegradation of the PUFs by the action of microbial cellulase was confirmed.

Misincorporations of amino acids in p53 in human cells at artificially constructed termination codons in the presence of the aminoglycoside Gentamicin.

Readthrough of a translation termination codon is regulated by ribosomal A site recognition and insertion of near-cognate tRNAs. Small molecules exist that mediate incorporation of amino acids at the stop codon and production of full-length, often functional protein but defining the actual amino acid that is incorporated remains a challenging area. Herein, we report on the development a human cell model that can be used to determine whether rules can be developed using mass spectrometry that define the type of amino acid that is placed at a premature termination codon (PTC) during readthrough mediated by an aminoglycoside. The first PTC we analyzed contained the relatively common cancer-associated termination signal at codon 213 in the p53 gene. Despite of identifying a tryptic peptide with the incorporation of an R at codon 213 in the presence of the aminoglycoside, there were no other tryptic peptides detected across codon 213 that could be recovered; hence we constructed a more robust artificial PTC model. P53 expression plasmids were developed that incorporate a string of single synthetic TGA (opal) stop codons at S127P128A129 within the relatively abundant tryptic p53 peptide 121-SVTCTYSPALNK-132. The treatment of cells stably expressing the p53-TGA129 mutation, treated with Gentamicin, followed by immunoprecipitation and trypsinization of p53, resulted in the identification R, W, or C within the tryptic peptide at codon-TGA129; as expected based on the two-base pairing of the respective anticodons in the tRNA to UGA, with R being the most abundant. By contrast, incorporating the amber or ochre premature stop codons, TAA129 or TAG129 resulted in the incorporation of a Y or Q amino acid, again as expected based on the two base pairings to the anticodons, with Q being the most abundant. A reproducible non-canonical readthrough termination codon-skip event at the extreme C-terminus at codon 436 in the SBP-p53 fusion protein was detected which provided a novel assay for non-canonical readthrough at an extreme C-terminal PTC. The incorporation of amino acids at codons 127, 128, or 129 generally result in a p53 protein that is predicted to be 'unfolded' or inactive as defined by molecular dynamic simulations presumably because the production of mixed wild-type p53 and mutant oligomers are known to be inactive through dominant negative effects of the mutation. The data highlight the need to not only produce novel small molecules that can readthrough PTCs or C-terminal termination codons, but also the need to design methods to insert the required amino acid at the position that could result in a 'wild-type' functional protein.

Oligomerization of Fischer-Tropsch Olefins by Radical Initiation Method for Synthesizing Poly Olefin Base Oils

In the present work we have investigated the oligomerization process of Fischer-Tropsch synthesis products – gasoline (C5-C10) and diesel (C11-C18) hydrocarbon fractions with a total olefin content (consisting mainly olefins with a branched isomeric chain) of 79.3 and 31.8 wt.%, respectively. Oligomerization was carried out by radical initiation method using azobisisobutyronitrile, benzoyl peroxide, dicumyl peroxide and methyl ethyl ketone peroxide (Butanox M-50) as initiators. It was established that the yield of the oligomerization process depending on the initiator used decreases in the following order: azobisisobutyronitrile > benzoyl peroxide > dicumyl peroxide > Butanox M-50. It was determined that when the oligomerization is carried out in polar solvents such as acetone and dichloromethane the yield of product increases by ~2.1 and ~1.7 times, respectively, while at the same time adding a non-polar solvent such as tetrachloromethane to the reaction mixture decreases the product yield by ~2.0 times. The optimal technological parameters for carrying out oligomerization process of synthetic gasoline and diesel fractions were determined: where azobisisobutyronitrile, content 0.5 wt.%., is used as an initiator, acetone as solvent, with reaction temperature of 200 °C, and duration of 12 hrs. under inert atmosphere. The product yield from the diesel fraction is 39.5 %, and from the synthetic gasoline fraction – 36.0 %. At the same time, in terms of characteristics, the oligomerization product of the diesel fraction showed properties similar to commercially available Base oil 3cSt (Group III), and the gasoline fraction showed properties on par with the commercially produced PAO-2 (Group IV). Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Inhibitory Effects of New Epicatechin Oligomers on Nitric Oxide Production.

The primary aim of this research was to identify the structural characteristics of three newly derived procyanidins from cold plasma-treated (-)-epicatechin, known for their anti-inflammatory properties. The newly generated compounds were isolated through column chromatography, and their chemical structures were elucidated through spectroscopic data analyses, including both one-dimensional and two-dimensional nuclear magnetic resonance (NMR) and mass spectrometry (MS) techniques. Furthermore, their absolute configurations were determined via circular dichroism (CD) spectroscopy. The inhibitory activity of the isolated compounds on nitric oxide (NO) production and expression levels of inducible NO synthase (iNOS) in lipopolysaccharide (LPS)-induced RAW 264.7 macrophages was evaluated. Three new procyanidins-methylenetrisepicatechin (2), isomethylenetrisepicatechin (3), and methylenebisepicatechin (4)-along with two reported dimeric flavan-3-ols (5 and 6), were identified from plasma-treated (-)-epicatechin (1). The unique oligomerized products 2 and 3 linked by methylene bridges significantly suppressed both NO production and iNOS expression, demonstrating higher anti-inflammatory activities in LPS-stimulated RAW 264.7 cells compared with the parent compound. The newly oligomerized procyanidins have potential applications in the treatment of inflammatory diseases owing to their significant anti-inflammatory properties.

Plant protein-based complex coacervation via protein deamidation

Protein-polysaccharide complex coacervates, as common electrostatic assembly, have been widely used in probiotic encapsulation, emulsifiers, and binders. However, due to their own compact structure, plant proteins usually complex with polysaccharides to form solid-like precipitates via liquid-solid phase separation (LSPS) instead of droplet-like coacervates via liquid-liquid phase separation (LLPS). In this study, we adopted an enzymatic deamidation approach to promote the transition of protein-polysaccharide complexes from precipitates to coacervates. β-conglycinin (β-CG), as a common plant protein, was modified by protein-glutaminase (PG) and complexed with chitosan oligosaccharide (COS) to obtain droplet-like coacervates. Native-PAGE and SDS-PAGE results demonstrated that depolymerization of β-CG occurred during deamidation, leading to the production of oligomers and changes in the surface charge patchiness of β-CG. Isothermal titration calorimetry (ITC) results showed that precipitates were mainly driven by exotherm, while coacervates were driven by entropy gain. This study offers a novel approach for the generation of plant protein-based coacervates.

Oligomerization of ethylene by dinuclear chromium catalysts bearing phenyl-bridged bifunctional imine-pyrrolide/thiophene ligands

Dinuclear chromium(III) complexes [Cr(Z)-2-(HCN)-2-OCH3C6H4)(THF)Cl2]2 (Z= C4H3N, L1-Cr2) or [Cr(Z)-2-(HCN)-2-OCH3C6H4)(THF)Cl3]2 (Z = C4H3S, L2-Cr2; Z = 5-methyl-C4H2S, L3-Cr2; Z = 5-phenyl-C4H2S, L4-Cr2) were synthesized by reaction of the phenyl-bridged bifunctional imine-pyrrole/thiophene ligands with [CrCl3(THF)3]. DFT calculations for L2-Cr2 revealed that both isomers (anti and syn) are stable presumably due to the nonrigid skeleton of this class of ligands. On activation with MAO, all chromium complexes showed catalytic activity in ethylene oligomerization, providing a non-selective distribution of α-olefins (C4-C12+) together with varying amounts of polymer (3.6 – 45.0 wt%). The nature of the pendant heterocyclic moieties plays a substantial influence on the catalytic performances of these binuclear Cr catalysts. L1-Cr2 bearing pyrrolide unit yielded a significant quantity of polymer (45.0 wt%) while the binuclear chromium complexes based on thiophene unit showed higher productivities towards production of oligomers (up to 94.4 wt%). These latter Cr complexes showed higher productivities in comparison to their mononuclear analogues. DFT calculations, assuming the formation of cationic chromium (III) species after treatment with MAO in ethylene atmosphere, suggested the coordination of the thiophene group to the chromium metal center, and thus influencing the catalytic performance of L2Cr2– L4-Cr2. By adjusting the reaction conditions, L3-Cr2 showed TOF of 131,100 mol ethylene·mol Cr−1·h−1 producing predominantly oligomers (89.3 wt% of total products) with high selectivity for α-olefins (>91.5 wt%).

Assessing the influences of kinetics and intrazeolite diffusion on propene oligomerization product selectivity in MFI zeolites

The inherently coupled influences of kinetics and intrazeolite diffusional constraints, together with the concurrent changes in zeolite properties among materials crystallized by conventional synthesis methods, obscure the relationship between propene oligomerization product selectivity and zeolite properties. Herein, we use a suite of MFI zeolites crystallized with independently varied H+-site density (0.3–5.7 H+/u.c.) and crystallite size (0.1–0.9 μm) together with effectiveness factor formalisms to assess the influences of kinetics and intrazeolite diffusional constraints on propene oligomerization selectivity, and the independent contributions of H+-site density and crystallite size to these influences. Extracting the kinetic influences of MFI properties and reaction conditions on propene oligomerization selectivity requires data measured at conditions where the extent of intrazeolite diffusional constraints imposed by products that occlude within MFI micropores and decrease effective diffusivity is fixed. Applying this framework to analyze product selectivity on MFI samples of varied crystallite size (0.3 H+/u.c.) reveals that selectivity to higher-rank products decreases with crystallite size because larger crystallites cause more severe intrazeolite propene concentration gradients, thereby decreasing rates of trimerization and higher-rank oligomerization reactions disproportionately relative to dimerization. MFI samples of higher H+-site density exhibit lower selectivity to higher-rank products, but a higher selectivity to oligomer products, reflecting differences in both kinetic rate constants and the composition of occluded products among these samples. Together, these findings demonstrate and rationalize the influences of H+-site density and crystallite size on propene oligomerization selectivity on MFI zeolites and provide a framework through which selectivity in transport-limited systems involving chain-growth reactions can be evaluated.

Moment dynamics of oligomer formation in protein amyloid aggregation with secondary nucleation

The abnormal aggregation of proteins into amyloid fibrils, usually implemented by a series of biochemical reactions, is associated with various neurodegenerative disorders. Considering the intrinsic stochasticity in the involving biochemical reactions, a general chemical master equation model for describing the process from oligomer production to fibril formation is established, and then the lower-order statistical moments of different molecule species are captured by the derivative matching closed system, and the long-time accuracy is verified using the Gillespie algorithm. It is revealed that the aggregation of monomers into oligomers is highly dependent on the initial number of misfolded monomers; the formation of oligomers can be effectively inhibited by reducing the misfolding rate, the primary nucleation rate, elongation rate, and secondary nucleation rate; as the conversion rate decreases, the number of oligomers increases over a long time scale. In particular, sensitivity analysis shows that the quantities of oligomers are more sensitive to monomer production and protein misfolding; the secondary nucleation is more important than the primary nucleation in oligomer formation. These findings are helpful for understanding and predicting the dynamic mechanism of amyloid aggregation from the viewpoint of quantitative analysis.

Obtaining materials for additive manufacturing based on modified oligomeric products of glycolysis of recycled polyethylene terephthalate with diethylene glycol

A technology has been developed for producing a photopolymerizing composition based on modified glycolysis products of recycled polyethylene terephthalate with diethylene glycol. The effect of dimethacrylic ether of triethylene glycol (TGM-3), used as an active diluent monomer, on the physical and mechanical characteristics of finished products is analyzed.

Template-based copying in chemically fuelled dynamic combinatorial libraries

One of science’s greatest challenges is determining how life can spontaneously emerge from a mixture of molecules. A complicating factor is that life and its molecules are inherently unstable—RNA and proteins are prone to hydrolysis and denaturation. For the de novo synthesis of life or to better understand its emergence at its origin, selection mechanisms are needed for unstable molecules. Here we present a chemically fuelled dynamic combinatorial library to model RNA oligomerization and deoligomerization and shine new light on selection and purification mechanisms under kinetic control. In the experiments, oligomers can only be sustained by continuous production. Hybridization is a powerful tool for selecting unstable molecules, offering feedback on oligomerization and deoligomerization rates. Moreover, we find that templation can be used to purify libraries of oligomers. In addition, template-assisted formation of oligomers within coacervate-based protocells changes its compartment’s physical properties, such as their ability to fuse. Such reciprocal coupling between oligomer production and physical properties is a key step towards synthetic life.

Tuning a Cr-Catalyzed Ethylene Oligomerization Product Profile via a Rational Design of the N-aryl PNP Ligands

An approach towards incorporating varied degrees of steric profiles around the ligand’s backbone, which were envisaged to alter the catalytic paths leading to targeted 1-C8/1-C6 olefin products, were explored. Cr-pre-catalysts designed with PNP ligands comprising a fused aryl moiety were delivered at a relatively higher C8 olefin selectivity (up to 74.6 wt% and C8/C6 of 3.4) when the N-connection to the aromatic unit was placed at the 2-position. A relatively higher C6 olefin selectivity (up to 33.7 wt% and C8/C6 of 1.9) was achieved with the PNP unit anchored at the 1- or 6-position. Based on detailed catalytic studies, we confirm the fact that by introducing a controlled degree of bulkiness on the N-site through a judicious selection of the N-aryl moiety of different sizes, the selectivity of the targeted olefin product could be tuned in a rational manner.

Oxidative Carboxylation of Lignin: Exploring Reactivity of Different Lignin Types.

The increased interest in the utilization of lignin in biobased applications is evident from the rise in lignin valorization studies. The present study explores the responsiveness of lignin toward oxidative valorization using acetic acid and hydrogen peroxide. The pristine lignins and their oxidized equivalents were analyzed comprehensively using NMR and SEC. The study revealed ring opening of phenolic rings yielding muconic acid- and ester-end groups and side-chain oxidations of the benzylic hydroxyls. Syringyl units were more responsive to these reactions than guaiacyl units. The high selectivity of the reaction yielded oligomeric oxidation products with a narrower dispersity than pristine lignins. Mild alkaline hydrolysis of methyl esters enhanced the carboxylic acid content of oxidized lignin, presenting the potential to adjust the carboxylic acid content of lignin. While oxidation reactions in lignin valorization are well documented, this study showed the feasibility of employing optimized oxidation conditions to engineer tailored lignin-based material precursors.

Influence of precursor aging and condensation progression on silica thin films grown by electrochemically induced sol-gel deposition

Electrochemically induced sol-gel enables the fast synthesis of functional oxide coatings. In the case of silica, the condensation reaction can be catalysed by electrogenerated hydroxides. Using this technique, highly organized nanostructured thin films can be deposited onto conductive substrates by combining structure-directing templates with the electrochemically induced silica sol-gel process that occurs locally at the electrode surface. This specific template-directed process, called electrochemically assisted self-assembly (EASA), utilizes a sol-gel precursor solution optimized for a minimal spontaneous condensation (and gelation) rate in the absence of an electrochemical trigger. Despite the slow kinetics of the condensation reaction, the solution remains unstable and some incipient condensation reactions will still occur over time, continuously modifying the Si(IV) precursor solution. In this work, we discuss how precursor's aging affects the deposition rate and the properties of the deposited coatings. Two distinct aging effects are observed: an aging effect which occurs over time and an aging effect which occurs through electrochemical activation during preceding depositions. Both these aging effects result in accelerated film growth rates, up to 200 × faster than the deposition rate from a fresh precursor solution. Additionally, it was observed that time aging yields less resistive, weaker films, while electrochemical aging leads to films which retain similar properties as films grown using fresh precursor solutions. The time aging effect could be inhibited by storing the precursor solution at -35 °C. These observations are explained based on the different condensation pathways during acidic and alkaline condensation, which is known to yield inherently different silica oligomer products. The results and insights described here contribute to upscaling the electrochemical sol-gel process for mesoporous silica films and provides further fundamental insights into the underlying silica condensation reactions.

Aβ Oligomer Dissociation Is Catalyzed by Fibril Surfaces.

Oligomeric assemblies consisting of only a few protein subunits are key species in the cytotoxicity of neurodegenerative disorders, such as Alzheimer's and Parkinson's diseases. Their lifetime in solution and abundance, governed by the balance of their sources and sinks, are thus important determinants of disease. While significant advances have been made in elucidating the processes that govern oligomer production, the mechanisms behind their dissociation are still poorly understood. Here, we use chemical kinetic modeling to determine the fate of oligomers formed in vitro and discuss the implications for their abundance in vivo. We discover that oligomeric species formed predominantly on fibril surfaces, a broad class which includes the bulk of oligomers formed by the key Alzheimer's disease-associated Aβ peptides, also dissociate overwhelmingly on fibril surfaces, not in solution as had previously been assumed. We monitor this "secondary nucleation in reverse" by measuring the dissociation of Aβ42 oligomers in the presence and absence of fibrils via two distinct experimental methods. Our findings imply that drugs that bind fibril surfaces to inhibit oligomer formation may also inhibit their dissociation, with important implications for rational design of therapeutic strategies for Alzheimer's and other amyloid diseases.

In-situ synthesized MgIn2S4/CdWO4 type-II heterojunction as a light-driven photoelectrochemical sensor for ultrasensitive detection of catechol in environmental water samples

As an essential chemical intermediate, catechol (CC) residues may have adverse effects on human health. Herein, an effective and facile photoelectrochemical sensor platform based on MgIn2S4/CdWO4 composite is constructed for monitoring CC. MgIn2S4 increases light absorption range and activity, while CdWO4 enhances photoelectronic stability, and the type-II heterojunction formed can significantly enhance photocurrent response. Due to the autoxidation process, CC is converted into oligomeric products, which increase the spatial site resistance and attenuate the overall photocurrent response. It is worth noting that the cauliflower-like structure of MgIn2S4 can provide a large specific surface area, and the presence of Mg2+ promotes autoxidation, thus providing a suitable condition for detecting CC. Under optimal conditions, the MgIn2S4/CdWO4/GCE photoelectrochemical sensor has a prominent linear relationship in the range of CC concentration from 2 nM to 7 μM, with a limit of detection of 0.27 nM. With satisfactory selectivity, excellent stability, and remarkable reproducibility, this sensor provides a crucial reference value for effectively and rapidly detecting pollutants in environmental water samples.

Homogenous Oxidizing Oligomerization Coupled with Coagulation for Water Purification

Natural manganese oxides could induce the intermolecular coupling reactions among small-molecule organics in aqueous environments, which is one of the fundamental processes contributing to natural humification. These processes could be simulated to design novel advanced oxidation technology for water purification. In this study, periodate (PI) was selected as the supplementary electron-acceptor for colloidal manganese oxides (Mn(IV)aq) to remove phenolic contaminants from water. By introducing polyferric sulfate (PFS) into the Mn(IV)aq/PI system and exploiting the flocculation potential of Mn(IV)aq, a post-coagulation process was triggered to eliminate soluble manganese after oxidation. Under acidic conditions, periodate exists in the H4IO6− form as an octahedral oxyacid capable of coordinating with Mn(IV)aq to form bidentate complexes or oligomers (Mn(IV)-PI*) as reactive oxidants. The Mn(IV)-PI* complex could induce cross-coupling process between phenolic contaminants, resulting in the formation of oligomerized products ranging from dimers to hexamers. These oligomerized products participate in the coagulation process and become stored within the nascent floc due to their catenulate nature and strong hydrophobicity. Through coordination between Mn(IV)aq and H4IO6−, residual periodate is firmly connected with manganese oxides in the floc after coagulation and could be simultaneously separated from the aqueous phase. This study achieves oxidizing oligomerization through a homogeneous process under mild conditions without additional energy input or heterogeneous catalyst preparation. Compared to traditional mineralization-driven oxidation techniques, the proposed novel cascade processes realize transformation, convergence, and separation of phenolic contaminants with high oxidant utilization efficiency for low-carbon purification.