Mild Modification Research Articles

Transforming tire-derived char into powerful arsenic adsorbents by mild modification

A large amount of arsenic-containing wastewater discharged by the non-ferrous metal industry will cause serious environmental problems if it is not properly treated. Pyrolysis char of waste tire is a kind of solid waste. Since the surface properties of tire derived char (TC) are affected by tar/ash adhesion during pyrolysis, it is necessary to modify TC to treat wastewater containing As(V) effectively as an adsorbent. At present, most studies on the modification of TC are prepared into activated carbon by high temperature activation in N2 atmosphere. In this study, TC was modified at room temperature and air atmosphere, and Fe(OH)3-TCNaOH adsorbent with particle size of 61–75 μm was obtained under the premise of the removal rate of As(V) and the settling performance of the adsorbent. When the initial concentration of As(V) was 5 mg/L, the removal rate of As(V) by Fe(OH)3-TCNaOH with a particle size of 61–75 μm could reach 90% within 30 min under a wide pH range (3–9). The adsorption of As(V) by Fe(OH)3-TCNaOH was most affected by the coexistence of PO43-, which resulted in the removal rate of As(V) decreased by about 20%. The adsorption mechanism shows that the significant increase in the number of 3–5 nm mesoporous pores of Fe(OH)3-TCNaOH and the formation of H bonds are beneficial to the adsorption of Fe(OH)3-TCNaOH to As(V), and improve the stability of Fe-As complex.

Mild condition lignin modification enabled high-performance anticorrosive polyurethane coating

The diverse active hydroxyl groups of lignin pose challenges in the preparation of lignin-based polyurethane coatings with exceptional long-term anticorrosive properties. Here, the dense and defect-free lignin-based polyurethane coating with a thickness of 25 ± 5 μm was successfully synthesized using a mild hydroxypropyl lignin modification approach, exhibiting outstanding barrier properties (|Z| > 109 Ω cm2) and long-term anti-corrosion performance exceeding 120 d. Under ambient conditions (i.e., 25 °C and atmospheric pressure), propylene oxide was directly blended with the alkali solution of lignin to effectively convert phenolic hydroxyl groups into more reactive aliphatic hydroxyl groups, while also minimizing the significant increase in molecular weight caused by lignin condensation. As a result, the high crosslinking density of lignin polyurethane coatings effectively prevented the penetration of corrosive media and enhanced the long-term corrosion resistance of the coatings. Overall, the results demonstrate that a mild hydroxypropyl modification process is an effective and facile strategy to prepare highly reactive lignin-based polyols, which is crucial for the development of high-performance bio-based polyurethane anticorrosive coatings.

Efficient and facile dual post-polymerization modification using acetoacetate-acrylate Michael addition

Post-polymerization modification (PPM) is a valuable strategy for achieving diversified functional polymers; nonetheless, the pursuit of achieving mild and efficient dual modification along the polymeric backbone remains as a challenge. In this work, the Michael addition reaction of acetoacetates and acrylates have been demonstrated as a robust PPM technique. The reversible addition-fragmentation chain transfer polymerization of commercially available 2-(acetoacetoxy)ethyl methacrylate provides a polymer scaffold with controlled molecular weight and acetoacetate groups. These pendant groups are capable of undergoing efficient double addition reactions with acrylates, leading to an increased density of functional moieties within the polymeric backbone. This PPM reaction exhibits unique advantages such as mild reaction conditions (at 40 °C), rapid kinetics (completion within 1 h), and high atom economy. Consequently, a series of polymers with tunable thermal stability, glass transition temperature, and hydrophilicity have been successfully synthesized. Applications have been demonstrated for both the synthesis of polymers exhibiting aggregation-induced luminescence and the preparation of luminescent materials with adjustable mechanical properties. This pioneering work unveils a robust post-polymerization modification technique, significantly advancing the synthesis of innovative functional polymers.

In-situ deposition modification of hydrophilic polytetrafluoroethylene (PTFE) membranes using surfactants as anchoring points for long-term stability

Polytetrafluoroethylene (PTFE) membranes are renowned for their excellent thermal stability, resistance to strong acids and alkalis, and superior mechanical stability. However, its inherent strong hydrophobicity significantly limits its use in water treatment. In this study, a SiO2 coating was successfully deposited in-situ on the surface of PTFE membranes using a hydrolyzed solution of tetraethyl orthosilicate (TEOS) compounded with the commercial fluorinated polyoxyethylene ether surfactant FS-31 (C6F13CH2CH2O(CH2CH2O)nH). The modification mechanism involves using the low surface energy nonionic fluorocarbon surfactant FS-31, which interacts hydrophobically with the PTFE substrate, serving as an “anchor” point around which the TEOS hydrolyzes and condenses around the fibers and nodes of the PTFE membrane, forming a complete and stable chemical network structure. The results show that the initial water contact angle of the modified membrane dropped to 36.5°, and the water flux reached 537.9 L m−2 h−1. After being continuously immersed in strong acid (5 wt% HCl), strong alkali (4 wt% NaOH), and oxidizing agent (5 wt% NaClO) for one week, the membrane maintained excellent hydrophilicity and stability. This study proposes a mild and efficient modification method to prepare durable hydrophilic PTFE membranes, portending great potential for applications in harsh environments.

Microbial Decontamination of Cuminum cyminum Seeds Using "Intensification of Vaporization by Decompression to the Vacuum": Effect on Color Parameters and Essential Oil Profile.

Cumin seeds are frequently utilized in herbal infusions and as flavoring agents in home cuisine. Nevertheless, studies have demonstrated that spices are frequently contaminated with pathogenic bacteria, including bacterial spores. The aim of this study was to assess the effectiveness of a new decontamination method called "Intensification of Vaporization by Decompression to the Vacuum" (IVDV) on intentionally contaminated Cuminum cyminum seeds. The study also examined the impact of this treatment on the color and oil profile of the treated samples. The untreated samples were inoculated with Escherichia coli (ATCC 25922) and Salmonella Typhimurium (ATCC 14028) and then subjected to IVDV treatment. Response surface methodology was employed to obtain safe, high-quality cumin seeds presenting a balance between microbial load, color, and oil profile. The optimal IVDV conditions were achieved at a pressure of 3.5 bar and a time of 133.45 s, resulting in typical 4 log reductions observed with 99.99% of Escherichia coli and Salmonella Typhimurium inactivation. The treated spices presented a mild color modification compared to the untreated ones, manifested by a darker shade (decreased L* value), reduced greenness (increased a* value), and heightened yellowness (increased b* value). The GC-MS analysis detected the existence of seven compounds in the treated cumin, with cuminaldehyde being the primary compound (83.79%). Furthermore, the use of IVDV treatment resulted in an increase in the total content of essential oils in some samples, whereby six monoterpenes were identified in the untreated sample compared to seven monoterpenes in IVDV-treated samples. This innovative technology demonstrated high efficacy in decontaminating C. cyminum seeds, improving the extractability of the essential oils while only slightly affecting the color.

Mild modification of sponge-like carbon: Ammonia post-treatment for enhanced CO2 adsorption and suitability for supercapacitors

During the synthesis of carbon-based CO2 adsorbents and supercapacitors, the introduction of nitrogen atoms into the carbon matrix has been identified as a means to enhance their performance. Nevertheless, the intricate effects of nitrogen doping on material properties pose a significant challenge in developing efficient methodologies. In this investigation, porous carbons resembling sponges were fabricated utilizing macadamia nut shells as a precursor and a dual salt comprising K2C2O4-KCl as an activating agent. Subsequent modification of the materials through ammonia post-treatment facilitated the production of nitrogen-doped porous carbon. The alterations in surface characteristics and pore morphology after ammonia treatment were meticulously examined to unravel the underlying mechanism of this modification process. The samples under scrutiny showcased remarkable CO2 adsorption capacities, peaking at 6.97 mmol/g at 0 °C and 4.65 mmol/g at 25 °C. Employing mathematical models to probe the influence of pore structure and surface properties on CO2 adsorption efficacy proved to be fruitful. A linear correlation was established to depict CO2 adsorption behavior, underscoring the joint impact of ultramicropore volume and nitrogen content on the adsorption process. Notably, the material exhibited a specific capacitance of 290.4F/g at a current density of 0.5 A/g within a three-electrode configuration, demonstrating commendable rate capability and cyclic stability. The pivotal findings from this inquiry emphasize that ammonia post-treatment represents a gentle modification strategy exerting minimal influence on the pore architecture, thereby efficaciously enhancing both CO2 adsorption and electrochemical performance.

Chemical Composition of Larch Oleoresin before and during Thermal Modification

Larch is a strong timber, which grows rapidly in the UK climate, but can contain abundant resin pockets. To address the resin exudation issue, a mild thermal modification process has been developed, promoting the curing of the resin. This paper reports a series of studies which characterised the chemical profile of larch oleoresin before and after the mild thermal treatment, explaining the changes which occur when resin is dried. Further experiments were used to simulate specific points in time during the mild treatment process. The non-polar components of the fresh (untreated) and treated larch oleoresin were profiled using gas chromatography mass spectrometry (GC-MS). Fresh larch oleoresin was also subjected to isothermal experiments at different temperatures in a thermogravimetric analyser–differential scanning calorimeter (TGA/DSC), followed by re-analysing the resin composition. This demonstrated the loss of monoterpenes at temperatures of 120 °C and above, with complete loss by isothermal conditions of 150 °C and 60 min. The partial loss of sesquiterpene alkanes and alkenes were also observed at all temperatures, although completeness of this loss was achieved at isothermal temperatures of 150 °C and above. The diterpene composition was seen to change for isothermal experiments conducted at 150 °C and above, with a dehydration of terpenols to form the equivalent terpene alkenes. The observed physical changes in the TGA/DSC experiment were in good agreement with observations of the oleoresin sampled from thermally modified larch planks.

A novel eco-friendly and economical approach of bamboo colorization through biomimetic polymerization of dopamine melanin inspired by photonic microstructure of bird plumage

Bamboo is a low-carbon, sustainable, and versatile substitute for many synthetic materials, but limited variety of color restricts bamboo's decoration performance and added value. Traditional chemical colorization suffers poor generality, massive resource consumption, low colorfastness, high pollution, and remarkable damage to bamboo. This research pioneered an eco-friendly, economical approach to tailor bamboo color while keeping natural texture. Through a facile, mild modification by dopamine (a tyrosine derivative), its biomimetic polymerization endowed bamboo surface with a double-layered polydopamine melanin system mimicking morphology and composition of (keratin layer)/(melanin granules) microstructure of colorful bird plumage. Chromatic-optical and microstructural characterizations showed that polydopamine system's upper layer was nanoscale ∼ submicronscale (thickness 55∼215 nm) film bestowing on bamboo structural colors through thin-film interference. All colors at visible wavelength could be formed through controlling film thickness by adjusting dopamine concentration. Thicker film was more continuous and smoother, while thinner film was stabler. Polydopamine system's lower layer was micronscale (thickness 1.2∼4.4 μm) aggregate of particles enhancing color saturation through suppressing light scattering. Amorphous arrangement of polydopamine system made structural colors on bamboo display weak angle dependence. Physicochemical characterizations proved that bamboo featured non-covalent interaction with deposited polydopamine, which never destroyed bamboo's crystalline structure. Structural colors on bamboo exhibited satisfactory stability in long-term exposure and mechanical washing tests. Overall, proposed colorization was confirmed eco-friendly, convenient, and effective, thus contributing novel ideas to cleaner production in bamboo utilization.

Influence of Brönsted Acid Sites on Activated Carbon-Based Catalyst for Acetylene Dimerization.

Activated carbon (AC) has been widely used as a support material with both tunable acidity and abundant functional groups for solid acid catalysts in various chemical processes such as acetylene dimerization. A facile, mild acid modification method that directly activates AC to generate rich defects and oxygen functional group surface structures with Brönsted acid sites and an enhanced conductivity is presented here. Impressively, the catalyst with optimized Brönsted acid sites and an enhanced dispersion of active components exhibited a superior acetylene dimerization catalytic activity. Moreover, theoretical calculations indicated that an increase in hydrogen concentration could inhibit the formation of coke. This research offered a feasible potential way to devise and construct a carbon-based solid acid catalyst with an excellent catalytic performance.

Regulating oxygenated groups and carbon defects of carbon-based catalysts for electrochemical oxygen reduction to H2O2 by a mild and self-recycled modification strategy

It is a green route to prepare H2O2 through electrochemical oxygen reduction at normal temperature and pressure using only oxygen and water as feedstock. This method is suitable for the distributed production of H2O2, avoiding the safety problems caused by long-term storage and long-distance transportation. We propose a mild strategy modulating carbon materials i.e., the carbon black is treated by a low-concentration H2O2, where the oxidation reactions occur by hydroxyl radicals. The oxygenated groups and carbon defects were regulated by adjusting the concentration H2O2 used. The modified carbon black showed excellent selectivity and stability in the electrosynthesis of H2O2 under neutral conditions. The optimal catalyst had a selectivity of 99% for H2O2 at a potential of 0.25 V vs. reversible hydrogen electrode and remained above 90% in a wide potential window. The activity of optimal catalyst was increased by 19% compared to the pristine carbon black. It was found that the improvement of catalytic activity and selectivity was mainly ascribed to carbon defect. The concentration of H2O2 produced was 0.33 mol L−1 with 80% Faradaic efficiency at 4.5 V in the flow cell. The productivity of H2O2 could reach 2.23 mol g−1 h−1 during a continuous operation of 10 h.Graphical

Electrochemical oxidative heterodifunctionalization of dehydroalanine: access to unnatural α,α-disubstituted amino esters

A general, efficient, and mild Dha electrochemical modification strategy is reported, which enables a divergent route to various α,α-disubstituted amino esters via anodic cascade oxidation and nucleophilic attack.

Portable hydroxyl-functionalized coal gangue-based cordierite porous ceramics sheets for effective adsorption of fluorine-containing wastewater.

Monolithic adsorbent removal of fluoride from water is considered an effective and non-secondary pollution method. Here, a portable hydroxyl-functionalized coal gangue-based cordierite porous ceramic sheet (ACGC-Fe) is prepared by using coal gangue solid waste with a specific silicon-aluminum-rich composition ratio and a small amount of magnesium oxide as a raw material through powder compression molding and mild chemical modification. The prepared ACGC-Fe can be used to treat fluorine-containing wastewater and the maximum adsorption of fluorine can reach 18.69 mg g-1. The Langmuir (Freundlich) adsorption isotherm model and pseudo-second-order kinetic model here provided a satisfactory description of the fluoride removal operating mechanism, and it is confirmed that the adsorption mechanism of ACGC-Fe is mainly attributed to the chemisorption of hydrogen bonds (with hydroxyl group) and ionic bonds (with metal), and physical adsorption based on cordierite porous ceramic pores. This research will provide a new idea for designing high-performance materials by mining and analyzing the composition and structure characteristics of coal gangue solid waste itself and broaden the application range of high-value-added coal gangue solid waste.

Tetrazine-based linkers as intrinsically tagged alternatives for click functionalization of metal-organic frameworks.

Reticular chemistry has in the post-synthetic modification (PSM) of frameworks one of the most versatile tools to adapt the systems' physicochemical properties to the specific requirements which are imposed by their application in different contexts. We can safely say that PSM methodologies in all their variants are currently one of the main resources that reticular chemists turn to when they need to diversify a framework compositionally. Practically all these modifications require the integration of functional groups appended to the organic linkers in the framework, either by direct synthesis or by post-synthetic exchange. The reactivity of these tags allows, at a subsequent stage, covalent modification of the framework under conditions that ideally respect its structural integrity. In this perspective article we introduce the use of tetrazine-based linkers as intrinsically tagged alternatives to integrate PSM with click chemistry reactivity. This strategy is ideally suited to molecular frameworks, as it combines very mild modification conditions with direct control over the organisation of built-in appendices and the acknowledged potential of click chemistry to build framework libraries.

Mild Acid-Alkali Modification of Ceramsite: a Low-Cost Adsorbent for Lead Removal

Mild Acid-Alkali Modification of Ceramsite: a Low-Cost Adsorbent for Lead Removal

Modulating covalent organic frameworks with accessible carboxyl to boost superior extraction of polar nitrobenzene compounds from matrix-complicated beverages.

The wide use and high polarity of nitrobenzene compounds (NBCs) have caused a concern for their residues in daily beverages. Herein, the covalent organic frameworks (COFs) with abundant carboxyl were ingeniously designed by introducing a novel modulator, and further developed as solid phase microextraction (SPME) coatings. Due to the enhanced polar interaction, the extraction efficiencies of modified COF for NBCs were sharply increased. After coupling the high-performance SPME fiber with gas chromatograph-mass spectrometry (GC-MS), an ultrasensitive analytical method was developed, with a wide linear range (0.50-5000ng/L), and low limits of detection (0.15-3.0ng/L). More importantly, the method was highly feasible and practical, leading to the precise determinations of trace NBCs from variously matrix-complicated samples. This work provides a viable and efficacious approach for the extraction and analysis of polar pollutants form complicated matrices, and is of great significance for mild COF modification and its extended applications in analytical chemistry.

Iron-Catalyzed Synthesis of Peroxylpyrrolo[2,1-a]isoquinolines through Oxidative Dearomatization.

A mild late-stage modification of pyrrolo[2,1-a]isoquinolines was established through iron-catalyzed oxidative dearomatization and peroxidation. Peroxylated pyrroloisoquinolines have been prepared readily with hydroperoxide in low to good yields (up to 72%) at room temperature. Interestingly, the treatment of fully aromatized pyrrolo[1,2-a]quinolines under the current reaction system resulted in the formation of ring-opening products.

Bio-AFM exploits enhanced response of human gingival fibroblasts on TiO2 nanotubular substrates with thin TiO2 coatings

The present work studies anodic TiO2 nanotube (TNT) layers and their surface modifications for enhancing the cell behavior of human gingival fibroblast cells (hGFs) with the contribution of bio-AFM (Atomic Force Microscopy) method. TNT layers, prepared via electrochemical anodization of Ti, with an average tube diameter of 15, 30, and 100 nm, were used as primary substrates for the study. Flat Ti foils were used as reference substrates. Part of the substrates was coated by ultrathin TiO2 coatings (≈ 0.3 nm thin) using Atomic Layer Deposition (ALD). The cell growth and adhesion of hGFs on the TNT layers and Ti foils were compared between ALD coated and uncoated ones. The supplemental coatings altered the surface chemistry of the TNT layers, particularly shading the fluorine and carbon impurities within anodic TiO2, while preserving the original structure and morphology. The presented approach of very mild surface modification remarkably effects the material's biocompatibility and possess great prospect as implant materials. For the first time, the TNT/cell interface was investigated using bio-AFM in terms of Young's modulus, stiffness, cell adhesive force and roughness. Improved biocompatibility was studied in terms of increased cell viability, density, cell cytoskeleton orientation and overall stiffness of the hGFs.

Preparation of amidoxime polyacrylonitrile membrane with excellent mechanical strength for adsorption of uranium in simulated wastewater

The effective extraction and recovery of uranium from uranium-containing wastewater are of great significance to environmental protection and the reuse of uranium resources. However, many new methods are generally limited by either sustainability, technical complexity or manufacturing cost. Here we designed an amidoxime polyacrylonitrile membrane (APM) with excellent mechanical strength, high removal efficiency, and low cost for the extraction of uranium from weakly acidic uranium-containing simulated wastewater. The APM was prepared by hydroxylamine hydrochloride modified polyacrylonitrile membrane (PM) with a simple process and mild modification conditions. Batch experiments were performed to explore the adsorption effect of the APM in simulated uranium-containing wastewater and investigate the adsorption mechanism of the adsorption process. The results showed that the APM had a high nitrile conversion rate (43.90 %) and strong mechanical strength (tensile fracture stress was 0.335 MPa) as the modification condition of 60 °C, 30 min. The static adsorption rate of uranium reached 96.96 % in simulated wastewater. The adsorption process was a multi-molecular layer chemical adsorption process, which involved electric charge attraction and ligand exchange. To sum up, this work presented a simple and environmental-friendly preparation method of membrane for effectively extracting uranium from weakly acidic uranium-containing wastewater.

Boronic acid-functionalized magnetic porphyrin-based covalent organic framework for selective enrichment of cis-diol-containing nucleosides

In this study, a novel boronic acid-functionalized magnetic porphyrin-based covalent organic framework (COF) with a core-shell structure was designed and synthesized for the selective enrichment and detection of nucleosides. Firstly, brominated porphyrin-based COF was in situ grown on Fe3O4-NH2 nanospheres (denoted as Fe3O4@Br-COF), then a post-synthetic modification strategy was used to introduce boronic acid into the framework via Suzuki-Miyaura cross-coupling reaction to obtain boronic acid functionalized magnetic COF (denoted as Fe3O4@BA-COF). Suzuki-Miyaura cross-coupling possesses the advantages of mild synthesis conditions, high tolerance to functionalities, and ease of handling and separation, which is considered as a promising candidate for functionalizing COF. It is worth mentioning that the porphyrin-based COF possesses a unique nitrogen-rich skeleton and “trap” structure formed by four pyrrole rings, which can provide hydrogen bond and make it more suitable for trapping analytes than other types of COF. The boronic acid group provides boronate affinity, which enables better selective enrichment of cis-diol-containing nucleoside. The morphology and structure of the prepared Fe3O4@BA-COF was characterized by various methods. Based on the Fe3O4@BA-COF, a facile magnetic solid phase extraction coupled with high performance liquid chromatography method (MSPE-HPLC) was used to extract and detect adenosine, guanosine, uridine, and cytidine in urine samples. This work not only provides a mild and feasible post-synthetic modification method for fabrication of boronic acid-functionalized magnetic COF, but also provides an efficient and rapid method to selectively enrich and detect hydrophilic nucleosides.

Solution Plasma for Surface Design of Advanced Photocatalysts

Rational design of the surface of photocatalysts can conveniently modulate the photo-stimulated charge separation, influence the surface reaction kinetics, and other pivotal factors in the photocatalytic processes for efficient photocatalysis. Solution plasma, holding promise for mild modification of the surface structure of materials, has recently been recognized as an emerging technology for surface engineering of high-performance photocatalysts. In this review, we will briefly introduce the fundamentals of solution plasma and its applications in materials preparation and summarize the recent research progress in the surface design of advanced photocatalysts by solution plasma. Lastly, we will indicate some possible new directions. This review is expected to provide an instructive guideline for the surface design of heterogeneous photocatalysts by solution plasma.