Organic Surfactants Research Articles

NaCe(MoO4)2 microcrystals: Hydrothermal synthesis, characterization and photocatalytic performance

Sodium-cerium molybdate - NaCe(MoO4)2 - crystals were synthesized by the conventional hydrothermal method at 150 °C without using organic additives or surfactants. This material was characterized by X-ray diffraction (XRD), Raman and Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), UV–vis diffuse reflectance and zeta potential. The XRD pattern showed that the NaCe(MoO4)2 crystallizes in a scheelite-type tetragonal structure without secondary phases, as well as Raman and FT-IR spectroscopy confirm the formation of the NaCe(MoO4)2 tetragonal. SEM images show that the obtained samples have a truncated octahedral morphology with an average side length of ∼1.2 μm and high uniformity. The removal and degradation of Remazol Brilliant Blue (RB) and Methylene Blue (MB) dyes under visible light irradiation were analyzed, showing that the NaCe(MoO4)2 microcrystals exhibit favorable performance for the removal and/or degradation of these dyes, especially in the MB case.

Synthesis of a cationic organic silicone surfactant and its application in the flotation of smithsonite

A cationic organic silicone surfactant (DTA) with specially designed functional groups was developed as a flotation collector for smithsonite. This surfactant was synthesized via the reaction between hexaethyldisiloxane and N-β-(aminoethyl)-γ-aminoisobutylmethyldimethoxy silane using tetramethylammonium hydroxide as a catalyst. Its flotation performance was validated by flotation tests using pure minerals. The results illustrated that DTA has strong collecting ability and better selectivity for smithsonite against quartz, calcite and dolomite compared to the traditional collectors such as octadecylamine, tetradecylamine and dodecylamine. Based on the analysis of FTIR spectra, zeta-potential measurements, X-ray photoelectron spectroscopy and density functional theory calculations, it can be concluded that the adsorption mechanism of DTA on the surface of smithsonite was mainly dominated by chemisorption and electrostatic adsorption. DTA's unique properties, which include two coordination sites (NH2 and NH), and the “parachute” shape structure of OSi(C2H5)3, resulted in superior collecting powers for smithsonite.

Development of polycationic amphiphilic cyclodextrin nanoparticles for anticancer drug delivery.

Background: Paclitaxel is a potent anticancer drug that is effective against a wide spectrum of cancers. To overcome its bioavailability problems arising from very poor aqueous solubility and tendency to recrystallize upon dilution, paclitaxel is commercially formulated with co-solvents such as Cremophor EL® that are known to cause serious side effects during chemotherapy. Amphiphilic cyclodextrins are favored oligosaccharides as drug delivery systems for anticancer drugs, having the ability to spontaneously form nanoparticles without surfactant or co-solvents. In the past few years, polycationic, amphiphilic cyclodextrins were introduced as effective agents for gene delivery in the form of nanoplexes. In this study, the potential of polycationic, amphiphilic cyclodextrin nanoparticles were evaluated in comparison to non-ionic amphiphilic cyclodextrins and core–shell type cyclodextrin nanoparticles for paclitaxel delivery to breast tumors. Pre-formulation studies were used as a basis for selecting the suitable organic solvent and surfactant concentration for the novel polycationic cyclodextrin nanoparticles. The nanoparticles were then extensively characterized with particle size distribution, polydispersity index, zeta potential, drug loading capacity, in vitro release profiles and cytotoxicity studies.Results: Paclitaxel-loaded cyclodextrin nanoparticles were obtained in the diameter range of 80−125 nm (depending on the nature of the cyclodextrin derivative) where the smallest diameter nanoparticles were obtained with polycationic (PC) βCDC6. A strong positive charge also helped to increase the loading capacity of the nanoparticles with paclitaxel up to 60%. Interestingly, cyclodextrin nanoparticles were able to stabilize paclitaxel in aqueous solution for 30 days. All blank cyclodextrin nanoparticles were demonstrated to be non-cytotoxic against L929 mouse fibroblast cell line. In addition, paclitaxel-loaded nanoparticles have a significant anticancer effect against MCF-7 human breast cancer cell line as compared with a paclitaxel solution in DMSO.Conclusion: According to the results of this study, both amphiphilic cyclodextrin derivatives provide suitable nanometer-sized drug delivery systems for safe and efficient intravenous paclitaxel delivery for chemotherapy. In the light of these studies, it can be said that amphiphilic cyclodextrin nanoparticles of different surface charge can be considered as a promising alternative for self-assembled nanometer-sized drug carrier systems for safe and efficient chemotherapy.

Simultaneous effect of dissolved organic carbon, surfactant, and organic acid on the desorption of pesticides investigated by response surface methodology.

Desorption of pesticides (fenobucarb, endosulfan, and dichlorodiphenyltrichloroethane (DDT)) from soil to aqueous solution with the simultaneous presence of dissolved organic carbon (DOC), sodium dodecyl sulfate (SDS), and sodium oxalate (Oxa) was investigated in batch test by applying a full factorial design and the Box-Behnken response surface methodology (RSM). Five concentration levels of DOC (8 to 92mgL-1), SDS (0 to 6.4 critical micelle concentration (CMC)), and Oxa (0 to 0.15M) were used for the experiments with a rice field topsoil. The results of RSM analysis and analysis of variance (ANOVA) have shown that the experimental data could be well described by quadratic regression equations with determination coefficients (R 2) of 0.990, 0.976, and 0.984 for desorption of fenobucarb, endosulfan, and DDT, respectively. The individual effects and interaction of DOC, SDS, and Oxa were evaluated through quadratic regression equations. When the aqueous solution includes 50mgL-1 DOC, 3.75 CMC SDS, and 0.1 M Oxa, the maximum desorption concentrations of fenobucarb, endosulfan, and DDT were 96, 80, and 75μgL-1, respectively. The lowest concentration of SDS, DOC, and Oxa caused the minimum desorption. This point at conditions of concern for flooding water is high content of organic compounds causing potentially high contamination by desorption, and the remarkably lower desorption at organic matter-free conditions. The suspended organic matter is one of the common characteristics of flooding and irrigation water in rice fields, and surfactants from pollution increase the problem with desorption of legacy pesticides in the rice fields.

Surfactant- and Binder-Free Hierarchical Platinum Nanoarrays Directly Grown onto a Carbon Felt Electrode for Efficient Electrocatalysis.

The future of fuel cells that convert chemical energy to electricity relies mostly on the efficiency of oxygen reduction reaction (ORR) due to its sluggish kinetics. By effectively bypassing the use of organic surfactants, the postsynthesis steps for immobilization onto electrodes, catalytic ink preparation using binders, and the common problem of nanoparticles (NPs) detachment from the supports involved in traditional methodologies, we demonstrate a versatile electrodeposition method for growing anisotropic microstructures directly onto a three-dimensional (3D) carbon felt electrode, using platinum NPs as the elementary building blocks. The as-synthesized materials were extensively characterized by integrating methods of physical (thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, inductively coupled plasma, and X-ray photoelectron spectroscopy) and electroanalytical (voltammetry, electrochemical impedance spectrometry) chemistry to examine the intricate relationship of material-to-performance and select the best-performing electrocatalyst to be applied in the model reaction of ORR for its practical integration into a microbial fuel cell (MFC). A tightly optimized procedure enables decorating an electrochemically activated carbon felt electrode by 40-60 nm ultrathin 3D-interconnected platinum nanoarrays leading to a hierarchical framework of ca. 500 nm. Half-cell reactions reveal that the highly rough metallic surface exhibits improved activity and stability toward ORR (Eonset ∼ 1.1 V vs reversible hydrogen electrode, p(HO2-) < 0.1%) and the hydrogen evolution reaction (-10 mA cm-2 for only 75 mV overpotential). Owing to its unique features, the developed material showed distinguished performance as an air-breathing cathode in a garden compost MFC, exhibiting better current and faster power generation than those of its equivalent classical double chamber. The enhanced performance of the material obtained herein is explained by the absence of any organic surfactants on the surface of the nanoarrays, the good metal-support interaction, particular morphology of the nanoarrays, and the reduced aggregation/detachment of particles. It promises a radical improvement in current surface reactions and paves a new way toward electrodes with regulated surface roughness, allowing for their successful application in heterogeneous catalysis.

Synthesis of dodecylamine-functionalized graphene quantum dots and their application as stabilizers in an emulsion polymerization of styrene

Pickering emulsions have attracted considerable interest due to their potential applications in many fields, such as the food, pharmaceutical, petroleum and cosmetics industries. The study reports the synthesis of dodecylamine-functionalized graphene quantum dots (d-GQDs) and their implementation as stabilizers in an emulsion polymerization of styrene. First, d-GQDs are prepared by thermal pyrolysis of citric acid and dodecylamine in 0.1M ammonium hydroxide. The resulting d-GQDs consist of small graphene sheets with abundant amino, carboxyl, acylamino, hydroxyl and alkyl chains on the edge. The amphiphilic structure gives the d-GQDs high surface activity. The addition of d-GQDs can reduce the surface tension of water to 30.8mNm−1 and the interfacial tension of paraffin oil/water to 0.0182mNm−1. The surface activity is much better than that of previously reported solid particle surfactants for Pickering emulsions and is close to that of sodium dodecylbenzenesulfonate, which is, a classical organic surfactants. Then, d-GQDs are employed as solid particle surfactants for stabilizing styrene-in-water emulsions. The emulsions exhibit excellent stability at pH 7. However, stability is lost when the pH is more than 9 or less than 4. The pH-switchable behaviour can be attributed to the protonation of amino groups in a weak acid medium and dissociation of carboxyl groups in a weak base medium. Finally, 2,2′-azobis(2-methylpropionitrile) is introduced into the Pickering emulsions to trigger emulsion polymerization of styrene. The as-prepared polystyrene spheres display a uniform morphology with a narrow diameter distribution. The fluorescent d-GQDs coated their surfaces. This study presents an approach for the fabrication of amphiphilic GQDs and GQDs-based functional materials, which have a wide range of potential applications in emulsion polymerization, as well as in sensors, catalysts, and energy storage.

Zeolite modification for adsorptive removal of nitrite from aqueous solutions

Considering the occurrence of nitrite in drinking water sources, this paper investigated the modification of natural zeolite by acid, base, salt, organic surfactant, calcination and ultrasonication for eliminating nitrite from aqueous solutions. The structural and surface properties were analysed by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and nitrogen adsorption-desorption isotherm, and were used to explain the nitrite adsorption capacities of the zeolites. The results show that except acid modification, the rest measures did not impose notable influences on the zeolite properties. Modification of zeolite by acids markedly increased the specific surface area and strongly protonated the material, which greatly favored the nitrite adsorption onto the resulting zeolite. The adsorption isotherms were in good agreement with Langmuir-Freundlich models, and indicated an endothermic process. At 25 °C, the nitrite adsorption capacity of the zeolite modified by 0.75 mol L−1 of H2SO4 for 12 h (ACMZ) was 54.5 mg N g−1, being over 7-fold higher than that by the raw zeolite. The adsorption of nitrite onto ACMZ followed pseudo-first order kinetics. These facts suggest that the uptake of nitrite by acid modified zeolite was a chemical adsorption in nature.

Introduction of Anionic Surfactants to Copolymer Micelles: A Key to Improving Utilization Efficiency of P123 in Synthesis of Mesoporous Aluminosilicates

Mesoporous aluminosilicates (MAs) with high hydrothermal stability by assembly of zeolite Y precursors have been emerging as the most promising materials for cracking heavy oil molecules. A means to improve utilization efficiency of organic surfactants is of vital importance in synthesis of MAs. In this work, this goal was achieved by the introduction of ionic surfactant micelles in low concentration of copolymer. It is found that the strong interactions between the hydrophobic chain of sodium dodecyl sulfate (SDS) and poly(propylene oxide) (PPO) units of P123 lead to the formation of mixed micelles even at low concentration of P123. The self-aggregation of SDS molecules could induced the formation of mixed micelles with a core consisting of SDS micelles with PPO units and a corona of poly(ethylene oxide) (PEO) units. The mixed surfactants (SDS/P123) exhibited excellent performance for enhancing utilization efficiency of P123. This strategy developed a novel route for synthesis of MAs with high efficiency...

Spontaneous Pt Deposition on Defective Surfaces of In2O3 Nanocrystals Confined within Cavities of Hollow Silica Nanoshells: Pt Catalyst-Modified ITO Electrode with Enhanced ECL Performance.

Although the deposition of metallic domains on a preformed semiconductor nanocrystal provides an effective pathway to access diverse hybrid nanocrystals with synergistic metal/semiconductor heterojunction interface, those reactions that take place on the surface of semiconductor nanoscrystals have not been investigated thoroughly, because of the impediments caused by the surface-capping organic surfactants. By exploiting the interfacial reactions occurring between the solution and nanoparticles confined with the cavities of hollow nanoparticles, we propose a novel nanospace-confined strategy for assessing the innate reactivity of surfaces of inorganic semiconductor nanoparticles. This strategy was adopted to investigate the newly discovered process of spontaneous Pt deposition on In2O3 nanocrystals. Through an in-depth examination involving varying key reaction parameters, the Pt deposition process was identified to be templated by the defective In2O3 surface via a unique redox process involving the oxygen vacancies in the In2O3 lattice, whose density can be controlled by high-temperature annealing. The product of the Pt-deposition reaction inside the hollow silica nanoparticle, bearing In2O3-supported Pt catalysts inside the cavity protected by a porous silica shell, was proved to be an effective nanoreactor system which selectively and sustainably catalyzed the reduction reaction of small-sized aromatic nitro-compounds. Moreover, the surfactant-free and electroless Pt deposition protocol, which was devised based on the surface chemistry of the In2O3 nanoparticles, was successfully employed to fabricate Pt-catalyst-modified ITO electrodes with enhanced electrogenerated chemiluminescece (ECL) performance.

Cu(II)‐Catalyzed Ligand‐Free Oxidation of Diarylmethanes and Second Alcohols in Water

We developed a simple and efficient Cu(II)‐catalyzed ligand‐free oxidation of diarylmethanes and secondary alcohols using 70% tert‐butyl hydroperoxide (TBHP) in water. A series of diarylmethanes were directly oxidized into diaryl ketones in 67%–98% yields. Additionally, various secondary alcohols were also transformed into the desired products in 48%–98% yields. Importantly, the catalytic system in the absence of any organic solvent, surfactant, or phase transfer agent, had a wide substrate scope and a high tolerance for various functional groups.

Influence of surfactants on electrochemical growth of CdSe nanostructures and their photoelectrochemical performance

Cadmium selenide (CdSe) thin films were grown by electrochemical technique on fluorine-doped tin oxide (FTO)-coated conducting glass substrates in the presence of organic surfactants. The influence of organic surfactants like polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) on different physico-chemical properties and its subsequent impact on photoelectrochemical (PEC) performance of CdSe thin films have been investigated. It has observed that the organic surfactants play an important role in modifying the surface morphology of CdSe thin films. The compact grain like morphology of pure CdSe is tuned to interconnected nanofibrous network on addition of PEG and to sprouting nanorods like morphology on addition of PVP. Among these nanostructures, CdSe sprouting nanorods exhibits improved power conversion efficiency of 0.55% as compared to nanofibrous (0.24%) and granular CdSe (0.16%) nanostructures. It reveals the fourfold enhancement in the PEC performance on PVP-mediated growth which can be attributed to conversion of compact dense nanostructure to porous and relatively high surface area nanostructure. This work exemplifies the ability of organic surfactant to modulate the surface morphology of the electrodeposits and pinpoints the organic surfactant that gives rise to the suitable morphology for PEC solar cell application.

Greywater characterization and loadings – Physicochemical treatment to promote onsite reuse

Greywater is the wastewater produced in bathtubs, showers, hand basins, kitchen sinks, dishwashers and laundry machines. Segregation of greywater and blackwater and on site greywater treatment in order to promote its reuse for toilet flushing and/or garden irrigation is an interesting option especially in water deficient areas. The objective of this study was to characterize the different greywater sources in Greek households and to evaluate the performance of alternative physicochemical treatment systems to treat several types of greywater. Based on the results average daily greywater production was equal to 98 L per person per day and accounts for approximately 70–75% of the total household wastewater production (135 L per person per day). Among the different sources, laundry and kitchen sink are the main contributors to the total greywater load of organic carbon, suspended solids and surfactants, whereas dishwasher and bathroom greywater are the main sources of phosphorus and endocrine disrupting chemicals respectively. Depending on sources, greywater accounts for as low as 15% of the total wastewater load of organic carbon (in the case of light greywater sources), to as high as 74% of the total load organic load (in the case of the heavy greywater sources). On the other hand, the nutrients load of greywater is limited. The application of a physical treatment system consisting of coagulation, sedimentation, sand filtration, granular activated carbon filtration and disinfection can provide for a final effluent with high quality characteristics for onsite reuse, especially when treating light greywater.

Surface tension prevails over solute effect in organic-influenced cloud droplet activation.

The spontaneous growth of cloud condensation nuclei (CCN) into cloud droplets under supersaturated water vapour conditions is described by classic Köhler theory. This spontaneous activation of CCN depends on the interplay between the Raoult effect, whereby activation potential increases with decreasing water activity or increasing solute concentration, and the Kelvin effect, whereby activation potential decreases with decreasing droplet size or increases with decreasing surface tension, which is sensitive to surfactants. Surface tension lowering caused by organic surfactants, which diminishes the Kelvin effect, is expected to be negated by a concomitant reduction in the Raoult effect, driven by the displacement of surfactant molecules from the droplet bulk to the droplet-vapour interface. Here we present observational and theoretical evidence illustrating that, in ambient air, surface tension lowering can prevail over the reduction in the Raoult effect, leading to substantial increases in cloud droplet concentrations. We suggest that consideration of liquid-liquid phase separation, leading to complete or partial engulfing of a hygroscopic particle core by a hydrophobic organic-rich phase, can explain the lack of concomitant reduction of the Raoult effect, while maintaining substantial lowering of surface tension, even for partial surface coverage. Apart from the importance of particle size and composition in droplet activation, we show by observation and modelling that incorporation of phase-separation effects into activation thermodynamics can lead to a CCN number concentration that is up to ten times what is predicted by climate models, changing the properties of clouds. An adequate representation of the CCN activation process is essential to the prediction of clouds in climate models, and given the effect of clouds on the Earth's energy balance, improved prediction of aerosol-cloud-climate interactions is likely to result in improved assessments of future climate change.

Recent Advances in the Synthesis of Metal Oxide Nanofibers and Their Environmental Remediation Applications

Recently, wastewater treatment by photocatalytic oxidation processes with metal oxide nanomaterials and nanocomposites such as zinc oxide, titanium dioxide, zirconium dioxide, etc. using ultraviolet (UV) and visible light or even solar energy has added massive research importance. This waste removal technique using nanostructured photocatalysts is well known because of its effectiveness in disintegrating and mineralizing the unsafe organic pollutants such as organic pesticides, organohalogens, PAHs (Polycyclic Aromatic Hydrocarbons), surfactants, microorganisms, and other coloring agents in addition to the prospect of utilizing the solar and UV spectrum. The photocatalysts degrade the pollutants using light energy, which creates energetic electron in the metal oxide and thus generates hydroxyl radical, an oxidative mediator that can oxidize completely the organic pollutant in the wastewater. Altering the morphologies of metal oxide photocatalysts in nanoscale can further improve their photodegradation efficiency. Nanoscale features of the photocatalysts promote enhance light absorption and improved photon harvest property by refining the process of charge carrier generation and recombination at the semiconductor surfaces and in that way boost hydroxyl radicals. The literature covering semiconductor nanomaterials and nanocomposite-assisted photocatalysis—and, among those, metal oxide nanofibers—suggest that this is an attractive route for environmental remediation due to their capability of reaching complete mineralization of organic contaminants under mild reaction conditions such as room temperature and ambient atmospheric pressure with greater degradation performance. The main aim of this review is to highlight the most recent published work in the field of metal oxide nanofibrous photocatalyst-mediated degradation of organic pollutants and unsafe microorganisms present in wastewater. Finally, the recycling and reuse of photocatalysts for viable wastewater purification has also been conferred here and the latest examples given.

Single step hydrothermal synthesis of carbon nanodot decorated V2O5 nanobelts as hybrid conducting material for supercapacitor application

Carbon nanodot (C-dot) decorated V2O5 (C-dot@V2O5) nanobelts are synthesized by single step, low cost hydrothermal route at low temperature by using V2O5 and glucose as precursors. We have not added any extra organic solvents or surfactants which are commonly used for the preparation of different nanostructures of V2O5. Electron microscopy analyses demonstrate that C-dot is entrapped inside V2O5 nanobelts which in turn enhance the conductivity and ion propagation property of this composite material. The C-dot@V2O5 nanobelts exhibit an excellent three electrode electrochemical performance in 1M Na2SO4 and which showed a specific capacitance of 270Fg−1 at 1Ag−1, which is ~ 4.5 times higher than the pristine V2O5 electrode. The electrochemical energy storage capacity of this hybrid is investigated towards solid state supercapacitor application also for the first time by employing electrophoretically deposited C-dot as the counter electrode and Li based gel as the electrolyte. The hybrid material delivers an energy density of 60Whkg−1 and a reasonably high power density of 4.1kWkg−1 at 5Ag−1 and good cycling stability and capacitance retention of about 87% was observed even after 5000 cycles. Above mentioned results clearly show that C-dot embedded hybrid, nanostructured transition metal oxides has great potential towards fabrication of electrodes for energy storage devices.

Two-phase hollow fiber-liquid microextraction based on reverse micelle for the determination of quercetin in human plasma and vegetables samples

A new two-phase hollow fiber-liquid microextraction based on reverse micelle as sensitive and efficient method for the extraction of quercetin in human plasma, onion and tomato samples was developed for the first time. The extraction is based on the solubilization of analyte in the aqueous core of the reverse micelle of cationic cethyltrimethyl ammonium bromide surfactant, CTAB, which are present in the organic phase and are used as acceptor phase in hollow fiber-liquid phase microextraction. Experimental results show that the electrostatic interaction between the oppositely charged surfactant head group present in the reverse micelles and the analyte molecule has a key role in the extraction. Extraction parameters including the organic phase, pH, surfactant concentrations, stirring rate, extraction time, temperature and ionic strength were optimized. The optimum condition is obtained when the variables are set to: pH= 7.5, organic solvent= 1-octanol, CTAB concentration= 7mmolL−1, stirring rate= 900rpm at room temperature and extraction time= 30min. Under the mentioned condition, the calibration range was found to be linear over 0.5–1000ngmL−1 with the limit of detection of 0.1ngmL−1. The extraction recovery of 97.4%, with relative standard deviation of 3.5%, was obtained via tree replicated measurements on a 15ngL−1 quercetin standard solution. Finally, the newly developed method was successfully used for the preconcentration and determination of quercetin in plasma, onion and tomato samples.

Enzyme mediated kinetic resolution of δ-hydroxy-α,β-unsaturated esters as a route to optically active δ-lactones

A novel synthetic route to optically active saturated and unsaturated δ-lactones based on enzymatic kinetic resolution and ring-closing metathesis reactions has been proposed. The influence of temperature, co-solvent, organic additives and the substrate structure on the catalytic behavior of selected hydrolases was studied. The substantial impact of the organic co-solvent and surfactant type on the enzymatic activity and enantioselectivity was observed providing enantiomerically pure δ-hydroxy-α,β-unsaturated esters. The established protocol combining enzymatic kinetic resolution with ring closing metathesis was successfully applied in the synthesis of the enantiomerically pure (6R)-phenyl-5,6-dihydro-2H-pyran-2-one which plays crucial role in the synthesis of the number of bioactive compounds.

Analysis of Water Barrier, Mechanical and Thermal Properties of Nanocoposites Based on Cassava Starch and Natural Clay or Modified by Anionic Exchange

Biopolymer films have several industrial applications because they are environmentally sustainable. Cassava starch is a biopolymer that is easily available, but has limitations: it is hydrophilic, poorly resistant and degradable. The improvement of these properties was proposed in this research from the use of bentonite clay (BT) as a filling material. The compatibilization of this in the polymer matrix was obtained by ion exchange with an organic anionic surfactant. The formation of intercalated or exfoliated starch nanocomposites in the presence of natural or modified clay was characterized by XRD, FTIR, AFM and SEM. The improvement of water vapor, thermal and mechanical properties was investigated by WVP, solubility, TGA and tensile test. The starch nanocomposites in the presence of modified clay showed a better result than those of natural clay. There was no significant difference in the color of the starch film in the presence of the natural or modified clay.

Solid state fermentative lignocellulolytic enzymes production, characterization and its application in the saccharification of rice waste biomass for ethanol production: An integrated biotechnological approach

This work evaluates lignocellulolytic enzymes production by a selected strain Streptomyces sp. MDS cultivated in various agricultural wastes under solid-state fermentation (SSF). Maximum activities (U/gds) of endoglucanase (132.6 ± 1.15), exoglucanase (14.6 ± 0.62), cellobiase (125.6 ± 1.75), filter paperase (19.7 ± 0.42), amylase (278.5 ± 3.53), and xylanase (342.5 ± 3.36) were produced with rice waste biomass (RWB). Operational parameters and supplementation of nitrogen sources, metal additives, and surfactants were systematically optimized with a view to maximizing enzyme production. The harvested enzyme exhibited good stability at high pH (5 to 8) and temperature (50 to 80 °C) and showed robust nature in the presence of organic solvents, surfactants, and commercial detergents. The potential of crude enzyme mixture for hydrolysis of mild alkaline pretreated RWB was demonstrated, resulting in equivalent saccharification (64.85 ± 1.11%) relative to commercial enzymes (69.41 ± 1.15%). Yeast co-culture of Saccharomyces cerevisiae and Kluyveromyces marxianus resulted in higher ethanol production (21.12 ± 0.82 g/L) and sugar consumption (88%) from enzymatic RWB hydrolysates (50 g/L) than monoculture. Finally, the leftover spent slurry from SSF effectively decolorized individual dyes and the actual textile wastewater, which increases the practical applicability of the developed bioprocess.

Characterization of commercial artists’ acrylic paints and the influence of UV light on aging

ABSTRACTA large part of Mexican artistic heritage was created with artists’ acrylic emulsion paints, so it is crucial to investigate their composition, behavior, and decay. Acrylic films are complex chemical systems combining organic and inorganic compounds; therefore, the degradation studies require a variety of techniques. We characterize three acrylic films before and after ultraviolet aging. The relative composition of the polymer matrix was studied by nuclear magnetic resonance, pyrolysis—gas chromatography—mass spectrometry and direct analysis in real time mass spectrometry with direct analysis in real time. The inorganic compounds and surfaces were characterized by microscopic techniques, such as digital microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and micro X-ray diffraction. The combined use of these techniques proved to be effective for an in-depth study of the acrylic painting degradation process. The main results were the gradual degradation for the organic surfactant and the loss of inorganic aggregates (talc and carbonates), that led to the disruption of the paint film, which points out the importance of studying the role and interaction of all compounds.