Preparation and characterization of activated carbon from cotton stalks in a two-stage process

Activated carbons are prepared from cotton stalks by chemical activation with ZnCl₂, H₂SO₄ and physical activation using CO₂ and steam-CO₂ mixture for temperatures of 750, 850 and 900 °C. The effects of activation temperature and duration time, impregnation concentration of agent, impregnation times, and physical activating agent are examined. These materials are characterized by adsorption/desorption of N₂ to determine the BET areas, thermogravimetric analysis (TG, DTA), FTIR and scanning electron microscopy (SEM). ZnCl₂ under CO₂ atmosphere was found more effective than H₂SO₄ as a chemical reagent under identical conditions in terms of porosity development. The maximum BET surface area is found to be 2053 m²/g for active carbons produced with ZnCl₂ activation under CO₂ atmosphere.     

Degradation mechanism of green biopolyester nanocomposites with various cellulose nanocrystal based nanohybrids

Oceans and soils have been contaminated with traditional plastic due to its lack of degradability. Therefore, green biopolymer composites reinforced with cellulose nanocrystal-zinc oxide hybrids (ZnO hybrids) with good biodegradation ability provided a positive impact on reducing environmental challenges. In this work, the effect of various morphologies of ZnO hybrids on the biodegradation ability of poly(butylene adipate-co-terephthalate), PBAT) under seawater, soil burial, and UV aging conditions were investigated. Sheet-like ZnO hybrids (s-ZnO hybrid) efficiently enhanced the mechanical, UV-blocking properties and biodegradation ability of PBAT nanocomposite films. Compared to neat PBAT, the best tensile strength of PBAT nanocomposite with 2 wt% s-ZnO hybrid was increased by 15.1%, meanwhile this nanocomposite films showed the highest biodegradation rate after 80 days of soil degradation and 90 days of seawater degradation. Besides, three possible biodegradation mechanisms of green PBAT nanocomposite films were presented, hinting that such PBAT nanocomposite have great promising packaging applications.

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Synthesis of high-performance green nanocomposites from renewable natural oils

This paper describes preparation and properties of green nanocomposites from renewable resources. The nanocomposites were synthesized by an acid-catalyzed curing of epoxidized natural oils in the presence of silane coupling agents. The resulting nanocomposites were transparent and highly glossy. Their hardness and Young's modulus of the nanocomposite coatings improved, as compared with those only from the epoxidized natural oils. Dynamic viscoelasticity analysis and TEM observation showed the homogeneous structure of the nanocomposites. The properties of the nanocomposites were strongly affected by the structure and feed ratio of the monomers.     

Thermal analysis of eucalptus camaldulensis and cotton stalks at different heating rates

The thermal decomposition of Eucalptus Camaldulensis and Cotton Stalks at different heating rates showed three exothermic peaks. The heating rate is the factor that affects their sharpness and position. The peaks are sharp at low heating rates. IR spectra of pyrolized residue at different temperature were also studied.     

Textile grade long natural cellulose fibers from bark of cotton stalks using steam explosion as a pretreatment

Textile grade long natural cellulose fibers with fineness of 27 dtex have been extracted from bark of cotton stalks by a combination of steam explosion, potassium hydroxide and peroxide treatments (explosion–KOH–H₂O₂). It was reported that natural cellulose fibers from bark of cotton stalks had significantly better mechanical properties than those from other lignocellulosic agricultural byproducts such as rice and wheat straws. Fibers from bark of cotton stalks were used to reinforce thermoplastic composites but could not be spun into yarns for textile applications due to their high fineness value (around 50 dtex) and/or low aspect ratio (around 660). In this research, barks of cotton stalks were treated using three methods, including steam explosion, a combination of steam explosion and potassium hydroxide treatments (explosion–KOH) and explosion–KOH–H₂O₂. The morphology, composition, carding yield, crystalline structures and tensile properties of three different cotton stalk fibers were analyzed. Results showed that cotton stalk fibers extracted by explosion–KOH–H₂O₂ had the lowest fineness value of 27 dtex and moderate aspect ratio of 1,150 in three kinds of fibers. The fibers also had most clean and smooth surfaces, highest carding yield of 68.6 %, and highest cellulose content of 82.1 wt% due to effective removal of non-cellulose impurities. Moreover, the fibers had tensile properties close to cotton fibers. Overall, the cotton stalk fibers presented a better potential to be used as textile fibers than those reported by previous researches. explosion–KOH–H₂O₂ could be an efficient method for exploring textile applications of bark of cotton stalks.     

Pilot production of activated carbon from cotton stalks using H3PO4

Cotton stalks, an agricultural waste, were chemically activated in a batch process using H₃PO₄ in a locally designed carbonizer at 420 °C in the absence of any purging gases. Mechanically cut short sticks were soaked in diluted H₃PO₄ for a short duration (Batch 1) and an extended period (Batch 2) prior to thermal treatment. The derived carbons contained both coarse and fine grains with acidic effect. Porosity was characterized by N₂ adsorption at −196 °C and the isotherms analyzed by the α-method to estimate total and microporous surface areas in addition to total and microporous volumes. The produced carbons exhibited well-developed porosity that was essentially microporous in composition. Several key performance parameters were altered considerably as a result of impregnation with H₃PO₄ and the extended chemical activation period (Batch 2). Most of the internal porosity of both carbons was accessible to adsorption of iodine, whereas the uptake of methylene blue dye was proportional to the average size of micropores which were larger for the batch with a longer acid soaking time. SEM and FTIR investigations revealed the presence of a developed honeycomb structure and different oxygen functionalities on surfaces of the activated products which are advantageous in liquid-phase applications. Preliminary laboratory-scale experiments with Pb(II) indicate that adsorption capacity of target heavy metals compares favorably with commercially available activated carbons. The raw material, pre-processing, and activation process prove feasible for the production of activated carbon on a large scale, thereby providing a sustainable strategy for treatment of toxic waste streams.     

Advanced functional polymer nanocomposites and their use in water ultra-purification

The application of nanotechnology has become inevitable in almost all sectors such as pharmaceuticals, food and beverages, electronics, transport, etc. The continuous development in the area has led to the emergence of the polymer nanocomposites. The polymer nanocomposites due to their improved mechanical, thermal, electrical, optical, and magnetic properties are widely used in various fields and slowly they have become an integral part of our life. As the application of polymer nanocomposite is going to be inexorable in the near future, this review aims to provide some insight on the need for the polymer nanocomposites, their basic classification, and their manufacturing methods. The study also outlines the analyses that are required to characterize the polymer nanocomposites. Further, the study discusses the existing application of polymer nanocomposites in various fields. As the polymer nanocomposites are going to play a major role in the field of waste water treatment for the years to come, the study has also attempted to shed some light on the application of nanocomposites in water purification.     

Effective sequestration of Congo red dye with ZnO/cotton stalks biochar nanocomposite: MODELING,reusability and stability

Widespread application of dyes and disposal of their untreated effluents into water bodies adversely affect the ecosystem due to their complex aromatic structures and persistent nature. The present study aims to utilize the cotton stalks biochar (CSB) and its composite with zinc oxide nanoparticles (CSB/ZnONPs) to evaluate for the decontamination their batch scale potential of Congo red dye from wastewater. The characterization of CSB and CSB/ZnONPs was performed with Fourier-transform infra-red (FTIR) spectroscopy, scanning electron microscopy, energy-dispersive X-ray (EDX) and point of zero charge (PZC) to get insight of their potential for the decontamination of CR. The effects of initial CR concentration (25–500 mg/L), dosage of CSB and CSB/ZnONPs (0.5–2 g/L), solution pH (2–10) and contact time (0–180 min) were evaluated on CR removal at temperature (25 ± 1.5 °C). The results disclosed that CSB/ZnONPs showed excellent adsorption potential (556.6 mg/g) in comparison with CSB (250 mg/g) and most of the other adsorbents previously studies in the literature. The equilibrium experimental data were equally explained with Freundlich and Langmuir isotherm models (R² > 0.98) while kinetic data demonstrated the best fit with pseudo second order model. The CSB/ZnONPs composite exhibited excellent reusability (89.65%) after five adsorption/desorption cycles for the sequestration of CR from contaminated systems. The present study demonstrated that metallic nanocomposite of CSB (CSB/ZnONPs) is an excellent candidate for the cost effective and environment friendly decontamination of CR from industrial wastewater and is suggested to be considered for the decontamination of other pollutants from the wastewater.     

Multifunctionalization of cotton through in situ green synthesis of silver nanoparticles

A convenient method for in situ synthesis of silver nanoparticles was developed to realize the multifunction of cotton. The silver nanoparticles were obtained through reduction of silver ions by cotton under basic condition at room temperature. The as-synthesized silver nanoparticles achieved the coloration of cotton fibers. Heating increased the color strength of cotton fibers with silver nanoparticles. Mercerization treatment as a common finishing process enhanced the properties of cotton fibers modified by silver nanoparticles. The mercerized cotton exhibited brighter color and had very good colorfastness to washing. The cotton fibers treated with in situ synthesized silver nanoparticles possess strong antibacterial activity with excellent washing durability.     

Deactivation mechanism of the green fluorescent chromophore

We report time-resolved fluorescence data for the anion of p-hydroxybenzylidene dimethylimidazolinone (p-HBDI), a model chromophore of the green fluorescence protein, in viscous glycerol-water mixtures over a range of temperatures, T. The markedly nonexponential decay of the excited electronic state is interpreted with the aid of an inhomogeneous model possessing a Gaussian coordinate-dependent sink term. A nonlinear least-squares fitting routine enables us to achieve quantitative fits by adjusting a single activation parameter, which is found to depend linearly on 1/T. We derive an analytic expression for the absolute quantum yield, which is compared with the integrated steady-state fluorescence spectra. The microscopic origins of the model are discussed in terms of two-dimensional dynamics, coupling the phenyl-ring rotation to a swinging mode that brings this flexible molecule to the proximity of a conical intersection on its multidimensional potential energy surface.     

A thermal degradation mechanism of polyvinyl alcohol/silica nanocomposites

The thermal degradation mechanism of a novel polyvinyl alcohol/silica (PVA/SiO₂) nanocomposite prepared with self-assembly and solution-compounding techniques is presented. Due to the presence of SiO₂ nanoparticles, the thermal degradation of the nanocomposite, compared to that of pure PVA, occurs at higher temperatures, requires more reaction activation energy (E), and possesses higher reaction order (n). The PVA/SiO₂ nanocomposite, similar to the pure PVA, thermally degrades as a two-step-degradation in the temperature ranges of 300-450 °C and 450-550 °C, respectively. However, the introduction of SiO₂ nanoparticles leads to a remarkable change in the degradation mechanism. The degradation products identified by Fourier transform infrared/thermogravimetric analysis (FTIR/TGA) and pyrolysis-gas chromatography/mass spectrometric analysis (Py-GC/MS) suggests that the first degradation step of the nanocomposite mainly involves the elimination reactions of H₂O and residual acetate groups as well as quite a few chain-scission reactions. The second degradation step is dominated by chain-scission reactions and cyclization reactions, and continual elimination of residual acetate groups is also found in this step.     

Depletion mechanism of antioxidants in MDPE-clay nanocomposites under thermal aging

The depletion behavior of two types of hindered phenolic antioxidants (AO), Irganox^® 1010 (I-1010) and Irganox^®1076 (I-1076), in medium density polyethylene (MDPE)/nanoclay composite was evaluated by incubating samples in a forced air oven at 85 °C. The presence of 4 wt% nanoclay accelerated the depletion of both types of AO, particularly at the surface region of the sample. However, the depletion mechanism in the interior of sample was governed by the AO molecular structure. For samples containing the bulky Irganox®1010, OIT decreased exponentially with aging time consistent with a first order reaction. In contrast, an increase of OIT was detected in first 60 days of heat aging for sample containing I-1076 and afterward the OIT decreased slowly with aging time. The hypothesis for the initial increase of OIT is that the relatively small and linear structure of I-1076 may enable it to be trapped inside the nanoclay galleries and then subsequently released into the polymer matrix during heat aging.     

Kinetics of the release of brilliant green from nanoporous polylactide obtained by a crazing mechanism

Structurally variable nanoporous polylactide (PLA) films containing brilliant green (BG) as a functional antiseptic additive have been obtained by a crazing mechanism. The in vitro release of BG from the porous PLA films into a sodium phosphate buffer solution at 37 °C has been examined by spectrophotometry.     

Thermal stability and flame-retardancy mechanism of poly(ethylene terephthalate)/boehmite nanocomposites

The thermal stability and flame-retardancy properties of poly(ethylene terephthalate)/nano-boehmite composites (PET/AlOOH) were investigated using composites prepared in situ. Combustion behaviour and flammability were assessed using the limiting oxygen index (LOI) and cone calorimetry. The incorporation of nano-boehmite increased the LOI of PET from 18 to greater than 25. Cone calorimetry showed that the heat release rates and total smoke production values of PET/AlOOH composites were significantly less than those of pure PET. It also showed that PET/AlOOH combustion produced greater quantities of char residues than did PET combustion. These results showed that nano-boehmite is an effective flame-retardant for PET. Combustion residues were examined using scanning electron microscopy, indicating that nano-boehmite addition produced consistent, thick char crusts. Thermal stability and pyrolysis were investigated using thermogravimetric analysis and pyrolysis-gas chromatography-mass spectrometry, showing that thermal stability of PET/AlOOH was superior to that of pure PET, fewer cracking products were produced in nanocomposite combustion than in pure PET combustion, and pyrolysis of the flame-retardant polyester was incomplete. We propose a condensed phase mechanism for the PET/AlOOH flame-retardancy effect.     

Ethanol production from pretreated olive tree wood and sunflower stalks by an SSF process

Olive tree wood and sunflower stalks are agricultural residues largely available at low cost in Mediterranean countries. As renewable lignocellulosic materials, their bioconversion may allow both obtaining a value-added product, for fuel ethanol, and facilitating their elimination. In this work, the ethanol production from olive tree wood and sunflower stalks by a simultaneous saccharification and fermentation (SSF) process is studied. As a pretreatment, steam explosion at different temperatures was applied. The water insoluble fractions of steam-pretreated sunflower stalks and steamed, delignified olive tree wood were used as substrates at 10% w/v concentration for an SSF process by a cellulolytic commercial complex and Saccharomyces cerevisiae. After 72-h fermentation, ethanol concentrations up to 30 g/L were obtained in delignified steam-pretreated olive tree wood at 230°C and 5 min. Sunflower stalks pretretated at 220°C and 5 min gave maximum ethanol concentrations of 21 g/L in SSF experiments.     

Dyeing behavior and mechanism of Crocein Orange G on carboxymethyl cotton fabric

Cellulose - Traditional cotton fiber dyeing requires an abundance of salt, which leads to environmental pollution. Consequently, decreasing or eliminating the use of salt has become the primary...     

Activation mechanism of intra-and extracellular cotton peroxidases by wilt infection

It was found that intra- and extracellular cotton peroxidases were involved in infection by the phytopathogen Verticillium dahliae. Extracellular peroxidase was more active. Its activity was greater in resistant variety AN-Bayaut-2 than in susceptible C-4727. It was found that activation in the susceptible cotton variety caused by pathogen infection occurred via de novo protein synthesis whereas in the resistant variety it occurred via synthesis of new ones and activation of already existing peroxidases.     

Thermal decomposition mechanism and kinetics of Pd/SiO2 nanocomposites in air atmosphere

Journal of Thermal Analysis and Calorimetry - SiO2 and Pd/SiO2 nanocomposites were prepared using sol–gel method and characterized by X-ray diffraction, Fourier transform infrared spectra,...