Characterizations of biochar from hydrothermal carbonization of exhausted coffee residue

The aim of this study was to produce renewable energy from exhausted coffee residue, which is a form of biomass. As coffee preference continues to increase, the importation of coffee beans has been increasing sharply. However, the amount of coffee that is actually consumed is only about 0.2% of coffee beans, while the spent coffee beans are discarded in the form of exhausted coffee residue. Hydrothermal carbonization is a method of producing an improved fuel from renewable energy sources by changing the physical and chemical properties of biochars. Biochars were obtained from a variety of reaction temperatures during hydrothermal carbonization and analyzed using elemental analysis, ultimate analysis, and calorific value measurement. The atomic C/O and C/H ratios of all obtained biochars decreased and were found to be similar to those of lignite and sub-bituminous coal. The highest energy recovery efficiency of biochar indicates that the optimum reaction temperature for hydrothermal carbonization was between 210 and 240 °C, which produced biochars with calorific value of approximately 26–27 MJ/kg. The spectra of biochars obtained from Fourier transform infrared spectroscopy (FTIR) showed fewer C–O and aliphatic C–H functional groups, but more carbonyl C=O functional groups and aliphatic CH _x groups. The results of this study indicate that hydrothermal carbonization can be used as an effective means to generate highly energy-efficient renewable fuel resources from coffee residue. The thermogravimetric analysis provided the changing combustion characteristics due to increased fixed carbon content.     

Preparation of Viscose Fibres Stripped of Reactive Dyes and Wrinkle-Free Crosslinked Cotton Textile Finish

The chemical recycling of cellulosic fibres may represent a next-generation fibre–fibre recycling system for cotton textiles, though remaining challenges include how to accommodate fibre blends, dyes, wrinkle-free finishes, and other impurities from finishing. These challenges may disrupt the regeneration process steps and reduce the fibre quality. This study examines the impact on regenerated viscose fibre properties of a novel alkaline/acid bleaching sequence to strip reactive dyes and dimethyloldihydroxyethyleneureas (DMDHEU) wrinkle-free finish from cotton textiles. Potentially, such a bleaching sequence could advantageously be integrated into the viscose process, reducing the costs and environmental impact of the product. The study investigates the spinning performance and mechanical properties (e.g., tenacity and elongation) of the regenerated viscose fibres. The alkaline/acid bleaching sequence was found to strip the reactive dye and DMDHEU wrinkle-free finish from the cotton fabric, so the resulting pulp could successfully be spun into viscose fibres, though the mechanical properties of these fibres were worse than those of commercial viscose fibres. This study finds that reactive dyes and DMDHEU wrinkle-free finish affect the viscose dope quality and the regeneration performance. The results might lead to progress in overcoming quality challenges in cellulosic chemical recycling.     

Biodegradation of pretreated polyethylene film by Pseudomonas aeruginosa AMB-CD-1

A comparative study evaluated the acid, alkali, and heat-treated polyethylene biodegradation efficiency of Pseudomonas aeruginosa AMB-CD-1. The polyethylene (PE) pieces were separately treated with heat (50°C), acid (1N HCl), and alkali (1N NaOH) and then washed with water before use. All the treated samples were analyzed through thermogravimetric analysis. In addition, weight and temperature changes during the decomposition reactions were also measured and determined. In these treatments, the PE films of heat-treated and acid-treated low-density polyethylene (LDPE) indicated more significant weight loss at 120°C (48.99% and 40.75%, respectively) as compared to their control or untreated PE and alkali-treated LDPE (21.84% and 24.68%, respectively). A biodegradation assay was then conducted with treated and untreated LDPE films with P. aeruginosa AMB-CD-1 strain. Fourier transform infrared spectroscopy analysis revealed that the heat or acid-pretreated samples with isolate AMB-CD-1 displayed peaks at 2922.84, 2923.97, and 1450.31, 874.22 cm⁻¹ for C–H stretching deformation vibration, CH₂ scissoring vibration, –CHO stretching, and strong alkyl structure, respectively. Furthermore, the new peaks with a significant difference at 2500–2000 cm⁻¹ (O═C═O, O–H stretching vibration: carboxylic acid) and 1500–1000 cm⁻¹ (–CHO and C═O stretching) were noticed in the infrared spectral range of LDPE degradation. Modifications in the functional group provided evidence that biodegradation had impacted the chemical structure of the LDPE film. Additionally, it was demonstrated that pretreating LDPE films with heat or acid could speed up their biodegradation.     

Reactively Compatibilized Cellulosic Polylactide Microcomposites

Poly(lactic acid) (PLA) possesses a suite of favorable material properties that are enabling its penetration into diverse markets (e.g., as packaging material or textile fibers). In order to increase the range of applications for this material, it is necessary to modify its properties and for certain applications, reduce its cost. The introduction of fibers into a polymeric matrix is an established route towards property enhancement provided good dispersion and intimate interfacial adhesion can be achieved. In addition, cellulosic microfibers are obtainable at low to moderate cost. In this study, reactive compatibilization of cellulosic fibers with PLA is pursued. Hydroxyl groups available on the surface of cellulosic fibers are used to initiate lactide polymerization. Various processing strategies are investigated: (1) blending preformed PLA with the fiber material, (2) through a one-step process in which lactide is polymerized in the presence of the fibers alone, or (3) reactive compatibilization in the presence of preformed high molecular weight polymer. The results show that materials prepared by simultaneous introduction of lactide and preformed high molecular PLA at the beginning of the reaction possess superior mechanical properties compared to composites made by either purely mechanical mixing or solely polymerization of lactide in the presence of fibers. The modulus of materials containing 25% fibers which are prepared by reactive compatibilization of 30% preformed PLA and 70% lactide (30/70 P/L) improves by 53% compared to the homopolymer, whereas 36% reinforcement can be achieved upon purely mechanical mixing. A further increase to 35% fiber loading leads to a reduction in modulus due to an excess in initiating groups. The same trend was observed in systems containing 65% preformed PLA and 35% lactide (65/35 P/L) with an overall achievable reinforcement that was slightly lower.     

Biopolymers Based Green Composites: Mechanical, Thermal and Physico-chemical Characterization

Natural cellulosic fibers are one of the smartest materials for use as reinforcement in polymers possessing a number of applications. Keeping in mind the immense advantages of the natural fibers, in present work synthesis of natural cellulosic fibers reinforced polymer composites through compression molding technique have been reported. Scanning Electron microscopy (SEM), Thermo gravimetric/Differential thermal/Derivative Thermogravimetry (TGA/DTA/DTG), absorption in different solvents, moisture absorbance, water uptake and chemical resistance measurements were used as characterization techniques for evaluating the different behaviour of cellulosic natural fibers reinforced polymer composites. Effect of fiber loading on mechanical properties like tensile strength, flexural strength, compressive strength and wear resistances has also been determined. Reinforcing of the polymer matrix with natural fibers was done in the form of short fiber. Present work indicates that green composites can be successfully fabricated with useful mechanical properties. These composites may be used in secondary structural applications in automotive, housing etc.     

Application of Cellulose Microfibrils in Polymer Nanocomposites

Cellulose microfibrils obtained by the acid hydrolysis of cellulose fibers were added at low concentrations (2–10% w/w) to polymer gels and films as reinforcing agents. Significant changes in mechanical properties, especially maximum load and tensile strength, were obtained for fibrils derived from several cellulosic sources, including cotton, softwood, and bacterial cellulose. For extruded starch plastics, the addition of cotton-derived microfibrils at 10.3% (w/w) concentration increased Young’s modulus by 5-fold relative to a control sample with no cellulose reinforcement. Preliminary data suggests that shear alignment significantly improves tensile strength. Addition of microfibrils does not always change mechanical properties in a predictable direction. Whereas tensile strength and modulus were shown to increase during addition of microfibrils to an extruded starch thermoplastic and a cast latex film, these parameters decreased when microfibrils were added to a starch–pectin blend, implying that complex interactions are involved in the application of these reinforcing agents.     

Poly(lactic acid)/Cellulose Composites Obtained from Modified Cotton Fibers by Successive Acid Hydrolysis

This work is focused on the hydrolysis of cotton fibers from waste textiles to obtain micro and nanofibers to be used as reinforcements in polymer composites. To promote their compatibility with polymeric matrix, hydrolyzed cotton fibers were surface modified with various silane compounds. Thus, these fibers were mixed with commercial poly(lactic acid) (PLA) at 5% w/w loading by melt compounding. Acid treatments caused a decrease of the crystallinity index whereas the thermal stability was significantly improved, especially for cellulose fibers hydrolyzed in two steps. Morphological analysis revealed a reduction of the fibers diameter and a decrease of their length as a consequence of the hydrolysis. NMR analysis confirmed the silanization of the fibers by reaction with the silane agent. Tensile tests revealed that silanization treatments were able to increase the composite Young’s modulus and the stress at break with respect to the neat matrix, indicating that silanization improved the polymer/fiber compatibility interfacial adhesion. The overall results demonstrated that applying suitable surface modification strategies, waste cotton textiles can be effectively recycled as fillers in polymer based composites.     

A novel process for ethanol or biogas production from cellulose in blended-fibers waste textiles

A novel process has been developed for separation of the cellulose, i.e. cotton and viscose, from blended-fibers waste textiles. An environmentally friendly cellulose solvent, N-methylmorpholine-N-oxide (NMMO) was used in this process for separation and pretreatment of the cellulose. This solvent was mixed with blended-fibers textiles at 120 °C and atmospheric pressure to dissolve the cellulose and separate it from the undissolved non-cellulosic fibers. Water was then added to the solution in order to precipitate the cellulose, while both water and NMMO were reused after separation by evaporation. The cellulose was then either hydrolyzed by cellulase enzymes followed by fermentation to ethanol, or digested directly to produce biogas. The process was verified by testing 50/50 polyester/cotton and 40/60 polyester/viscose-blended textiles. The polyesters were purified as fibers after the NMMO treatments, and up to 95% of the cellulose fibers were regenerated and collected on a filter. A 2-day enzymatic hydrolysis and 1-day fermentation of the regenerated cotton and viscose resulted in 48 and 50 g ethanol/g regenerated cellulose, which were 85% and 89% of the theoretical yields, respectively. This process also resulted in a significant increase of the biogas production rate. While untreated cotton and viscose fibers were converted to methane by respectively, 0.02% and 1.91% of their theoretical yields in 3 days of digestion, the identical NMMO-treated fibers resulted into about 30% of yield at the same period of time.     

Analysis of Flax and Cotton Fiber Fabric Blends and Recycled Polyethylene Composites

Manufacturing composites with polymers and natural fibers has traditionally been performed using chopped fibers or a non-woven mat for reinforcement. Fibers from flax (Linum usitatissimum L.) are stiff and strong and can be processed into a yarn and then manufactured into a fabric for composite formation. Fabric directly impacts the composite because it contains various fiber types via fiber or yarn blending, fiber length is often longer due to requirements in yarn formation, and it controls the fiber alignment via weaving. Composites created with cotton and flax-containing commercial fabrics and recycled high-density polyethylene (HDPE) were evaluated for physical and mechanical properties. Flax fiber/recycled HDPE composites were easily prepared through compression molding using a textile preform. This method takes advantage of maintaining cotton and flax fiber lengths that are formed into a yarn (a continuous package of short fibers) and oriented in a bidirectional woven fabric. Fabrics were treated with maleic anhydride, silane, enzyme, or adding maleic anhydride grafted polyethylene (MAA-PE; MDEX 102-1, Exxelor^® VA 1840) to promote interactions between polymer and fibers. Straight and strong flax fibers present problems because they are not bound as tightly within yarns producing weaker and less elastic yarns that contain larger diameter variations. As the blend percentage and mass of flax fibers increases the fabric strength, and elongation generally decrease in value. Compared to recycled HDPE, mechanical properties of composite materials (containing biodegradable and renewable resources) demonstrated significant increases in tensile strength (1.4–3.2 times stronger) and modulus of elasticity (1.4–2.3 times larger). Additional research is needed to improve composite binding characteristics by allowing the stronger flax fibers in fabric to carry the composites load.     

Waste polyvinylchloride derived pitch as a precursor to develop carbon fibers and activated carbon fibers

Polyvinylchloride (PVC) was successfully recycled through the solvent extraction from waste pipe with an extraction yield of ca. 86%. The extracted PVC was pyrolyzed by a two-stage process (260 and 410 degrees C) to obtain free-chlorine PVC based pitch through an effective removal of chlorine from PVC during the heat-treatment. As-prepared pitch (softening point: 220 degrees C) was spun, stabilized, carbonized into carbon fibers (CFs), and further activated into activated carbon fibers (ACFs) in a flow of CO2. As-prepared CFs show comparable mechanical properties to commercial CFs, whose maximum tensile strength and modulus are 862 MPa and 62 GPa, respectively. The resultant ACFs exhibit a high surface area of 1200 m2/g, narrow pore size distribution and a low oxygen content of 3%. The study provides an effective insight to recycle PVC from waste PVC and develop a carbon precursor for high performance carbon materials such as CFs and ACFs.     

Coal fly ash as raw material for the manufacture of geopolymer-based products

In this work coal fly ash has been employed for the synthesis of geopolymers. Two different systems with silica/alumina ratios stoichiometric for the formation of polysialatesiloxo (PSS, SiO2/Al2O3=4) and polysialatedisiloxo (PSDS, SiO2/Al2O3=6) have been prepared. The alkali metal hydroxide (NaOH or KOH) necessary to start polycondensation has been added in the right amount as concentrated aqueous solution to each of the two systems. The concentration of each alkali metal solution has been adjusted in order to have the right liquid volume to ensure constant workability. The systems have been cured at four different temperatures (25, 40, 60, and 85 degrees C) for several different times depending on the temperature (16-672 h at 25 degrees C; 72-336 h at 40 degrees C; 16-120 h at 60 degrees C and 1-6h at 85 degrees C). The products obtained in the different experimental conditions have been submitted to the quantitative determination of the extent of polycondensation through mass increase and loss on ignition, as well as to qualitative characterization by means of FT-IR spectroscopy. Furthermore, physico-structural and mechanical characterization has been carried out through microscopic observations and the determination of unconfined compressive strength, elasticity modulus, apparent density, porosity and specific surface area. The results have indicated that the systems under investigation are suited for the manufacture of pre-formed building blocks at room temperature.     

Degradation of Cellulosic Materials Under the Alkaline Conditions of a Cementitious Repository for Low- and Intermediate-Level Radioactive Waste. II. Degradation Kinetics

The degradation of cellulosic materials, differing mainly in the degree of polymerization and the number of reducing end groups, was studied under the alkaline conditions similar to those existing in a cementitious repository for low- and intermediate-level radioactive waste (pH 13.3, T = 25°C). The kinetics of alkaline degradation (peeling-off reaction) were studied and the data analyzed by the model of Haas et al. [13]. The observed kinetic parameters for the propagation reaction and overall stopping reaction were compared with literature data. Although measured under different experimental conditions, literature data and data from this study show a consistent picture. Differences in the extent of degradation observed for the different cellulosic materials could be satisfactorily explained by differences in reducing end group content and, consequently, by differences in the degrees of polymerization. Besides the number of reducing end groups, the degree of amorphousness also plays an important role. The main degradation products formed under the experimental conditions used are - and -(gluco)isosaccharinic acid. This is in agreement with many other studies on alkaline degradation of cellulose. The two isomers are formed in roughly equal amounts.     

Characterization of post-consumer polyolefin wastes by hyperspectral imaging for quality control in recycling processes

In this paper new analytical inspection strategies, based on hyperspectral imaging (HSI) in the VIS–NIR and NIR wavelength ranges (400–1000 and 1000–1700 nm, respectively), have been investigated and set up in order to define quality control logics that could be applied at industrial plant level for polyolefins recycling. The research was developed inside the European FP7 Project W2Plastics “Magnetic Sorting and Ultrasound Sensor Technologies for Production of High Purity Secondary Polyolefins from Waste”. The main aim of the project is the separation of pure polyethylene and polypropylene adopting an innovative process, the magnetic density separation (MDS). Spectra of plastic particles and contaminants resulting from post-consumer complex wastes and of virgin polyolefins have been acquired by HSI and by Raman spectroscopy. The classification results obtained applying principal component analysis (PCA) on HSI data have been compared with those obtained by Raman spectroscopy, in order to validate the proposed innovative methodology. Results showed that HSI sensing techniques allow to identify both polyolefins and contaminants. Results also demonstrated that HSI has a great potentiality as a tool for quality control of feed (identification of contaminants in the plastic waste) and of the two different pure polypropylene and polyethylene flow streams resulting from the MDS-based recycling process.     

Layer-by-Layer Deposition of Antibacterial Polyelectrolytes on Cotton Fibres

The introduction of molecules with biological properties on textile materials is essential for a number of biotechnological applications. With the purpose of testing new processes applied to textiles, in this study, we present the first results on the feasibility of using the Layer-by-Layer (LbL) deposition process in natural fibers such as cotton, with natural polyelectrolytes like chitosan (CH) and alginic acid sodium salt (ALG), the durability of CH/ALG multilayer on cotton were evaluated. The increase of negative charges to the substrate cotton was made with NaBr and TEMPO, to ensure the success of the process of LbL. Three characterization methods to assess electrostatic LbL deposition were performed: the contact angle between a liquid (water) and the sample surface, in order to characterize the wettability of the samples with the different layers of CH and ALG; dyeing of the CH/ALG assembled cotton fabric with cationic methylene blue that shows regular changes in terms of color depth (K/S value), which indicate that the surface were alternately deposited with CH and ALG layers and, finally, the analysis by infrared spectroscopy using Fourier Transform with Attenuated Total Reflection (ATR-FTIR), to assess the changes in the interaction between CH and ALG deposited on cotton samples.     

Nitrous Oxide Emissions from Two Riparian Ecosystems: Key Controlling Variables

Nitrous oxide (N₂O) emissions were measured weekly to fortnightly between April 2001 and March 2002 from two riparian ecosystems drainingdifferent agricultural fields. The fields differed in the nature of the crop grown and the amount of fertiliser applied. Soil water content and soil temperature were very important controls of N₂O emission rates, with a ‘threshold’ response at 24% moisture content (by volume) and 8 °C, below which N₂O emission was very low.N₂O fluxes were higher at the site that had receivedthe most fertiliser N, but NO₃ ^- was not a limiting factor at either site. There was also a ‘threshold’ effect of rainfall, in which major rainfall events (≥10 mm) triggered a pulse of high N₂O emission if none of the other environmental factors were limiting. These results suggest the existence of multiple controls on N₂O emissions operating at a range of spatial and temporal scales and that non-linear relationships, perhaps with a hierarchical structure, are needed to model these emissions from riparian ecosystems.     

Cellulose Fiber Isolation and Characterization from Sweet Blue Lupin Hull and Canola Straw

In this study, cellulose fibers were removed from crop by-products using a combination of sodium hydroxide treatment followed by acidified sodium chlorite treatment. The objective was to obtain high recovery of cellulose by optimizing treatment conditions with sodium hydroxide (5–20%, 25–75 °C and 2–10 h) followed by acidified sodium chlorite (1.7%, 75 °C for 2–6 h) to remove maximum lignin and hemicellulose, as well as to investigate the effect of lignin content of the starting materials on the treatment efficiency. Samples were characterized for their chemical composition, crystallinity, thermal behavior and morphology to evaluate the effects of treatments on the fibers’ structure. The optimum sodium hydroxide treatment conditions for maximum cellulose recovery was at 15% NaOH concentration, 99 °C and 6 h. Subsequent acidified sodium chlorite treatment at 75 °C was found to be effective in removing both hemicellulose and lignin, resulting in higher recovery of cellulose in lupin hull (~?95%) and canola straw (~?93%). The resultant cellulose fibers of both crop by-products had increased crystallinity without changing cellulose I structure (~?68–73%). Improved thermal stabilities were observed with increased onset of degradation temperatures up to 307–318 °C. Morphological investigations validated the effectiveness of treatments, revealing disrupted cell wall matrix and increased surface area due to the removal of non-cellulosics. The results suggest that the optimized combination of sodium hydroxide and acidified sodium chlorite treatments could be effectively used for the isolation of cellulose fibers from sweet blue lupin hull and canola straw, which find a great number of uses in a wide range of industrial applications.     

Effect of Agar and Cotton Fiber on Properties of Thermoplastic Waxy Rice Starch Composites

Biodegradable polymer from thermoplastic waxy rice starch (TPWRS) was prepared by internal mixer and compression molding. Since tensile properties and water uptake of the TPWRS was still the main disadvantages, the TPWRS sample was, therefore, modified by agar and/or cotton fibers. The effect of different ratios of agar:cotton fibers on properties of the TPWRS matrix were also studied. It was found that new hydrogen bonds could be found for the TPWRS matrix with the addition of different ratios of agar: cotton fibers by the detection of IR peak shift. Tensile properties of the TPWRS sample were significantly improved by the addition of agar or cotton fibers and the highest tensile properties were obtained from the TPWRS composite modified with 4:6 agar:cotton fibers. In addition, thermal degradation temperature and thermal stability of the starch were improved by the incorporation of agar and/or cotton fibers. Moreover, color measurement, morphology, water uptake and biodegradability from soil burial test were also examined.     

Thermal behaviour of chromium electroplating sludge

Galvanic sludge is classified as a hazardous waste and incineration is one of the techniques used for its treatment. The aim of this work is to study the thermal behavior of a galvanic sludge which contains only chromium as a restriction metal. Simultaneous DTA/TG coupled with mass spectrometer tests were performed to characterize the thermal behavior of the sludge. Besides thermal analysis, sludge samples were heated in a specially designed furnace and these samples were submitted to X-ray diffraction. Vapor from the heated sludge was condensed and the particles were analyzed by EDS microprobe coupled in a scanning electron microscope. The slag formed after the calcination of the galvanic sludge was mainly composed of a mixture of calcium phosphate and fluoride. and minor concentrations of metals. A total weight loss of 34% was observed. The greatest part of this weight loss corresponds to CO2, H2O and SO2. H2O is liberated in the temperature range of 500-1,250 degrees C. CO2 in the range of 500-750 degrees C and SO2 near 1,000 degrees C. Chromium evaporation was not observed in relevant quantities, about 99.6% of the Cr remained incorporated in the slag.     

Isolation and Characterization of Cellulose Micro/Nanofibrils from Douglas Fir

Cellulose micro/nanofibrils were successfully extracted from softwood Douglas fir in three distinct stages. Initially raw Douglas fir wood chips were subjected to a hot water extraction (HWE) treatment. Then HWE treated cellulosic fibers underwent a bleaching process followed by a mild ultrasonication. Chemical composition analysis according to ASTM standards confirmed that most of hemicelluloses and nearly all lignin were removed during the first two stages, respectively. Microscopy studies showed formation of nanofibrils during the ultrasonication process, and increasing ultrasonication time led to generation of greater percentage of nanofibrils. With the removal of the matrix materials, the crystallinity of the cellulosic fibers was increased, whereas thermal stability was maintained. HWE opened up the cell wall structure, thereby facilitating the subsequent fractionation into micro/nanofibrils. The obtained cellulose micro/nanofibrils could serve as reinforcing material in composite products or raw material for other applications, such as filtration membrane.     

低温等离子体协同催化降解含硫恶臭污染物

采用共沉淀—喷涂法制备了（Cu5Mn7Zr1O22）0.08/（γ-Al2O3）0.1/堇青石蜂窝陶瓷催化剂。表征结果显示：催化剂孔隙率较高，表面均匀分散着粒径介于20~100 nm的晶体颗粒。以硫化氢和乙硫醇为典型含硫恶臭污染物进行了低温等离子体协同催化降解实验，结果表明：污染物的降解率随着输入功率的增加而提高；与单纯低温等离子体相比，低温等离子体协同催化能获得更好的降解效果。降解机理可能为：在高能电子和活性粒子作用下，H2S或C2H5SH分子中键能较弱的H—S、C—S和C—C键断裂形成·SH、·C2H5、·CH2SH、·CH3等小碎片基团，这些小碎片基团进一步发生聚合、氧化或自由基链式反应，最终降解为CO2、SO2、SO3、H2O等无毒小分子。