Thermal behavior of residues (sludge) originating from the sugarcane industry

The Brazilian sugarcane industry shows a great amount of generated sludge which should be utilized adequately. Two sludge samples, aerobic and anaerobic, were collected. Both were evaluated by thermogravimetry and differential thermal analysis (DTA) as well as X-ray power diffraction. These compounds show variations of mass between 30 and 140 °C due to the dehydration stage. The DTA curves show that the compounds have an exothermic reaction between 450 and 550 °C, which indicates that this can be used as an energy source. Details concerning the kinetic parameters of the dehydration and thermal decomposition have also been described here. The kinetic study of these stages was evaluated in open crucibles under nitrogen atmosphere. The obtained data were evaluated with the isoconversional kinetic method. The results show that different activation energies were obtained for thermal decomposition.     

Dissipation behavior of chlorpyrifos residues and risk assessment in sugarcane fields

As chlorpyrifos is used globally to control pests in sugarcane fields, analysis of its residues on food crops is essential to assess product safety for humans. In this study, chlorpyrifos content in sugarcane plants, soil and juice was determined using a gas chromatography with an electron capture detector. The limit of quantification was 0.01 mg/kg for plant and soil, and 0.01 mg/L for juice. The degradation and residual risk in sugarcane fields after applying chlorpyrifos to two sample sites (Changsha and Danzhou, China) were assessed. Chlorpyrifos concentrations in plants and soil decreased rapidly over time, reaching a degradation rate ranging from 98.82 to 99.25% on day 35. The half‐life of chlorpyrifos in both plants and soil was only 5.97–6.12 days. Regardless of application dosage (standard or high) at a pre‐harvest interval of 60 days, chlorpyrifos was undetectable in the harvested sugarcane. Risk assessment indicated that chlorpyrifos residue in sugarcane did not pose a health risk to humans.     

Characterization and thermal behavior of kaolin

The effect of nitric oxide (NO) on heat production and oxygen consumption was studied in excised roots of 5-day-old wheat seedlings grown in CaCl₂ solution (2.5 × 10⁻⁴ mol/L). Sodium nitroprusside (SNP), NaNO₃, NaNO₂ were used as NO donors. Incubation of the cut roots (wound stress) in the presence of NO donors led to the decrease of heat production and suppressed oxygen consumption. The increase of potassium (K⁺) ions exit was observed, pointing to the increase of the plasma membrane permeability and to the disruption of the adaptive processes development in roots in the NaNO₂ presence.     

Characterization of sugarcane and coconut fibers by thermal analysis and FTIR

Pyrolysis of sugarcane bagasse and coconut fiber was studied by thermal analysis in order to characterize their thermal behavior and to identify their constituents by the aid of their thermogravimetric curves and to determine their heat capacity by means of DSC. The Fourier Transform Infrared Spectrum (FTIR) was used to determine the main constituents present in both residues. The thermal degradation of sugarcane bagasse and coconut fiber presents two mass loss steps attributed to the release of humidity and to the decomposition of organic material (hemicellulose, cellulose and lignin). It was expected that the results of DSC analysis were almost the same for both types of biomasses.     

Characterization and thermal behavior of hydroxyapatite prepared by precipitation

Journal of Thermal Analysis and Calorimetry - The aim of this study was to find appropriate precipitation conditions (Ca/P ratio, pH and precipitation rate) for the synthesis of hydroxyapatite...     

Thermogravimetric investigation on prediction of thermal behavior of petroleum distillation residues

Summary Thermogravimetry (TG) is a potential tool to evaluate petroleum distillation residues, obtained in the crude oil distillation. Analyses were done at different heating rates, mass samples and gas flow rates. No differences were observed in the yields of the products formed during the pyrolysis at different analytical conditions. Linear correlation was found between the results of the TG and the standard methods for the prediction of the light fraction rates given by the pyrolysis.     

Preparation of adsorbents from sugarcane manufacturing by-product filter-mud by thermal activation

A series of experiments with thermal activation were carried out on filter-mud waste from the sugarcane refining process in a rotary reactor. The influence of activation parameters on the agro-industrial waste by varying the operation temperature of 600–800 °C was determined. The variations of pore properties as well as the change of chemical characteristics in the resulting solids (FM series) were also studied. The results show that the resulting samples are type IV with hysteresis loops corresponding to type H3 from nitrogen adsorption–desorption isotherms, indicating slit-shaped mesoporous characteristics (BET surface areas of 57–132 m² g⁻¹). The results also show that the surface areas of the unwashed products and water-washed products are lower than those of the washed products because of residues left in the crude products. The adsorption of paraquat on FM sample was preliminarily evaluated. The isotherm showed that the FM adsorbent had a high affinity for this herbicide and can be well fitted by Freundlich model. Thus, the agro-industrial waste is one resource for producing the mesoporous materials, and it may be applied to the water treatment for the removal of organic contaminants.     

Characterization of sugarcane bagasse by autofluorescence microscopy

The spatial distribution of chemical compounds in sugarcane bagasse is an important issue in its use as a raw material for second generation ethanol production from cellulose hydrolysis. Lignocellulosic materials including whole bagasse, fiber, pith, and respective samples obtained after chemical bleaching were investigated using confocal fluorescence microscopy and spectroscopy with one and two-photon excitation. Autofluorescence from unbleached samples revealed that emission from fiber walls containing the lignin fraction was longitudinally oriented. After bleaching treatment, the oriented emission was partially disrupted. Autofluorescence from bleached samples with a residual lignin content of about 1 % was ascribed to improved dispersion of remaining fluorophores throughout the samples inducing a concomitant reduction of fluorescence self-quenching in the samples. The combination of autofluorescence images with spectral emission and lifetime measurements provides a tool for microscopic characterization of natural bagasse samples. Moreover, the technique allows monitoring bleaching processes related to lignin removal.     

Kinetic of thermal decomposition of residues from different kinds of composting

Non-isothermal kinetic parameters regarding to the thermal decomposition of the ligninocellulosic fraction present in compost from urban solid residues (USR) obtained through stack covered (SC) with composted material, comes from the usine in composing of Araraquara city, Săo Paulo state, Brazil, and from stack containing academic restaurant organic solid residues (SAR). The samples were periodically revolved round 132 days of composting. Results from TG, DTG and DSC curves obtained on inert atmosphere indicated that the lignocellulosic fraction present, despite the slow degradation during the composting process, is thermally less stable than other substances originated during that process. The lignocellulosic fraction decomposition, between 200 and 400°C, were kinetically evaluated through non-isothermal methods of analysis. By using the Flynn-Wall and Ozawa isoconversional method, the medium activation energy, Ea, and pre-exponential factor, lgA, were 283.0±14.6, 257.6±1.3 kJ mol^-1 and 25.4±0.8, 23.2±0.2 min^-1, to the SC and SAR, respectively, at 95% confidence level. From E _a and lgA values and DSC curves, Malek procedure could be applied, suggesting that the SB (Sesták-Berggren) kinetic model is suitable for the first thermal decomposition step. This revised version was published online in August 2006 with corrections to the Cover Date.     

Two-step preparation and thermal characterization of cationic 2-hydroxypropyltrimethylammonium chloride hemicellulose polymers from sugarcane bagasse

Cationic sugarcane bagasse hemicellulose derivatives with a relatively low degree of substitution (0.01-0.54) containing quaternary ammonium groups were prepared by etherification with 3-chloro-2-hydroxypropyltrimethylammonium chloride or preferably with 2,3-epoxypropyltrimethylammonium chloride using sodium hydroxide as a catalyst in aqueous solution. The extent of etherification was measured by yield percentage and degree of substitution (DS). The DS values of the products could be controlled by adjusting the molar ratio of etherifying agent to anhydroxylose units in hemicelluloses and the molar ratio of sodium hydroxide to etherifying reagent. In comparison, the etherified hemicellulose preparations were characterized by both degradative methods such as thermal analysis, and non-degradative techniques such as gel permeation chromatography (GPC), Fourier transform infrared (FT-IR), and ¹³C nuclear magnetic resonance (NMR) spectroscopy. It was found that a significant degradation of the hemicellulose polymers occurred during etherification under the alkaline conditions used. The thermal stability of the etherified hemicelluloses was lower than that of the unmodified hemicellulose polymers.     

Characterization of transition metal nitride formation in rapid thermal processing (RTP)

The potential of RTP for the preparation of transition metal nitrides by reaction of metal thin films in molecular nitrogen was investigated. The films and the nitridation process were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive x-ray analysis (EDX) in a scanning electron microscope (SEM) and secondary neutral mass spectrometry (SNMS). The chemical states of vanadium at the utmost surface, detected by XPS, are related to V₂O₅ before RTP and to vanadium nitride, oxide and oxynitride after RTP. The deposition of a 3 nm Si top layer prevents V from oxidation and its selective removal before RTP enhances the proportion of nitride determined by XPS after RTP. From comparative experiments in a conventional tube furnace the advantages of RTP became obvious. With short process times of the RTP technique the integral amount of residual oxygen is kept low and oxide formation is largely avoided. The nitrogen content and the different polycrystalline phases formed by varying process time and temperature provide information about reactivity and the nitridation process. The nitrogen to vanadium ratio was determined by EDX and SNMS, revealing that the N content reaches saturation after only 5 seconds at 1100?°C.     

Characterization and biodegradability of polyester bioplastic-based green renewable composites from agricultural residues

The biodegradability, morphology, and mechanical properties of composite materials consisting of acrylic acid-grafted poly(butylene succinate adipate) (PBSA-g-AA) and agricultural residues (rice husk, RH) were evaluated. Composites containing acrylic acid-grafted PBSA (PBSA-g-AA/RH) exhibited noticeably superior mechanical properties compared with those of PBSA/RH due to greater compatibility with RH. The dispersion of RH in the PBSA-g-AA matrix was highly homogeneous as a result of ester formation, and the consequent creation of branched and cross-linked macromolecules, between the carboxyl groups of PBSA-g-AA and hydroxyl groups in RH. Each composite was subject to biodegradation tests in an Azospirillum brasilense BCRC 12270 liquid culture medium. The bacterium completely degraded both the PBSA and the PBSA-g-AA/RH composite films. Morphological observations indicated severe disruption of the film structure after 20-40 days of incubation. The PBSA-g-AA/RH (20 wt%) films were not only more biodegradable than those made of PBSA but also exhibited lower molecular weight and intrinsic viscosity, implying a strong connection between these characteristics and biodegradability.     

Synthesis and thermal behavior of chiral oligomers derived from cholesterol

Synthesis and thermal properties of a series of Schiff base oligomers derived from naturally occurring cholesterol are described. In particular, four of them show smectic A and/or chiral nematic phase/s or an unknown mesophase, while the other is non-mesomorphic. Molecular packing in the SmA phase has been determined by the HRXRD experiment.     

红外光谱法研究重质油分子的轻度热转化

为了从分子水平快速经济地分析重质油在热转化过程中的变化规律,利用四种模型化合物萘、四氢萘、十氢萘和正庚烷组成的混合体系来模拟重质油及其热转化缩合产物分子的基本组成,研究其红外吸收特性与平均分子参数（亚甲基和甲基的数目之比 N CH2/NCH3、芳氢率faH、芳香环系氢碳原子比NHar/NCar等）的关系。将重质油焦化重蜡油馏分进行轻度热转化,利用不同强度的系列溶剂将热转化产物的重质馏分顺序分离成系列溶剂族组分,将这些族组分进行红外分析。结果表明,混合物系列模拟体系的〖ＷＴＢＸ〗f〖ＷＴＢ１〗aH同其红外吸收在2750cm－1～3100cm－1的3000cm－1～3100cm－1强度分率（S3000~3100/S2750~3100）之间存在良好的线性关系,同时NCH2/NCH3 同2920cm－1和2960cm－1处的吸光度比值A2920/A2960之间也存在良好的线性关系。依据这些关系式可以合理解释重质油分子在热转化过程中分子结构的变化规律。随着重质油热转化的进行,NCH2/NCH3 饱和烃分子先增大后减小,芳香性族组分分子则持续降低;faH或NHar/NCar芳香性族组分分子呈现升高的趋势。     

Assessment of copper(II) biosorption from aqueous solution by agricultural and industrial residues

In this study, newspaper scraps (NS) and maize spatha (MS) treated in turn by HNO₃ and MeOH were evaluated for the biosorption of Cu²⁺ ions, on the basis of batch experiments. The effects of several parameters were investigated, including contact time, solution pH, shaking speed, biosorbent dosage and ionic strength. Under optimal conditions, the maximum sorption capacities (Q_max) were (60.386 ± 0.006) and (44.90 ± 0.02) μmol Cu²⁺ per g of sorbent, respectively, for NS and MS chemically treated with HNO₃. The optimal parameters were pH: 5, contact time: 40 min and shaking speed: 100 rpm for NS, while for MS the same parameters were pH 5, 20 min and 150 rpm, respectively. It was found that Cu²⁺ biosorption is disfavored by an increase in ionic strength and by the presence of some interfering cations. The experimental data obtained with NS best matched the Langmuir’s sorption model (R² = 0.994) while the Temkin model best described biosorption on MS (R² = 0.987). The biosorption of Cu²⁺ on both materials followed pseudo-second order kinetics, and the desorption of Cu²⁺ ions was effective in 0.01 M HCl solution.     

Impact of rock fabric,thermal behavior,and carbonate decomposition kinetics on quicklime industrial production and slaking reactivity

This paper deals with thermal analyses, burning trials and reactivity tests on 15 carbonate rocks, i.e., pure and impure carbonates, mud-supported and grain-supported limestones, crystalline marbles, and dolomites, used for the production of different lime products in industrial vertical shaft kilns worldwide. In particular, thermogravimetric and differential thermogravimetric analysis (TG–DTG) on massive (80–120 g) fine-grained (< 3.35 mm) samples allowed the extrapolation of the Arrhenius kinetic parameters, i.e., the (apparent) activation energy (E_a) and the pre-exponential or frequency factor (A). Other calcination parameters, i.e., the duration time, starting and ending calcination times and temperatures, and peaks of maximum calcination rate were also extrapolated in order to enhance their relationships with quicklime reactivity. Moreover, thermal analyses (TG–DTG–DTA) were repeated on powders (90 mg) using a more accurate analyzer to compare results. The study is completed by a thorough chemical–physical and mineralogical–petrographic characterization of carbonate rocks and derived burnt products. Results pointed out that medium-to-coarse crystalline materials, i.e., grain-supported limestones, diagenetic dolomites, and granoblastic marbles presented the highest activation energy, burnability and slaking reactivity. Conversely, microcrystalline carbonates with the highest micrite-to-sparite ratio, i.e., mud-supported limestones, and impure carbonates, enriched in quartz, clay minerals, and other subordinated non-carbonate impurities, presented the lowest activation energy, burnability, and slaking reactivity. This study also investigated the effect of BET-specific surface area and real density, depending on specific sintering tendency, on quicklime reactivity. Results from this multidisciplinary research activity put further constraints on carbonate rocks calcination kinetics and their suitability in the lime industry.

     

Structural and thermal characterization of sugarcane bagasse phthalates prepared with ultrasound irradiation

Chemical modification of sugarcane bagasse was achieved by esterification with phthalic anhydride in pyridine after ultrasound irradiation. The parameters including ultrasonic irradiation time 0-40 min, phthalic anhydride dosage 2.5-7.5 g, reaction time 30-150 min, and reaction temperature 80-115 °C were optimised and the extent of phthalation was measured by weight percent gain. It was found that degradation of the cell wall polymers occurred at higher temperature (>90 °C) under the experimental conditions used.FT-IR and CP/MAS ¹³C NMR spectroscopy studies also clearly produced evidence for phthalation reaction. The phthalated bagasse preparations showed decreased thermal stability after chemical modification.     

Characterization,thermal and ceramic properties of phyllite clays from southeast Spain

Journal of Thermal Analysis and Calorimetry - The present research studied a set of phyllite clays from several deposits in southeast Spain. These phyllite clays have traditionally been used as...