Quantitative characterization of chemical degradation of heat‐treated wood surfaces during artificial weathering using XPS

The X‐ray photoelectron spectroscopy (XPS) study of three heat‐treated North American wood species (jack pine, birch and aspen) was carried out to evaluate chemical modifications occurring on the wood surface during artificial weathering for different times. The results suggest that the weathering reduces lignin content (aromatic rings) at the surface of heat‐treated wood, consequently, the carbohydrates content increases. This results in surfaces richer in cellulose and poorer in lignin. Heat‐treated wood surfaces become acidic due to weathering, and the acidity increases as the weathering time increases. Three possible reasons are given to account for the increase of acidity during weathering. The lignin content increases, whereas the hemicelluloses content decrease due to heat treatment. Heat‐treated woods have lower acidity to basicity ratios than the corresponding untreated woods for all three species because of the decrease in carboxylic acid functions mainly present in hemicelluloses. The wood composition changes induced by weathering are more significant compared to those induced by heat treatment at wood surface. Exposure to higher temperatures causes more degradation of hemicelluloses, and this characteristic is maintained during weathering. However, the wood direction has more effect on chemical composition modification during weathering compared to that of heat treatment temperature. The heat‐treated jack pine is affected most by weathering followed by heat‐treated aspen and birch. This is related to differences in content and structure of lignin of softwood and hardwood. The use of XPS technique has proved to be a reliable method for wood surface studies. Copyright © 2012 John Wiley & Sons, Ltd.     

Polyhedral Analysis for Concentrator Location Problems

The concentrator location problem is to choose a subset of a given terminal set to install concentrators and to assign each remaining terminal node to a concentrator to minimize the cost of installation and assignment. The concentrators may have capacity constraints. We study the polyhedral properties of concentrator location problems with different capacity structures. We develop a branch and cut algorithm and present computational results.     

Aromatization of Hantzsch Ester 1,4‐Dihydropyridines with Iodine under Normal Conditions and Ultrasound Irradiation

A variety of Hantzsch ester 1,4‐dihydropyridines are efficiently oxidized to their corresponding pyridine compounds with iodine under normal conditions and ultrasound irradiation. The reactions were carried out in refluxing CH₃CN.     

Aqueous Ammonia Soaking of Switchgrass Followed by Simultaneous Saccharification and Fermentation

Simultaneous saccharification and fermentation (SSF) of switchgrass was performed following aqueous ammonia pretreatment. Switchgrass was soaked in aqueous ammonium hydroxide (30%) with different liquid–solid ratios (5 and 10 ml/g) for either 5 or 10 days. The pretreatment was carried out at atmospheric conditions without agitation. A 40–50% delignification (Klason lignin basis) was achieved, whereas cellulose content remained unchanged and hemicellulose content decreased by approximately 50%. The Sacccharomyces cerevisiae (D₅A)-mediated SSF of ammonia-treated switchgrass was investigated at two glucan loadings (3 and 6%) and three enzyme loadings (26, 38.5, and 77 FPU/g cellulose), using Spezyme CP. The percentage of maximum theoretical ethanol yield achieved was 72. Liquid–solid ratio and steeping time affected lignin removal slightly, but did not cause a significant change in overall ethanol conversion yields at sufficiently high enzyme loadings. These results suggest that ammonia steeping may be an effective method of pretreatment for lignocellulosic feedstocks.     

Novel hybrid process for the conversion of microcrystalline cellulose to value-added chemicals: part 1: process optimization

In this paper, a novel hybrid process for the treatment of microcrystalline cellulose (MCC) under hot-compressed water was investigated by applying constant direct current on the reaction medium. Constant current range from 1A to 2A was applied through a cylindrical anode made of titanium to the reactor wall. Reactions were conducted using a specially designed batch reactor (450 mL) made of SUS 316 stainless steel for 30–120 min of reaction time at temperature range of 170–230 °C. As a proton donor H₂SO₄ was used at concentrations of 1–50 mM. Main hydrolysis products of MCC degradation in HCW were detected as glucose, fructose, levulinic acid, 5-HMF, and furfural. For the quantification of these products, High Performance Liquid Chromatography (HPLC) and Gas Chromatography with Mass Spectroscopy (GC–MS) were used. A ½ fractional factorial design with 2-level of four factors; reaction time, temperature, H₂SO₄ concentration and applied current with 3 center points were built and responses were statistically analyzed. Response surface methodology was used for process optimization and it was found that introduction of 1A current at 200 °C to the reaction medium increased Total Organic Carbon (TOC) and cellulose conversions to 62 and 81 %, respectively. Moreover, application of current diminished the necessary reaction temperature and time to obtain high TOC and cellulose conversion values and hence decreased the energy required for cellulose hydrolysis to value added chemicals. Applied current had diverse effect on levulinic acid concentration (29.9 %) in the liquid product (230 °C, 120 min., 2 A, 50 mM H₂SO₄).     

Determination of molybdenum in biological samples by flame atomic spectrometry after preconcentration on activated carbon

Abstract  

Molybdenum is well known for its toxic effects, although it is also essential for N₂-fixing cyanobacteria and several enzymes. This study proposes a simple and accurate procedure for separation, preconcentration, and determination of trace amounts of molybdenum in biological samples by flame atomic absorption spectrometry. It is based on complexation of Mo by cupferron and sorption onto activated carbon. Effects of parameters such as pH, stirring time, and amounts of activated carbon and cupferron on recovery were examined. The results demonstrated that Mo at pH range of 2.5–3.5 was quantitatively sorbed onto activated carbon as its cupferron complex. The optimum stirring time was found to be 30 min. The relative standard deviation was found to be 12% for 200 cm³ 50 ng/cm³ Mo using 10 replicate preconcentration procedures. The limits of detection and quantification were found to be 1.0 and 3 ng/cm³, respectively, by preconcentration of 200 cm³ initial sample to 2 cm³ final volume. As a result, an enrichment factor of 100-fold was achieved. The proposed preconcentration procedure was applied to determine Mo in biological samples such as vegetables, milk, and animal liver. The molybdenum concentrations were found (as μg/dm³ or μg/kg) in the range of 70–5,500 for plants, 3–124 for milk and milk powder, and 960 for liver samples.     

A new green technology: hydrothermal electrolysis for the treatment of biodiesel wastewater

Recently, biodiesel has become more attractive as an alternative diesel fuel because it is renewable, biodegradable, non-toxic, and environmentally friendly. In this study, we have developed a new green process called ??hydrothermal electrolysis??, by which industrial wastewater can be converted to more value-added chemicals under high-temperature and high-pressure aqueous conditions. We prepared model biodiesel wastewater and carried out hydrothermal electrolysis experiments by using both a continuous flow reactor and a batch autoclave. Current efficiencies and the effects of reaction time and reaction temperature on the decomposition of biodiesel wastewater and removal of total organic carbon (TOC) were investigated under various operating conditions. It was found that conversions of both TOC and glycerol inside the model biodiesel wastewater increased with increasing applied current. With the autoclave, the maximum glycerol conversion was recorded as 83% by applying 1 A current at 250 °C, whereas with the flow reactor, 75% of glycerol was converted into gas and liquid products under the effect of 1 A current for 60 min at a reaction temperature of 280 °C. In the case of TOC removal from the liquid product solution, under identical conditions, it was found that 23 and 15.9% TOC conversions were achieved by the batch and continuous flow reactors, respectively.     

WEFTA interlaboratory comparison on total lipid determination in fishery products using the Smedes method

Lipid determination by the Smedes method was tested in an interlaboratory trial performed by nine laboratories from seven countries belonging to the West European Fish Technologists Association Analytical Methods Working Group. Five samples of fish and fishery products with different lipid contents, including two blind duplicates, were distributed among the participants. All laboratories applied a slightly modified Smedes method, which included extraction of lipids by cyclohexane and isopropanol, transfer of lipids to the cyclohexane phase by addition of water, phase separation by centrifugation, and gravimetric lipid determination. The results indicate that the RSD for reproducibility (RSD(R)) was between 4.11 and 6.31% for samples with moderate (7%) and high (14%) lipid content, depending on the sample. Larger SDs among the laboratories were obtained for a cod sample with low lipid content of 0.5%. The method is judged to be suitable as a routine method for lipid determination in fish and fishery products.