受污染水稻秸秆热解产物中镉含量及溶出性研究

以镉污染土种植水稻秸秆为原料, 通过500℃不同时间(10~720min)处理制备秸秆热解产物(生物炭和秸秆灰), 测定产物中镉的含量及其溶出性. 结果表明, 水稻秸秆经热解处理后挥发镉总量的29.6%~48.4%; 样品产率随热解时间的增加而下降; 单位质量生物炭和秸秆灰中镉含量为2.35~7.05mg·kg-1和15.0~16.4mg·kg-1, 分别是水稻秸秆中镉含量(0.948mg·kg-1)的2.5~7.4倍和15.8~17.3倍; 通过不同提取剂得到镉溶出率由低到高依次为0%~43.2%(采用0.01mol·L-1 CaCl2提取)、0%~44.3%(采用Toxicity Characteristic Leaching Procedure提取)、28.8%~58.8%(采用1mol·L-1 pH5.0乙酸-乙酸钠单次提取)、35.1%~98.4%(采用1mol·L-1 pH5.0乙酸-乙酸钠连续4次提取); 随着热处理时间的延长, 样品中镉溶出率逐渐降低; 由于热解过程中镉的挥发和形态转变, 水稻秸秆转变为生物炭和秸秆灰后镉的可溶出总量(采用1mol·L-1 pH5.0乙酸-乙酸钠连续4次提取)由0.933mg·kg-1降至0.223~0.384mg·kg-1, 表明受镉污染的水稻秸秆热解转化为生物炭和秸秆灰可以有效缓解镉潜在的溶出风险.     

Thermal self-sustainability of biochar production by pyrolysis

The pyrolysis of several agricultural and biofuel production residues (grape residues, sugarcane residues, dried distiller's grain, palm oil residues, apple pomace and forestry residue) has been carried out in a pilot bubbling fluidized bed pyrolyzer operating under a range of temperature from 300 to 600 °C and two vapor residence times (2 and 5 s), with the aim of determining their pyrolysis behavior including products yields and heat balance. The composition of the product gases was determined, from which their heating value was calculated. The liquid bio-oil was recovered with cyclonic condensers. The thermal sustainability of the pyrolysis process was estimated by considering the energy contribution of the product gases and of the liquid bio-oil in relation to the pyrolysis heat requirements. The most promising biomass feedstocks for the sustainable production of biochar were indentified. Furthermore, this study presented the char yield in relation to the excess heat that could be obtained by combusting the gas and bio-oil coproducts of biochar production, as functions of pyrolysis temperature and vapor residence time.     

Potential impact of ultrasound,pulsed electric field,high-pressure processing and microfludization against thermal treatments preservation regarding sugarcane juice (Saccharum officinarum)

Sugarcane juice (Saccharum officinarum) is a proven nutritious beverage with high levels of antioxidants, polyphenols, and other beneficial nutrients. It has recently gained consumer interest due to its high nutritional profile and alkaline nature. Still, high polyphenolic and sugar content start the fermentation in juice, resulting in dark coloration. Lately, some novel techniques have been introduced to extend shelf life and improve the nutritional value of sugarcane juice. The introduction of such processing technologies is beneficial over conventional processes and essential for producing chemical-free, high-quality, fresh juices. The synergistic impact of these novel technologies is also advantageous for preserving sugarcane juice. In literature, novel thermal, non-thermal and hurdle technologies have been executed to preserve sugarcane juice. These technologies include high hydrostatic pressure (HHP), ultrasound (US), pulsed electric field (PEF), ultraviolet irradiation (UV), ohmic heating (OH), microwave (MW), microfludization and ozone treatment. This review manifests the impact of novel thermal, non-thermal, and synergistic technologies on sugarcane juice processing and preservation characteristics. Non-thermal techniques have been successfully proved effective and showed better results than novel thermal treatments. Because they reduced microbial load and retained nutritional content, while thermal treatments degraded nutrients and flavor of sugarcane juice. Among non-thermal treatments, HHP is the most efficient technique for the preservation of sugarcane juice while OH is preferable in thermal techniques due to less nutritional loss.     

Enzymatic Hydrolysis of Wheat Straw Irradiated by Electron Beam in Presence of Peracetic Acid Solution

Abstract

Radiation pretreatments of wheat straw in the presence of peracetic acid solutions were carried out using an electron beam accelerator, in which the effects of various treatment conditions on the enzymatic hydrolysis were investigated in detail. As irradiation dose was increased, the effect of a combination of peracetic acid and irradiation on the enzymatic hydrolysis was remarkable. The combination of irradiation and pulverization was effective for reducing the size of wheat straw. The enzymatic hydrolysis of wheat straw irradiated with high irradiation doses (500 kGy above) was accelerated by a water-washing treatment after irradiation.     

粗壮脉纹胞菌降解稻草粗纤维培养基的优化

稻草是农业生产的主要副产物,因粗纤维高,利用率不高,基本用于燃料和肥料。以稻草为原料,利用从江西传统发酵食品中分离诱变筛选的高产纤维素酶菌株Neurospora crassa来发酵降解稻草,以制得新型稻草发酵饲料。通过Plackett-Burman(P-B)试验设计从7种培养基成分中筛选出对对纤维降解有显著影响的3个关键因素米糠、硫酸铵和尿素,然后再通过最陡爬坡实验逼近纤维素降解的最大值点,以此作为响应面实验的中心点。最后通过响应面(RSM)试验设计得到粗壮脉纹孢菌发酵降解稻草粗纤维的最佳培养基组成:稻草为89.3%,米糠为8.39%,(NH4)2SO4为1.63%,尿素0.68%。在此最优化培养基组成条件下,粗纤维降解率为49.65%。     

Flux growth of straw‐like rutile monocrystals

Millimetric straw‐like rutile monocrystals were grown by the flux growth technique. A suitable mixture of flux (MoO₃, V₂O₅, Li₂CO₃) and amorphous TiO₂ gel was slowly cooled down to 750°C from 1250°C or 1350°C. The best yields of straw‐like rutile were obtained with a nutrient/flux ratio and a cooling rate in the range 0.015‐0.006 and 1.8‐1.9 K h^‐1, respectively. The hollowed crystals were characterized by powder and single‐crystal X‐ray diffraction, scanning electron microscopy, microthermometry, and µ‐Raman spectroscopy. As for skeletal crystal, the formation of axial canals in rutile is attributed to a lack of nutrient due to the viscosity of the melt and the high growth rate along [001]. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

利用麦秆制聚氨酯多元醇研究

以小麦秸秆为原料,在浓硫酸催化作用下以聚乙二醇(PEG400)为液化试剂进行液化,讨论了麦秆纤维粒径、催化剂用量、乙二醇(EG)加入量、反应温度和时间等因素对液化残渣率的影响.结果表明:当纤维为"＞12目",EG用量为20%,浓硫酸用量为4%,在160℃下反应60min时,所得残渣率最小,为0.8%.羟值、酸值的测试结果和红外分析结果表明,液化过程中羟值逐渐减小,而酸值则呈现先增大后减小的趋势,说明反应后期有酯缩合反应发生.将液化产物与二苯基甲烷二异氰酸酯(MDI)反应可制成泡沫材料,红外光谱证实生成物具有聚氨酯的典型特征.得到的泡沫材料密度为38kg/m3,抗压强度为118kPa,性能优良.     

PVA-Hydrogel Entrapped <Emphasis Type="Italic">Candida Guilliermondii</Emphasis> for Xylitol Production from Sugarcane Hemicellulose Hydrolysate

Viable cells of Candida guilliermondii were immobilized by inclusion into polyvinyl alcohol (PVA) hydrogel using the freezing–thawing method. Entrapment experiments were planned according to a 2³ full factorial design, using the PVA concentration (80, 100, and 120 g L⁻¹), the freezing temperature (−10, −15, and −20 °C), and the number of freezing-thawing cycles (one, three, and five) as the independent variables, integrated with three additional tests to estimate the errors. The effectiveness of the immobilization procedure was checked in Erlenmeyer flasks as the pellet capability to catalyze the xylose-to-xylitol bioconversion of a medium based on sugarcane bagasse hemicellulosic hydrolysate. To this purpose, the yield of xylitol on consumed xylose, xylitol volumetric productivity, and cell retention yield were selected as the response variables. Cell pellets were then used to perform the same bioconversion in a stirred tank reactor operated at 400 rpm, 30 °C, and 1.04 vvm air flowrate. At the end of fermentation, a maximum xylitol concentration of 28.7 g L⁻¹, a xylitol yield on consumed xylose of 0.49 g g⁻¹ and a xylitol volumetric productivity of 0.24 g L⁻¹ h⁻¹ were obtained.     

Mechanistic investigations in ultrasound-assisted xylitol fermentation

This study has investigated ultrasound-assisted xylitol production through fermentation of dilute acid (pentose-rich) hydrolysate of sugarcane bagasse using free cells of Candida tropicalis. Sonication of fermentation mixture at optimum conditions was carried out in ultrasound bath (37 kHz and 10% duty cycle). Time profiles of substrate and product in control (mechanical shaking) and test (mechanical shaking + sonication) fermentations were fitted to kinetic model using Genetic Algorithm (GA) optimization. Max. xylitol yield of 0.56 g/g and 0.61 g/g of xylose was achieved in control and test fermentations, respectively. The biomass yield also increased marginally (∼17%) with sonication. However, kinetics of fermentation increased drastically (2.5×) with sonication with 2× rise in xylose uptake and utilization by the cells. With comparative analysis of kinetic parameters in control and test experiments, this result was attributed to enhanced permeability of cell membrane that allowed faster diffusion of nutrients, substrates and products across cell membrane, higher enzyme-substrate affinity, dilution of toxic components and reduced inhibition of intracellular enzymes by substrate.     

Determination and dissipation of fipronil and its metabolites in/on sugarcane crop

Fipronil has label claim for managing shoot borer and root borer of sugarcane. The dissipation and metabolism of fipronil in/on sugarcane crop have been studied under tropical field condition by employing a modified quick, easy, cheap, effective, rugged and safe sample preparation method and gas chromatography equipped with electron capture detector. The method could provide 90.27–98.97% recoveries of target analytes from cane leaves and stem with relative standard deviations of less than 5%. The sulphide, desulfinyl and sulfone metabolites of fipronil were detected along with the parent compound even in the 0-day samples of sugarcane leaves and stem collected 2 h post-foliar spraying. The total residues comprising fipronil and its three major metabolites got dissipated to 4.366 µg/g from the initial deposit of 12.977 µg/g within a day after foliar spray. Fipronil sulphide and fipronil desulfinyl were the major metabolites on sugarcane crop. The residues (both parent compound and total residues) reached below the detectable level of 0.005 µg/g on 7 and 15 days after treatment on stem and leaves, respectively. Half-life of fipronil was less than a day on sugarcane crop. The total residues had the half-life of 1.66 and 0.91 days on leaves and stem, respectively.