Activation of waste MDF sawdust charcoal and its reactive dye adsorption characteristics

This paper reports an experimental investigation of converting waste medium density fibreboard (MDF) sawdust into chars and activated carbon using chemical activation and thermal carbonisation processes. The MDF sawdust generated during the production of architectural mouldings was characterised and found to have unique properties in terms of fine particle size and high particle density. It also has a high content of urea formaldehyde resin used as a binder in the manufacturing of MDF board. Direct thermal carbonisation and chemical activation of the sawdust by metal impregnation and acid (phosphoric acid) treatment prior to pyrolysis treatment were carried out. The surface morphology of the raw dust, its chars and activated carbon were examined using scanning electron microscopy (SEM). Adsorptive properties and total pore volume of the materials were also analysed using the BET nitrogen adsorption method. Liquid adsorption of a reactive dye (Levafix Brilliant red E-4BA) by the derived sawdust carbon was investigated in batch isothermal adsorption process and the results compared to adsorption on to a commercial activated carbon (Filtrasorb F400). The MDF sawdust carbon exhibited in general a very low adsorption capacity towards the reactive dye, and physical characterisation of the carbon revealed that the conventional chemical activation and thermal carbonisation process were ineffective in developing a microporous structure in the dust particles. The small size of the powdery dust, the high particle density, and the presence of the urea formaldehyde resin all contributed to the difficulty of developing a proper porous structure during the thermal and chemical activation process. Finally, activation of the dust material in a consolidated form (cylindrical pellet) only achieved very limited improvement in the dye adsorption capacity. This original study, reporting some unexpected outcomes, may serve as a stepping-stone for future investigations of recycle and reuse of the waste MDF sawdust which is becoming an increasing environmental and cost liability. (C) 2004 Elsevier Ltd. All rights reserved.

Avaliação da distribuição da densidade em MDF a partir da técnica da onda de ultra-som

The goal of this research was to determine the density distribution in medium density fiberboard (MDF), manufactured with polyurethane derived from castor oil using, ultrasonic wave technique. The equipment used in this test is Steinkamp BP7 with plan and exponential transducers, both with 45 kHz frequencies, located in several zones on the plate in order to determine wave ultrasonic velocity. The Pinus caribaea and Eucalyptus grandis fiberboard were manufactured in the quality control and products development laboratory of Duratex with 500 mm long, 500 mm large, 8 and 15 mm of thickness. Three MDF for each fiber specimen and thickness were fabricated, totalizing twelve plates tested. The MDF were produced with 5% polyurethane addition, in temperature of 160°C, tension press of 53 bars and addition of moisture content of 12%. For determination of fiberboard density, samples were extracted from the same zones where the wave ultrasonic velocity was determined. In this case, DAX-Ray equipment was used. Statistical analysis shows good agreement with wave ultrasonic velocity and the density profile, validating the application of non-destructive technique in order to determine the density profile of MDF's.

Estudo comparativo entre MDF e MDP utilizados na indústria moveleira

Increasingly, the furniture market is competitive. The construction industry presents itself in growth, mainly due to the lines of existing incentives and tax credits established by the government, assisting the impulse to purchase real estate, building materials and furniture. Factors that promote and strengthen the sector's growth. With high demand from the furniture market, demand for higher quality and increasing technological advances, research is often undertaken in search of solutions for process improvement and product features, focusing on the production of materials less harmful to the environment, provision of raw press to lower cost, improve the production process and product development of cost-effective. This research focuses on the comparative study between two materials widely used in furniture manufacturing. MDF (Medium Density Fiberboard) and MDP (Medium Density Particleboard). The subject provides the focus in furniture production, presenting and comparing data collected from three companies producing panels between physical and mechanical characteristics of the materials, also presenting some of the main factors of influence on the quality of the panels, their features and applications on mobile. The study shows the high potential of using the MDP (Medium Density Particleboard) in furniture designs, as well as MDF (Medium Density Particleboard), favoring the final terms of the project , resulting in better utilization of each material , avoiding waste and increase unnecessary cost . Currently, several projects are developed in MDP and MDF furniture, where there is no relevance to their characteristics regarding their limitations. Many of these furnishings are designed without a specific study of the best use and positioning of each material, with better utilization , favoring collateral design , especially furniture designed exclusively for each environment . The lack of technical ...

Fresamento de madeiras de média densidade: MDF

The technological expansion and market manufactured wood as wood paneling makes the research of processes involving this material are increasingly necessary . The present study examines the milling process MDF - fiberboard with average density endmill with helical teeth , with the analysis of the surface finish by evaluating the surface roughness ( Ra) and analysis of the power consumption . We analyzed three types of cuts in milling : concordant , discordant , and cut top . We used 5 rpm (6000 , 8000 , 10000 , 12000 and 14000 RPM) , establishing five-speed cutting, 301 , 402 ,502, 603 and 703 m / min respectively. Five forward speeds and 4, 6, 8, 10 and 12 m / min. Each condition was repeated six times , totaling 180 tests. The results of roughness were obtained from rugosimeter data and the power consumption were obtained by Hall-effect sensor . These results were statistically analyzed using analysis of variance and Tukey test . Finally it was concluded that there are few significant differences between the results themselves vary roughness when cutting speeds and feed and no major differences in power consumption . The best surface quality and lower power consumption were for cutting speed of 703 m / min . To varying forward speed , the speed of 4 m / min showed better surface quality and lower power consumption

Estudo da influência das resinas termofixas uréia formaldeído (UF) e melamina formaldeído (MF) nas características físicas e mecânicas de painéis MDF

Thermosetting resins are very important in the production of MDF panels. They act as an adhesive in the process of compacting and consolidating the fiberboard. Thermoset resins commonly used in this process are based resin urea formaldehyde (UF) and melamine formaldehyde (MF). The first has a higher demand due to its low cost and good performance in meeting the specifications and standards. The second has a high cost compared to MF resin, but adds greater value to the MDF panel, because it gives greater moisture resistance. The process of manufacture of MDF boards was briefly presented in this study to facilitate the understanding of the work. Samples of thermosetting resins (UF and MF) were subjected to physical-chemical seeking to relate these results to the technological performance presented by their respective samples of MDF boards. Two other samples of MDF panels were subjected to physical and mechanical tests. Results were analyzed and related to the award of their respective thermoset resin. Instruments like Dahmos Trend Manager ® and Grecon Dax 5000 and TG - DSC analysis were used in this study to assist in the analysis of the results. It was observed that the results of the analysis of thermosetting resins were within the specified. Such resins do not directly influence the technological tests provided by the MDF panels, but it has been found that the process variables such as humidity and fiber production rate interfere with the performance of the resin accelerating the reaction and therefore their influence on the physical-mechanical properties of the panels MDF. Samples of MDF panels with UF and MF met all the specifications required by the Brazilian standard with regard to the technological quality. The increased demand for UF resin market is justified by the service specifications...

Análise do processo de fresamento de MDF em centro de usinagem CNC

Pós-graduação em Engenharia Mecânica - FEG

MDF and PB composites wastes used in the production of activated carbons by physical activation

O desenvolvimento de materiais de carbono continua a ser, na atualidade, uma das áreas de grande interesse junto das comunidades científica e industrial [1]. Especial atenção é dada à valorização de resíduos da indústria, de baixo valor económico, tentando desta forma resolver problemas de gestão de grandes quantidades de desperdícios [2]. De especial relevo destacamos os resíduos potencialmente perigosos, segundo os dados da FAO – Food and Agriculture Organization das Nações Unidas [3]. O desenvolvimento de novos materiais para a indústria do mobiliário, substitutos da madeira, tem gerado uma enorme diversidade de produtos mas também de resíduos. Os mais comuns no mercado são os materiais compósitos, entre eles o PB – ParticleBoard e o MDF – Medium Density Fibreboard, os quais registam um aumento de consumo na Europa de 1,3% e 4,3%, respetivamente, mesmo em período de crise económica como a que estamos a atravessar [3]. O presente trabalho tem como objetivo o estudo do potencial destes resíduos para a produção de carvões ativados (CA) em formas monolíticas, gerando um produto com um elevado valor acrescentado e com características inovadoras para a posterior aplicação em processos de adsorção.

Nonequilibrium dynamics of photoexcited electrons in graphene: Collinear scattering, Auger processes, and the impact of screening

We present a combined analytical and numerical study of the early stages (sub-100-fs) of the nonequilibrium dynamics of photoexcited electrons in graphene. We employ the semiclassical Boltzmann equation with a collision integral that includes contributions from electron-electron (e-e) and electron-optical phonon interactions. Taking advantage of circular symmetry and employing the massless Dirac fermion (MDF) Hamiltonian, we are able to perform an essentially analytical study of the e-e contribution to the collision integral. This allows us to take particular care of subtle collinear scattering processes - processes in which incoming and outgoing momenta of the scattering particles lie on the same line - including carrier multiplication (CM) and Auger recombination (AR). These processes have a vanishing phase space for two-dimensional MDF bare bands. However, we argue that electron-lifetime effects, seen in experiments based on angle-resolved photoemission spectroscopy, provide a natural pathway to regularize this pathology, yielding a finite contribution due to CM and AR to the Coulomb collision integral. Finally, we discuss in detail the role of physics beyond the Fermi golden rule by including screening in the matrix element of the Coulomb interaction at the level of the random phase approximation (RPA), focusing in particular on the consequences of various approximations including static RPA screening, which maximizes the impact of CM and AR processes, and dynamical RPA screening, which completely suppresses them. © 2013 American Physical Society.

环丙烷衍生物的研究与合成

一 . 本工作利用超声技术，研究和改进了原位产生零价钴，零价镍络合物催化马来酸二甲酯与二溴甲烷的环丙烷化反应。发现，超声波不仅能够加速反应催化中间体Co(COOCH_3)-CH=CH-COOCH_3)_2·(CH_3CN)_2. Ni(COOCH_3)-CH=CH-COOCH_3)_2·CH_3CN的形成，而且可显著缩短环丙烷化反应时间，提高反应收率。如Ni催化体系文献报导，反应24小时产率为33％。而在超声波辐照下6小时产率可达90％；Co催化体系在超声波作用下，半小时产率高达94％，而相应的文献值为63小时64％。因此，本工作为合成化工原料1.2－环丙烷酸二甲酯提供了方便，快捷的方法，并为改进其它负电子烯的环丙烷化反应，提供了依据。二 . 本工作发现：在MDF（N,N-二甲基甲酯胺）、乙脂混合溶剂中，原位产生零价钴络合物催化下，负电子烯（如马来酸二甲酯，丙烯酸甲酯等）与二氯甲烷也能发生环丙烷化反应，开辟了零价金属或零价金属络合物“催化”脆二卤代烷中价格最便宜，最易提纯和保存的二氯甲烷与烯烂较高产率环丙烷化的先例。根据实验现象初步提出了如下机理。

渤海近代沉积物的古地磁与古环境研究

本论文的主要实验测量工作可分为古地磁学与地球化学二大部分。在古地磁学方面。对JX91-2A（168），JX91-2B（80），JX91-3A（66）和JX91-3B（137）共451个样品进行了天然剩磁（NRM）及交变退磁测量，还进行了磁化率及磁化率各向异性的测量。对JX91-2A，JX91-2B和JX91-3A开展了岩石磁学研究，测量了非粘滞性剩磁（ARM），等温剩磁（ARM），饱和等温剩磁（FIRM）以及个别样品的FIRM衰减曲线，对JX91-3B求出了中间破坏强度（MDF）。在地球化学方面，对JX91-2A（79），JX91-3B（67），JX91-3m(50)和JX91-4G（27）共223个样品进行了X光萤光（XRF）分析。包括10种主要元素及21种向量元素，以及X光衍射（XRD）分析。还对JX91-2A进行了有机碳、微体古生物学及稳定碳氧同位素分析；对JX-91-3B进行了~（210）Pb 测量。另外还对此四岩芯测定了含水量及粒度分布等。所有实验数据都用计算机进行了分析处理，并做了广泛的多学科综合对比研究。在充分借鉴前人成果的基础上，本论文就以下四个方面的问题得到了一点新的认识。一、渤海黄河口外的浊流系统及浅水浊流沉积。这一浊流系统的存在具有多方面的证据。二、渤海沉积物的高精度年代学。对于渤海中央盆地沉积物主要采用了全新世以来的海平面变化曲线及古地磁场强度曲线确定年代，定出JX91-2A底部年代为距今8，500年。三、古地磁记录改正方法及渤海地区古地磁长期变样本曲线的建立。四、渤海古环境综合分析及黄河全新世以来的河道变迁。