蛭石与人造沸石氨氮平衡吸附--基本关系式与二次方程的解

在给定pH值(pH=7.0)和温度(T=25℃)的条件下,采用纳氏试剂比色法(GB7479-87)测定了NH4Cl溶液中蛭石和人造沸石的氨氮平衡吸附量.在平衡吸附量Qe与溶液离子浓度C和介质有效吸附势P关系基础上建立了平衡吸附量Qe与溶质起始浓度C0、吸附介质用量W0的一元二次方程.测试结果证明.这一方程可在较大的C0和W0变化范围内用以描述蛭石和人造沸石的氨氮等温平衡吸附过程.     

天然沸石和蛭石的离子吸附性能研究

以天然沸石和蛭石为吸附剂,采用等温吸附方法,研究其对Cu2+的吸附性能.结果表明,天然沸石对Cu2+的去除率略高于蛭石.天然沸石和蛭石的吸附容量p值分别为8.85 mg/g和6.99 mg/g.在实际应用中,天然沸石的单价低,吸附容量大,单位处理成本低,因此,天然沸石是人工湿地吸附缓冲单元理想的介质填料.     

液/固离子吸附体系中的强度因子

在离子质量浓度25~500 mg.L-1和吸附剂(蛭石)质量浓度10~150 g.L-1范围内分析测试了平衡固液体系中Zn、Cd离子等温吸附量.试验数据表明:平衡离子吸附密度qe(离子吸附量与吸附剂量的比值)唯一由C0/W0(起始点液相离子浓度C0与吸附剂浓度W0的比值)与Ce/W0(平衡液相离子浓度Ce与W0的比值)的差屿来决定,与离子、吸附剂的浓度及吸附反应过程无关.重复测试证实:给定C0/W0时,qe与Ce/W0具有唯一对应的值.指出液/固相离子吸附体系中的强度因子不是离子的浓度而是离子量与吸附剂量的比值,离子吸附反应的方向与速率取决于系统中离子量与吸附剂量的相对水平,离子吸附反应达到平衡的条件是离子与吸附剂化学势之和在液、固相之间的差异为0.     

天然蛭石对污水中氨氮吸附去除率的影响

研究了蛭石对污水中氨氮的吸附容量及水中pH、温度、浓度、蛭石用量对氨氮去除率的影响.结果表明,当蛭石的饱和吸附量为20.83 mg/g,pH在2.0～6.0范围内时,蛭石吸附量随pH值升高而增大,而在pH6.0～9.0范围内随pH升高而降低;温度在10～35℃范围内对氨氮吸附具有负影响;氨氮初始浓度在小于50 mg/L时,其去除率随着蛭石用量的增加而增大.为蛭石作为一种新型填料提供了基础数据和理论依据.     

4种矿物填料吸附锌、镉离子能力比较研究

为了人工湿地污水处理系统选择吸附填料提供基础数据,比较了人工沸石、膨胀蛭石、天然沸石、硅藻土4种矿物吸附Zn2+和Cd2+离子的能力.结果表明:4种矿物吸附Zn2+和Cd2+离子的容量大小顺序为人工沸石天然沸石>膨胀蛭石>硅藻土;给定废水锌、镉离子去除率目标,4种矿物使用成本大小的顺序为硅藻土>人工沸石>膨胀蛭石>天然沸石.说明在比较的矿物吸附剂中,天然沸石与膨胀蛭石是最佳的人工湿地填料.     

水洗和酸洗蛭石体系中Mn2+吸附的差异分析

以水洗和酸洗蛭石为吸附剂,研究了固/液吸附体系中Mn2+的吸附特性.结果表明,水洗和酸洗蛭石体系Mn2+离子的吸附都存在明显的离子和吸附剂浓度效应,水洗蛭石体系Mn2+离子的去除率显著高于酸洗蛭石体系.在酸洗过程中,蛭石表面部分吸附位被H+离子占据,降低了阳离子的交换能力.酸洗蛭石的吸附容量低,在吸附过程中H+离子的解吸会降低出水溶液的pH值,不宜作为湿地基质填料.     

微生物发酵米糠对Cr^6＋的吸附性能研究

研究了微生物发酵米糠的用量、溶液温度、Cr^6＋浓度、溶液pH值和吸附时间对微生物发酵米糠吸附Cr^6＋性能的影响。实验结果表明：微生物发酵米糠对Cr^6＋具有很好的吸附效果,吸附率达95．7％。其最佳吸附条件为微生物发酵米糠用量10g／L,温度60℃,pH值为2,Cr^6＋质量浓度低于40mg／L,吸附时间40min。该吸附行为符合Freundlich吸附等温方程,吸附过程符合二级动力学模型。     

胶原纤维固化黑荆树单宁对钪吸附的研究

以胶原纤维为基质,通过醛交联剂将黑荆树单宁固化在胶原纤维上,制备了胶原纤维固化黑荆树单宁(IBWT)吸附材料并研究了IBWT对钪离子(Sc3 )的吸附特性.结果表明:在HOAc-NaOAc介质中,IBWT对Sc3 具有较强的吸附能力.50℃下,当溶液中Sc3 的质量浓度为100mg/L、pH值为6.40时,吸附容量达到83.3mg/g.IBWT对Sc3 的平衡吸附量随pH值和温度的升高而升高.吸附过程为吸热过程,吸附平衡符合Langmuir方程.IBWT对Sc3 的吸附主要为化学吸附.进一步实验表明,IBWT经3次重复使用后对Sc3 的吸附容量基本不变.     

胶原纤维固化杨梅单宁对Mo(Ⅵ)的吸附

研究了胶原纤维固化杨梅单宁(IBT)这一新型吸附材料对Mo6 的吸附特性.实验表明,温度对吸附容量影响不大,而pH值对吸附容量有显著影响,Mo6 的吸附容量随pH值降低而增加,表明其吸附机理是吸附剂与聚钼阴离子之间的静电结合.当Mo6 的初始质量浓度为100.0mg/L、吸附剂用量0.100 g、温度为303 K、pH值2.0时,IBT对Mo6 的吸附量为82.4 mg/g.Freundlich方程可以很好地描述IBT对Mo6 的吸附等温线.动力学研究表明,初始吸附速率很快,吸附达到平衡的时间约为600 min,其吸附动力学可很好地用拟二级速率方程描述,计算所得的平衡吸附量与实测值误差很小.解吸实验表明,0.02 mol/L EDTA溶液能使吸附剂再生,并能循环使用.选择性吸附研究表明,在酸性(pH值2.0)条件下,IBT对Mo6 的吸附率大于95%,而对Ni2 和Cu2 的吸附率低于5%,可用于Mo6 -Ni2 和Mo6 -Cu2 二元混合溶液中Mo6 的分离和提取.     

硅藻土对重金属离子Mn2+的吸附研究

以硅藻土为吸附剂,采用静态吸附试验考查了吸附剂浓度、离子初始浓度、吸附质溶液温度、吸附质溶液初始pH值、时间等因素对硅藻土吸附模拟废水中Mn2+的影响.研究表明,硅藻土对Mn2+的最大吸附量可达到4.0486 mg·g-1,效果较好,可被用于去除重金属锰.适当增加吸附剂用量、离子初始浓度、控制吸附温度(＜50)、pH值(＜6)、延长吸附时间都能提高硅藻土对Mn2+的吸附效果.Langmuir吸附等温式相比Freundlich吸附等温式能更好的描述硅藻土对Mn2+的吸附过程.硅藻土吸附M2+的吸附动力学则符合二级动力学方程.     

Analysis of the water vapour sorption isotherms of thermally modified acacia and sesendok

Abstract

Two Malaysian hardwoods, acacia (Acacia mangium) and sesendok (Endospermum malaccense), that had been subjected to oleo-thermal modification were studied to determine their sorption isotherm behaviour using a dynamic vapour sorption apparatus. All the specimens were thermally modified using palm oil at three different temperatures (180, 200 and 220°C) and three different times (1, 2 and 3 h). The results showed that there was a reduction in equilibrium moisture content at each target relative humidity due to the heat treatment, but that the two wood species showed different behaviour in this respect. The adsorption isotherms were analysed using the Hailwood and Horrobin model, with excellent fits to the experimental data. The monolayer water and polylayer water were both reduced at a range of relative humidity values of the treated samples, although behaviour between the two wood species differed. Heat treatment resulted in an increase in hysteresis ratio, which was probably due to the increase in matrix stiffness of the cell walls.     

Water sorption,surface structure and surface energy characteristics of wood composite fibres refined at different pressures

During fibre processing, wood fibres are subjected to a range of physical and chemical conditions sufficient to slightly alter their chemical composition and hence their ultimate performance when used in the manufacture of wood fibre-based composites. In order to better understand the effects of refiner conditions on material performance, wood fibres were subjected to processing at different refiner pressures (4, 6, 8 and 10 bar) and subsequently dried in a flash drier. The fibres were analysed for changes in surface area, surface energy, surface structure and water vapour sorption characteristics. The methods applied were nitrogen adsorption utilising the Brunauer–Emmett–Teller theory, inverse gas chromatography, scanning electron microscopy and dynamic vapour sorption. It was found that increasing refiner pressure resulted in fibres of lower surface area, accompanied by increasing dispersive surface energies up to operating refiner pressures of 8 bar. It was found with fibres refined at different pressures that as the refiner pressure increased the equilibrium moisture content of the fibre decreased at the set relative humidities. However, it was also noted that the hysteresis was not significantly different between each of the refiner pressures. The results suggest that different refiner pressures can be used to tune the surface characteristics which may be beneficial to product development and the improvement of the environmental profile of the wood fibre composites.     

白橡热压干燥材等温吸湿特性研究

以白橡热压干燥材为研究对象,利用动态水分吸附仪研究了不同热压温度干燥处理后白橡木材和未处理对照材的等温吸湿特性,并采用H-H模型拟合;分析热压干燥对木材吸湿特性的降低机理。结果表明:白橡木材等温吸湿线皆为IUPAC Ⅱ型等温吸湿线。在任意相对湿度下,热压干燥材平衡含水率均明显低于对照材,且热压温度越高,平衡含水率降低越明显。H-H模型对白橡木材等温吸湿数据表现出良好的拟合效果。单分子层和多分子层含水率降低共同作用使得热压干燥材吸湿性降低,且相对湿度越高,多分子层水的减少对吸湿性的降低作用越大。与对照材相比,热压干燥材(140、150 ℃和160 ℃)的纤维饱和点推测值分别降低8.89%、11.76%和13.62%。白橡热压干燥材吸湿性降低机理主要为游离羟基等亲水基团含量减少和细胞壁刚度增加等。     

木材吸湿机理及其应用

木材是一种多孔性、吸湿性和各向异性的天然高分子材料,水分影响着木材多方面的性质。文中从木材组分的角度综述了木材对水分的吸湿机理,介绍了木材对水分吸附的基本理论,解释了木材吸湿滞后现象的基本原因;在上述基础上评述了降低木材吸湿性的基本方法及其实现原因,还分析了机理应用方面存在的不足以及测试方法的不统一,并对未来研究趋势进行了展望。     

Contributions of Extractives and Lignin to the Fractal Geometry of Internal Wood Surfaces

Internal wood surfaces can be treated as fractals, which are between Euclidean geometry and complete randomness. The fractal dimension Dfs is very informative in investigating the roughness of the internal surfaces of wood. In this study, the water sorption isotherms, including adsorption and desorption isotherm, of untreated, benzene-alcohol extracted and delignified (after benzene-alcohol extracted) spruce (Cuninghamia lanceolata) were measured at 30℃. On the basis of these isotherms, the Dfs values were calculated by FHH equation, which is based on multimolecular sorption. The results showed that both groups of Dfs values (respectively calculated from adsorption and desorption isotherms) of untreated, benzene-alcohol extracted and delignified wood have same order, that is, untreated > benzene-alcohol extracted - delignified. Therefore, the conclusion can be made that the benzene-alcohol extractives have significant contribution to the fractal geometry of internal wood surfaces. Lignin also has influ     

Bending creep behavior of wood under cyclic moisture changes

This study examined the bending creep behavior in the longitudinal direction of six species under cyclic moisture content (MC) changes. For each species, tests were made at 20°C with five cyclic relative humidity changes between 65% and 95%, beginning from moisture adsorption. A load corresponding to 25% of short-term breaking load of the species was applied to the radial section of each specimen with four-point bending. The effect of MC change on instantaneous compliance was also investigated under the same condition. The quantitative relation between mechano-sorptive (MS) compliance and MC change was examined, and the material parameter KM for the relation in specific sorption was determined. Results indicated that the total compliance in the six species with different behavior increases with sorption time. As an integral part of total compliance, instantaneous compliance changes linearly with MC and influences to a greater or lesser extent the total compliance behavior. In general, with increasing MC change, the MS compliance linearly increases during the first adsorption and all desorption and decreases slightly during subsequent adsorption. The material parameterK _M varies markedly not only with species but also with specific sorption. The first adsorption causes the largest deformation, followed by desorption.This paper was presented at the 48th annual meeting of the Japan Wood Research Society in Shizuoka, Japan. April 1998     

Water Sorption Behaviors of Five Woods above Fiber Saturation Point

Woods from Korean Larch, Chinese Fir, Aspens, Manchumian, and Fortunes Paulownia were chosen for investigation. Specimens cut from the air-dried woods had a cubic shape with nominal air-dried size of 17.0 mm and 8.5 mm. Oven-died specimens were put in containers filled with water and water sorption was implemented at atmospheric pressure and room temperature. Results from the experiment could not described exactly by the model of steady state flow from Darcy' law. An empirical equation is put forward for the relationship between the water uptake and immersion time. Meanwhile the immersion time for the maximum water uptake (MWU) was predicted from the water sorption rate. The water sorption behaviors above the fiber saturation point (FSP) differed among five tested woods. Size of specimens had an influence on the water sorption. Small specimens reached their MWU more quickly than large specimens, while large specimens have a higher water sorption rate than those of small ones. MWU was estimated, and the     

Moisture sorption and swelling of Norway spruce [Picea abies (L.) Karst.] impregnated with linseed oil

Abstract

The moisture sorption and swelling of spruce specimens impregnated with linseed oil and unimpregnated controls were studied in two sorption experiments: from 0 to 55% relative humidity (RH) and from 55% RH to water saturation. Sorption isotherms were also determined using a sorption balance. The impregnated specimens had lower rates of both moisture sorption and swelling than the unimpregnated controls; however, there was no significant difference in final moisture contents. In addition, the linseed oil impregnation did not improve the dimensional stability of the wood; in most cases the specimens impregnated with linseed oil swelled more than the unimpregnated controls. For the impregnated specimens, reductions in swelling rates were in most cases seen without corresponding reductions in final swelling. The moisture sorption rate was reduced for the impregnated specimens but there were generally no reductions in equilibrium moisture content.     

Moisture storage and transport properties of preservative treated and untreated southern pine wood

Moisture storage and transport properties of southern pine (Pinus spp.) wood were measured for implementation into hygrothermal models. Specimens were untreated or pressure-treated with alkaline copper quaternary (ACQ) preservative. Moisture storage was characterized with sorption isotherms in the hygroscopic region (high capillary pressures) and documented with mercury intrusion porosimetry in the overhygroscopic region (low capillary pressures). The data were then combined into a single moisture retention curve as a function of capillary pressure. Moisture transport was evaluated from steady-state water vapor transmission and dynamic capillary water absorption experiments. These data were used to calculate the moisture permeability over the entire range of capillary pressures using the diffusivity approach of Carmeliet et al. Moisture storage and transport properties were similar for the untreated and ACQ-treated southern pine, except for the permeability of the treated wood which was lower in the radial direction. The data presented here can be used to improve the accuracy of hygrothermal and combined hygrothermal–corrosion modeling simulations.