黄芩甙在蚕丝上的染色热力学研究

为了探讨天然染料黄芩在蚕丝纤维上的染色机制,提高其对上染过程控制、染色效果预测及染色工艺优化的指导价值,对蚕丝纤维先用铝离子预媒染后用黄芩提取物黄芩甙进行染色平衡实验。运用3种理论吸附模型即Langmuir、Freundlich和Nernst对30、45、60℃下的实验数据进行模拟,计算黄芩甙在蚕丝纤维上的热力学参数。结果表明,黄芩甙在蚕丝上的吸附最符合Langmuir吸附模型,并用拟合系数和正规偏差验证了吸附模型,该过程是吸热过程,染色热为2.303 4 kJ/mol,染色熵为6 J/mol,染色亲和力和饱和吸附量随温度的升高而增加。     

硅胶吸附甘油磷脂酰胆碱的动力学和热力学研究

本论文主要研究硅胶吸附L-α-GPC的动力学和热力学特性对吸附过程的控制,发现界面扩散控制速率模型1-3(1-X)2/3 2(1-X)能很好的拟合硅胶的吸附过程。通过Freundlich方程和Langmuir方程对吸附平衡模拟,得到了Langmiur方程拟合硅胶吸附L-α-GPC的吸附等温线,计算出不同温度条件下的回归方程,相关系数均在0.99以上,并证实了硅胶的吸附为放热反应。同时,利用Clausius-Clapeyron方程计算出三个吸附量的硅胶吸附热力学参数分别为80 mg/g、160 mg/g和240 mg/g,焓变(△HAm)分别为24.85 kJ/mol、23.82 kJ/mol、22.72 kJ/mol。研究结果为进一步探讨工业化硅胶柱色谱制备高纯L-α-GPC提供了基础数据和理论支撑。     

苯乳酸发酵液脱色体系中活性炭吸附的研究

通过静态吸附实验,研究了活性炭对苯乳酸发酵液脱色体系的吸附特性.将0.5%、1.O%、1.5%、2.0%、2.5%、3.O%的活性炭分别加入到发酵液(pH=4.5～5.O)中,分别在40、60、80、100℃条件下进行等温吸附,采用Langmuir方程和Freundlich方程进行拟合.结果显示,活性炭对苯乳酸发酵液脱色的吸附符合Freundlieh(R2＞0.9597)方程和Langmuir(R2＞0.9656)方程.吸附焓AH为-2.45～6.26kJ/mool,吸附自由能AG为-6.98～-10.69kJ/tool.吸附熵△S为12.6～42.3J/mol·K.活性炭对苯乳酸发酵液中色素的吸附是自发进行的.     

果葡糖浆在制备色谱柱上吸附等温线的测定

吸附等温线表明了被分离组分在固定相和流动相之间的浓度分配关系,在顺序式模拟移动床色谱分离过程模拟和工艺参数计算中具有重要意义。采用吸附-脱附法确定了65℃下果葡糖浆中葡萄糖和果糖在制备钙型色谱柱上的竞争吸附等温线,比较了竞争Langmuir和bi Langmuir2种不同模型对实验数据的拟合结果,其中bi Langmuir模型拟合程度最好,同时得出葡萄糖和果糖的竞争吸附等温线模型参数。     

二氧化硅溶胶在棉织物上吸附的动力学研究

为确定二氧化硅溶胶在棉织物上的吸附动力学,采用硅钼蓝法对其进行了研究。通过对Langmuir吸附模型和Freundlich吸附模型的比较,确定二氧化硅溶胶在织物上的吸附符合Langmuir吸附模型;通过对不同初始浓度溶胶液性能的测定,确定了其反应级数为一级;通过测定不同吸附温度下残液中硅浓度的方法得到了不同温度下的吸附速率常数,其活化能为13.56 kJ/mol,指前因子A0为1.287s-1。     

生物吸附剂壳聚糖对刚果红的吸附

为了确定生物吸附剂壳聚糖对刚果红的吸附行为特征,研究了pH值、初始浓度、时间及温度对刚果红在壳聚糖上吸附的影响。结果表明,pH值是影响壳聚糖吸附刚果红的重要因素,最佳pH值范围为4~7;动力学行为符合Lagergren准二级反应动力学模型,随着温度增加,平衡吸附量减少。吸附过程的表观活化能(Ea)为4.941 kJ/mol。壳聚糖对刚果红的吸附过程较好地符合Freundlich吸附等温方程。计算得到吸附过程的热力学参数△Go和△Ho分别为-10.10 kJ/mol(303 K)和-87.36 kJ/mol,表明壳聚糖对刚果红的吸附是一个自发的放热过程。红外光谱分析可知,壳聚糖吸附刚果红的过程中,壳聚糖分子中存在的大量羟基和氨基发挥了主要作用。     

大孔吸附树脂吸附染料木黄酮的研究

研究了AB-8、S-8两种吸附树脂对染料木黄酮的吸附行为和洗脱条件。结果表明,在298K下,pH=8.0时,S-8吸附树脂对染料木黄酮吸附效果最佳;用乙醇做解析剂,其解析率可达97.50%;其热力学参数为:ΔH=35.9kJ/mol,ΔS=0.128kJ/mol·K,ΔG298K=-2.22kJ/mol。等温吸附过程服从Freundlich方程,表观活化能为33.9kJ/mol。     

大孔吸附树脂吸附染料木素的研究

为了优化染料木素吸附工艺条件,研究了不同pH、洗脱剂浓度和温度等条件下3种大孔吸附树脂吸附染料木素的过程.试验结果表明在pH 4.0时对染料木素的吸附效果最佳;在298K下静态饱和吸附容量为277 mg/g树脂;用乙醇作解析剂,其解析率可达96.5%;其热力学参数为△H=-19.0 kJ/mol、△G=-17.8 kJ/mol、△S=-4.0 J/(mol·K);等温吸附服从Freundlich和Langmuir经验式;表观吸附常数为k298=3.83×10-5/s-1,表观吸附活化能Ea=19.3 kJ/mol.由于XDA-200吸附容量高、洗脱率高,因此适合于染料木素的吸附.     

用活性炭吸附玉米油中苯并芘的条件探讨及热力学研究

本文以活性炭作为吸附剂对玉米油中的苯并芘进行吸附研究,研究了活性炭吸附苯并芘的热力学模型,并且用吸附等温线对热力学参数进行了计算。结果表明:该吸附过程符合Langmuir等温吸附模型,383.15 K时活性炭对玉米油的Langmuir模型参数:苯并芘Csmax为344.83μg/g,b为0.217 718 g/μg。通过吸附过程热力学参数可知,吉布斯自由能为负值说明玉米油中的苯并芘在活性炭上的吸附是自发进行的过程,标准焓变是正值说明该吸附过程是一个吸热的过程,升高温度有利于吸附反应的进行。     

紫胶色素对锦纶纤维的染色热力学研究

为了探讨紫胶色素在锦纶纤维上的染色行为,为染色工艺的优化提供理论参考,进行紫胶上染锦纶纤维的染色平衡实验。用Freundlich、Langmuir和Redlich-Peterson型3种理论吸附模型对80、90℃下的实验数据进行拟合,并计算出染色亲和力、染色热和染色熵等热力学参数。结果表明,紫胶色素在锦纶上的吸附最符合RedlichPeterson型吸附模型,亲和力和吸附量都随着温度的升高而减小,染色热和染色熵分别为-55.45 kJ/mol和-111.96 J/(mol·K),说明染色过程是放热和自发的过程。     

Nylon fibers coated with diclofenac: adsorption properties

Dried gauzes properly coated with anti-inflammatory drugs could be helpful in providing topical treatment in inflammatory process. Therefore, thermodynamic of adsorption of Diclofenac Sodium, over Nylon fibers, as a function of concentration, temperature, and pH of the medium, have been studied. Maximum amount adsorbed in the best conditions tested, pH 5.6, 323 K and initial concentration of 150 mg/L has been 2.6 mg/g. Isotherm adsorption data were well fitted to the Langmuir and Freundlich model; therefore, multilayer formation must be considered. Negative and low values of free-energy change, ?17.9 kJ/mol and ?15.9 kJ/mol, in addition to moderate value of activation energy 13.14 kJ/mol point to physical interactions governing the process that, besides, is exothermic with negative enthalpy-change, ?43.44 kJ/mol, and also follows pseudo-first order kinetic model that is typical of this interaction. Desorption experiments carried out under physiological conditions confirm that the proposed procedure for DCF administration could be achieved.     

Patulin Adsorption Kinetics on Activated Carbon, Activation Energy and Heat of Adsorption

The kinetics of adsorption of patulin on activated carbon were studied at different initial patulin concentrations (100–400 ppb) for the temperature range 20–80°C. Apparent adsorption rate constants (k_aapp) were changed from 1.07 × 10^?3 to 1.86 × 10^?3 g^?1 min^?1 while the temperature increased from 20 to 80°C. For equilibrium adsorption curves; the Langmuir model was attempted and model parameters (K and Q°) were obtained for different temperatures. Energy of activation and heat of adsorption were determined in a batch adsorption system (E_a= 2.02 kcal/mol and ΔH = 2.24 kcal/mol). The adsorption occurred endothermically and by physical mechanisms.     

蚕丝纤维吸附辛基酚聚氧乙烯醚的动力学研究

为实现蚕丝产品中烷基酚聚氧乙烯醚( APEO)的高效监控检测,研究蚕丝纤维对辛基酚聚氧乙烯醚(OPEO)的吸附特性.结果表明,OPEO在蚕丝纤维上的吸附符合Langmuir模型,吸附动力学符合拟二级动力学模型,并且初始浓度越大,平衡速率常数越小,到达平衡的时间越长.OPEO溶液的温度越高,平衡速率常数越大.毛孔内扩散是...     

Effect of strongly competing background compounds on the kinetics of trace organic contaminant desorption from activated carbon

Strongly competing (SC) compounds, naturally found in any drinking water source, are known to decrease the adsorption capacity of activated carbon for trace contaminants. While the effect of these substances on the capacity and adsorption kinetics of trace contaminants is fairly well studied, relatively little is known about their impact on desorption kinetics. The purpose of this study was to investigate the relationship between SC matter and trace compound desorption kinetics. A surrogate SC compound, 1,4-dichlorobenzene (p-DCB), was used to displace the preadsorbed target trace contaminant, atrazine, from powdered activated carbon (PAC). The initial concentrations of p-DCB and atrazine were varied to achieve different degrees of competition to atrazine. Atrazine's desorption diffusion coefficient was found to increase with increasing adsorbed concentration of the SC matter, expressed as an equivalent background compound (EBC).The EBC was modeled with atrazine-like adsorption properties, thus representing the portion of p-DCB that competed to occupy atrazine adsorption sites. The increase in atrazine diffusion rate can be explained by a shift from surface diffusion to diffusion through the carbon's pores as the availability of surface sites decreased due to the EBC's competition. The observed desorption kinetic relationship was consistent with the effect of SC competition on adsorption kinetics; further, the effect was consistent for three different types of SC matter. These findings highlight that the impact of SC matter on activated carbon applications could be either detrimental (displacing adsorbed trace contaminants and enhancing their rate of release) or beneficial (offsetting pore constriction effects by enhancing their rate of uptake).     

Examination of hydrophobic contaminant adsorption in mineral micropores with grand canonical Monte Carlo simulations

A molecular level understanding of the interactions between hydrophobic organic contaminants (HOCs) and sediments is needed in order to assess contaminant fate in the environment. Grand canonical Monte Carlo simulations were performed to investigate water and trichloroethylene (TCE) adsorption in slit micropores confined by charged and uncharged silica surfaces. Gas-phase single-sorbate simulations with water or TCE were performed as well as mixture simulations of bulk water containing TCE at 1% of its saturation concentration. Gas-phase isosteric heats for water adsorption in the uncharged pores ranged from -40 to -52 kJ/mol, and the densities of the adsorbed water phases were always less than that for bulk water. Gas-phase isosteric heats for water adsorption in the charged pores ranged from -79 to -170 kJ/mol, and the densities of the adsorbed water phases were close to that for bulk water. The isosteric heats and water densities indicated that the uncharged pores were mildly hydrophobic, and the charged pores were very hydrophilic. In mixture simulations of adsorption from solution, the presence of water promoted TCE adsorption in uncharged pores with widths between 14 and 20 A. The isosteric heats for TCE adsorption from solution ranged from -14 to -27 kJ/mol in the uncharged pores and from -9.3 to -50 kJ/mol in the charged pores. Strong attractions to the pore surfaces were significantly diminished after adsorption of the first two monolayers of either adsorbate. Aqueous-phase TCE at a concentration equal to 1% of its saturation concentration was able to completely displace adsorbed water in uncharged pores. Even in highly hydrophilic pores, TCE at this concentration was able to displace up to 50% of the adsorbed water. Apparent differential enthalpies of adsorption determined from the temperature dependence of TCE adsorption isotherms underestimated the magnitude of the true isosteric heats of adsorption by up to 30 kJ/mol. This shows that HOC adsorption enthalpies determined from the temperature dependence of their adsorption isotherms underestimate the true strength of HOC-adsorbent interactions.     

Three-component competitive adsorption model for flow-through PAC systems. 2. Model application to a PAC/membrane system

A three-component competitive adsorption kinetic model, developed and validated in part 1 of this study, was applied to a continuous-flow PAC/membrane system to study the effects of various system and operating parameters on organic removal. The model quantitatively describes the two competitive adsorption mechanisms that occur during adsorption of trace organic compounds by powdered activated carbon (PAC) in flow-through systems where the PAC is retained in the system: pore blockage and direct competition for adsorption sites. Model simulations were conducted to investigate the effects of influent water composition, membrane cleaning water quality, PAC pore size distribution, and system operation conditions such as hydraulic retention time, membrane cleaning interval, and PAC dosing method on treatment efficiency. Effects of these factors on adsorption capacity as well as surface diffusion rate and consequent removal of the trace organic compound were discussed. It was found that optimal operating conditions for maximum trace organic compound removal must be determined on the basis of the adsorption properties and concentrations of the competing compounds in the influent. For the conditions investigated in this study, the small strongly competing compound, p-DCB, had greater impact on atrazine removal than the large pore-blocking compound, PSS-1.8k. Various process design and operating parameters had complex and interrelated effects on the impact of competitive adsorption and corresponding trace contaminant removal efficiency in hybrid PAC/membrane systems.     

Measurement and modeling of single- and multi-component adsorption equilibria of VOC on high-silica zeolites

From pure and binary gas adsorption equilibria measurements carried out using a volumetric method for three volatile organic compounds (methyl ethyl ketone, toluene (TOL), and 1,4-dioxane) on two high-silica zeolites, desaluminated faujasite Y (Fau Y) and ZSM-5 (Sil Z), co-adsorption was investigated and modeled. Apart from steric exclusion taking place with TOL-containing mixtures on Sil Z, micropore filling was similar to distillation since the component with the lower volatility adsorbed preferentially. At low coverage, chemisorption on specific sites happened in favor of polar or major compound, whereas at saturation the adsorbent was selective for the minor compound. Second, a quantitative prediction of binary equilibria was performed using the ideal adsorbed solution theory (IAST), examining the influence of pure component adsorption fitting model. The efficiency of correlations when extending AST to real mixture behavior was satisfactory in most cases. For engineering purposes, Fau Y is to be considered as a high-adsorption capacity adsorbent, whose selectivity can be described qualitatively by the distillation analogy and predicted quantitatively with the IAST in case of quasi-ideal mixtures.     

Effects of powdered activated carbon pore size distribution on the competitive adsorption of aqueous atrazine and natural organic matter

The pore size distribution (PSD) of adsorbents has been found to be an important factor that affects adsorption capacity for organic compounds; consequently, it should influence competitive adsorption in multisolute systems. This research was conducted to show howthe PSD of activated carbon affects the competition between natural organic matter (NOM) and the trace organic contaminant atrazine, with a primary emphasis on quantifying the pore blocking mechanism of NOM competition. Isotherm tests were performed for both atrazine and NOM from a groundwater on five powdered activated carbons (PACs) with widely different PSDs. The capacity for NOM correlated best with the surface area of pores in the diameter range of 15-50 A, although some NOM also adsorbed in the smaller pores as evidenced by a reduction in capacity for atrazine when NOM was present. Kinetic tests for atrazine on PACs with various levels of preadsorbed NOM showed that the magnitude of the pore blockage effect by NOM was lower for PACs with higher surface area of pores with diameter in the range of 15-50 A. Therefore increasing pores in the size range where NOM adsorb can reduce the extent of the pore blockage competitive effect on the target compound atrazine. The effect of PSD was further studied with a flow-through PAC-membrane hybrid watertreatment system, in which experimental results successfully verified model simulations by the COMPSORB model.