Bleaching of alkali-refined vegetable oils with clay minerals

Bleaching efficiencies of bentonites, montmorillonites and sepiolites for alkali-refined rapesseed, soybean, wheatgerm, safflower, corn, cottonseed and sunflower oils were investigated by a batch method at 110°C. The sepiolites with more acid sites at −5.6 < H_o ≥ −3.0 were the most effective in bleaching of each alkali-refined oil. Surface area and acidity at −5.6>H_o ≥ −3.0 were highly significant with bleaching efficiency. The sepiolites (numbers 2 and 3) were more suitable than standard activated clay because they were more effective both in retaining tocopherols and in reducing free fatty acids after bleaching.     

Adsorption isotherms in bleaching hazelnut oil

Adsorption isotherms in bleaching hazelnut oil were determined to investigate the applicability of the Langmuir and Freundlich equations and to elucidate the adsorption characteristics of oil on bentonite EY-09 (Bensan Co. Ltd., Edirne, Turkey). The degree of bleaching was monitored spectrophotometrically. Absorbance measurements were carried out to investigate the adsorption force of clay during bleaching of hazelnut oil with 0.3, 0.5, 0.7, and 0.9 wt% clay at 50, 60, 70, 80, and 90°C. Bentonite EY-09 was used as the bleaching clay (adsorbent). Plots of log(x/m) vs. log X _e (for the Freundlich isotherm) and X _e /(x/m) vs. X _e (for the Langmuir isomtherm) were made (where x is the amount of pigment removed per unit mass of the adsorbent, m, and X _e is the equilibrium concentration of the pigment). The Freundlich constants were found to increase with temperature for a given oil/bleaching agent ratio, showing the formation of more active sites on the adsorbent with a rise in temperature. Since the heat evolved during adsorption (0.32–1.03 kJ mol⁻¹) was less than 20 kJ mol⁻¹, the forces between the adsorbent and adsorbate appeared to be van der Waals forces. This type of adsorption is defined as physical or van der Waals adsorption. The results obtained show good agreement with the Freundlich isotherm, indicating that the adsorption of the pigment from the oil proceeds by monolayer formation on the surface of the adsorbent.     

Friction properties of vegetable oils

Vegetable oils are a renewable and an environmentally friendly alternative to petroleum-based oils in lubrication and other important application areas. Vegetable oils fall into two broad chemical categories: triesters (or TG) and monoesters. Most vegetable oils are triesters of glycerol with FA, whose characteristics are dependent on the chemistry and composition of the FA residues. A small percentage of vegetable oils are monoesters of long-chain FA and fatty alcohols of varying chemistries. In this work, the free energy of adsorption (ΔG _ads) of safflower (SA), high-oleic safflower (HOSA), and jojoba (JO), methyl oleate (MO), and methyl palmitate (MP) on steel were investigated. SA and HOSA are TG of vegetable oils with FA residues of radically different degrees of unsaturation. JO is a monoester vegetable oil. ΔG _ads is one of the major factors affecting the boundary friction properties of lubricant ingredients. ΔG _ads was found to increase in the order: HOSA≤SA<JO<MO≤MP. The results are consistent with the degree of functionality and other chemical properties of the oils studied.     

黏土矿物基无机杂化颜料研究进展

近年来,无机杂化颜料成为无机颜料领域的研究热点之一。黏土矿物是储量丰富、廉价易得的天然纳米物质,因具有独特的纳米片状、棒状和管状结构,成为构筑各种无机杂化颜料的理想基体材料。本文介绍了黏土矿物的结构特点,综述了黏土矿物基钴蓝、铋黄、铁红和其它色系杂化颜料的研究和应用进展,展望了黏土矿物基无机杂化颜料的未来发展方向。     

Decoloration of vegetable oils and oleoresins with recovery of unaltered pigments

The present study confirms that N,N-dimethylformamide for the extraction of chloroplast pigments from vegetable tissues shows no differences from the usual acetone or methanol. Therefore, it can be applied to fats, as it allows separation of lipids and pigments by means of phase distribution between light petroleum ether and N,N-dimethylformamide. The ether phase retains the decolored fatty matter, and the pigments dissolved in N,N-dimethylformamide can be recovered totally unaltered. This method has been applied to oleoresins and oils from different products and origins. Satisfactory results have been obtained in terms of the degree of decoloration and the percentage of oil recovered. At the same time, the unaltered pigment concentrate obtained from the hypophase could be used as a color enhancer in the chemico-pharmaceutical industry.     

The Adsorption of p-nitrophenol on anion exchange resin at various temperatures

The isotherms of p-nitrophenol adsorbed on the anion exchange resin Ionac AFP-329 at temperatures in the range of 278.1 to 338.1 K are correlated with the Freundlich equation. The temperature dependences of the Freundlich constants and the effect of the amount adsorbed on the isosteric heat of adsorption are discussed. The results indicate that the relationships between k, n and temperature can be expressed as. n = 0.00129 T ln k = 5.12 – 0.0152 T and ln k = 5.05 – 11.63 n and that the isosteric heat of adsorption varies linearly with the logarithm of amount adsorbed.     

Adsorption isotherms of fatty acids on rice hull ash in a model system

The adsorption of lauric, myristic and stearic acids on rice hull ash (RHA) from isooctane as solvent was studied and conformed to a Langmuir isotherm. Monolayer coverage was determined to be 35.7±2.5, 43.5±2.2 and 36±5 mg/g, respectively. The free energy of adsorption, †G°, for the adsorption was determined to be-6.64,-6.23 and-6.49 kcal mol⁻¹ for the adsorbates, respectively. The equilibrium parameter indicated that RHA is a good adsorbent for the three fatty acids examined.     

吸附热预测吸附等温线

实验测定了N2 在沸石分子筛、C2 H6 在活性炭、CO2 在硅胶上的吸附等温线 ,研究用Clausius Clapeyron方程求得等量吸附热、再利用所得的吸附热预测其它温度的吸附等温线数据的方法。将吸附热预测的等温线与实验值及插值法内插得到的吸附等温线数据进行了比较 ,结果表明吸附热预测值与实验值吻合较好。此外还对文献数据利用等量吸附热预测较高压力 ( 65 0kPa)下的等温线 ,均与文献中的实验值一致。为吸附工业操作需要不同温度下的等温线数据和吸附过程的模拟与设计提供了简便、准确的计算方法     

磷化氢在改性13X分子筛上的吸附行为

为回收工业废气中的磷化氢(PH3)并资源化,采用浸渍法制备了一种CaCl2改性13X分子筛吸附剂,通过容积法研究了25—70℃PH3气体在改性13X分子筛上的等温吸附行为。结果表明,在实验条件范围内25,40,55,70℃下PH3的饱和吸附量(质量分数)分别为2.528,1.901,1.591,0.925mg/g。Freundlich吸附等温方程很好地模拟了改性13X分子筛对PH3的等温吸附,Langmuir和Henry吸附等温方程对吸附平衡数据的拟合效果不佳表明了改性13X分子筛表面吸附位的不均匀分布。当初始吸附量为0.10mg/g时,等量吸附热值最大,为17.81353kJ/mol,即等量吸附热不超过18kJ/mol,过程为物理吸附,便于PH3气体的解吸。     

Effect of temperature on the removal of lead(II) by adsorption on China clay and wollastonite

The removal of Pb(II) from aqueous solution by adsorption on china clay and wollastonite is an attractive process. The amount of Pb(II) removed by adsorption is highly dependent on the temperature of the adsorbate solution and favours low temperature. The equilibrium times were noted, i.e. 90 min for china clay and 120 min for wollastonite. The various rate parameters of the adsorption process have been determined at different temperatures. The activation energies were determined and found to be ?5.345 kJ mol^?1 and ?8.730 kJ mol^?1 for Pb(II)-china clay and Pb(II)-wollastonite systems, respectively. The adsorption isotherm was measured experimentally at various temperatures. The negative values of enthalpy change (ΔH = ?77.95 kJ mol^?1 and ?16.40 kJ mol^?1 for china clay and wollastonite, respectively) indicate the exothermic nature of the adsorption processes for both systems. The isosteric heats of the adsorption process have been determined at various surface coverages of the adsorbents used. The various thermodynamic parameters have been calculated to elucidate the mechanism involved in the adsorption process.     

Study of the CO2 adsorption isotherms on El Hicha clay by statistical physics treatment: microscopic and macroscopic investigation

ABSTRACT

CO₂ introduction in deep aquifers based on adsorption phenomena represents geological tanks that reduce CO₂ emission. Thus, investigating carbon dioxide adsorption on rocks is becoming more interesting. In our work, carbon dioxide adsorption on El Hicha clay is extensively studied. Experimental data for CO₂ adsorption on this clay are given for the first time. All the corresponding parameters are simulated and interpreted using the multilayer model with two interaction energies. The effect of the key parameters involved in the adequate model on the isotherm curves are thus elucidated and interpreted. The formulation of this model is based on statistical physic formalism. Several hypotheses involving some physicochemical parameters which describe perfectly the adsorption process are used.

The characteristic parameters of the adsorption isotherm such as the number of carbon dioxide molecules per site (n), the receptor site densities (N_M), the number of adsorbed layers (N_L) and the energetic parameters (-ε₁) and (-ε₂) are estimated for the studied systems by a nonlinear least square regression. These parameters are discussed and interpreted considering their temperature dependence. In order to provide new macroscopic interpretations of adsorption mechanisms, three thermodynamic functions are also determined such as the entropy, the internal energy and the free enthalpy of Gibbs from experimental data. Thus, we prove theoretically and experimentally that CO₂ adsorption on El Hicha clay is feasible, spontaneous and exothermic in nature.     

A kinetic model for bleaching vegetable oils

Very little data and very few kinetic models are available describing and evaluating the performance of bleaching processes, earths, and equipment. This work presents a general kinetic model for the adsorption of pigments by adsorbent earths in several edible oils. It reports the kinetic parameters found for two bleaching earths (one developed in the laboratory and one commercial) for the clarification of soybean oil, as well as their activation energies. The proposed kinetic model is second order in the dimensionless pigment concentration and is in good agreement with our experimental data. A very simple mechanistic explanation based on adsorption/deactivation is offered to justify its application. We also present mathematical modeling based on balance equations to show how the kinetic parameters can be used for bleaching earths and for industrial equipment evaluation and design, such as for the transient fed-batch stirred bleaching vessel. The model seems appropriate to represent data under different operating conditions such as temperature and adsorbent load. The simulation shows that startup procedures are very important in the bleaching process—at least as important as the batch step, in which the oil color reaches its desired standard.     

Adsorption of toluene from aqueous solutions using clay-based nanostructures

In this study, porous clay heterostructures (PCH) are synthesized through gallery template approach and characterized using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Nitrogen adsorption–desorption techniques. Batch adsorption studies are conducted to investigate the effect of parameters such as adsorbent dosage, pH, concentration, and contact time on adsorption of toluene by PCH in aqueous solutions. Equilibrium data were fitted to the Langmuir and Freundlich models. Based on the results, by increasing the PCH dosage from 0.5 g/L to 4 g/L, toluene removal is enhanced from 34% to 88.1%.     

Adsorption and intercalation of tetracycline by swelling clay minerals

Many of commonly used pharmaceuticals are hydrophilic. In aqueous solutions, these molecules will have strong interaction with swelling clay minerals, resulting in intercalation of these compounds in the interlayer of the minerals and retention by these minerals. In this research, we studied the intercalation of tetracycline (TC) into swelling clay minerals as represented by montmorillonite and rectorite of different surface charges and different charge densities. The maximum interlayer expansion was seen at a higher pH when the TC molecules adopted an extended conformation, even though, the amount of TC intercalated at higher pH is lower. Under pH 4–5, the intercalated TC produced an interlayer gallery height of 9.2 Å compared to 10.3 Å produced at pH 8.7 in the interlayer space of rectorite. Due to TC intercalation, the full width at half maximum (FWHM) becomes much broader, suggesting that the number of fundamental layers stacking along c axis decreased to 2–3. Depending upon the nature of the swelling clay minerals and the TC concentration, the intercalation process can be transitional, involving in the occurrence of mechanical mixtures, materials of intermediate layer thicknesses, and/or mixed layering of different ordering states.     

Distribution of clay minerals in the process streams produced by the extraction of bitumen from Athabasca oil sands

This study investigates the affinity of clay minerals in oil sands for the water‐continuous tailings and hydrocarbon‐continuous froth streams produced from the extraction of bitumen from oil sands. Clay minerals in oil sands processing impact bitumen flotation in separation vessels, emulsion formation during froth treatment, and fine tailings behaviour. X‐ray diffraction of oriented clay slides and random powder samples were used to quantify the clay minerals in the oil sands ore and process streams. Particle size distribution and clay activity balances were also conducted around the extraction process. The degree of partitioning during the conditioning and flotation stages in a batch extractor was determined by the surface properties of the clay minerals present. The water‐continuous tailings stream was further separated into fine and coarse tailings fractions through sedimentation. The bulk of the clay minerals reported to the fine tailings stream. Illite and mixed layered illite‐smectite partitioned less to the hydrocarbon‐continuous froth than kaolinite. Also, the illite‐smectite in the froth stream appeared to be different from the illite‐smectite in the water continuous streams.     

Friction and adsorption properties of normal and high-oleic soybean oils

The steel/steel boundary friction properties of soybean oil (SBO) and high-oleic soybean oil (HOSBO) are compared. HOSBO is significantly more saturated than SBO and more oxidatively stable. Changes in degree of unsaturation affect lateral interactions of adsorbate molecules, which in turn affects their adsorption and, hence, their boundary lubrication properties. To investigate this possibility, the free energies of adsorption (ΔG _ads) of SBO, HOSBO, and methyl laurate (ML) were determined from the analysis of friction-derived adsorption isotherms using the Langmuir and Temkin adsorption models. The results showed a stronger adsorption for the vegetable oils than for ML, an indication of multiple interactions between the ester groups of the triglycerides and the steel surface. The result also showed no difference in the ΔG _ads values of SBO and HOSBO obtained using either the Langmuir or Temkin models. This was interpreted as an indication of the lack of appreciable net lateral interaction between triglyceride adsorbates.     

气体吸附等温线回归准确性分析

针对由吸附等温线模型回归气体吸附平衡数据的准确性进行了研究,从实验误差和表面覆盖率两个因素出发,主要考查了它们对回归Langmuir、DR方程两种等温线模型中各参数的影响,并对回归参数的可靠性作了分析。实验误差和表面覆盖率对各模型参数回归的准确性均有影响。对于Langmuir和DR方程,提高测试的表面覆盖率可以更可靠地计算出饱和吸附量以及模型中的其它参数。另外,仅通过减小实验误差来保证模型中所有参数的准确性是不可取的。     

Adsorption of aluminium from wastewater by chitin and chitosan produced from silkworm chrysalides

Chitin, extracted from silkworm chrysalides, was employed for the production of a high‐purity and porous chitosan, as observed by scanning electron microscopy. Chitin and the chitosan produced from it were also analysed using ¹³C NMR spectroscopy to show the efficiency of deacetylation. The extracted chitin was investigated as an adsorbent material for aluminium removal from textile wastewater, by the column chromatographic method. After the treatment, the residual aluminium was lower than the limitation criterion of 0.2 mg L^?1. The isotherms of adsorption on chitin and chitosan surfaces were investigated and the best fits were observed using the Freundlich isotherm. At pH 5.0, the maximum adsorption capacity was 21.3 mg of aluminium per gram of chitosan over 70 h of experiments. Copyright © 2006 Society of Chemical Industry     

用Aspen Adsorption模拟氯化氢脱水

利用Aspen Adsorption模拟氯化氢吸附脱微量水过程。通过吸附平衡试验数据估算吸附等温线的常数项,用简化的单塔模型进行了穿透曲线的模拟,得到吸附塔内空隙中水的浓度分布以及塔内吸附剂的吸附量随时间的变化情况,可以看到传质区在轴方向上移动;进一步研究了传质系数和操作压力的变化对穿透曲线的影响,变化趋势与文献报道一致。