Adsorption of pigments and free fatty acids from shea butter on activated Cameroonian clays

Adsorption of pigments and free fatty acids from shea butter on acid‐activated Cameroonian local clays was investigated. The adsorption of the pigments was followed by the reduction of the absorbance of the shea butter at 295 nm. The kinetic study revealed that both the temperature at which the experiment was performed and the degree of activation of the clays influence the time of contact required to reach adsorption equilibrium of the pigments and the amount of pigments adsorbed. Thus, at 90 °C, the time required was 30 min for the clays activated with 0.5 M (A0.5M) and 1.0 M solutions (A1M) of sulphuric acid, and 45 min for the clay activated with a 2.0 M solution (A2M) of sulphuric acid. At 80 °C, the adsorption equilibrium was reached after 45 min for clays A0.5M and A1M, and 60 min for clay A2M. At 65 °C, the contact time to reach adsorption equilibrium was longer than 75 min for all the adsorbents used. At 90 °C, the amount of pigments adsorbed at equilibrium by clay A2M was about two thirds of that adsorbed by clay A0.5M, and one half of the amount adsorbed by clay A1M. For each adsorbent, the amount of pigment adsorbed decreased with temperature. A1M was the most efficient local clay for the adsorption of shea butter pigments and compared favourably with the industrial clay used as reference. The same evolution was observed with the adsorption of free fatty acids on different clays. The contact time needed for the elimination of peroxides was 40 min for all the clays used. The most efficient adsorbents for the adsorption of the pigments and free fatty acids were also the ones that gave the best results in the elimination of peroxides. The energy of activation for the adsorption of the pigments, as determined by the adsorption kinetic model of Brimberg, were 61 ± 9 kJ/mol, 73 ± 11 kJ/mol, 67 ± 10 kJ/mol, and 47 ± 7 kJ/mol for the industrial adsorbent (EN) and clays A0.5M, A1M and A2M, respectively. These values of activation energies indicate that the shea butter pigments are chemisorbed on acid‐activated clays. It was found that the adsorption isotherms follow the Freundlich equation.     

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.     

The use of toxic solid waste for the adsorption of dyes from waste streams

The use of chromium‐containing toxic solid wastes from the leather industry for the removal of dyes from waste‐waters has been studied. A batch adsorption model has been employed and the role of various experimental parameters on the efficiency of the process evaluated. The extent of dye removal was studied by varying parameters such as pH, contact time, initial concentration of the dye and amount of adsorbent. The experimental equilibrium data for this system has been analyzed using the linearized forms of Langmuir and Freundlich isotherms. The Langmuir isotherm was found to provide the best theoretical correlation of the experimental data and the adsorption was found to follow pseudo‐second‐order kinetics. The dye adsorbed solid wastes were used for the preparation of pigments. In essence, this study provides a greener solution for chromium‐containing solid wastes, dye containing waste‐waters and dye‐adsorbed chromium solid wastes. Copyright © 2007 Society of Chemical Industry     

Adsorption Isotherms for Bleaching Soybean Oil with Activated Attapulgite

Activated attapulgite was characterized and used as bleaching clay (adsorbent) for soybean oil. Adsorption isotherms for bleaching soybean oil were determined to investigate the applicability of the Langmuir and Freundlich equations and to elucidate the adsorption characteristics of oil on activated attapulgite. The Freundlich model was found to provide a better fit with the experimental data than the Langmuir model. The larger Freundlich constant, K _F at higher temperature indicated more effective adsorption. The heat evolved for oil bleaching increased as the levels of activated attapulgite increased from 0.5 to 3%, due to the increase in adsorptive sites with increasing attapulgite levels as well as multilayer adsorption driven by van der Waals’ forces at smaller amounts of adsorbents. There are enough adsorptive sites with 3% attapulgite to adsorb the pigments associated with soybean oil bleaching. The amount of attapulgite has no effect on ΔH _a when it is >3%, and ΔH _a is about 32 kJ/mol.     

Adsorption of Cr(VI) ions onto poly(ethylene glycol dimethacrylate‐1‐vinyl‐1,2,4‐triazole)

Poly(ethylene glycol dimethacrylate‐1‐vinyl‐1,2,4‐triazole) [poly(EGDMA‐VTAZ)] beads (average diameter = 150–200 μm) were prepared by copolymerizing ethylene glycol dimethacrylate (EGDMA) with 1‐vinyl‐1,2,4‐triazole (VTAZ). Poly(EGDMA‐VTAZ) beads were characterized by swelling studies and scanning electron microscope (SEM). The adsorption of Cr(VI) from solutions was carried at different contact times, Cr(VI) concentrations, pH, and temperatures. High adsorption rates were achieved in about 240 min. The amount of Cr(VI) adsorbed increased with increasing concentration and decreasing pH and temperature. The intraparticle diffusion rate constants at various temperatures were calculated. Adsorption isotherms of Cr(VI) onto poly(EGDMA‐VTAZ) have been determined and correlated with common isotherm equations such as Langmuir and Freundlich isotherm models. The Langmuir isotherm model appeared to fit the isotherm data better than the Freundlich isotherm model. The pseudo first‐order kinetic model was used to describe the kinetic data. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy changes. The dimensionless separation factor (R_L) showed that the adsorption of metal ions onto poly(EGDMA‐VTAZ) was favorable. It was seen that values of distribution coefficient (K_D) decreasing with Cr(VI) concentration in solution at equilibrium (C_e) indicated that the occupation of activate surface sites of adsorbent increased with Cr(VI). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

椰壳活性炭对加替沙星的吸附及缓释性能研究

研究了水溶液中椰壳活性炭对喹诺酮药物加替沙星（GTFX）的吸附性能,测定了不同温度下的吸附等温线并分析了其吸附热力学参数。结果表明：活性炭对加替沙星的吸附符合Freundlich方程,ΔH=-1.7374kJ/mol,说明活性炭对GTFX的吸附过程为放热过程,且ΔH<20kJ/mol,表明吸附过程主要为物理吸附。同时,测得吉布斯自由能ΔG<0,表明吸附质从溶液到吸附剂表面的吸附过程是自发过程,其吸附主要是熵驱动。对椰壳活性炭进行了硝酸及氨水改性,研究了3种不同活性炭对GTFX的缓释性能,结果显示,与椰壳活性炭相比,经硝酸氧化改性后的活性炭缓释性能有较大的提升,而经氨水改性的活性炭缓释性能有所下降,3种不同活性炭对GTFX的缓释均符合Higuchi方程释药模式。     

Adsorption of reaction species for hydrogenation of nitrobenzene on copper chromite at catalytic conditions

Adsorption of nitrobenzene, aniline and water on copper chromite has been investigated at the temperatures (483–558 K) and partial pressures (0–40 kPa) involved in the catalytic process (viz. hydrogenation of nitrobenzene), using the gas chromatographic pulse technique. The adsorption of reaction species was found to follow the Freundlich adsorption isotherm. The data on isosteric heats of adsorption (at different surface coverages) were obtained from the adsorption isotherms. The results indicated that nitrobenzene and water are physically adsorbed, whereas aniline is chemisorbed on the catalyst. The variation in the heat of adsorption with surface coverage for the adsorption of aniline indicated the presence of surface heterogeneity on the copper chromite.     

Adsorption of gold-thiourea complex on activated carbon

The adsorption kinetics of the gold-thiourea complex on activated charcoal was studied. Experimental runs were made in a batch reactor at constant temperatures and stirred by a magnetic system. Samples were taken at different periods of time and were analyzed for gold in a Perkin-Elmer Model 360 atomic absorption spectrophotometer. The samples were prepared with synthetic solution of gold with thiourea, sulfuric acid, and iron sulfate with concentrations similar to the ones in the leaching process. The gold adsorbed on activated charcoal was 99% at 20°C. The adsorption behavior was characterized by the Freundlich model at different temperatures (20°C, 35°C and 50°C).     

椰壳炭对肌酐吸附性能及动力学研究

采用水蒸气活化法制备得到微孔发达的椰壳活性炭,并研究其对肌酐的吸附性能。以850℃活化所得微孔率最高的活性炭为吸附剂,考察了活性炭投加量、吸附时间、溶液pH值及肌酐初始质量浓度对肌酐吸附性能的影响,并采用准一级、准二级动力学方程对实验数据进行拟合处理。结果表明,制备所得4种椰壳活性炭对肌酐均有较强的吸附能力;微孔率越高,吸附量越大;37℃下,椰壳活性炭对肌酐的吸附平衡时间为6 h,平衡吸附量达到97.88 mg/g;酸性环境更有利于肌酐吸附;平衡吸附量随肌酐初始质量浓度增加而升高;吸附过程符合准二级动力学模型,以化学吸附为主。     

凹凸棒石对水中Mn~(2+)的吸附特性研究

通过静态试验,对凹凸棒石吸附去除水中Mn2+的特性进行了研究,重点讨论了焙烧和酸化处理对吸附的影响。结果表明,凹凸棒石对水中Mn2+吸附过程可以班厄姆公式进行拟合。弗兰德利希吸附等温式可以更好地描述Mn2+在凹凸棒石上的吸附过程。当焙烧温度在105～400℃,焙烧处理对凹凸棒石吸附去除Mn2+的影响不明显,当焙烧温度在500℃时,凹凸棒石对Mn2+的吸附去除率显著降低。凹凸棒石对Mn2+的吸附去除率随着酸化浓度的增加先减小而后增大,在HCl浓度为4 mol·L-1时达到最低。     

Adsorption of lutein from soybean oil on silicic acid I. Isotherms

Adsorption of lutein from crude soybean oil miscella on dispersed silicic acid resulted in three different Freundlich type isotherms, depending on the amount of adsorbent used. Normally, changing the amount of adsorbent gives a new point on the same isotherm. Further investigation of the lutein adsorption revealed that addition of 1% isopropanol to the hexane solvent and deactivation of the silica acid with water decreased lutein adsorption. Purification of the lutein resulted in increased adsorption, indicating that triglyceride was competing for adsorption sites. The triglyceride competition was confirmed by calculating an adsorption isotherm for triglyceride from crude soybean oil miscella. Use of silicic acid as a column rather than dispersed yielded multiple isotherms for lutein adsorption based on the amount of adsorbent used. Also, lutein adsorption on columns was concentrated at the entrance to the column. Experiments showed that lutein adsorption was not due to partitioning between bound triglyceride and hexane solvent.     

重量法测定对二甲苯在Silicalite-1上的吸附

采用重量法研究了温度为423 K、373 K、343 K和323 K时对二甲苯在Silicalite-1分子筛上的吸附和脱附行为。结果表明, 温度为323 K和343 K时吸附等温线出现了两个吸附平台。根据吸附等温线计算了热力学参数（吸附等容热、吉布斯自由能变、熵变和吸附相熵）。随着吸附量的增大,吸附等容热增大,吸附的吉布斯自由能变稍有下降,吸附熵变逐渐增大,吸附相的熵逐渐减小,分子间的相互作用逐渐增强。对吸附和脱附动力学进行了研究,发现在吸附量大约为4 m·(u.c.)^－1时,扩散系数出现了峰值。     

Synthesis of activated carbons from black sapote seeds,characterization and application in the elimination of heavy metals and textile dyes

Many different techniques may be used to remove industrial pollutants from wastewater. Adsorption using activated carbon has been reported to be an effective method. This work proposes the use of a vegetable residue (black sapote seeds) as a raw material for its synthesis. These carbons were chemically activated using phosphoric acid and carbonized at 673 and 873 K. Adsorption isotherms were constructed for the textile dyes on the carbons, and this data was treated using Langmuir's equation to quantitatively describe the adsorption process. The synthesized carbons were characterized using FTIR, EA, SEM, Nitrogen adsorption (specific surface areas of 879 and 652 m²·g^-1), and their points of zero charge (2.1 and 2.3). It was possible to adsorb both heavy metals and textile dyes present in aqueous solutions and wastewaters using these activated carbons. Heavy metals were adsorbed almost completely by both carbons. Cationic dyes where adsorbed (58-59.8 mg·g^-1) in greater amounts compared to anionic dyes (10-58.8 mg·g^-1). The amount of anionic dyes adsorbed increased almost 30% by changing the pH of the solutions. One of the carbons was thermally regenerated on three occasions without losing its adsorption capacity and it was proved in a flow system.     

HDX-8树脂吸附咖啡因的研究

研究了HDX-8树脂对咖啡因的吸附性能。结果表明,柱长8 cm,内径1.0 cm,内装2.5 g HDX-8树脂的吸附柱,静态条件下,在pH 2~7盐酸介质中,对咖啡因具有良好的吸附性能,最大静态吸附量为17.5 mg咖啡因/g树脂。等温吸附符合Freund lich方程式,相关系数在0.99以上;当咖啡因平衡浓度≥3.1μg/mL(起始浓度≥40μg/mL)时,吸附还符合Langmu ir等温式。负载柱可用40%乙醇完全洗脱。     

Adsorption of lactic acid onto three ionic liquid‐modified porous polymers

Three ionic liquid (IL)‐modified porous polymers were synthesized and used for the adsorption of lactic acid. The experimental adsorption kinetics and equilibrium data from the IL‐modified polymers were obtained. The kinetic study revealed a low temperature to be advantageous to the adsorption process. The dependence of the level of lactic acid adsorption on the amount of polymer, initial lactic acid concentration, and pH was examined at equilibrium. The maximum efficiency was obtained using the maximum adsorbent dose. A comparison of lactic acid adsorption at different pH revealed anion exchange to be the main interaction between the lactic acid and polymers, not molecular adsorption. The amounts adsorbed were fitted to the Langmuir, Freundlich, and Temkin equations. The equilibrium data for modified polymers (imidazole modified polymer, methylimidazole modified polymer, and ethylimidazole modified polymer) were best represented by the Langmuir and Freundlich isotherm with R² values of 0.99. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of Magnesium Ions on the Adsorption of Poly(acrylic acid) onto Alumina

The adsorption isotherms of poly(acrylic acid) (PAA) onto alumina powder have been determined as a function of pH, ionic strength, and magnesium-ion concentration. The adsorption of PAA is strongly enhanced by magnesium ions in alkaline media but less affected under acidic conditions. The adsorption isotherms display a maximum when PAA is fully complexed with magnesium ions in the solution, corresponding to a ratio of 0.25 ± 0.05 [Mg²⁺]/[acrylic acid monomer]. The decrease in adsorbed amount with an increase in PAA concentration at constant magnesium-ion concentration is related to a decrease in the complexation ratio.     

Investigation of zinc(II) adsorption on Cladophora crispata in a two‐staged reactor

In this study, the adsorption of zinc(II) ions on Cladophora crispata, a green alga, was studied with respect to initial pH, temperature, initial metal ion and biomass concentration in order to determine the optimum adsorption conditions. Optimum initial pH values for zinc(II) ions were found to be 5.0 at optimum temperature, 25 °C. The initial adsorption rates increased with increasing initial zinc(II) ion concentration up to 100 mgdm⁻³. The Freundlich and Langmuir adsorption isotherms were developed at various initial pH and temperature values. Then, the adsorption of zinc(II) ions to C crispata was investigated in a two‐staged mixed batch reactor. The residual metal ion concentrations (C_eq) at equilibrium at each stage for a given quantity of dried algae (X_o)/volume of solution containing heavy metal ion (V_o) ratio were calculated by using Freundlich and Langmuir isotherm constants. It was observed that the experimental biosorption equilibrium data for zinc(II) ions are in good agreement with those calculated using both Freundlich and Langmuir models. The adsorbed zinc(II) ion concentration increased with increasing X_o/V_o ratios while the adsorbed metal quantities per unit mass of dried algae decreased. © 2000 Society of Chemical Industry     

Kinetics of zirconium ions adsorption on activated charcoal from aqueous solutions

The batch kinetics of adsorption of the zirconium ions from aqueous solutions on activated charcoal has been investigated over a wide range of concentration of zirconium ions (1.0–5.0 g/l) and temperatures (10–50°C). The adsorption process of zirconium ions proceeds via two stages; the first stage is rather fast, followed by a much slower one. The Bangham equation was used to study the kinetics of the zirconium ions' adsorption on activated charcoal. It is observed that the diffusion of zirconium ions into the pores of the activated charcoal controls the kinetics of the adsorption process. Moreover, zirconium ion adsorption obeys the Freundlich and Langmuir isotherms in the concentration range studied. The adsorption equilibrium constant (k_c) values for zirconium ions adsorption on activated charcoal have also been calculated at different temperatures. Various thermodynamic quantities, ΔG, ΔH, and ΔS were computed from k_c values. The results showed that the adsorption of zirconium ions on activated charcoal is an endothermic process.     

改性膨润土对苯胺与苯酚混合液的吸附性能

研究酸活化膨润土和有机改性膨润土对苯胺和苯酚混合溶液的吸附性能,结果表明,酸活化膨润土对苯胺的吸附效果明显优于苯酚,具有较强的吸附选择性;有机膨润土对苯胺和苯酚的吸附无明显差别。吸附动力学研究表明,酸活化膨润土与有机改性膨润土对苯胺的吸附均符合准二级吸附动力学模型,相关系数分别为R²=0.999 8和R²=0.997 9。酸活化膨润土对苯胺的吸附符合Freundlich等温线模型,有机膨润土对苯胺的吸附数据对Freundlich等温线模型与Langmuir等温线模型均有较好的拟合。     

Effect of Sonication in the Preparation of Activated Carbon Particles on Adsorption Performance

The impact of acid and base adsorption capacities of activated carbon (AC) particles with activation condition, contact time, specific surface area (SSA), particle size, concentration, and temperature was studied. AC was pre-treated by sonication to improve the surface characteristics and enhance its adsorption capacity. Sonication increased the SSA of AC. SEM imaging showed good dispersion and uniform AC particles with an average diameter of about 0.6 μm. The adsorption results demonstrated that AC surfaces possessed effective interactions with acids and bases, and the greatest adsorption capacity was achieved with CH₃COOH, where data were analyzed by Freundlich and Langmuir isotherms. It was found that the isotherm data correlated well with the Freundlich isotherm. Adsorption of raw AC particles increased under sonication conditions. The adsorption process with sonicated and unsonicated AC particles obeyed pseudo first-order kinetics.