Adsorption of carotene from palm oil by acid-treated rice hull ash

Rice hull ash obtained by heat treatment and acid activated followed by washing was not effective as an adsorbent for carotene in palm oil in contrast to that reported for adsorption of soy oil lutein. However, unwashed acid-activated ash had activity much higher than carbon and silica but slightly less than a commercial bleaching clay. Heat treatment of raw rice hulls at temperatures below 300°C resulted in the most active adsorbent after acid activation. Drying the unwashed acid-activated ash at temperatures higher than 200°C reduced the activity. The activity of the acid ash was attributed to adsorbed acid. The results also suggested that the removal of carotene in palm oil was caused by chemical interactions involving the adsorbed acid and the carotene. The small amount of Fe³⁺ in the ash was not responsible for the activity.     

Unperturbed molecular dimensions and the theta temperature of dextran in dimethylsulfoxide (DMSO) solutions

Summary The unperturbed molecular dimensions of dextran samples have been determined in dimethylsulfoxide (DMSO) solutions from intrinsic viscosity measurements at different temperatures. The unperturbed dimension parameter, K_o, has been calculated from extrapolation methods.The unperturbed root-mean-square end-to-end distance, <r²>_o ^1/2, found for the polymer samples in DMSO solutions, indicate that the polymer coils are contracted. This distance varies from 3.25 × 10⁻⁷ cm to 2.94 × 10⁻⁷ cm for the sample T 40 and from 8.28 × 10⁻⁷ cm to 7.48 × 10⁻⁷ cm for the sample T 500, in the chosen solvent as the temperature is raised from 25°C to 45°C. In the system of dextran/DMSO, the long-range interaction parameter, B, was also determined and a significant decrease is observed between 25°–45°C. The theta temperatures, Θ, were obtained as Θ= 327.25 K, Θ= 327.41 K and Θ= 323.38 K from the temperature dependence of the interaction parameter in Kurata-Stockmayer-Fixman, Berry and Inagaki-Suzuki-Kurata equations, respectively. Received: 19 January 1998/Revised version: 9 June 1998/Accepted: 10 June 1998     

Adsorption and desorption of m-xylene vapor on organically modified montmorillonite

m-Xylene vapor was adsorbed to organically modified montmorillonite (organoclay). Hexadecyltrimethylammonium (HDTMA) was used to modify the surface of the clay. In adsorption experiments, the organoclay, along with the non-modified (washed) clay, was used. m-Xylene was adsorbed from a gaseous phase by using a fixed adsorption bed. The adsorption breakthrough curves and the adsorption isotherms were determined at three different temperatures (24, 34, and 44 °C). The adsorption data were modeled with the BET isotherm equation. It was found that the adsorption isotherms of washed clay exhibited a favorable Type I behavior, which implies that the adsorption capacity is strongly dependent on vapor concentration at low concentration ranges. In regards to the organoclay, isotherms showed a marginally favorable Type II behavior with a reduced adsorption capacity at low concentrations, and exhibited a linear increase at elevated vapor concentrations. The adsorption capacity of both washed clay and organoclay obviously decreased with the temperature. The desorption of m-xylene from the clays was also performed by using pure nitrogen, and the desorption rate constant k was on the order of 10⁻⁵ min⁻¹ for all types of clay.     

Ethylene Oligomerizations by Diazene Bridged Ni(II) Catalysts Derived from Pyrazole-Scaffold-Based Binucleating Ligands with Alkyl and Aryl Pendant Arms

Abstract  

The coordination and organometallic chemistry of a series of diazene (N₂)-bridged Ni(II) catalysts derived from pyrazole-scaffold-based ligands bearing alkyl and aryl pendent arms was investigated. Binucleating ligands were obtained as products of the condensation reaction between 3,5-dichloroformyl-1H-pyrazole and aliphatic/aromatic primary/secondary amines under anhydrous conditions. The Ni(II) catalysts were activated with ethyl aluminum sesquichloride (EASC) to oligomerize the ethylene mainly into C4, C6, C8, and C10 fractions with activities up to 1.2 and 0.5 × 10⁶ g (mol-Ni)⁻¹ bar⁻¹ h⁻¹ at 30 and 50 °C, respectively. All catalysts were found to be electrochemically active in the working potential range of −2 to +2 V. A change in the potential of Ni(II) was provoked by the N₄ donor bridging ligands, increasing the ethylene oligomerization activity.     

Preparation and Characterization of Activated Carbon from Chestnut Shell and its Adsorption Characteristics for Lead

Activated carbons were prepared from chestnut shell by phosphoric acid activation and the prepared activated carbons were used to remove lead(II) from aqueous solutions. The effects of impregnation ratio (IR) and activation temperature on activated carbon production were investigated. The produced activated carbons were characterized by N₂ adsorption, scanning electron microscopy (SEM), and atomic force microscopy (AFM) techniques. The highest surface area (1611 m²/g) and total pore volume (0.7819 cm³/g) were obtained at a carbonization temperature of 500°C with an impregnation ratio of 3/1. The resulting activated carbon was used for removal of lead(II) from aqueous solution. The effects of temperature, contact time, and adsorbent dosage were investigated. The adsorption isotherm studies were carried out and the obtained data were analyzed by the Langmuir, Freundlich, and Temkin equations. The rate of adsorption was found to conform to the pseudo-second-order kinetic model. The Langmuir isotherm equation showed better fit for all temperatures and the maximum adsorption capacities of lead(II) was obtained as 138.88 mg/g at 45°C.     

Porous properties of activated carbon produced from Eucalyptus and Wattle wood by carbon dioxide activation

This work focused on the preparation of activated carbon from eucalyptus and wattle wood by physical activation with CO₂. The preparation process consisted of carbonization of the wood samples under the flow of N₂ at 400°C and 60 min followed by activating the derived chars with CO₂. The activation temperature was varied from 600 to 900°C and activation time from 60 to 300 min, giving char burn-off in the range of 20/2-83%. The effect of CO₂ concentration during activation was also studied. The porous properties of the resultant activated carbons were characterized based on the analysis of N2 adsorption isotherms at −196°C. Experimental results showed that surface area, micropore volume and total pore volume of the activated carbon increased with the increase in activation time and temperature with temperature exerting the larger effect. The activated carbons produced from eucalyptus and wattle wood had the BET surface area ranging from 460 to 1,490 m²/g and 430 to 1,030 m²/g, respectively. The optimum activation conditions that gave the maximum in surface area and total pore volume occurred at 900°C and 60 min for eucalyptus and 800°C and 300 min for wattle wood. Under the conditions tested, the obtained activated carbons were dominated with micropore structure (∼80% of total pore volume).     

Catalytic dry oxidation of aniline,benzene, and pyridine adsorbed on a CuO doped activated carbon

Adsorption of aniline, benzene and pyridine from water on a copper oxide doped activated carbon (CuO/AC) at 30 °C and oxidation behavior of the adsorbed pollutants over CuO/AC in a temperature range up to 500 °C are investigated in TG and tubular-reactor/MS systems. Results show that the AC has little activity towards oxidation of the pollutants and CuO is the active oxidation site. Oxidation of aniline occurs at 231–349 °C and yields mainly CO₂, H₂O and N₂. Oxidation of pyridine occurs at a narrower temperature range, 255–309 °C, after a significant amount of desorption starting at 150 °C. Benzene desorbs at temperatures as low as 105 °C and shows no sign of oxidation. The result suggests that adsorption-catalytic dry oxidation is suitable only for the strongly adsorbed pollutants. Oxidation temperatures of CuO/AC for organic pollutants are higher than 200 °C and pollutants desorbing easily at temperatures below 200 °C cannot be treated by the method. This work was presented at the 7 ^th China-Korea Workshop on Clean Energy Technology held at Taiyuan, Shanxi, China, June 26–28, 2008.     

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.     

Highly efficient and fast adsorption of Au(III) and Pd(II) by crosslinked polyethyleneimine-glutaraldehyde

An adsorbent (PEI-GA) is prepared by crosslinking polyethyleneimine with glutaraldehyde. PEI-GA shows outstanding adsorption performance towards Au(III) and Pd(II). PEI-GA presents large adsorption capacity towards Au(III) in a wide application pH range from 1 to 9. The adsorption capacities of PEI-GA for Au(III) and Pd(II) at 25°C reach 2575 and 497 mg/g, respectively. Au(III) and Pd(II) can be adsorbed completely within 10 min for 8.3 mg/L Au(III) and 20 min for 9.7 mg/L Pd(II). The adsorption equilibrium time required for 523.9 mg/L Au(III) and for 565.6 mg/L Pd(II) is 2 and 9 h, respectively. The Sips model is the most suitable to describe the adsorption isotherms which leads to more realistic adsorption capacities for both metals. PEI-GA also exhibits high selectivity and repeatability towards Au(III) and Pd(II). The adsorption mechanism involves redox, chelation coordination, and electrostatic interactions for Au(III), and coordination and electrostatic interactions for Pd(II).     

High surface area-activated carbon from Glycyrrhiza glabra residue by ZnCl2 activation for removal of Pb(II) and Ni(II) from water samples

A high-surface-area activated carbon was prepared by chemical activation of Glycyrrhiza glabra residue with ZnCl₂ as active agent. Then, the adsorption behavior of Pb(II) and Ni(II) ion onto produced activated carbon has been studied. The experimental data were fitted to various isotherm models. According to Langmuir model, the maximum adsorption capacity of Pb(II) and Ni(II) ions were found to be 200 and 166.7 mg g⁻¹, respectively, at room temperature. Kinetic studies showed the adsorption process followed pseudo second-order rate model. High values of intra-particle rate constants calculated shows the high tendency of activated carbon for removal of Pb(II) and Ni(II) ions.     

Characterization of surface chemistry and pore structure of H3PO4-activated poly(vinyl alcohol) coated fiberglass

H₃PO₄-activated poly(vinyl alcohol) coated fiberglass mats (PAPCF) were prepared in air at temperatures below 400 °C. The surface chemistry and pore structure of PAPCF were characterized by using N₂ adsorption at 77 K, XPS, DRIFTS, TGA, NaOH uptake and Ag⁺ adsorption. PAPCF prepared at 300 °C yields a high BET surface area (up to 1745 m²/g of coating) with a structure composed mainly of micropores. Some oxygen-containing functional groups, such as carboxylic, phenolic hydroxyl groups, and phosphorus species, are incorporated into the PVA-based char coating, with higher activation temperatures leading to increased formation of these groups. Post-treatment with sulfuric acid decreases the content of phosphorus species, but increases that of oxygen-containing groups in the coating. NaOH uptake and Ag⁺ adsorption show substantial cationic exchange capacity with the PAPCF or acid-treated PAPCF. TGA data show that PAPCF is more thermally stable in air than acid-treated PAPCF. Furthermore, PAPCF activated at 300 °C can be regenerated at least 5 times with no change in ion exchange capacity.     

The catalytic activity of Ni/W bimetallic sulfide nanostructured catalysts in the hydrodesulfurization of dibenzothiophene

Two types of catalysts containing NiW bimetallic sulfide nanostructures were prepared by a chemical method employing ammonium thiotungstate and nickel nitrate as metal-sulfide precursors followed by sulfidation in H₂S/H₂ at 400 °C. The nanostructures were grown with excess of Ni, at atomic ratio R = 0.75, 0.85 (R = Ni/Ni + W). High resolution electron microscopy (HRTEM) micrographs revealed the formation of two types of nanostructures, nickel sulfide nanoparticles and long nanorods of tungsten suboxide, both coated by WS₂ layers. The Ni/W catalyst containing mostly nanorods presented twice the catalytic activity (pseudo-zero order constant rate k = 12 × 10⁻⁷ mol/s.g) of the Ni/W catalyst containing nanoparticles (k = 6.3 × 10⁻⁷ mol/s.g) with a low selectivity for tetrahydrodibenzothiophene (THDBT) and high selectivity to cyclohexylbenzene (CHB, 50 mol%). In turn the Ni/W catalyst containing nanoparticles presented a catalytic activity comparable to a Ni/Mo catalyst without inorganic fullerene (IF) nanostructures (k = 7.2 × 10⁻⁷ mol/s.g) but with higher selectivity for hydrogenation to THDBT, (14 mol%) than the sample with nanorods.     

Chemical and thermal properties of organoclays derived from highly stable bentonite in sulfuric acid

Generally, acid activation modified the physico-chemical properties of the raw clay minerals. The extent of these modifications depended on the type, origin of the clay minerals and the conditions of the acid activation. In this study, a bentonite exhibited a strong stability toward the acid treatment at 90 °C and at higher acid/clay mineral ratios, with slight depletion of Mg^2 +, Fe^3 + and Al^3 + cations (about 5%). The resulting organo-acid activated clays prepared after a reaction with cetyltrimethylammonium (C16TMA) hydroxide solution, exhibited uptaken amounts of surfactants between 0.80 mmol and 0.7 mmol/g with interlayer spacings of 2.20 nm and 1.80 nm, independently of the initial concentrations of the organic molecules. These organoclays were stable in acidic and basic solutions. However, after heating at 200 °C, the interlayer spacing shrunk due to the degradation of the organic surfactants as indicated by thermogravimetric analysis. The rehydration of the calcined organoclays at temperatures below 200 °C, did not lead to the increase of the basal spacings, due to change in configuration of the C16TMA cations.     

Effect of the isotopic composition of lithium carriers on the ionic conductivity of lanthanum lithium titanate ceramic

The ionic conductivity of the solid electrolyte La_{2/3 − x} Li_3x TiO₃ at temperatures 20–600°C with different isotopic composition of the lithium current carriers is measured. It is shown that it has two components — low-and high-temperature — with very different activation energies. NMR on ⁷Li nuclei is used to measure the spin-lattice relaxation rate of the carriers. It is determined that the activation energies of short-and long-range carrier motion are the same at temperatures 20–500°C and are sharply different at higher temperatures. The effect of the concentration of cationic vacancies on the motion of carriers with different isotopic composition is investigated. __________ Translated from Steklo i Keramika, No. 7, pp. 31–34, July, 2007.     

Adsorption of methyl ethyl ketone onto poly(vinyl alcohol)(PVA)/peat/organoclay composite beads in aqueous solution

A new type of poly(vinyl alcohol)(PVA)/peat/organoclay composite beads was prepared. This composite bead was a porous spherical particle with a diameter of 3.0–5.0 mm and a porosity of about 50%. The oragnoclay is prepared by hexadecyl trimethyl ammonium bromide (HDTMA) exchanged clay. The dynamic adsorption behavior between methyl ethyl ketone (MEK) and this composite bead was investigated. The adsorption process occurs in two stages with external mass transport occurring in the early stage and intraparticle diffusion occurring in the later stage. The rate of MEK diffusion in the external mass transport process and the intraparticle diffusion process in the adsorption temperature 20–35 °C was 3.28–76.98 × 10⁻⁸ cm²/s and 1.62–3.17 × 10⁻⁷ cm²/s, respectively. The rate of MEK diffusion in both processes was concentration independent, and it increased with increasing the adsorption temperature. Langmuir isotherm adsorption model was more suitable for describing the adsorption equilibrium of MEK. The calculated Q values in the adsorption temperature 20–35 °C were 5.90–22.78 mg/g composite bead. The adsorption capacity of this composite bead increased with increasing the adsorption temperature. The adsorption process was physical adsorption, endothermic and non-spontaneous process.     

Activated carbon from sewage sludge for removal of sodium diclofenac and nimesulide from aqueous solutions

Sludge based activated carbons (ACs) were used to remove selected pharmaceuticals such as diclofenac (DCF) and nimesulide (NM) from aqueous solutions. The powered sewage sludge was mixed with different proportions of ZnCl₂. The mixture was pyrolyzed in a conventional oven using three different temperatures under inert atmosphere. Afterwards, in order to increase the specific surface area and uptake capacity the carbonized materials were acidified with 6mol L^?1 HCl under reflux at 80 °C for 3 hours. The characterization of ACs was achieved by scanning electron microscopy, FTIR, TGA, hydrophobicity index by water, n-heptane vapor adsorption and nitrogen adsorption/desorption curves. The specific surface area (S _BET ) of adsorbents varied between 21.2 and 679.3m²g^?1. According to the water and n-heptane analysis data all ACs had hydrophobic surface. Experimental variables such as pH, mass of adsorbent and temperature on the adsorption capacities were studied. The optimum pH, mass of adsorbent and temperature for adsorption of DCF and NM onto ACs were found to be 7.0 (DCF) and 10.0 (NM), 30mg and 25 °C, respectively. The kinetic adsorption was investigated using general-order, pseudo-first order and pseudo-second order kinetic models, while the general-order model described the adsorption process most suitably. The maximum amounts of DCF and NM adsorbed were 156.7 and 66.4mg g^?1 for sample 1(500-15-0.5), respectively.     

SYNTHESIS OF ACTIVATED CARBON FROM JATROPHA SEED COAT AND APPLICATION TO ADSORPTION OF IODINE AND METHYLENE BLUE

This article provides evidence that jatropha seed coat residues can be used as a carbon source for preparing activated carbons that have good adsorption properties for iodine and methylene blue. Activated carbons were prepared using three different methods of activation, physical, chemical, and physico-chemical, for a range of activation temperatures (600°, 700°, 800°, and 900°C) and activation hold times (1, 2, and 3 h). The highest BET surface area (1479 m² g^?1) and the highest iodine adsorption (1511 mg g^?1) were obtained with physico-chemical activation at a temperature of 900°C and a hold time of 2 h. This activated carbon gave higher BET surface area and iodine adsorption than commercial activated carbon (1169.1 m² g^?1 and 1076 mg g^?1). The activated carbons prepared by physico-chemical activation at 900°C and 2 h were then tested for adsorption of methylene blue at a range of concentrations of methylene blue (100, 200, 300, 400, and 500 mg L^?1). It was found that a Langmuir isotherm gave a better fit (R ² = 0.999) to the observed adsorptions than a Freundlich isotherm (R ² = 0.884). For the adsorption kinetics, a pseudo-second-order model gave a better fit (R ² > 0.998, Δq _e  = 3.7%) than a pseudo-first-order model (R ² ≈ 0.95, Δq _e  = 85.6%). These results suggest that chemisorption is the rate-controlling step for the adsorption of methylene blue. The experimental results show that jatropha seed coat is a lignocellulosic waste precursor for preparation of activated carbon that is an alternative source for preparation of commercial-grade activated carbons.     

Preparing tin-doped indium oxide ceramic bulk via explosive consolidation and sintering of nanopowders

The tin-doped indium oxide (ITO) ceramic ultra-dense target is the crucial material in spurting preparation of optical-electric films. The difficulty in target fabrication is due to ITO decomposing at high temperatures. In this paper, commercial ITO nanometer powders are used and are explosively shock consolidated with two different sets and different explosives. Experiment data indicate that the shock velocity should be less than 4000 m/sec, and the shock pressure should be more than 6 and even 12 GPa for obtaining good consolidation. The samples are rapidly sintered at a high temperature after shock treatment. A suitable sinter temperature of ITO nanopowders compacted via explosive consolidation (≈1000°C) is determined by a differential thermal analysis. Scanning electron microscope images show that ITO ceramic decomposes and sublimates at a high temperature. The expansion factors of the samples from our experiments and commercial targets obtained by high isostatic pressing (HIP) are measured: α _l = 7.81 → 10⁻⁶ K⁻¹ for samples sintered at 1000°C, α _l = 8.8 → 10⁻⁶ K⁻¹ for samples sintered at 900°C, and α _l = 6.89 · 10⁻⁶ K⁻¹ for HIP samples. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 2, pp. 114–122, March–April, 2007.     

Adsorption of Ni(II) and Co(II) Using Microballoons Containing Mg-Silicate and CYANEX923 Prepared by the Emulsion Liquid Membrane System

Abstract

The Mg-silicate microballoons containing CYANEX923 were prepared by W/O/W emulsion. The diameter of obtained micro-sphere particles was ～10 µm and shell thickness was 2 µm. The adsorption of Co(II) and Ni(II) from aqueous solutions using prepared micro-sphere particles was investigated. Experiments were carried out as a function of solute concentration and temperature (25–60°C). Several kinetic models were used to test the experimental rate data and to examine the controlling mechanism of the adsorption process. Equilibrium adsorption data were analyzed using Langmuir isotherm model. The results indicated that prepared micro-sphere particles can be used as an efficient adsorbent for the removal of Ni(II) and Co(II) from aqueous solution.     

A parametric study of a platinum ruthenium anode in a direct borohydride fuel cell

Data on the performance of a direct borohydride fuel cell (DBFC) equipped with an anion exchange membrane, a Pt–Ru/C anode and a Pt/C cathode are reported. The effect of oxidant (air or oxygen), borohydride and electrolyte concentrations, temperature and anode solution flow rate is described. The DBFC gives power densities of 200 and 145 mW cm⁻² using ambient oxygen and air cathodes respectively at medium temperatures (60 °C). The performance of the DBFC is very good at low temperatures (ca. 30 °C) using modest catalyst loadings of 1 mg cm⁻² for anode and cathode. Preliminary data indicate that the cell will be stable over significant operating times.