Alumina Adsorbents Research Articles

Solid–liquid equilibrium of glycolic acid with alumina

This work aims to present novel adsorption equilibrium data for glycolic acid with alumina at aqueous solutions. The adsorption experiments were carried out with aqueous glycolic acid solutions with various initial concentrations (0.38–2.1) mol L−1. Adsorbent alumina of (0.2–2) g was used. To show the effect of temperature, also adsorption equilibrium experiments were made at various temperatures (298, 308, and 318K). The equilibrium concentrations of glycolic acid have been found. Removal of glycolic acid was 20.51% as the maximum percentage. The equilibrium data show well fitting with Langmuir isotherm. Also, Elovich model have been applied to adsorption data.

Influence of the Chemical Composition of Silica–Alumina Adsorbents in Sulfur and Nitrogen Compounds Removal from Hydrotreated Diesel

The removal of sulfur and nitrogen compounds from oil derivatives is fundamental to fulfill the new environmental laws. Traditionally, this removal is carried out through hydrotreatment processes; however, regarding environmental and economic issues, the refining oil industry has been studying adsorption processes to reduce sulfur and nitrogen compound levels in diesel streams. The aim of this work was to study the influence of chemical composition and acid–base properties of commercial alumina, silica, and silica–alumina samples on the removal of sulfur and nitrogen compounds from diesel streams. It was observed that acid and textural properties and surface composition influence the adsorptive capacity of the samples. The results indicated that the adsorbents tested were more efficient for the removal of nitrogen compounds. Kinetic and adsorption experiments using model fuel containing sulfur and nitrogen compounds were also carried out. Freundlich and Sips models described the adsorption of 4,6-dimethyldibenzothiophene and quinoline on silica–alumina, respectively.

La3+-modified activated alumina for fluoride removal from water

A La3+-modified activated alumina (La-AA) adsorbent was prepared for effective removal of fluoride from water. The surface properties of adsorbent were characterized with zeta potential analysis, SEM-EDS and EXAFS. Batch and column experiments were conducted to evaluate improvement of F− removal by the La-AA. SEM/EDS and EXAFS analyses determined the formation of La(OH)3 coating on the AA and strong bonding interactions between La3+ and the Al atoms. The points of zero charge (pHPZC) of AA and La-AA were at pH 8.94 and 9.57, respectively. Batch experimental results indicated that the La-AA had much higher adsorption rate and capacity than the AA. The F− adsorption processes on La-AA and AA followed the pseudo-second-order kinetics and the Langmuir isotherm. Column filtration results shows that the La-AA and AA treated 270 and 170 bed volumes of the F−-spiked tap water, respectively, before F− breakthrough occurred. The results demonstrated that the La-AA was a promising adsorbent for effective removal of F− from water.

Response of Different Types of Sulfur Compounds to Oxidative Desulfurization of Jet Fuel

Oxidative desulfurization (ODS) removes organic sulfur compounds from liquid transportation fuels (including diesel and jet fuels) in a two-step process: (1) chemical oxidation to form sulfones and (2) adsorption (or extraction) of the sulfones onto a polar adsorbent such as alumina. Continued development of ODS is limited in part by a lack of understanding of how different sulfur types in real fuels respond to its constituent oxidation and extraction steps. We treated two JP-8 jet fuels (described by here as 3773 and 4177, respectively) using the two-step ODS process. These two fuels had similar physical properties and hydrocarbon compositions but differing sulfur contents: the 3773 fuel was 720 ppmw, while that of the 4177 fuel sulfur content was 1400 ppmw. For the two-step ODS process, we used activated carbon-promoted performic acid as the oxidant and activated alumina as the adsorbent. The complete ODS treatment reduced the sulfur content of the 3773 fuel to a level below the detection limits of our total sulfur analyzer (40 ppmw), implying >94% sulfur removal. However, ODS treatment reduced the sulfur content of the 4177 fuel to 350 ppmw, or 75% sulfur removal. To investigate this discrepancy at the molecular level, we targeted sulfur compounds in the stock and treated fuels using one-dimensional gas chromatography and comprehensive two-dimensional gas chromatography with both sulfur selective detection and time-of-flight mass spectrometry. Initially, the 4177 fuel was dominated by a suite of compounds identified as sulfides, disulfides, and thiophenes (SDT), whereas the 3773 fuel was dominated by its benzothiophene (BT) content. The SDT compounds were easily oxidized, but the corresponding sulfones were not efficiently removed using the alumina adsorbent. The BT compounds were more resistant to oxidation than the SDT compounds, but the oxidized BT compounds were more efficiently removed using the adsorbent than either the BT compounds or oxidized SDT compounds. Development of ODS technologies should account for the different responses of different sulfur compounds to the oxidation and adsorption treatments.

Silica scale mitigation for high recovery reverse osmosis of groundwater for a mining process

The feasibility of silica removal in RO treatment of groundwater from a Western Australian mining and processing operation to prevent scaling and enhance water recovery was investigated. This study has shown that it is possible to decrease the silica concentration in RO concentrate to levels that would allow an overall water recovery of 90% to 95% using 10g/L of regenerable activated alumina adsorbent. Regeneration of the adsorbent using 2% NaOH was found to be effective for at least three regeneration cycles. A preliminary costing of the high water recovery RO process using silica removal by adsorption indicated product water (permeate) costs of $5.6/kL and savings due to a reduction in brine volume from the current 40% of feed volume to 5–10% of feed volume. It also allows better utilisation of a scarce groundwater resource, allowing the production of up to 1.6 times more low salt water from a given volume of groundwater. These results warrant larger scale investigation of silica removal and adsorbent regeneration for high recovery RO processing for mining operations, and application of silica removal to RO treatment of other silica laden waters such as coal seam gas produced water.

On-line preconcentration and determination of ultra trace amounts of mercury using surfactant coated alumina modified by dithizone with cold vapor atomic absorption spectrometry

The potential of an inexpensive dithizone immobilized on ammonium lauryl sulfate alumina adsorbent to separate and preconcentrate traces of mercury from vegetables and ground water has been evaluated. A cartridge filled with 100 mg of adsorbent was incorporated to an on-line vapor generation accessory system. Traces of mercury in sample solutions were pumped through the cartridges for 2 min (flow rate of 5 mL min−1) and then eluted from the cartridges with 1 M hydrochloric acid for 1 min at a flow rate of 1 mL min−1. At the same time that mercury is eluted from the cartridges, the eluate is mixed with a 0.02% (m/v) sodium borohydride solution and the mercury cold vapor is swept through the atomization cell with a nitrogen flow of 50 mL min−1. The overall procedure (mercury separation–preconcentration and mercury cold vapor generation–atomization) is completed in around 3 min. The developed method achieves an enrichment factor of 125 with a limit of detection of 0.12 ng mL−1. The repeatability and the accuracy of the overall procedure were successfully assessed.

Dimensional stability of adsorbents subjected to thermal cycling

The dimensional stability of adsorbent beads subjected to varying temperature conditions must be understood to assess the effect of thermal cycling on both the adsorbent and the structure that contains it. Most of the literature on the coefficient of thermal expansion (CTE) of adsorbents relates to zeolite crystals or clusters of crystals with application to membranes. Such crystals or powder materials have been shown to exhibit both positive and negative volume expansion coefficients depending upon the temperature range. This duality in the CTE with increasing temperature and the large variation in the CTE magnitude for a given zeolite structure suggest that the dimensional stability of zeolite crystals under varying thermal conditions is not likely a good indicator of the thermal stability of agglomerated zeolites. In this study, a method has been developed and applied to measure the CTE of activated alumina and 13X molecular sieve adsorbent beads. A McBain gravimetric microbalance was modified in a simple manner to be used as a dilatometer. The method was validated by measuring the CTE of a 316 stainless steel rod and showing that the measured CTE of this study agreed with the published CTE within 3.3 %. Average CTEs for alumina and 13X adsorbents were determined as 4.88 × 10−6 and 2.96 × 10−6 mm/mm/ °C, respectively for the range of temperature 20–400 °C.

Evaluation of Mesoporous Alumina Adsorbent for the Purification of Paclitaxel

Several types of mesoporous alumina adsorbents with different physical properties were prepared by spray pyrolysis and were used for the separation/purification of the anticancer agent paclitaxel. The pore diameter of the adsorbents had a greater effect than did the surface area and the pore volume on the removal of plant-derived impurities. An appropriate pore diameter (~10.8 nm) was required for effective impurity removal. At a constant pore diameter, the surface area of the adsorbent affected not only the purity but also the yield of paclitaxel. Also, increasing the surface area of the adsorbent resulted in an increase in the adsorption of paclitaxel and impurities (biomass-derived tar and wax components). Removal of these impurities was confirmed by HPLC analysis of the absorbent after the treatment and TGA of the organic substances that were bound to the adsorbent.

Removal of Cu (II) from Aqueous Solution Using a Novel Crosslinked Alumina-Chitosan Hybrid Adsorbent

A novel biosorbent was developed by coating chitosan, a naturally and abundantly available biopolymer, on to activated alumina based on oil shale ash via crosslinking. The adsorbent was characterized by various techniques, such as Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric-differential thermal analysis, and X-ray photoelectron spectroscope. Batch isothermal equilibrium adsorption experiments were condcted to evaluate the adsorbent for the removal of Cu(II) from wastewater. The effect of pH and agitation time on the adsorption capacity was also investigated, indicating that the optimum pH was 6.0. The equilibrium adsorption data were correlated with Langmuir and Freundlich models. The maximum monolayer adsorption capacity of chitosan coated alumina sorbent as obtained from Langmuir adsorption isotherm was found to be 315.46 mg·g−1 for Cu(II). The adsorbent loaded with Cu(II) was readily regenerated using 0.1 mol·L−1 sodium hydroxide solution. All these indicated that chitosan coated alumina adsorbent not only have high adsorption activity, but also had good stability in the wastewater treatment process.

Determination of 11 anabolic hormones in fish tissue by multi- function impurity adsorption solid-phase extraction-ultrafast liquid chromatography-tandem mass spectrometry

A method was developed for the determination of 11 anabolic hormones (boldenone, androstenedione, nandrolone, methandrostenolone, methyltestosterone, testosterone, testosterone acetate, trenbolone, testosterone propionate, stanozolol, fluoxymesterone) in fish by multi-function impurity adsorption solid-phase extraction-ultrafast liquid chromatography-tandem mass spectrometry. After the sample was extracted by methanol, the extract was cleaned-up quickly by C18 adsorbent, neutral alumina adsorbent and amino-functionalized nano-adsorbent. The separation was performed on a Shim-Pack XR-ODS II column (100 mm x 2.0 mm, 2.2 microm) using the mobile phases of 0.1% (v/v) formic acid in acetonitrile and 0.1% (v/v) formic acid solution in a gradient elution mode. The identification and quantification were achieved by using electrospray ionization in positive ion mode (ESI+) in multiple reaction monitoring (MRM) mode. The matrix-matched external standard calibration curves were used for quantitative determination. The results showed that the calibration curves were in good linearity for the eleven analytes with the correlation coefficients (r) more than 0.999. The limits of detection (LODs, S/N > 3) for the 11 anabolic hormones were from 0.03 microg/kg to 0.4 microg/kg and the limits of quantification (LOQs, S/N > 10) were from 0.1 microg/kg to 1.5 microg/kg. The average recoveries ranged from 80.9% to 98.1% with the relative standard deviations between 5.2% and 11.5%. The method is simple, rapid, sensitive, accurate and suitable for the quantitative determination and confirmation of the 11 anabolic hormones in fish.

Extraction Pb(II) by (Z)-Furan-2-carbaldehyde Thiosemicarbazone adsorbed on surfactant coated alumina before determination by FAAS

A simple, highly sensitive, accurate and selective method for determination of trace amounts of Pb(II) in water samples is presented. The method is based on selective chelation of Pb(II) on surfactant coated alumina, modified with a Schiff’s base (Z)-Furan-2-carbaldehyde Thiosemicarbazone (I). The retained ions were then eluted with 4 ml of 4 M nitric acid and determined by flame atomic absorption spectrometry(FAAS) at 283.3 for Pb. The influence of flow rates of sample and eluent solutions, pH, breakthrough volume, effect of foreign ions on chelation and recovery were investigated. 1.5 g of surfactant coated alumina adsorbs 40 mg of the Schiff’s base which in turn can retain 15.0±0.9mg of each of the two ions. The limit of detection (3σ) for Pb(II) was found to be 5.57 ng l -1. The enrichment factor for both ions is 100. The mentioned method was successfully applied on determination of lead in different water samples. The ions were also speciated by means of three columns system.

Gas chromatographic separation of hydrogen isotopes on columns packed with alumina, modified alumina and sol–gel alumina

The stationary phase of alumina adsorbents, prepared by different chemical processes, was used to study the separation behaviour of hydrogen isotopes. Three types of alumina, obtained by conventional hydroxide route alumina coated with silicon oxide and alumina prepared by internal gelation process (IGP), were used as packing material to study the separation of HT and T(2) in a mixture at various temperatures. The conventional alumina and silicon oxide coated alumina resolved HT and T(2) at 77K temperature with different retention times. The retention times on SiO(2) coated columns were found to be higher than those of other adsorbents. However, the column filled with IGP alumina was found to be ideal for the separation of HT and T(2) at 240 K. The peaks were well resolved in less than 5 min on this column.

Adsorption Equilibrium of Water Vapor on Selexsorb-CDX Commercial Activated Alumina Adsorbent

Adsorption equilibrium data of water vapor on a commercially available activated alumina, Selexsorb-CDX, were measured by a static gravimetric technique. The relative humidity and temperature were varied between 0 % and 90 % and between (5 and 35) °C, respectively. The measured data were fitted to the dual mechanism adsorption potential (DMAP) equation. The pore structure of the adsorbent material was characterized by nitrogen adsorption and mercury intrusion measurements. The DMAP equation predicted that the first 50 % of the total water adsorbed was held on the adsorbent by the combined action of chemisorption and physisorption, which was attributed to filling of the micropores and the first adsorbed layers in the mesopores. The remainder of the adsorbed water was attributed to capillary condensation in the mesopores. The heat of adsorption as a function of fractional loading was calculated using the fitted DMAP equation parameters in conjunction with the van't Hoff equation, with and without an assumption of the Clausius–Clapeyron equation. The two methods for the heat of adsorption calculation were in excellent agreement, differing by no more than 0.2 kJ·mol–1. The reported experimental data and correlation parameters can be readily applied in the modeling, design, and optimization of dehumidification processes utilizing the Selexsorb-CDX activated alumina adsorbent used in this study.

Effect of surface acidity and basicity of aluminas on asphaltene adsorption and oxidation

This study investigates the effect of surface acidity and basicity of aluminas on asphaltene adsorption followed by air oxidation. Equilibrium batch adsorption experiments were conducted at 25°C with solutions of asphaltenes in toluene at concentrations ranging from 100 to 3000g/L using three conventional alumina adsorbents with different surface acidity. Data were found to better fit to the Freundlich isotherm model showing a multilayer adsorption. Results showed that asphaltene adsorption is strongly affected by the surface acidity, and the adsorption capacities of asphaltenes onto the three aluminas followed the order acidic>basic and neutral. Asphaltenes adsorbed over aluminas were subjected to oxidation in air up to 600°C in a thermogravimetric analyzer to study the catalytic effect of aluminas with different surface acidity. A correlation was found between Freundlich affinity constant (1/n) and the catalytic activity. Basic alumina that has the lowest 1/n value, depicting strongest interactions, has the highest catalytic activity, followed by neutral and acidic aluminas, respectively.

Effect of nonionic structure-directing agents on adsorption and structural properties of mesoporous alumina

Mesoporous aluminas (MAs) with tailored adsorption, framework, and surface basic–acidic properties were prepared using different structure-directing agents (SDAs) such as Brij®78, Pluronic F108, poly(ethylene oxide)–poly(butylene oxide)–poly(ethylene oxide) B50-6600 and Vorasurf™ 504 block copolymers, which so far were not explored for the synthesis of this important material viasolvent evaporation-induced self-assembly (EISA) strategy. Thermogravimetry, Fourier transform infrared spectroscopy, small-angle X-ray diffraction, nitrogen adsorption, transmission electron microscopy, and CO2 and NH3 temperature programmed desorption techniques were used to characterize the samples studied. Depending on the SDAs and aluminium precursors used in the EISA process, the BET surface area, pore volume and the average pore size of the MA samples were tailored in the range of 300–433 m2 g−1, 0.33–1.07 cm3 g−1, and 2.7–11.5 nm, respectively. Importantly, the use of F108 as a SDA and aluminium isopropoxide as an aluminium precursor gave a highly ordered MA with a large pore volume of 1.07 cm3 g−1 and enlarged mesopores centering at 11.5 nm, which are larger than those reported for the P123 and F127 Pluronic block copolymer-templated MA samples. However, the use of F108 as the SDA and AlCl3 as the aluminium precursor resulted in disordered MA with much smaller mesopores centering at 2.7 nm, enhancing the adsorption affinity towards CO2 (1261 μmol g−1) and NH3 (350 μmol g−1). This study shows that the EISA strategy does not require a stringent selection of SDA, and that the F108 block copolymer is an excellent SDA for the preparation of MA with a large pore volume and high adsorption capacity towards CO2, which exceeds substantially the value obtained for conventional alumina samples and for the previously reported ordered MA prepared in the presence of P123 and F127, which are commonly used as SDAs.

Fluoride Removal from Ground Water by γ-Alumina Coated Ceramic Honeycomb

Studies have been carried out on defluoridation of ground water using gamma alumina coatings on a ceramic honeycomb. The sol gel coated gamma alumina adsorbent was found to adsorb fluoride rapidly and effectively. Coatings on ceramic honeycomb were prepared using a sol of dispersible precursor of boehmite (γ-AlOOH). The boehmite coating, on calcination at 500°C transformed to γ-alumina. The fluoride removal performance was investigated as a function of the fluoride concentration and flow rate. It was observed that fluoride removal is low at higher flow rate. The specific fluoride uptake capacity was 15400mg of F− removed /kg of coated γ-alumina on the ceramic honeycomb from de-ionized water, whereas in case of ground water, the capacity was 11080 mg of F− per kg of coated alumina. The regeneration was effected by passing a dilute solution of aluminum sulfate solution. A fluoride removal kit consisting of five ceramic honeycombs in series was evaluated to defluoridate ground water. Around 200 liters of ground water (initial F− conc. of 5 ppm) could be defluoridated to permissible level of F− concentration. It is much easier and convenient to regenerate the alumina coated on the honeycombs due to open channel structures of the honeycomb.

Adsorption equilibrium and kinetics of fluoride on sol–gel-derived activated alumina adsorbents

Adsorption equilibrium and kinetics of fluoride on a sol–gel-derived activated alumina and its modifications with calcium oxide or manganese oxide were studied to explore the feasibility of applying these adsorbents for fluoride removal from drinking water. The activated alumina adsorbents were characterized with SEM/EDS and N 2-adsorption for their chemical and pore textural properties. The adsorption isotherms were correlated with the Langmuir and Freundlich adsorption equations. The fluoride adsorption isotherms on the sol–gel-derived activated alumina followed the Freundlich model while the fluoride adsorption isotherms on the calcium oxide- or manganese oxide-modified activated alumina adsorbents followed the Langmuir model. The calcium oxide-modified alumina adsorbent showed the highest fluoride adsorption capacities of 0.99 and 96.23 mg/g at fluoride concentrations of 0.99 and 432 mg/L, respectively. A pseudo-second-order model and an intraparticle kinetic model fitted well the adsorption kinetic data. It was found that both external and intraparticle diffusions contribute to the rate of removal of fluoride from the activated alumina-based adsorbents produced in our laboratory. The adsorption kinetic models evaluated in this work fitted well the adsorption uptake of fluoride from a Mexican groundwater on both calcium oxide- and manganese oxide-modified alumina adsorbents.

Copper Loaded on Sol-Gel-Derived Alumina Adsorbents for Phosphine Removal

The hydride gas of phosphine (PH3) is commonly used for semiconductor and optoelectronic industries. The local scrubbers must immediately abate it because of its high toxicity. In this study, copper (Cu) loaded on the sol-gel-derived γ-alumina (Al2O3) adsorbents are prepared and tested to investigate the possibility of PH3 removal and sorbent regeneration. Test results showed that during the breakthrough time of over 99% PH3 removal efficiency, the maximum adsorption capacity of Cu loaded on the sol-gel-derived γ-Al2O3 adsorbent is 18 mg-PH3/gadsorbent. This is much higher than that of Cu loaded on the commercial γ-Al2O3 adsorbent— 8.6 mg-PH3/gadsorbent. The high specific surface area, narrow pore size distribution, and well dispersion of Cu loaded on the sol-gel-derived γ-Al2O3 could be the reasons for its high PH3 adsorption capacity. The regeneration test shows that Cu loaded on the sol-gel-derived γ-Al2O3 adsorbent can be regenerated after a simple air purging procedure. The cumulative adsorption capacity for five regeneration cycles is 65 mg-PH3/g-adsorbent, which is approximately double that of the Cu/zeolite adsorbent demonstrated in the literature.

Hybrid inorganic/organic alumina adsorbents-functionalized-purpurogallin for removal and preconcentration of Cr(III), Fe(III), Cu(II), Cd(II) and Pb(II) from underground water

Metal pollution is well recognized as one of the major environmental problems that must be imperatively addressed and solved. In this study, three types of alumina adsorbents (I–III) were physically immobilized with purporogallin as a chelating ion exchangers. These were found to exhibit strong capability and selectivity characters for a series of heavy metal ions. Surface modification of hybrid alumina was characterized and identified from the determination of surface coverage and infrared analysis. Hybrid alumina adsorbents were identified for their strong resistivity to acid leaching in pH > 2–7 as well as their high thermal stability up to 350 °C. The ability of newly synthesized hybrid inorganic/organic alumina adsorbents (I–III) to bind and extract various metal ions was examined and evaluated in various buffer solutions (pH 1.0–7.0) via determination of the metal adsorption capacity values. These were identified as high as 420–560, 500–580 and 500–590 μmol g −1 for alumina adsorbents (I), (II) and (III), respectively in the case of high concentration levels of Cr(III), Fe(III) and Cu(II). The influence of alumina matrices were highly characterized when low concentration levels (μg ml −1 and ng ml −1) of metal ions were used. Hybrid alumina adsorbents were successfully applied for selective extraction, removal and preconcentration of various heavy metals from underground water samples with percentage recovery values of 92–100 ± 1–3%.

Carbon xerogels: Nano- and adsorption textures, chemical nature of the surface and gas chromatography properties

Nano- and adsorption textures, gas chromatography features of carbon xerogels obtained by carbonization of phenol–formaldehyde resins have been studied. The properties of carbon xerogels were compared with those of carbon-containing and silica–alumina adsorbents. Depending on carbonization, they have properties typical of carbons or carbons combined with silica–alumina materials. The application of carbon xerogels in practical gas chromatography has been exemplified.