Showing papers on "Activated alumina published in 2019"

Treatment of fluoride-contaminated water. A review

Abstract: Delivering the right amount of fluoride to drinking water protects the teeth from decay and reduces the risk of cavities. Nonetheless, fluorosis has been diagnosed as the result of excessive exposure of fluoride, which induces brain impairment, muscle disorders and hyperactivity. Fluoride ingestion during the formation of the tooth enamel is the main reason for fluo-rosis, which is characterized by hypomineralization. Dissolution of fluoride-containing rock minerals contributes to naturally occurring fluoride contamination in water. The intentional addition of fluoride to water in dental care is alarming in growing countries such as India. This article reviews the origin of fluoride, the analysis of fluoride derivatives and the technologies to remove fluoride from water. The manuscript presents adsorption techniques for fluoride removal, using different types of adsorbents. The adsorption capacities of adsorbents under various conditions, such as contaminant concentration, adsorbent dosage, time, pH and temperature, are presented. Adsorbent types include alumina, zeolites, organic waste, shell-based and carbon-based including graphite and carbon nanotubes. Defluoridation of water using clays and muds, modified activated alumina, chitosan derivatives and composites are also discussed.

Synthesis and Study of an Efficient Metal-Organic Framework Adsorbent (MIL-96(Al)) for Fluoride Removal from Water

Abstract: Long-term consumption of drinking water that contains excessive amounts of fluoride can endanger human health; therefore, the preparation and application of a high-efficiency defluorination adsorbent for advanced purification of drinking water are of significant interest. This study presents a metal-organic framework adsorbent (MIL-96(Al)) with the granular structure of rice, which was generated by hydrothermal reaction. The specific surface area of MIL-96(Al) was ~220 m2 g-1, and it showed a good thermal stability. Several experiments were conducted wherein conditions, including adsorbent dosage, initial concentration, pH, and coexisting anions, were varied to understand the defluorination performance of the material. Results showed that pH (6–9) and coexisting anions had little effect on the removal efficiency of fluoride. The adsorption isotherm can be described by the Langmuir model, and the theoretical fluoride adsorption capacity of MIL-96(Al) was up to 42.19 mg Fg-1 at 298 K, which is much higher than that of the commonly used activated alumina. The adsorption process of fluoride is endothermic and follows pseudo second-order kinetics. In addition, MIL-96(Al) was shown to still achieve ~61.8% of the adsorption capacity after seven regenerations. This study shows that MIL-96(Al) is a good application prospect and could be widely used to remove fluoride from water.

Remediation of Selenium in Water: A Review

Abstract: Selenium has emerged as a contaminant of concern, which has natural and anthropogenic sources. Treatment of aqueous selenium levels to achieve stringent regulatory water limits in the range of from 5 to 50 μg Se/L poses a challenge. Two anionic forms of inorganic selenium are Se(IV) (selenite) and Se(VI) (selenate) which are the dissolved species of Se most commonly present in water sources. Se(IV) is present under reducing conditions while Se(VI) dominates in oxidizing environments. This chapter summarizes the chemical treatment methods for removing selenium from water, which include adsorption and reduction processes. Examples are given for adsorbing Se(IV) and Se(VI) onto solid surfaces of double hydroxides, activated alumina, chitosan, peanut shells, and biopolymers. Reduction techniques to remove Se(IV) and Se(VI) in water involve the application of zero-valent iron, iron(II) sulfide, and oxides of Fe(II) and Fe(III). Photocatalytic approaches can also be applied to reduce Se(IV) and Se(VI) to obtain removal of selenium from water.

On the Conversion of Bauxite Ores to Highly Activated Alumina Media for Water Remediation

Abstract: Author(s): Haddad, AZ; Pilgrim, CD; Sawvel, AM; Hohman, JN; Gadgil, AJ | Abstract: Good quality drinking water is necessary to maintain a high quality of life. Millions lack access to clean and safe drinking water, and current trends suggest that billions will face acute water shortages in the coming decades. Development of new materials has led to technological impacts on water purification, from desalination membranes to atmospheric water scavenging. However, the most challenging aspect of technological solutions is cost: if the community being serviced cannot afford the solution, it is not likely to be sustainable. Repurposing Earth-abundant materials to replace highly engineered solutions is an atractive solution. Herein, minimal processing of bauxite rocks produces a high-porosity and reactive activated alumina in situ, without purification directly from the ore. This acid-treated, thermally activated bauxite (ATAB) exhibits a high surface area of 401 ± 6 m2 g−1, a 40-fold increase relative to its parent ore, and a 2× increase relative to the state-of-the-art fluoride adsorbent, activated alumina. The composition, preparation, and mechanism of adsorption are studied by X-ray diffraction, X-ray photoelectron spectroscopy, and multiple-quantum magic-angle spinning 27Al nuclear magnetic resonance (NMR). The maximum adsorption density of ATAB is comparable with that of activated alumina, but ATAB requires fewer processing steps, thus warranting future consideration as a primary adsorbent of choice for fluoride removal from water.

Defluoridation of synthetic and industrial wastewater by using acidic activated alumina adsorbent: characterization and optimization by response surface methodology

Abstract: Excessive contamination of fluoride in wastewater is the cause of several chronic health problems. For this purpose, an adsorbent was prepared from alumina by acidic activation using sulfuric acid....

Arsenate and arsenite adsorbents composed of nano-sized cerium oxide deposited on activated alumina

Abstract: Cerium oxide composited activated alumina was prepared and used as arsenate and arsenite adsorbents by oxidation of cerium chloride in H2O2 solution. The preparation conditions affected arsenic adsorption capabilities in the Al2O3–CeO2. Efficient adsorption of arsenic was achieved when CeO2 was deposited on 6.0 g of powdered activated alumina at 0.01 M Ce3+ concentration and H2O2/Ce = 0.5. The arsenic adsorption was particularly enhanced in the presence of the nano-size CeO2 on the Al2O3 support, obeying the Langmuir adsorption isotherm model with maximum adsorption capacities of 13.6 and 10.5 mg/g, respectively, for arsenate and arsenite.

Adsorptive Removal of Phenol by Activated Alumina and Activated Carbon from Coconut Coir and Rice Husk Ash

Abstract: Phenol (C6H5OH) is considered as a serious environmental pollutant, and therefore, the study for its removal from wastewater by adsorption has gained momentum by many researchers. The purpose of this research was to study the phenol removal efficiency using three adsorbents viz. activated alumina and activated carbon from coconut coir and rice husk ash. Initially, the characterizations of the adsorbents were performed. The phenol removal percentage was then investigated in batch experiments with the change of process variables, e.g., initial phenol concentration, contact time, pH, temperature, and adsorbent dose. The experimental results showed that at optimum conditions, the maximum phenol removals for activated alumina and activated carbon from coconut coir and rice husk ash were 21.8%, 95.2%, and 94.23% respectively. These results were tested using several isotherms and kinetic and thermodynamic models. The test of kinetic models showed that pseudo-second-order model was fitted better than the pseudo-first-order model for all three adsorbents. The test of isotherm models showed that the Freundlich isotherm was better for activated alumina and activated carbon from coconut coir, whereas the Langmuir isotherm was better for rice husk ash. The thermodynamic study showed that the adsorption process was non-spontaneous, non-random, and exothermic for activated alumina; spontaneous, non-random, and exothermic for activated carbon from coconut coir; and spontaneous, random, and endothermic for rice husk ash. The safe disposals of the spent adsorbents were also deliberated in this study. The research discovered that the preference of adsorbents for phenol removal was rice husk ash, activated carbon from coconut coir, and activated alumina. The novelty of this study was that the paper had included exhaustive analysis using testing of numerous models viz. pseudo-first-order model, pseudo-second-order model, Reichenberg model, Fick model, Furusawa and Smith model, Elovich model, Boyd model, Langmuir model, Freundlich model, Temkin model, and Dubinin–Radushkevich model.

Magnetic Field Usage Supported Filtration Through Different Filter Materials

Abstract: Currently, methods of water purification and aqueous solutions leading to effective reduction of introduced chemical compounds into water purification systems have become the subject of research. Physical methods have become an alternative, because by subjecting water and aqueous solutions to UV (ultraviolet) radiation or magnetic fields (MF), either ultrasonic or electric, it is possible to influence the change of structure, which results in changes in the properties of water and aqueous solutions. This paper attempts to verify the influence of a weak magnetic field on the removal of iron and manganese compounds in the filtration process on gravel of 1–2 mm granulation, sand of 0.4–0.8 mm granulation, activated alumina and activated carbon. The conducted research proved that MF has a significant influence on the effectiveness of iron and manganese removal from water in the case of alumina, while in the filtration process through other filter materials the effect of MF was small.

Protection of lead in an environment containing acetic acid vapour by using adsorbents and their characterization

Abstract: Historical museums and depositories contain collections with a number of lead objects or historical documents with lead seals. Lead is a metal which has good corrosion resistance under atmospheric conditions. On the other hand, lead corrodes in an activity in an environment which contains volatile organic compounds (mainly acetic acid and formic acid). In a depository environment, sources of volatile compounds can be the historical documents themselves, wood, plastics (those made from cellulose acetate), polyvinyl acetate adhesives, varnishes, oil or emulsion paints, etc. The aim of this work was to compare the efficiency of commercial adsorbents (activated carbon, activated alumina, zeolite, and bentonite) in the acetic acid vapours. The lead corrosion rates were determined by using lead resistometric probes. Activated alumina and activated carbon were found to be the most effective adsorbents of acetic acid vapours. On the other hand, the available zeolite had the worst sorption ability compared with the other tested substances.

Adsorption Equilibria of Water Vapor on Surface-Modified Activated Carbons and Alumina

Abstract: The adsorption equilibria of water vapor on surface-modified activated carbons (ACs) and activated alumina (AA) were measured at 283.15, 293.15, and 303.15 K at relative pressures of up to 0.9. The...

Community-Based Defluoridation of Groundwater by Electrocoagulation Followed by Activated Alumina Adsorption

Abstract: Water is essential to human life, yet over billion people across the world have no access to safe drinking water. It is evident in the report of WHO that there is an excess fluoride concentration in groundwater of more than 25 countries including developed and developing countries across the world. Widespread fluorosis cases related to the presence of fluoride in groundwater supplies are major public health problems. Electrocoagulation is an emerging technology for fluoride removal. Activated alumina is a common adsorbent for fluoride removal. In this study, electrocoagulation along with sand filtration was tried as a pretreatment followed by activated alumina adsorption. This technology has been installed in Chhoto Irga village of Purulia district of West Bengal. The results show that electrocoagulation can remove fluoride to a significant extent. Provision of activated alumina bed helps to take care of fluoride removal in case of the electrocoagulation setup malfunctions. Electrocoagulation removes a significant amount of fluoride, and therefore, the challenge to the subsequent alumina bed is reduced helping to prolong the life of alumina bed before exhaustion. In this design, the alumina bed is split into two columns – lead and lag. It helps to utilize more adsorption capacity of alumina and also allows for a time before regeneration of an exhausted alumina column can be actually performed without jeopardizing the safety of the treated water. The aluminum concentration was found to be below permissible limit in the drinking water. The community-based and self-sustained defluoridation unit is functioning till date.

Wettability analysis of desiccant beads for HVAC systems

Abstract: Vapour adsorption plays a fundamental role in the operation and performance of innovative heat and mass transfer devices for latent heat recovery in HVAC systems. Materials to be used for such devices should present a high affinity with water vapour; at the same time pores should not be flooded in case the surface finds itself in contact with liquid water (e.g., due to moisture formation) and the surface should minimize the wetted parts. From the latter point of view hydrophobic microporous surfaces would be the most suitable; on the contrary, commonly used materials have hydrophilic and/or macroporous surfaces and their behaviour in presence of moisture is still not fully understood. Therefore, this paper is aimed at studying (mostly experimentally, with the support of numerical simulations) wettability and interaction with water, together with adsorption isotherms, of three commercially available desiccant beads (Silica Gel, Silica Gel impregnated with LiCl, Activated Alumina). Results evidence that the behaviour is significantly different between the three materials, even if their static and dynamic wettability is quite similar.

Selenium removal using a bacteria cultured reactor packed with alumimpregnated activated alumina

Abstract: Selenium is a primary pollutant that brings a number of threats to the aquatic lives as well as human beings. Bacterial selenium reduction was observed as an effective way for selenium remediation. However, Se(IV) accumulation may occur during Se(VI) reduction due to the slow reduction rate of Se(IV). In this study, an alum-impregnated activated alumina packed bioreactor cultured with Shigella fergusonii strain TB42616 was applied in order to remove Se(IV) during Se(VI) reduction. Approximately 70% selenium was removed under an hydraulic retention time of 3.1 days with no Se(IV) accumulation observed, indicating that Se(IV) removal was enhanced by the adsorption of the alum-impregnated activated alumina. A 10% more selenium removal was also observed by employing alum-impregnated activated alumina instead of unmodified ones.

Nickel-based reforming catalyst for circulating fluidized bed, preparation method therefor, and application thereof

Abstract: Disclosed are a nickel-based reforming catalyst for a circulating fluidized bed, a preparation method therefor, and an application thereof. The nickel-based reforming catalyst comprises a carrier and active metal nickel supported on the carrier. The carrier is activated alumina microspheres, the particle size thereof is 50-500 μm, the D50 is 80-300 μm, the specific surface area is greater than or equal to 50 m2/g, the total pore volume is greater than or equal to 0.1 cm3/g, and the attrition index is less than 0.1%/h. The method comprises: 1) dissolving a nickel salt and a second active metal salt in water to prepare a mixed salt solution; 2) dissolving hexamethylenetetramine in an organic solvent to prepare a precipitant solution; 3) mixing the mixed salt solution and the precipitant solution, and adding activated alumina microspheres for impregnation, so that active metal nickel and the second active metal are supported on the surface of and in pores of the alumina carrier; 4) adding the precipitant solution into the suspension, and performing reflux or crystallization; and 5) performing drying at a low temperature and calcination at a high temperature. The catalyst is high in reforming activity, low in attrition, and excellent in wear resistance.

A Comparative Study on Removal of Toxic Mercury and Chromium Using Synthesized Inorganic Complex (WOx-EDA) and Compound (AA) Through a Batch Adsorption Process

Abstract: Toxic metals ions are well known undesirable pollutant in drinking water. Since they are barely biodegradable and can be accumulated in human body through the food chain to induce a severe threat to human health; it is of great importance to develop low cost, safe and highly effective adsorbents for the adsorptive removal of those toxic metals. Synthesis and Characterization of Inorganic–organic hybrid Tungsten oxide-ethylenediamine (WO x –EDA) nanowires have been carried out by a simple, low-cost and high-yield solvo-thermal method. Activated Alumina was also synthesized using direct method. Both Tungsten Oxide ethylenediamine and Activated Alumina (AA) were characterized using, Fourier Transform Infrared (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The synthesized inorganic adsorbents adsorption capacities for removing mercury and chromium were investigated using batch adsorption process. The equilibrium data were applied to various sorption kinectic models. The adsorbents adsorptive capabilities were compared. The adsorbents displayed exceptional adsorptive properties; however, WOx-EDA proved to be better adsorbent than activated alumina in terms of removal efficiency. This could be linked to hybrid structure integrated in the functionality of ethylenediamine with the stability of the WO x frameworks. The nanowire morphology and abundant functional amino groups possibly endowed the complex with versatile abilities and highly adsorptive properties. Keywords : Adsorption, Toxic, alumina, Tungsten Oxide Ethylenediamine, Kinetic. DOI : 10.7176/CMR/11-5-03 Publication date :May 31 st 2019

Sorbex : Industrial-Scale Adsorptive Separation

Abstract: The search for a suitable adsorbent is generally the first step in the develpoment of a Sorbex process application. A practical adsorbent has four primary requirements: selectivity, capacity, mass transfer rate, and long-term stability. Sorbex applications have been developed for a wide range of liquid properties, and bulk-phase mass transfer is one of the criteria used in determining process temperature. The simulated countercurrent, solid-liquid contacting in the Sorbex process provides the efficient staging of the separation elements needed for industrial-scale separations. Universal Oil Products has investigated many new adsorptive separations as a result of general market studies as well as specific client interest. Materials such as silica gel, activated alumina, activated carbons, polymeric resins, and molecular sieve zeolites are suitable, practical adsorbents. Traditional adsorbents, such as silica gel, activated alumina, and activated carbon, exhibit large surface area and micropore volume.

Simple desalination process for making agricultural cultivation solution from seawater using natural zeolite and activated alumina

Abstract: We attempted to make agricultural cultivation solution from seawater with a two-step process using natural zeolite and activated alumina. Natural zeolite used in this study is Japanese mordenite-type zeolite with high content of Ca2+ as exchangeable cation. Activated alumina can remove anions, SO42- and Cl-, and divalent cations, Mg2+ and Ca2+, better than monovalent cations, Na+ and K+, from seawater. By treating seawater with natural zeolite, the obtained solution contains higher divalent cations and lower monovalent cations than seawater, due to the ion exchange of natural zeolite, and removal of cations from the obtained solution is higher than that from seawater using activated alumina, while removal of anions is almost same. Radish sprouts can be grown in the solution after two-step treatment of natural zeolite and activated alumina, while they cannot be grown in seawater and the solutions after one-step treatment of natural zeolite and activated alumina. Article DOI: https://dx.doi.org/10.20319/mijst.2019.51.159166 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.

Application of spheroidal agglomerates of γ-Al2O3 in the fluoride removal from aqueous medium

Abstract: A spheroidal agglomerate γ-Al2O3 adsorbent obtained from pseudoboehmite for effective removal of fluoride from aqueous medium was investigated in the present study. The surface properties were characterized by several techniques: XRD, physisorption of N2, FE-SEM/EDS, 27Al NMR, FT-IR Pyridine adsorption, PZ and particle size. Batch experiments were conducted and they were compared with a commercial activated alumina (AA). The process was carried out at pH 5, 7, and 9, then at 25 and 35 oC. Batch experimental results indicated that the spheroidal agglomerates of γ-Al2O3 remove up to 15 mg/g with a higher adsorption capacity than AA of 13 mg/g, at pH 5, studied at 25 and 35 °C. The F−adsorption processes in γ-Al2O3 and AA followed the pseudo-first-order kinetics and the Langmuir isotherm. The results showed an adsorbent effective for removal of F−.

Magnetic Field Usage for the Removal of Iron by Filtration-Assisted Different Filter Materials

Abstract: The conducted research concerned the effect of a magnetic field (MF) on the removal of iron compounds. The tested process was filtration through a quartz sand bed with a grain size of 0.4–0.8 mm. Another examined material was activated alumina. The obtained results proved that the MF had a significant impact on the efficiency of iron removal from a water filtrated trough than activated alumina. It was proven that the effect of the magnetic field on the filtration process using other filtration materials, was insignificant.