Showing papers on "Activated alumina published in 2015"

Arsenic Adsorption on Lanthanum-Impregnated Activated Alumina: Spectroscopic and DFT Study.

Abstract: Rare earth-modified adsorbents (REMAs) have been widely used to remove oxyanion pollutants from water, including arsenic (As). However, the molecular-level structural information and reactions at the liquid/solid interface are still murky, which limits the design of applicable REMAs. Herein, a lanthanum-impregnated activated alumina (LAA) was synthesized as a representative REMA, and its As uptake mechanisms were explored using multiple complementary characterization techniques. Our adsorption experiments showed that LAA exhibited 2–3 times higher As adsorption capacity than AA. In contrast to the bidentate configuration formed on most metal oxide surfaces, our EXAFS and DFT results suggest that As(III) and As(V) form monodentate surface complexes on LAA through As-O-La coordinative bonding. In situ flow cell ATR-FTIR observed a strong dependence of As-O peak positions on pH, which could be interpreted as the change in the fractions of As(V) surface complexes with zero- to double-protonation on LAA, AA, a...

Enhanced fluoride removal by hydroxyapatite-modified activated alumina

Abstract: Fluoride in drinking water is beneficial at low concentrations but is considered harmful for the human health when present at concentrations exceeding 1.5 mg/L. Prevalence of high concentration of fluoride in drinking water, combined with the nonavailability of alternate viable sources, makes the treatment of the contaminated water an essential task. In this study, we report the synthesis and characterization of a hybrid adsorbent; hydroxyapatite-modified activated alumina (HMAA) prepared by dispersing nanoparticles of hydroxyapatite inside activated alumina granules. The composite adsorbent provided a synergy toward fluoride removal from contaminated drinking water. The hybrid adsorbent possesses a maximum adsorption capacity of 14.4 mg F/g which is at least five times higher than the virgin-activated alumina, which has been used extensively for fluoride removal. HMAA was regenerated using six bed volumes of a solution containing commonly available innocuous chemicals. The adsorbent was subjected to multiple numbers of operating cycles within a column, each cycle consisting of one adsorption run followed by regeneration.

Development of solid super desiccants based on a polymeric superabsorbent hydrogel composite

Abstract: A solid super desiccant was developed based on the concept of impregnating a super liquid hygroscopic agent in a superabsorbent polymer to take advantage of the vast vapour absorption capacity of the hygroscopic agent and the liquid withholding capacity of the superabsorbent polymer. The maximum hygroscopic salt loading was determined based on different salt concentrations in sodium polyacrylate. The newly developed desiccant showed a vapor absorption capacity of 276 ± 20%, which is superior in comparison to that of conventional solid desiccants such as silica gel, activated alumina and molecular sieves. Thus they have great potential in applications requiring solid desiccants such as desiccant cooling, air conditioning, storage of moisture sensitive materials, and dehydration of natural gas.

Filter and methods for heavy metal remediation of water

Abstract: A liquid filter article, including: a housing having an inlet, an outlet, and an adsorbent bed there between, the bed comprising: a first stage having a first adsorbent, the first adsorbent including an activated carbon honeycomb infused with a plurality of zero valent iron nanoparticles ("Fe-AC"); and a second stage having a second adsorbent, the second adsorbent being selected from iron oxide particles supported on activated carbon honeycomb ("FEOX-AC"), iron oxide particles supported on activated alumina honeycomb ("FeOX-AA"), or a combination thereof, wherein the first stage is in fluid communication with the second stage. Also disclosed is a method of using the liquid filter article to remediate heavy metals in water.

Fluoride removal from water using high-activity aluminum hydroxide prepared by the ultrasonic method

Abstract: Different Al(OH)3 powders were used as adsorbents for fluoride removal from water. The results showed that the defluoridation performance of ultrasonically prepared Al(OH)3 (UAH) is much better than that of commercially available Al(OH)3 and is comparable to that of activated alumina, because the ultrasonic waves effectively break the agglomerates in the suspension so that the UAH particles are fine and have a beneficial phase constituent. Furthermore, the residual aluminum concentration in aqueous solution after defluoridation by Al(OH)3 was found to be one order of magnitude lower than that obtained with activated alumina which is below the World Health Organization (WHO) guideline for aluminum (0.2 mg L−1) in drinking water. The defluoridation dynamics and mechanism for UAH are discussed in detail.

Adsorption of fluoride on Mg/Fe layered double hydroxides material prepared via hydrothermal process

Abstract: A nitrate containing Mg/Fe layered double hydroxides (Mg/Fe-LDHs) material was prepared via hydrothermal process and the calcination product (Mg/Fe-LDHO) was used as adsorbent to remove fluoride from aqueous solution. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and pHpzc analysis were used to characterize the samples. Inductively coupled plasma-atomic emission spectrometry (ICP-AES) was employed to analyse the dissolution of the metal ions from the synthesized adsorbent and commercial activated alumina respectively. Compared with commercial activated alumina, the synthesized adsorbent entirely avoided the potential risk of alumina and had a lower leakage of metal ions. A series of batch experiments were performed to investigate the effects of various experimental parameters, such as calcination temperature, adsorbent dosage, fluoride concentration, initial pH, contact time, adsorption temperature and co-existing anions. The results showed that 270 °C was the optimal calcination temperature. The adsorption rapidly occurred in the initial 45 min and adsorption equilibrium was established within 2.5 h. Maximum desorption of 97.2% was achieved in the fluoride desorption studies at different pH. The adsorption data were well described by the pseudo-second-order kinetics model and the Langmuir isotherm model, and the adsorption capacity calculated by Langmuir equation was 28.65 mg g−1. In addition, the effects of co-existing anions on the adsorption capacity declined with the following order: PO43− > CO32− > SO42− > NO3− > Cl−. It can be concluded that the synthetic adsorbent in this study is a promising material for fluoride removal from solutions.

Defluoridation of aqueous solution using alkali–steam treated water hyacinth and elephant grass

Abstract: Inexpensive and abundantly available water hyacinth petioles and elephant grass leaves, ground into powder form after alkali–steam treatment, have been studied for their fluoride removal potential. About 85% of fluoride present within 5 mg/l NaF-spiked distilled water could be removed using only 1.0 g of treated water hyacinth and 1.5 g of similarly treated elephant grass. Compared to activated alumina, a commonly used defluoridation agent that removes about 2 mg of fluoride per gram of adsorbent, treated water hyacinth (that removed about 5 mg of fluoride per gram of adsorbent) and elephant grass (that removed about 7 mg of fluoride per gram of adsorbent) exhibited greater fluoride removal efficiencies. Fluoride removal efficiency was found to decrease with increasing pH and anion concentrations of fluoride solution and increase with duration of exposure. Chemical characterization of these biosorbents before and after exposure to fluoridated water indicated that the fluoride removal process is attributable to chemical adsorption driven primarily by C─F bond formation and hydrogen bonding between fluoride ions and protonated surface groups of the biomasses. The process also appears to be advantageous because it is inexpensive, does not produce sludge, or increase water hardness, or release hazardous leachates.

Removal of arsenic from drinking water using dual treatment process

Abstract: This paper focuses on determining an efficient and simple method to remove arsenic from groundwater. Arsenic is a naturally occurring element widely distributed in the earth’s crust. Arsenic is very toxic when found in large quantities in drinking water. This report documents the selected treatment method and laboratory experimentation of arsenic removal from drinking water in small water delivery systems and domestic water systems. The objective is to expand upon research of new and existing arsenic removal technologies or promote a new, alternative process. Several treatment technologies have been considered to perform this function, but cost and reliability concerns prompted the decision to analyze small-scale, community-based filtration units, specifically. Based upon initial test data, the use of dual treatment method comprising of oxidation-coagulation-filtration and adsorption by activated alumina has proven to be more economic having more capacity and superior reliability as compared to other arsenic removal processes using various other media.

Arsenic sorption onto titanium dioxide, granular ferric hydroxide and activated alumina: Batch and dynamic studies

Abstract: The aim of this work was to evaluate and compare the efficiencies of three different adsorbents for arsenic (As) removal from water: titanium dioxide (TiO2), granular ferric hydroxide (GFH) and activated alumina (AA). Equilibrium experiments for dissolved arsenite and arsenate were carried out through batch tests. Freundlich and Langmuir isotherm models were adopted and their parameters were estimated by non-linear regressions. In addition, dynamic experiments were performed in mini fixed bed columns and breakthrough curves were obtained for each combination of sorbate/adsorbent. Experimental results obtained by column assays were compared with predictions of well-known breakthrough models (Bohart–Adams and Clark). Results indicate that As(V) is more easily adsorbed than As(III) for AA and GFH, while TiO2 has a similar behavior for both species. The titanium-based material is the most efficient adsorbent to carry out the process, followed by the GFH.

Removal of cyanide in aqueous solution by oxidation with hydrogen peroxide in presence of activated alumina

Abstract: This work is dedicated to the removal of free cyanide from aqueous solution by oxidation with hydrogen peroxide H2O2 catalyzed by neutral activated alumina. Effects of initial molar ratio [H2O2]0/[CN−]0, catalyst amount, pH, and temperature on cyanide removal have been examined. The presence of activated alumina has increased the reaction rate showing thus, a catalytic activity. The rate of removal of cyanides increases with rising initial molar ratio [H2O2]0/[CN−]0 but decreases at pH 10 to 12. Increasing the alumina amount from 1.0 to 30 g/L has a beneficial effect, and increasing the temperature from 20 °C to 35 °C improves cyanide removal. The kinetics of cyanide removal has been found to be of pseudo-first-order with respect to cyanide and the rate constants have been determined.

Aluminium hydro(oxide)-based (AO) adsorbent for defluoridation of drinking water: Optimisation, performance comparison, and field testing

Abstract: In this study, the performance of different aluminium hydroxide.based adsorbents was compared in terms of fluoride adsorption capacity, potential for repetitive regeneration, surface acidity and surface site concentrations. The adsorbents were aluminium hydro(oxide) (AO), activated alumina (AA), and pseudoboehmite (PB). The AO adsorbent was synthesised at different OH:Al ratios to optimise the fluoride adsorption capacity. The AO was pilot tested in a rural community in the Ethiopian Rift Valley where groundwaters are heavily enriched with fluoride. The maximum fluoride uptake was achieved for the AO adsorbent synthesised at OH:Al ratios between 2.5 and 2.7. The fluoride adsorption capacity of the adsorbents determined from mini-column studies was found to be 10.6, 1.9, and 2.4 mg/g for AO, AA, and PB, respectively. This significant difference in fluoride adsorption capacity is strongly related to the surface acidity and surface site concentration. The surface acidity (1.57 meq/g) and surface site concentration (0.74 meq/g) for AO is higher than that for AA and PB. The elemental composition analysis showed that AO has a lower % Al2O3 content than AA and PB, but higher sulphate (19.4%) and iron (2.2%) content. High resolution 27Al Magic Angle Spinning Nuclear Magnetic Resonance (27Al MAS NMR) spectra of AO, AA, and PB were recorded, to analyse the coordination geometry of solid Al species and the results showed that aluminium is coordinated octahedrally and tetrahedrally in all cases. Regeneration experiments showed that AA and PB can be regenerated for more than 3 cycles, whereas the potential for regeneration of AO for more than 3 cycles is limited. The results from a community defluoridation plant showed that fluoride in the feed water (8.10 mg/.) is removed below 0.1 mg/.. The average adsorption capacity was determined to be 2.11 mg/g based on continuous field monitoring results obtained until the fluoride content in the treated water exceeded the breakthrough value of 1.5 mg/.. No major operational problems and complaints from the beneficiaries were experienced during operation. Keywords : fluoride, adsorption, surface acidity, regeneration, defluoridation, Ethiopia

Preparation and Characterization of Polyalthia longifolia Based Aluminaas a Novel Adsorbent for Removing Fluoride from Drinking Water

Abstract: This research addresses i) synthesis of an alumina composite based on high capacity adsorbent using a leaf as a template and ii) the issue of handling spent regenerant resulting from regeneration of such high capacity adsorbents. A low-cost composite type adsorbent has been synthesized for removal of excess fluoride from drinking water, using Polyalthia longifolia (false Ashoka tree) leaf as a template and alum as a source of alumina. The composite adsorbent having heterogeneous phases of Al(OH)3 and Al2O3 is associated with carbon and free Al(OH)3 and alumina has been identified using XRD, SEM, FTIR and BET surface area analysis. Batch adsorption experiments were carried out including the effect of various physico-chemical parameters, such as adsorbent dose, pH, contact time, initial fluoride ion concentration and temperature to ascertain optimal performance conditions. The elemental composition of material and SEM analysis suggests a composite material with different phases. Polyalthia longifolia based adsorbent (PBA) effectively removes fluoride with substantially high adsorption capacity of 17.57 mg g-1 at initial fluoride concentration of 5 mg l-1 using very low dose of 0.4 g l-1 as compared to 1.82 mg g-1 for activated alumina. PBA has been regenerated to the tune of about 80% using alum solution. The spent regenerant has been subjected to two new options i) recovery of alum and formation of chitosan/CaF composite by treating with slaked lime and ii) immobilization of AlF in chitosan to form chitosan/AlF composite. These composites may prove to be useful optic materials for UV absorption.

Evaluation of Novel Modified Activated Alumina as Adsorbent for Arsenic Removal

Abstract: In this research work, the feasibility of using novel activated alumina (AA) and modified AA adsorbents for arsenic (As) removal from drinking water was evaluated. A sol-gel derived activated alumina adsorbent was prepared. Equilibrium adsorption studies were conducted to evaluate the As removal efficiency of synthesized and modified adsorbents. Results on As adsorption using Solgel AA and modified Solgel AA adsorbents demonstrated that ZnO nanoparticle-modified AA (Nanogel AA) provided better adsorption performance. The high As adsorption capacity of Nanogel AA is attributed to the enhanced pore textural and surface properties as well as to the pH independency of the adsorbent. The Freundlich adsorption isotherm fitted well with the adsorption of arsenic over modified AA.

Fluoride removal by industrial, agricultural and biomass wastes as adsorbents: review

Abstract: Fluoride and fluorosis issues are common in a few nations including India. Fluorosis is pandemic in more than 20 states of India. The fluoride comes into ground water by various ways, for example, weathering of rocks, industrial effluents and geochemical reactions. Alternate wellsprings of fluoride come to people in the form of air, foods, cosmetics, and so on.The traces of fluoride in ground water is beneficial for strengthening the dental enamel. Fluoride in overabundance amount higher than 1.5 mg/l causes dental and skeletal fluorosis other than infertility, kidney harm and affects nervous systems as well. The fluoride removal from drinking water and wastewater has been successful by different techniques, for example, coagulation and precipitation, adsorption, ion-exchange, membrane separation, dialysis, electro-dialysis, electrocoagulation and so on. Adsorption process for defluoridation has favoured for the most part in developing countries as it is techno-economical viable method, environmental friendly and straightforwardness in operation. The various adsorbents including activated carbon, activated alumina, metal oxides-hydroxides, bone chars and agricultural and industrial wastes were attempting to keep up the standard limit of fluoride concentration in drinking water by adsorption. Usage of plant materials and agricultural wastes as adsorbents are most adopted in developing country like India in light of the fact that they are low cost materials, available in abundance, biodegradable and natural existence. The industrial by-products are additionally needed to reuse them in advantageous ways for defluoridation as accessible in huge amount and economical. This paper reviews the fluoride uptake capacities of industrial by-products, agricultural wastes and biomass materials from plants, grass, etc. and their modified forms as adsorbents in batch and column performance against different experimental limits.

Enhancement of Saharan groundwater quality by reducing its fluoride concentration using different materials

Abstract: According to the environmental protection regulations, fluoride concentration is considered as a substance of priority for assessment of drinking water quality to determine their impacts on the environment and public health. Saharan groundwater (Algeria) contains an excess of fluoride ions. Regular consumption of this water by the population of the region may cause endemic fluorosis. To solve this problem, we propose to treat this water by adsorption on different materials, such as activated alumina (AA), sodium clay (SC), and hydroxyapatite (HAP) in order to enhance its quality by reducing its fluoride concentration. The maximum adsorption is achieved with an adsorption capacity of the order of 0.9, 0.667, and 0.370 mg/g and with a percentage of 90, 83.4, and 73.95% for AA, HAP, and SC, respectively. Indeed, the acidity and alkalinity of the medium significantly affect the adsorption of fluoride ions. Results deduced from the curves of adsorption isotherms of fluoride ions showed that the retenti...

Photocatalytic degradation of humic acids using substrate-supported Fe3+-doped TiO2 nanotubes under UV/O3 for water purification

Abstract: In this paper, Fe(3+)-doped TiO2 nanotubes (Fe-TNTs) were successfully synthesized using hydrothermal method. Four different types of substrates, more specifically, ceramsite, zeolite, activated alumina, and activated carbon (AC), have been investigated in the study. The substrate-supported Fe-TNTs were used to effectively decompose humic acids (HAs) in water under O3/UV conditions. The experiment results show that the highest photocatalytic activity was obtained in the presence of AC-supported 1.0 atomic percent (at.%) Fe-TNTs calcined at 500 °C, as HAs was removed by 97.4%, with a pseudo-first-order rate constant of 0.126/min. The removal efficiencies of HAs reduced when the catalysts was repeatedly used, since the amount of adsorption sites of the supporting substrates decreased. However, even after the catalyst was repeatedly used for five times, the removal efficiency of HAs in the presence of AC-supported catalyst, which was 78.5%, was still sufficient in water treatment. The enhanced photocatalytic activity of AC-supported Fe-TNTs was related to a synergistic effect of AC adsorption and Fe-TNT photocatalytic ozonation.

Engineering application of activated alumina adsorption dams for emergency treatment of arsenic-contaminated rivers

Abstract: A batch of lab-based adsorption experiments were performed to investigate the arsenic (As) removal efficacy by activated alumina. Four factors including contact time, pH, initial As concentration and different coexisting ions were examined. The adsorbent made of activated alumina (AA) with particles of 2–4 mm diameter showed a high As removal efficiency and the As concentrations of the samples were below 0.05 mg/L when the hydraulic retention time (HRT) was operated above 5 min. The As concentrations of the samples could remain below 0.05 mg/L for 30 days. A series of AA adsorption dams coupled with several other supporting adsorption techniques were employed for As-contaminated river restoration. The engineering project functioned well, and the effluent As concentration was below 0.05 mg/L when the influent was between 0.2 and 0.7 mg/L, which met the discharge requirement of the Surface Water Quality Standards criteria III in China. The results demonstrated that AA adsorption dams could be applied for em...

Graphene-decorated porous ceramics for efficient removal of Cr(VI)

Abstract: Porous ceramics (such as activated alumina (AA)) is a common adsorbent material in water purification. Its purifying capacity can be greatly improved through modification of porous ceramics. In this paper, a facile method has been established to prepare a graphene-decorated porous ceramic (GDPC) material. Citric acid (CA) was absorbed into the inner surface of the porous ceramics and transformed to graphene via sintering. The as-prepared material showed excellent adsorption capacity for chromium (Cr(VI)) over a wide range of pH (2 to 10) compared with the blank sample. The maximum uptake capacity for Cr(VI) exceed 699.43 mg g−1. UV and ICP-OES tests indicated that chromium ions in aqueous solution were completely removed via the GDPC. Thus the GDPC could be a potential adsorbent for the environmental cleanup, especially for the chromium-contained wastewater disposal.

Development of a Household Water Defluoridation Process Using Aluminium Hydroxide Based Adsorbent.

Abstract: In this study, the removal of fluoride from water using aluminium hydroxide based adsorbent has been investigated in continuous operation. The effect of fluoride influent concentration, feed flowrate, and adsorbent bed height onto the breakthrough characteristics of the adsorption system were examined. The fixed-bed adsorption system was found to perform better with lower influent fluoride concentration, lower flowrate, and higher bed depth. Thermodynamic evaluation using the bed depth service time model indicated that the fluoride adsorption capacity was 25.8 mg F-/g of adsorbent, which is high compared to commercially available activated alumina (1.8 to 1.9 mg/g). Kinetic studies showed that the rate of adsorption in continuous studies was in the range of 6.12×10(-3) to 39.3×10(-3) L/mg.h under different operating conditions. The household defluoridation unit (HDU) was tested at an up-flow mode and it was determined that the HDU packed with 0.9 kg of adsorbent with 28.3 cm of bed depth resulted in a specific safe water yield of 823.79 L. Regeneration of the exhaust media using 1% NaOH and 0.1 M HCl showed that the adsorbent could be reused. The estimated running cost of the unit was 2.0 U.S. dollar/m3 of treated water, with the potential to minimize further. Hence, it was concluded that the proposed method is simple and exhibits superior performance for the treatment of fluoride-contaminated water with the potential for household application.

Highly Efficient Removal of Chromium (VI) from Water by Mesoporous Alumina

Abstract: Mesoporous Activated alumina (MAA) was used for removal of hexavalent chromium fromwater. The activated alumina wascharacterized for Powder X-ray diffraction (XRD), Scanning Electron Microscope (SEM).The characterized adsorbent was evaluated for the removal of chromium (VI) from water. The adsorption efficiency of activated alumina was studied by batch adsorption study. MAA exhibit highly efficient removal with more than 99% removal at initial concentration of 5 mg/l. The experimental data was fitted to Langmuir and Freundlich adsorption model and found that Langmuir model fits well confirming mechanism of monolayer adsorption on uniform surface. The adsorption kinetic data was well described by pseudo first order kinetics.The residual Cr(VI) concentrations after treatment with MAA were below the prescribed limits as per WHO and Indian Drinking water standards.

Methods and Apparatus For Selective Removal of Silica from Strong Brines

Abstract: Treatment of silica-laden wastewater is herein described. Unlike traditional fixed bed designs that cannot use an activated alumina sorbent due to the high volumes of sorbent needed in a fixed bed design, the herein disclosed continuous cycle enables smaller volumes of sorbent to be used and thereby enabling activated alumina to be used. Adsorption, regeneration, and rinse regions are provided. Activated alumina is provided to the adsorption region along with silica-containing wastewater. A pH below the zero point charge for alumina is set, and this causes the silica to load onto the alumina. Gravity brings the loaded alumina to the regeneration region, having a pH equal to or greater than the zero point charge of alumina such that the silica is released from the alumina. The silica and alumina are further separated in the rinse region, and the regenerated alumina can then be returned to the adsorption region.

Ammonium nitrate products and method for preparing the same

Abstract: The invention refers to a free-flowing ammonium nitrate (AN) product which comprises a mixture of AN particles and activated alumina (AA), a process for preparing the same and the use of AA as free-flowing external additive for AN particles.

Исследование свойств наполнителей противопригарных покрытий

Abstract: The influence of regimes of mechanical activation on geometric, energetic, and chemical parameters of activation of alumina used as a component of dressing coatings. The studies made it possible to determine the most rational treatment modes, notably, using an AGO-2 planetary-centrifugal mill: activation time is 20 min at material : balls ratio of 1 : 3. The dependences of the average particle size, the total surface, and variation in their phase composition on activation conditions are established. It is shown that the average particle size of alumina particles decreases from 3,2 to 1,6 μm with an increase in their total surface from 31·103 to 61·103 cm2/cm3. X-ray lines also broaden without decreasing their intensity; consequently, now new phases are formed in the course of activation during the decomposition of gibbsite γ-Al2O3. Two fractions are present in mechanically activated alumina, notably, initial α-Al2O3 having the crystallite size of the order of 1 μm (which corresponds to its very narrow lines in X-ray diffraction patterns of initial alumina) and finely dispersed α-Al2O3 with crystallite sizes approximately of 0,1 μm (which usually corresponds to the initial broadening stage of the lines of a new phase), which is formed due to the decomposition of gibbsite.