Aluminum Precipitation Research Articles

Principles of rational processing of red mud with the use of carboxylic acids

Due to the known limitations of economic nature, the global production complex continues to focus on the most accessible technologies of alumina production, leading to the accumulation of solid waste (red mud), which has created the well-known problem of their processing, and its scale and importance continue to grow in connection with the steady increase in the world volume of aluminum production and consumption. The priority of rational use of natural resources allows us to speak about the preference of principles of deep and waste-free processing of mineral raw materials, which are fully applicable to the processing of red mud, as accumulated raw materials of technogenic origin. At the same time, the key point of this approach becomes the hierarchical division of components into groups of technological products, taking into account the processes that ensure this selective-group division. In this regard, the use of carboxylic acids is of notable interest, as they have a known selectivity to the main components of red mud, which allows to separate low-soluble components (iron and silicon compounds) from light and rare-earth metals with minimum consumption rates. An experimental study has shown that flow-through leaching of thermochemically prepared red mud using formic acid provides high and acceptable recoveries of sodium, calcium, scandium, and rare earth metals. This makes it affordable to use the cheapest method of apparatus-free leaching when implementing this approach on an industrial scale. Experimentally determined the differences in the sequence of elution of sodium, calcium, aluminum and rare-earth metals formates during flow leaching, which creates favorable conditions for concentrating components and separate processing of sampled solutions. The regime parameters of the process that provides complete precipitation of aluminum, scandium and rare earth metals during the neutralization of formate solution with milk of lime, resulting in the necessary prerequisites for further concentration of rare earth metals to obtain technologically significant product are determined. The work was carried out with the financial support of the Russian Science Foundation under the Agreement No. 18-19-00577-П of April 28 2021 of grant for fundamental scientific research and exploratory scientific research.

Novel composite in situ obtained from coal gasification coarse slag and its mechanism of removing phosphate

A novel low-cost hematite–silicon mesoporous composite (HSMC) was synthesized in situ from coal gasification coarse slag (CGCS) via acid modification and its potential for phosphate removal from wastewater was studied. Calcium, aluminum and iron in CGCS were activated by hydrochloric acid, and formed crystalline hematite on the quartz and silicates substrates. Compared with traditional methods of preparing hematite, this in-situ preparation method effectively utilized the iron in CGCS instead of requiring added iron salts, which is highly cost-effective. The specific surface area increased from 4 m2/g for CGCS to 67 m2/g for HSMC, greatly enhancing the phosphate removal ability of HSMC. The maximum adsorption capacity of HSMC for phosphate was 28.62 mg/g, which is more than 28 times higher than that of CGCS. The HSMC had a high point of zero charge (pHPZC) of 7.5, providing good phosphate removal performance over a wide pH range. The phosphate removal mechanism of HSMC mainly involves ligand exchange induced by the large number of hydroxyl groups, inner-sphere complexation induced by the presence of major metal (hydr)oxides, the precipitation of calcium and aluminum with phosphate groups, and some electrostatic adsorption induced by the positively charged surface. The contribution of precipitation to the phosphate removal ability was approximately 27 %. This study provides a new method for the development of phosphate adsorbents while recycling CGCS.

Recovery of Scandium, Aluminum, Titanium, and Silicon from Iron-Depleted Bauxite Residue into Valuable Products: A Case Study

Bauxite residue is a high-iron waste of the alumina industry with significant contents of scandium, aluminum, and titanium. This study focuses on the recovery of Sc, Al, Ti, and Si from iron-depleted bauxite residue (IDBR) into valuable products. Iron depletion was carried out using reduction roasting followed by low-intensity magnetic separation to enrich bauxite residue in Al, Ti, and Sc and reduce an adverse effect of iron on scandium extraction. Hydrochloric high-pressure acid leaching, aluminum precipitation by saturation of the acid leachate, solvent extraction of scandium using di(2-ethylhexyl) phosphoric acid (HDEHP) and tributyl phosphate (TBP), alkaline leaching of the acid residue with subsequent silica precipitation were used to obtain appropriate selective concentrates. As a result, scandium concentrate of 94% Sc2O3, crude alumina of 93% Al2O3, titanium concentrate of 41.5% TiO2, and white carbon of 77% SiO2 were prepared and characterized. Based on the characterization of the treatment stages and the obtained valuable products, the prospect for the application of the suggested flowsheet was discussed.

Hypersaline produced water clarification by dissolved air flotation and sedimentation with ultrashort residence times

Treatment and reuse of some produced waters is made difficult due to their hypersalinity, high concentrations of myriad other dissolved and suspended components, specialized technology requirements (modularity, portability, and short residence times), and lack of existing information on their processing. In this work, produced water containing ∼100,000 mg/L total dissolved solids from the Permian Basin was coagulated with aluminum chlorohydrate (ACH) and flocculated with an anionic high molecular weight organic polymer prior to dissolved air flotation (DAF) and sedimentation to reduce turbidity to < 4 NTU and iron < 0.8 mg/L (>95% removal in both cases) with a total coagulation-flocculation-sedimentation/flotation residence time of only 5 min. Two advantages of DAF over sedimentation were noted: (i) DAF required only half the dosage of the pre-hydrolyzed ACH coagulant to remove ∼90% of turbidity and iron even without the organic polymeric flocculant and (ii) DAF even operated successfully without ACH coagulation (i.e., using only the organic polymeric flocculant) evidencing its lower chemical dosing needs. Further, DAF attained all water quality and operational goals at a recycle ratio of only 12% demonstrating that it outperformed sedimentation to generate clean brine at relatively reduced excess energies necessary for air saturation. Higher DAF recycle ratios reduced turbidity and iron removal possibly due to floc breakage. Colloids were effectively destabilized by double layer compression (due to high water salinity), charge neutralization (via adsorption of Al13 polycations), and enmeshment (precipitation of amorphous aluminum). They were flocculated via interparticle bridging (by the anionic organic polymeric flocculant) to create large, compact flocs facilitating ultrashort flotation/sedimentation times. Direct evidence for these individual coagulation and flocculation mechanisms were obtained using electrophoretic mobility measurements, thermogravimetric analysis, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, optical microscopy, computational image and video analysis, and scanning electron microscopy – energy dispersive X-ray spectroscopy.

Weld Strength and Cracking Susceptibility Analysis of Pulsed TIG Welded Al-Mg-Si Alloy by Experimental Approach

Aluminium is a non ferrous corrosive resistance metal mainly used in automotive coolers, inter coolers and radiators. They are the part of automobile vehicles and made from aluminium alloys. The joints in this application are created by fusion welding process specifically Tungsten Inert Gas (TIG) and Pulsed current TIG (PCTIG) welding process. The working temperature range of different coolers, radiators are 20° C to 300° C and pressure ranges from 2.5 bar to 3.5 bar. During actual working of coolers, the weld joint experiences sudden high level and low level temperature changes. These will create high thermal stresses in the joints. It leads to cracking in the weld region and create failure of the weld joints. Various factors such as mechanical, metallurgical and thermal are responsible for cracking in the weld joints. Range of solidification temperature is one of metallurgical factor, stress generation is mechanical factor and cooling rate of weld metal is thermal factor for cracking. Houldcroft weldability test is employed to identify the cracking susceptibility (CS) of the weld. The current investigation is intended to discover the effect of pulse TIG welding process parameters on the mechanical properties and cracking susceptibility of precipitated aluminium Al-Mg-Si alloy. Diverse pulsed TIG welding process parameters such as peak current (Ip), base current (Ib) and frequency (f) were investigated with the objective of identify the tensile strength, yield strength and cracking susceptibility. The corresponding findings of optimum parameters are 180 peak current (Ip), 60 A base current (Ib) and at 6 Hz frequency (f) with tensile strength of 185.55 MP, yield strength 156.62 MPa. The significant of each parameter for tensile strength are Ip, Ib, Ip*Ib, Ip*f and Ib*f. The corresponding contributions in % are 14.56, 49.49, 12.26, 5.44, 12.15, 5.04, and 1.05 respectively. The statistical method such as Taguchi was employed for experiment design. Weldability test (Fishbone test) was performed on standard specimen and the cracking susceptibility index was identified. The cracking susceptibility index 5.26 % were observed with the value of 180 A of Ip, 80 A of Ib &amp; 2 Hz of frequency (f).The results give an idea about the effect of pulsed TIG welding parameters on mechanical properties and cracking susceptibility.

Selective Precipitation of Titanium, Magnesium, and Aluminum from the Steelmaking Slag Leach Liquor

In this study, a separation process for the selective precipitation of titanium, magnesium, and aluminum from the steelmaking slag leach liquor is developed. This process involves hydroxide precipitation using a single precipitant (NaOH) to selectively recover these elements in a sulfate system without the use of other precipitants, stabilizing agents, or oxidizing/reducing agents. The systematic investigation is carried out to study the effect of several operating parameters, namely precipitation pH level, reaction temperature, stabilization time, and precipitant reagent type, on the metal recovery and product purity. After the process optimization, 83% titanium precipitate purity with 85% recovery alongside >90% magnesium and aluminum precipitate purity with 100% recovery are achieved. The quantification and characterization of the product solids and liquors are carried out to ensure the feasibility and profitability of the developed process. For the industrial-scale operation, the mass balance of the process at a large scale is estimated. The developed process proves to be a promising technique to produce several value-added solid products including TiO2, Al(OH)3, and Mg(OH)2 from the steelmaking slag leach liquor and in turn, help close the material's life cycle.

Study of Programmed Co–Precipitation of Aluminum Doped Zinc Oxide for High Precision Design of Gas Analytical Units

Study of Programmed Co–Precipitation of Aluminum Doped Zinc Oxide for High Precision Design of Gas Analytical Units

MODELLING OF THE PRECIPITATION PROCESS OF ALUMINIUM HYDROXIDE FROM ALUMINATE SOLUTIONS BASED ON FUZZY LOGIC THEORY

The article deals with the application of the fuzzy logic approach to the stage of precipitation of aluminum hydroxide from sodium aluminate solutions obtained from the alkaline solution of raw alunite by hydrogen peroxide as an eco-friendly reagent. Factors influencing the precipitation of aluminum hydroxide in the presence of H2O2 from poor aluminate solutions include the concentration of hydrogen peroxide, the volume of hydrogen peroxide, and other parameters. The application of fuzzy logic to this process allows calculating the probabilities that the parameters can occur not only in one value but in a wide range as well, to find the optimal conditions for obtaining high-yield aluminum hydroxide. Based on the results of the experiments, it is possible to precipitate aluminum hydroxide with a yield of 92% using 15.5 ml of 17% hydrogen peroxide at 25 °C using fuzzy sets suitable for low, medium and high levels, and this figure can be increased or decreased by changing the parameters. The simulation of process control through a fuzzy logic controller is compiled using membership functions in Matlab.

Термическое разложение химически осажденного нанопорошка гидроксида алюминия

In this study, the phase formation of aluminum oxide nanopowder during thermal heating of chemically precipitated aluminum hydroxide was discussed. Nanopowders of aluminum oxide and hydroxide were characterized by X-ray diffraction and thermogravimetric analysis, electron microscopy, energy dispersive X-ray spectroscopy analysis. XRD analysis detected a complex phase composition consisting of different modifications of aluminum hydroxide. It was shown that the precipitated aluminum hydroxide has a flake morphology with an average particle diameter of 5.5 nm. The differential thermal analysis showed that as-deposited aluminum hydroxide undergoes a multiple stage phase transformation. The deconvolution of the experimental differential curve by the Gaussian function and comparison of the temperature intervals of mass change with the literature data revealed that the precipitated aluminum hydroxide powder consists of bayerite α-Al(OH)3 and aluminum oxyhydroxide AlOH. It was found that bayerite is transformed to boehmite in the temperature range of 100 – 400 °C. After that γ-Аl2O3 is formed during the thermal decomposition of boehmite in the temperature range of 400 – 530 °C. The second hydroxide phase formed during the chemically precipitated method has a single stage phase transformation from AlO(OH) to γ-Аl2O3 in the temperature range of 260 – 500 °C. The nanopowder of γ-Аl2O3 formed at the temperature of higher than 600 °C has an equiaxed particle shape and an average size of 7 nm.

Controlled Hydrothermal Precipitation of Alunite and Natroalunite in High-Aluminum Vanadium-Bearing Aqueous System

During the acid leaching process of black shale, with the destruction of the aluminosilicate mineral structure, a large amount of aluminum (Al) is leached, accompanied by the release of vanadium (V). To separate aluminum from the vanadium-containing solution, the precipitation behavior of aluminum ions (Al3+) was investigated under hydrothermal conditions with the formation of alunite and natroalunite. In the solution environment, alunite and natroalunite are able to form stably by the Al3+ hydrolysis precipitation process at a temperature of 200 °C, a pH value of 0.4 and a reaction time of 5 h. When Al3+ was precipitated at a K/Al molar ratio of 1, the aluminum precipitation efficiency and the vanadium precipitation efficiency were 64.77% and 1.72%, respectively. However, when Al3+ was precipitated at a Na/Al molar ratio of 1, the precipitation efficiency of the aluminum decreased to 48.71% and the vanadium precipitation efficiency increased to 4.36%. The thermodynamics and kinetics results showed that alunite forms more easily than natroalunite, and the reaction rate increases with increasing temperature, and the precipitation is controlled by the chemical reaction. Vanadium loss increases as the pH value increases. It can be deduced that the ion state of tetravalent vanadium (VO2+) was transformed into the ion state of pentavalent vanadium (VO2+) in the hydrothermal environment. The VO2+ can be adsorbed on the alunite or natroalunite as a result of their negative surface charges, ultimately leading to vanadium loss.

The activation threshold evaluation of metallization for aluminum nitride ceramic under nanosecond laser pulses in air

Laser activation is an efficient metallization method for producing conductive paths on Aluminum Nitride (AlN) ceramic surface. The problem is that the precipitated aluminum on AlN ceramic is sensitive to laser energy density. The fluence range of laser pulses is the most important parameter to control the activation quality of AlN ceramic. However, It is still very difficult to obtain an accurate value of this parameter, due to the non-uniform intensity distribution of the laser focal spot. Then, a new evaluation method is introduced, by accurately calculating the intensity distribution of the focal spot and changing the scanning velocity. The fluence range of laser pulses is evaluated as 21.53J/(cm^2)~26.02J/(cm^2) for laser activation through the verification experiments. It is also found that the roughness of the flattop laser beam for AlN ceramic should be controlled within ±9.44% when a flattop beam is available.

Natural acid rock drainage in alpine catchments: A side effect of climate warming.

A historical series of aerial photographs spanning more than 70years (1945-2018) revealed that natural acid rock drainage (ARD) has experienced an intensification in the Noguera de Vallferrera alpine catchment (Central Pyrenees) due to climate change during the last decade. ARD manifests by the precipitation of whitish aluminum-compounds that strikingly cover the beds of some gullies and streams in high-mountain catchments. The total length of affected streams has increased from ca. 5km (1945) to more than 35km (2018). Up to 68 water samples were collected in three main areas to determine the spatial variation in acidity and concentration of dissolved metals, representative of surface and subsurface waters. Concentration of aluminum clearly correlates with acidity of waters. Aluminum precipitation occurs where acidic waters, enriched in metals due ARD related to the oxidation of sulfides, mix with non-acidic waters. In addition to aluminum, other potentially toxic trace metals are present at concentrations well above the quality standards for natural waters. Here, we show that climate warming and the severe droughts recorded in the last decade are the most plausible causes for the observed ARD intensification. This result is supported by a good correlation between the regional ascending rate of the periglacial limits (ca. 46m-height/decade) and the rising rate of the maximum elevations at which ARD occurs (ca. 45 to 55m-height/decade). In addition to climatic control, we also show that the local geomorphology is playing a major role. The distribution of periglacial deposits (rock glaciers, protalus ramparts, cones and talus slopes) and deep-seated gravitational slope deformations exert a strong control on the spatial patterns and hydrodynamics of ARD. A better understanding of the phenomenon and the monitoring of its evolution can provide clues on these side effects of climate warming, here and in many other alpine catchments worldwide.

Comparing analytical methods to detect SARS-CoV-2 in wastewater

Wastewater based epidemiology (WBE) has emerged as a reliable strategy to assess the coronavirus disease 2019 (COVID-19) pandemic. Recent publications suggest that SARS-CoV-2 detection in wastewater is technically feasible; however, many different protocols are available and most of the methods applied have not been properly validated. To this end, different procedures to concentrate and extract inactivated SARS-CoV-2 and surrogates were initially evaluated. Urban wastewater seeded with gamma-irradiated SARS-CoV-2, porcine epidemic diarrhea virus (PEDV), and mengovirus (MgV) was used to test the concentration efficiency of an aluminum-based adsorption-precipitation method and a polyethylene glycol (PEG) precipitation protocol. Moreover, two different RNA extraction methods were compared in this study: a commercial manual spin column centrifugation kit and an automated protocol based on magnetic silica beads. Overall, the evaluated concentration methods did not impact the recovery of gamma-irradiated SARS-CoV-2 nor MgV, while extraction methods showed significant differences for PEDV. Mean recovery rates of 42.9 ± 9.5%, 27.5 ± 14.3% and 9.0 ± 2.2% were obtained for gamma-irradiated SARS-CoV-2, PEDV and MgV, respectively. Limits of detection (LoD95%) for five genomic SARS-CoV-2 targets (N1, N2, gene E, IP2 and IP4) ranged from 1.56 log genome equivalents (ge)/mL (N1) to 2.22 log ge/mL (IP4) when automated system was used; while values ranging between 2.08 (N1) and 2.34 (E) log ge/mL were observed when using column-based extraction method. Different targets were also evaluated in naturally contaminated wastewater samples with 91.2%, 85.3%, 70.6%, 79.4% and 73.5% positivity, for N1, N2, E, IP2 and IP4, respectively. Our benchmarked comparison study suggests that the aluminum precipitation method coupled with the automated nucleic extraction represents a method of acceptable sensitivity to provide readily results of interest for SARS-CoV-2 WBE surveillance.

TREATMENT OF SULPHATES-RICH SOLUTIONS THROUGH ETTRINGITE PRECIPITATION WITH INDUSTRIAL REAGENTS

Mine wastewaters are often characterised with high concentrations of sulphates, heavy metals and increased electrical conductivity. It is mandatory for the industry to implement convenient treatment methods in order to reduce these parameters. The aluminium precipitation with the simultaneous formation of ettringite was chosen for laboratory testing as it is appropriate when the concentrations of sulphates have to be reduced– up to 300 mg/l according to the Bulgarian regulatory framework. In the present study synthetic waters were treated, as their composition was similar to that of typical mining effluents. Initially, the pH of the solutions was adjusted to 9.0 with Ca(OH)2 and thus the heavy metals precipitated in the form of hydroxides. Then, an aluminium source was added as Al-cement, industrial Na-aluminate or aluminium oxychloride. The best results in terms of sulphates and electrical conductivity decrease were obtained with Al-cement (69 – 100 % sulphates removal rate), but the quantities of the generated sludges were large, which raises the question of their proper disposal. With the industrial Na-aluminate the rate of removal of sulphates was very low and with AlOCl it was 96%. However, the use of both reagents showed an increase in the electrical conductivity of the treated solutions.

Geochemical Modeling of Iron and Aluminum Precipitation during Mixing and Neutralization of Acid Mine Drainage

Geochemical modeling of precipitation reactions in the complex matrix of acid mine drainage is fundamental to understanding natural attenuation, lime treatment, and treatment procedures that separate constituents for potential reuse or recycling. The three main dissolved constituents in acid mine drainage are iron, aluminum, and sulfate. During the neutralization of acid mine drainage (AMD) by mixing with clean tributaries or by titration with a base such as sodium hydroxide or slaked lime, Ca(OH)2, iron precipitates at pH values of 2–3 if oxidized and aluminum precipitates at pH values of 4–5 and both processes buffer the pH during precipitation. Mixing processes were simulated using the ion-association model in the PHREEQC code. The results are sensitive to the solubility product constant (Ksp) used for the precipitating phases. A field example with data on discharge and water composition of AMD before and after mixing along with massive precipitation of an aluminum phase is simulated and shows that there is an optimal Ksp to give the best fit to the measured data. Best fit is defined when the predicted water composition after mixing and precipitation matches most closely the measured water chemistry. Slight adjustment to the proportion of stream discharges does not give a better fit.

Microbial weathering signatures in lateritic ferruginous duricrusts

Iron-rich duricrusts (canga) that blanket iron ore deposits in tropical regions in Brazil have a complex formation and evolution. The direct role of microorganisms in the biogeochemical cycling of iron and remarkably aluminium, which is critical for the preservation of these duricrusts, is becoming more apparent. In this study we combine nanoscale secondary ion mass spectrometry (NanoSIMS) with Raman spectroscopy and scanning electron microscopy to distinguish highly weathered and recycled grains, portions of which have been metasomatised by iron in solution, from new mineral precipitates within canga. Microbially-accelerated weathering of grains within canga appears to promote iron, aluminium and titanium oxide mineral dissolution. Anatase forms at the boundaries of rutile grains, highlighting titanium dissolution and re-precipitation at the mineral-scale. Titanium is absent from the authigenic cements in canga. Aqueous ferrous iron, which is sensitive to changes in the oxidation potential of the solution, readily oxidises and re-precipitates in the pore spaces in proximity to preserved microorganisms, leaving aluminium as the most abundant cation in solution. Changes in solution pH and/or organic chemistry causes aluminium to precipitate from solution as gibbsite that infills pore spaces as the final geological texture. Evidence for microbially-promoted weathering includes the fossilisation of microorganisms along grain boundaries, in which aluminium, titanium, chromium and iron are depleted. Immobile elements including titanium, chromium and thorium, associated with rounded fossilised biofilms also indicate that microorganisms have completely weathered grains and become fossilised in place, texturally replacing the grain in the process. Microorganisms also play a role in iron and aluminium precipitation, providing sites for mineral nucleation. These results highlight the microscale changes in oxidation potential, pH and organic chemistry throughout canga that are likely to be influenced by the microbiome and associated flora. Understanding the role of microorganisms in iron biogeochemical cycling will contribute to the accelerated re-cementation of iron-rich duricrusts after the completion of iron ore mining, providing a substrate for revegetation using native plant species. This study also sheds light on direct (microfossils) and indirect (biologically-influenced element mobility) biosignatures in iron-rich geological materials.

Emulsions Stabilized with Alumina-Functionalized Mesoporous Silica Particles.

Alumina-functionalized ordered mesoporous silica SBA-15 particles have been proposed to stabilize Pickering emulsions. Functionalization of SBA-15 particles have been performed by depositing alumina using a two-step synthesis (first, silica condensation, followed by alumina precipitation). Three different Al to Si ratios have been prepared. The calcined materials have been characterized by TEM, SEM, XRD, N2 physisorption, and zeta potential, in order to determine key physicochemical properties, and the alumina localization. The emulsifying and stabilizing properties of the calcined particles have been evaluated for water/toluene-based Pickering emulsions.

Variations in soil chemical and physical properties explain basin-wide Amazon forest soil carbon concentrations

Abstract. We investigate the edaphic, mineralogical and climatic controls of soil organic carbon (SOC) concentration utilising data from 147 primary forest soils (0–30 cm depth) sampled in eight different countries across the Amazon Basin. Sampled across 14 different World Reference Base soil groups, our data suggest that stabilisation mechanism varies with pedogenetic level. Specifically, although SOC concentrations in Ferralsols and Acrisols were best explained by simple variations in clay content – this presumably being due to their relatively uniform kaolinitic mineralogy – this was not the case for less weathered soils such as Alisols, Cambisols and Plinthosols for which interactions between Al species, soil pH and litter quality are argued to be much more important. Although for more strongly weathered soils the majority of SOC is located within the aggregate fraction, for the less weathered soils most of the SOC is located within the silt and clay fractions. It thus seems that for highly weathered soils SOC storage is mostly influenced by surface area variations arising from clay content, with physical protection inside aggregates rendering an additional level of protection against decomposition. On the other hand, most of the SOC in less weathered soils is associated with the precipitation of aluminium–carbon complexes within the fine soil fraction, with this mechanism enhanced by the presence of high levels of aromatic, carboxyl-rich organic matter compounds. Also examined as part of this study were a relatively small number of arenic soils (viz. Arenosols and Podzols) for which there was a small but significant influence of clay and silt content variations on SOM storage, with fractionation studies showing that particulate organic matter may account for up to 0.60 of arenic soil SOC. In contrast to what were in all cases strong influences of soil and/or litter quality properties, after accounting for these effects neither wood productivity, above-ground biomass nor precipitation/temperature variations were found to exert any significant influence on SOC stocks. These results have important implications for our understanding of how Amazon forest soils are likely to respond to ongoing and future climate changes.

Potential of Pseudomonas aeruginosa isolated from aluminium-contaminated site in aluminium removal and recovery from wastewater

Abstract This paper discusses the potential of Pseudomonas aeruginosa in treating aluminium containing wastewater and aluminium recovery potential from the produced biomass. The species of P. aeruginosa was isolated from aluminium contaminated site. This isolate had characteristics of acid resistant up to pH 5 and aluminium resistant up to 250 mg/L. Aluminium removal test showed that the isolated P. aeruginosa removed up to 46.08 ± 1.95% of 50mg/L aluminium initial concentration from wastewater. The potential of aluminium recovered from cells biomass reached 34.2 ± 4.25% with centrifugation and 16.8 ± 3.02% without centrifugation. Further application in real condition should accommodate the settling velocity of bacteria and aluminium precipitation during treatment, in order to achieve high removal and recovery efficiency.

Aluminum mobility in mildly acidic mine drainage: Interactions between hydrobasaluminite, silica and trace metals from the nano to the meso-scale

Aluminum precipitates control the hydrochemistry and mineralogy of a broad variety of environments on Earth (e.g., acid mine drainage, AMD, coastal wetlands, boreal and alpine streams, tropical acid sulfate soils, laterites and bauxites, …). However, the geochemical and mineralogical processes controlling Al (and other associated metals and metalloids) transport and removal in those environments are not fully understood. The geochemical system of Paradise Portal (Colorado, USA) comprises sulfate-rich mildly acidic waters, the hydrochemistry of which is directly controlled by the massive precipitation of hydrobasaluminite Al4(SO4)(OH)10·12-36H2O. Three connected but discernible aluminum precipitation stages were identified and described: 1) nanoparticle formation and size decrease along the creek, 2) hydrobasaluminite neoformation on the riverbed, and 3) precipitate accretion and accumulation on the riverbed leading to Al and Fe banded formations. The co-occurrence of Al and Si in the system was observed, recording significant amounts of Si accompanying the three different components of the system (i.e., nanoparticles and fresh and aged Al-precipitates). Also, abrupt and minor changes in the sedimentary record were described and proposed to be the response of the system to seasonal and interannual changes in AMD chemistry. Concerning the mobility of other metals and metalloids, P, Th, V, W, Ti and B showed a tendency to be preferentially incorporated into hydrobasaluminite, while others like Be, As, Se or Ba tend to remain dissolved in the water.