Formation Of Aluminum Hydroxide Research Articles

Improved bacterial elimination in wastewater through electrocoagulation: hydrogen generation, adsorption of colloidal bacteria-flocks, and electric field bactericidal action

ABSTRACT Electrocoagulation (EC) has emerged as a promising method for wastewater treatment, offering efficient removal of various contaminants, including bacteria. This study investigates the mechanisms underlying bacterial removal in EC processes, mainly the hydrogen-mediated foam, the effect of operational parameters, including initial pH, current density, and reaction time, and evaluates the associated energy consumption. The EC reactor employed aluminum electrodes and operated at a current intensity of 3.0 A. It demonstrated a notable bacterial removal efficiency, with 120.102 UFC ml−1 of mesophyll floral aerobic bacteria removed through colloid bacteria-flocs precipitation, 440.102 UFC ml−1 via bacterial-bulls flotation from foam, and 117.102 UFC ml−1 through attraction at the electrodes’ plate surface. We found that the EC process leads to the formation of aluminum hydroxide and ferrous hydroxide precipitates, which adsorb bacteria and facilitate their removal from the wastewater via electrostatic forces with an energy consumption of 45 kWh/m3. Overall, this research provides valuable insights into the mechanisms governing bacterial removal in EC and highlights the importance of energy consumption analysis for optimizing wastewater treatment processes.

Radiolytic Gas Production from Aluminum Coupons (Alloy 1100 and 6061) in Helium Environments-Assessing the Extended Storage of Aluminum Clad Spent Nuclear Fuel.

Corrosion of aluminium alloy clad nuclear fuel, during reactor operation and under subsequent wet storage conditions, promotes the formation of aluminium hydroxide and oxyhydroxide layers. These hydrated mineral phases and the chemisorbed and physisorbed waters on their surfaces are susceptible to radiation-induced processes that yield molecular hydrogen gas (H2), which has the potential to complicate the long-term storage and disposal of aluminium clad nuclear fuel through flammable and explosive gas mixture formation, alloy embrittlement, and pressurization. Here, we present a systematic study of the radiolytic formation of H2 from aluminium alloy 1100 (AA1100) and 6061 (AA6061) coupons in “dry” (~0% relative humidity) and “wet” (50% relative humidity) helium environments. Cobalt-60 gamma irradiation of both aluminium alloy types promoted the formation of H2, which increased linearly up to ~2 MGy, and afforded G-values of 1.1 ± 0.1 and 2.9 ± 0.1 for “dry” and “wet” AA1100, and 2.7 ± 0.1 and 1.7 ± 0.1 for “dry” and “wet” AA6061. The negative correlation of H2 production with relative humidity for AA6061 is in stark contrast to AA1100 and is attributed to differences in the extent of corrosion and varying amounts of adsorbed water in the two alloys, as characterized using optical profilometry, scanning electron microscopy, Raman spectroscopy, and X-ray diffraction techniques.

Bioleaching/enzyme-based recycling of aluminium and polyethylene from beverage cartons packaging waste

Multilayer materials are frequently used in food and beverage packaging, delivering favourable properties for storage and protection. However, their complex construction, consisting of several layers of plastics, aluminium and paperboard (i.e., beverage cartons) makes them difficult for complete material recycling. Currently, the common treatment process used is hydropulping, resulting in partial recovery of the paperboard only. The so-called beverage carton reject fraction, consisting of plastics, aluminium, and some fibres, is incinerated for energy recovery, leading to the loss of secondary resources. Here a novel recycling procedure based on enzymatic hydrolysis of cellulose, followed by bioleaching of aluminium finally allowing recovery of pure polyethylene is presented. Application of a cellulase cocktail resulted in the release of 15 mM glucose within 24 h, followed by over 95% aluminium bio-extraction within 3–7 days using bacterially produced sulfuric acid. Dissolved aluminium could afterwards be completely recovered by selective precipitation at pH 6.4, resulting in the formation of aluminium hydroxide. Pure polyethylene at the end of the process was used in re-processing and film production, showing comparable results to commercially available materials. Additionally, scaling up in a 1 L stirred tank reactor proofed the feasibility of the process in reject recycling. With this innovative, environmentally friendly recycling method, maximum material recovery could be achieved, leaving a minimum of impurities for incineration (<5%) behind.

Chemical mechanisms and kinetic modeling of calcium aluminate cements hydration in diluted systems: Role of aluminium hydroxide formation

Calcium aluminate cements are niche cements used in the refractory industry and in non-structural applications for building chemistry with short return-to-service delay. The later applications use theses cements in combination with calcium sulfates for long-term stability. By being niche cements, the knowledge of calcium aluminate cements hydration is not as extensive as that of Portland cement. In the present paper, the calcium aluminate cements are studied in diluted suspensions as a function of different parameters such as the suspension concentration or the quantity of added calcium sulfates. The objective is to identify their baseline chemical mechanisms. This work demonstrates the essential role of hydroxide ions fluxes, i.e. quantity going in and out of the liquid phase per unit of time. The main quantitative flux is the formation of aluminium hydroxide but the activation of this reaction is difficult. This difficulty allows calcium aluminate to be used as cement by creating a dormant period (workability) for the overall reactivity. The identification of the key role of aluminium hydroxide formation explains the influence of the temperature, some mechanisms of setting admixtures and the early age of calcium aluminate cements.

Graphene oxide—Polymethyl methacrylate coatings for Corrosion protection of aerospace aluminium alloy 7075—T651 surfaces

We report a corrosion study on Al 7075—T651 surface. The purpose of the study is to use Graphene oxide—Polymethyl methacrylate (GO—PMMA) coating as corrosion resistant layer on Al 7075—T651, an alloy of aluminium mainly used in aerospace industries. The study is done with and without GO—PMMA coating on Al 7075—T651 respectively, by varying the exposure time of material (24, 48 and 72 h) with HCl in atmospheric condition. The formation of corrosion is resisted by the GO—PMMA coated samples. The effect is studied by material characterization and non-destructive evaluation (NDE) techniques. The formation of aluminium hydroxide in uncoated samples is confirmed by Raman spectroscopy and x-ray diffraction (XRD). Corrosion formation, GO—PMMA coating on plain and coated samples are clearly visible in Scanning Electron Microscope (SEM) study. Shift in current is observed in I–V Characteristics study, due to pitting in plain samples. Material loss is observed, to be low in GO—PMMA coated samples, using pulsed thermography. The work proves that the GO—PMMA coating is very effective in corrosion resistance.

Pre-treatment and utilisation of municipal solid waste incineration bottom ashes towards a circular economy

Two billion tonnes of municipal solid wastes are generated globally, and incineration of non-recyclable wastes is done extensively in developed countries. A large part of the resulting ashes remains unutilized due to various obstacles and ends up in landfills. Use in concrete as aggregate or supplementary cementitious material is a potential high value application, which is deterred mainly by presence of metallic aluminium that causes cracks from aluminium hydroxide formation and high porosity from hydrogen release on reaction with water. Various researchers have used treatment with alkalis prior to utilization as a mitigation strategy. This paper studied an alternative technique, pre-treatment by immersing ash in water allowing the aluminium to react in presence of inherent alkalis in the ash and accelerating the reaction by increasing temperature. The effect of this treatment on mitigating expansion and hydration and strength development of mortar with 25% replacement of cement by ash has been studied and is reported in this article. The treatment was found to be effective and the strength of mortar with 25% pre-treated ash replacement exceeded 85% of that of the control mortar at 90 days of age. A possible beneficiation scheme for the industrial treatment of ashes to maximise the resource utilisation is also proposed.

Effective removal of cefazolin from hospital wastewater by the electrocoagulation process.

The present study evaluated the treatment of hospital wastewater by the electrocoagulation process using aluminum and iron electrodes. The effects of pH, voltage and reaction time on the removal efficiencies of the antibiotic cefazolin, chemical oxygen demand (COD) and turbidity were investigated. The results showed that by increasing reaction time and input voltage, the removal efficiency of pollutants was increased. The highest removal efficiency of cefazolin, COD, and turbidity occurred at neutral pH, which may have been related to the formation of aluminum hydroxide (Al(OH)3) flocs through the combination of aluminum released from the surface of the electrode and the hydroxide ions present in the solution. The conductivity of the treated wastewater at neutral to alkaline pH decreased compared to acidic pH, which may have been due to the adsorption of anions and cations from the solution by the Al(OH)3 flocs. The electrode and energy consumption in the present study was higher than in other studies, which may have been due to the high concentration of COD in and the turbidity of the solution.

Effect of curing temperature and relative humidity on the hydrates and porosity of calcium sulfoaluminate cement

Abstract The main objective of this study was to investigate the effect of curing temperature and relatively humidity (RH) on the hydrates and porosity of calcium sulfoaluminate (CSA) cement pastes. A series of experiments including X-ray diffraction (XRD), thermogravimetric (TG) and mercury intrusion porosimetry (MIP) were performed. The results indicate that the formation of hydration products and pore characteristics of CSA cement are dependent on the curing conditions. The formation of ettringite is favor of curing with low temperature and high RH. The rate of formation of aluminum hydroxide (AH3) and monosulfoaluminate (Ms) is well promoted when curing temperature and RH are rising. The total porosity of CSA cement paste is gradually decreased by curing with low temperature and high RH.

Synthesis and characterization of magnetic nanoparticles from raffinate of industrial copper solvent extraction plants

Abstract Magnetite nanoparticles successfully produced from the raffinate of an Iranian industrial copper solvent extraction unit. Removal of iron from leach solution is important for successful operation of hydrometallurgical recovery of copper. It includes reduction of Fe3+ to Fe2+ followed by precipitation of Al3+ as Al(OH)3, oxidation of Fe2+ to Fe3+ (the theoretical ratio for stoichiometric, Fe3+/Fe2+ = 2) and finally synthesize of nano-sized magnetite. Two different Fe2+ oxidation agents namely H2O2 and O2 were used. Using XRD, FTIR, FESEM, and TEM analysis, the phase structure, morphology, and size distribution of magnetic nanoparticles, produced under different conditions, were evaluated and compared. Under optimum conditions spherical magnetic nanoparticles with an average size of about 25 ± 3 nm can be produced. The XRD analysis of produced nanoparticles after purification of raffinate showed the slight formation of aluminum hydroxide, goethite and hematite phases. In addition, the VSM results indicate the highly ferromagnetic behavior for samples at the room temperature with a saturation magnetization of 41.25 emu/g.

Exploring Hybrid Imogolite Nanotube Formation via Si/Al Stoichiometry Control.

Hybrid imogolite aluminosilicate nanotubes with methylated internal surface can be obtained by introduction of the corresponding organosilane during their synthesis. However, similarly to pristine imogolite, a number of side products, including proto-imogolite (open-imoLS), allophanes, and aluminum hydroxides, are formed, which ultimately impact on the properties of the dispersions. In order to minimize the proportion of these side products, we have here systematically explored the impact of the initial Si/Al ratio on the content of hybrid imogolite dispersions before and after dialysis. By combining cryo-transmission electron microscopy, inductively coupled plasma mass spectrometry, infrared spectroscopy, and small-angle X-ray scattering, we evidenced that the Si/Al ratio has a large impact on the formation of aluminum hydroxides that can be minimized with a slight excess of Si precursor. However, a large excess of Si is detrimental to the reaction yield leading to an important proportion of proto-imogolite. We propose that the optimal Si/Al ratio of ca. 0.6 can both minimize the proportion of aluminum hydroxides and proto-imogolite. These results suggest that the dynamic and therefore reactive character of imogolite dispersions may have been so far underlooked.

The Impact of Aluminium Salt Dosing for Chemical Phosphorus Removal on the Settleability of Activated Sludge

The use of metal salts like aluminium in the precipitation of phosphorus in activated sludge plants has increased considerably in recent years due to the need to achieve tighter discharge consents for phosphorus in treated wastewater effluent. The impact of aluminium salt (Al3+) dosing on the settleability of activated sludge as a function of zone settling velocity (ZSV) and stirred specific volume index (SSVI) were investigated in batch settleability tests over a three-year period. The results showed that ZSV increased with increasing dose of aluminium salt as SSVI decreased. This trend was observed for dosing concentrations of less than 100 mg/L. At a dose concentration &gt;100 mg/L, the trend was reversed as ZSV decreased and SSVI increased. At dose concentrations of &lt;100 mg/L, Al3+ helped in the bioaggregation of dispersed activated sludge flocs, thereby improving settleability. The surface morphology from the scanning electron microscope (SEM) images indicated that the initial potential of interfloc bridging, open floc formation, and spindly bulking noticed in the undosed activated sludge flocs were remarkably reduced as the flocs became more compacted after Al3+ treatment. At &gt;100 mg/L of Al3+, the sludge settleability started to disintegrate due mainly to surface charge reversal linked to the formation of aluminium hydroxides and the resultant disintegration of the activated sludge floc structure.

Analysis of cutting-oil emulsion destabilization by aluminum sulfate

ABSTRACTThe destabilization mechanism of the high stable cutting-oil emulsion by aluminum sulfate (Al2(SO4)3) was investigated since it can affect properties of aggregates and following separation units. Al2(SO4)3 dosage and pH were key factors in the destabilization. The effective separation occurred when precipitated Al(OH)3 is dominated at the neutral pH of 6.5–7.0. The best separation can be achieved when solid flocs were formed at 1.0 mM, which exceeded the dosage from the critical coagulation concentration (CCC) of 0.75 mM. Two different mechanisms were proved for the emulsion destabilization depending upon the Al3+ concentration under this pH range. The first mechanism was the adsorption of Al(OH)3 on surface of oil droplets, which led to the droplet coalescence. By increasing the Al3+ dosage, the sweep flocculation by Al(OH)3 precipitates occurred. Al3+ dosage for effective destabilization was increased in accordance with oil concentration. The formation of aluminum hydroxide precipitates in bayerite structure was affirmed by analyzing elemental composition and crystalline structure of flocs from the destablization.

Study of diel hydrochemical variation in a volcanic watershed using principal component analysis: Tatun Volcano Group, North Taiwan

Heavy metal contamination commonly appears in mining areas and volcanic watersheds due to the acidic drainage water. Under the hydrochemical condition, the solar photocycle would result in changes of the water temperature, in photosynthesis and in iron photoreduction, which leads to substantial hydrochemical fluctuations, especially for heavy metals. It is important to consider the daily variations in water quality when developing a hydrochemical monitoring plan for an area with highly developed agriculture, such as the Tatun Volcano Group watershed area in this study. The results show that the water chemistry is highly complicated by both solar photocycles and hydrochemical fluctuations in the upstream area. Using principal component analysis, the contributions from the two factors can be successfully separated. During the daytime, the photocycle results in the formation of aluminum hydroxide, which can remove heavy metals from water. Consequently, the content of heavy metals, including As, Cu, Ni, Co and Ba, increases after sunset and can reach a maximum before sunrise, while Fe behaves inversely due to the photoreduction. The variation of As during a diel cycle can reach 97%. However, the content of most of the heavy metals during diel cycle is incomparable with those in the earlier studies due to the formation of aluminum hydroxide instead of iron hydroxide. The other significant factor, hydrochemical fluctuation, can explain the variation of major components in water including Cl, SO4. Rare earth elements (REEs) were also analyzed and can be an excellent natural tracer in this study. The distribution of REEs shows a depletion of light REEs and an even normalized concentration of middle and heavy REEs. It is theorized that the REEs in the water in this study derive mainly from the reservoir rock of geothermal water. In a hydrochemical monitoring plan, REEs can be an indicator for identifying an anthropogenic source.

Analysis and in situ observation of humidity dependent atomic layer deposited-Al2O3 degradation

The degradation of atomic layer deposited aluminum oxide (ALD-Al2O3) at high temperature and high humidity was investigated. The intrinsic hydroxyl concentration of as-deposited ALD-Al2O3 was evaluated using a temperature dependent deposition study and its impact on degradation behavior was analyzed. In addition, the degradation of ALD-Al2O3 was monitored in situ using a plate capacitor with ALD-Al2O3 as dielectric. A model for the ALD-Al2O3 degradation mechanism was proposed based on the penetration of water molecules into the ALD-Al2O3 and on the formation of aluminum hydroxide. Two parameters, delay-time (time till a change in capacitance occurs) and wetting speed (speed of molecular water penetration into the ALD-Al2O3), were extracted from the capacitance measurements in order to evaluate the dependence of ALD-Al2O3 degradation on temperature and humidity.

Operation System for Aluminum-Air Cell: A Strategy to Harvest the Energy from Low-Cost Aluminium

Aluminium (Al) -air cell holds a high volumetric capacity density of 8.05 Ah cm-3, benefit from the trivalence of Al ions. Additional benefits of Al-air cell are low price and environmental friendliness. Furthermore, the Al energy conversion process is characterized of 100% recyclability in theory. Along with a large base of raw material reserve, Al attracts considerable attentions as a promising material to be integrated within the global energy system. However, despite the early successful applications in military services, several problems exist that prevent the Al-air cells from widely civilian use. The most serious issue is the parasitic corrosion of Al when contacts with electrolyte. To overcome this problem, super-pure Al alloyed with various traces of metal elements are used to increase the corrosion resistance. Nevertheless, high-purity Al alloys are costly and require high energy consumption during production process. An alternative approach is to add inexpensive inhibitors directly into the electrolyte. However, such additives would increase the internal ohmic resistance and hamper the cell performance. So far these methods have not provided satisfactory solutions for the problem within Al-air cells. For the operation of alkaline Al-air cell, there are still other minor problems. One of them is the formation of aluminium hydroxide in the electrolyte. This process decreases ionic conductivity of electrolyte. Another one is the carbonation process within the gas diffusion layer of cathode, blocking the porosity of gas diffusion. Both these would hinder the performance of cells.The present work optimizes the above problems by building an Al-air cell operation system, consisting of four components. A top electrolyte tank containing fresh electrolyte is located at a high level, so that it can drive the electrolyte flow by gravity force. A mechanical rechargeable Al-air cell is fabricated with low-cost materials including low grade Al, carbon paper, and PMMA plates. An electrolyte waste tank with elaborate channel is designed to separate the hydrogen generated from the corrosion, which would be collected by gas collection device. In the first section of the research work, we investigated the performance of the mechanical rechargeable Al-air cell with a constant flow rate of electrolyte, to ensure the repeatability experiments. Then the whole system was assembled together and the feasibility of operating was demonstrated. During experiment, pure hydrogen is collected by collection device, which holds potential for various applications. By collecting this by-product, high utilization efficiency of aluminum is achieved. Considering both electricity and hydrogen generated, an overall utilization efficiency of around 90 % or even higher under different working voltages are achieved. Fluidic electrolyte could remove aluminum hydroxide precipitate and solve the electrolyte deterioration problem. This operation system provides a low-cost strategy for harvesting energy from the abundant secondary Al. The system could also be applied into other metal-air cells and is suitable for emergency power supply, power plant and other applications. The low cost feature implies great potential for commercialization. Further optimization, such as scaling up and optimization of fabrication, will help to refine the technology into practical market offerings.

Removal of clomazone herbicide from a synthetic effluent by electrocoagulation.

The aim of this work was to investigate the kinetics of removal of clomazone herbicide from an aqueous solution by electrocoagulation. The experiments were performed in a cylindrical batch reactor with six aluminum electrodes in monopolar mode, arranged in series and connected to a digital DC power. The aqueous solution (tap water + clomazone) with initial pH close to 7.9 was always treated at ambient temperature (≈20 °C) and atmospheric pressure for 5,400 s. For a confidence level of 95% the rate constant of electrocoagulation and the efficiency of removal of clomazone at equilibrium were 2.1 × 10(-3) ± 0.5 × 10(-3) s(-1) and 97.7 ± 2.2%, respectively. The final chemical oxygen demand was 88% lower than that measured initially, while turbidity and apparent color were totally removed from the synthetic solution at a rate close to that of formation of aluminum hydroxides. Some reaction intermediates, such as benzonitrile-2-chloro and 2-chloro-hex-2,4-diene-1,6-dioic-acid determined by gas chromatography mass spectrometry (GC-MS) analysis, explain the ratio of equilibrium to initial total organic carbon approximately between 0.6 and 0.8 at a probability of 95%.

Removal of organics from bilge water by batch electrocoagulation process

Abstract A batch electrocoagulation study was conducted using aluminium electrodes to check the treatability of synthetic bilge water. The studies were conducted to investigate the effect of various operational parameters on the treatment efficiency. At a pH of 7, applied voltage of 10 V, spacing of 1 cm and effective electrode area of 45 cm 2 , a maximum soluble COD (COD S ) removal efficiency of 85% was obtained after an electrolysis time of 120 min. The second order rate constant was derived and a maximum rate constant of 3 × 10 −6 L/mg-min was observed at optimum experimental conditions. COD S experimental measurements give an acceptable fit for both Langmuir model and Freundlich isotherm models. A comparative study between electrocoagulation and chemical coagulation was performed and chemical coagulation showed only 59.3% removal efficiency. The sludge formed after the electrocoagulation process was characterized for mineral composition and functional groups. XRD and FTIR results represent the formation of aluminium hydroxide during electro coagulation process and the presence of hydrocarbons and heavy metals in the sludge indicates the removal of these pollutants from bilge water by electrocoagulation process. Among different electrode combinations of aluminium and iron, Al Al combination showed maximum removal efficiency. A case study on real bilge water was conducted and a maximum removal of 89.84% was obtained at optimum conditions using aluminium electrodes.

Corrosion Protection of Al/Au/ZnO Anode for Hybrid Cell Application.

Effective protection of power sources from corrosion is critical in the development of abiotic fuel cells, biofuel cells, hybrid cells and biobateries for implantable bioelectronics. Corrosion of these bioelectronic devices result in device inability to generate bioelectricity. In this paper Al/Au/ZnO was considered as a possible anodic substrate for the development of a hybrid cell. The protective abilities of corrosive resistant aluminum hydroxide and zinc phosphite composite films formed on the surface of Al/Au/ZnO anode in various electrolyte environments were examined by electrochemical methods. The presence of phosphate buffer and physiological saline (NaCl) buffer allows for the formation of aluminum hyrdroxide and zinc phosphite composite films on the surface of the Al/Au/ZnO anode that prevent further corrosion of the anode. The highly protective films formed on the Al/Au/ZnO anode during energy harvesting in a physiological saline environment resulted in 98.5% corrosion protective efficiency, thereby demonstrating that the formation of aluminum hydroxide and zinc phosphite composite films are effective in the prevention of anode corrosion during energy harvesting. A cell assembly consisting of the Al/Au/ZnO anode and platinum cathode resulted in an open circuit voltage of 1.03 V. A maximum power density of 955.3 μW/ cm2 in physiological saline buffer at a cell voltage and current density of 345 mV and 2.89 mA/ cm2, respectively.

Influence of cations on the partition behavior of perfluoroheptanoate (PFHpA) and perfluorohexanesulfonate (PFHxS) on wastewater sludge

The effects of different cations on the sorption behavior of PFHpA and PFHxS on two types of sludge were investigated in this study. The sodium and potassium ions did not significantly affect PFHpA and PFHxS sorption on different sludge. For calcium and magnesium, the sorption amount of PFAS increased with calcium and magnesium concentration increasing from 1 to 30mM and then decreased with those increasing from 30 to 100mM. The sorption level of PFHxS or PFHpA greatly increased with increasing Al3+ and Fe3+ cation concentrations due to the strong sorption and coagulation effects by the formation of aluminum hydroxide (or ferric hydroxide) colloids or precipitates. After the organics in sludge has been removed by thermal treatment, the PFAS sorption on sludge was greatly reduced. Such finding indicated that sorption to organic matter is more important for anionic PFASs than adsorption to mineral surfaces. However, due to the higher content of biological organics, a secondary activated sludge has higher affinity toward PFAS species than chemically enhanced primary treatment sludge. It indicated that the organic types in sludge were also crucial to the sorption levels of PFASs by sludge.

Organic matter removal from oil-water emulsions by electrocoagulation - 1: thermodynamic analysis

A thermodynamic analysis of the organic matter (chemical oxygen demand - COD) removal from synthetic oil-water emulsions by the electrocoagulation process was performed with the objective of determining the most stable ionic species under diverse pH and aluminum concentration conditions and identifying possible removal mechanisms. The analysis suggests that the predominant species during the reactive stage are the amorphous aluminum hydroxide (for the mononuclear speciation of aluminum) and the positively charged trimeric species, Al3(OH)45+ (for the polynuclear speciation of aluminum). The emulsion destabilization probably occurs by charge neutralization, carried out jointly by the polynuclear species and by positively charged aluminum hydroxide. This sorption mechanism is likely to be the primary coagulation mechanism during the reactive stage. The formation of aluminum hydroxide and/or oxide during the stabilization stage may also take place, which indicates the gradual change of the dominant removal mechanism to sweep flocculation.