Hydrolysis Of Aluminum Research Articles

Synergistic mechanism of pH control by CO2 and CaO2 pre-oxidation to enhance algae dehydration

This study investigated the improvement of algal dehydration efficiency through CO2 pH adjustment and moderate pre-oxidation with CaO2 to enhance coagulation. Adjusting the pH of algal water to 6.0–9.5 with CO2 significantly affected zeta potential and photosynthesis, enhancing aluminum hydrolysis product aggregation. At pH 6.5, the composition of algal organic matter closely matched the original water, indicating minimal impact on algae and optimal cell activity. CaO2 pre-oxidation effectively reduced residual aluminum content and DOM release after coagulation. The DOM removal rate reached 44.50 % at pH 6.5, with the highest dehydration efficiency of 44.34 % and the lowest cell rupture rate of 5.55 %. Small molecular aromatic proteins decreased, while humic substances increased significantly. The chemical bonding between the EPS membrane and CaO2 improved system density and elasticity, enhancing dehydration performance. This study provides new insights and guidance for the ongoing study of pH and CaO2 enhanced algal dehydration.

Investigation of the effect of temperature and applied electric field on the aluminum-water reaction by ReaxFF molecular dynamics

Hydrogen energy is gaining attention as a non-polluting source. Aluminum’s reaction with water for propulsion and hydrogen production is widely used, but its nanoscale characteristics are unexplored. This study investigated aluminum hydrolysis in water vapor by ReaxFF-MD, examining effects of temperature and electric field. The oxidation of the aluminum surface is accompanied by aluminum dissolution, hydrogen generation and H3O+ formation, Formed hydrides and oxides were AlH3 and Al2O3. Hydrogen disappearance at 700 K and 900 K was due to conversion to AlH3. The diffusion of hydrogen and oxygen atoms in the Z direction was enhanced at increasing temperatures, Outer aluminum atoms preferentially reacted with oxygen to form Al2O3, while inner atoms reacted with hydrogen to form AlH3, the loosely packed outer oxide layer contains inclusions of AlH3. Studies at room temperature under different electric fields showed −Z field promoted the reaction while + Z field inhibited it, attributed to different electric field strengths’ effect on OH– ion electron-sharing Coulomb equilibrium, resulting in varying rates of hydroxide polar covalent bond cleavage. Our results clarify the atomic-scale effects of temperature and electric field on the aluminum-water reaction, providing guidance for optimizing experimental conditions and enhancing the efficiency of hydrogen production.

Aluminum hydrolysis for hydrogen generation enhanced by sodium hydride

Aluminum is the most abundant and promising material for hydrolytic hydrogen generation. It can be easily transported and stored. However, the oxide protective layer around Al limits its hydrolytic activity and hinders practical applications. To solve this problem, NaH is introduced to form the core-shell structure of Al-based NaH solid fuel powder by a simple hand mixing method in an open lab environment. The new core-shell structure of Al-based NaH solid fuel powder showed the best hydrolytic performance among Al-based materials and produced 98 % hydrogen yield at a 1 to 0.9 M ratio of NaH and Al in water. The hydrolytic activity consists of NaH hydrolytic splitting and Al hydrolysis. XRD and SEM analysis confirmed that NaH is the key to supporting complete Al hydrolysis and attaining maximum yield as compared to calcium hydride. Our research endorsed the practical implementation of inexpensive and transportable hydrolytic hydrogen generation materials and offered a new idea for the design of hydrolytic hydrogen generation materials for further development.

Fabrication of Al-Ni Alloys for Fast Hydrogen Production from Hydrolysis in Alkaline Water

Hydrogen generation through the hydrolysis of aluminum alloys has attracted significant attention because it generates hydrogen directly from alkaline water without the need for hydrogen storage technology. The hydrogen generation rate from the hydrolysis of aluminum in alkaline water is linearly proportional to its corrosion rate. To accelerate the corrosion rate of the aluminum alloy, we designed Al-Ni alloys by continuously precipitating an electrochemically noble Al3Ni phase along the grain boundaries. The Al-0.5~1 wt.% Ni alloys showed an excellent hydrogen generation rate of 16.6 mL/cm2·min, which is about 6.4 times faster than that of pure Al (2.58 mL/cm2·min). This excellent performance was achieved through the synergistic effects of galvanic and intergranular corrosion on the hydrolysis of Al. By raising the solution temperature to 50 °C, the optimal rate of hydrogen generation of Al-1 wt.% Ni in 10 wt.% NaOH solutions at 30 °C can be further increased to 54.5 mL/cm2·min.

Hydrogen Production from Aluminum Hydrolysis with Different Solutions

Günümüzde enerji kaynağı olarak yaygın bir şekilde fosil yakıtlar kullanılmaktadır. Fosil yakıtların kullanımının çevreyi oldukça tahrip edici etkileri bulunmaktadır. Bu yüzden temiz ve yenilenebilir enerji kaynaklarının kullanılması doğamız için oldukça önemlidir. Hidrojen enerji kaynağı olarak kullanıldığında su gibi çevreyi kirletmeyen temiz yan ürünler ortaya çıkmaktadır. Bu nedenle, temiz ve yenilenebilir enerji kaynağı kategorisinde yer almaktadır. Bu çalışmada hidrojen üretimi, farklı çözeltiler de kullanılarak alüminyum tozlarının hidrolizi yöntemiyle gerçekleştirilmiştir. Çalışmada, su, KOH, Mg(OH)2 ve NaOH çözeltileri, 35-65oC sıcaklık aralığı, %0 ile %15 arası NaCl ilavesi, 5 ile 15 h arası alüminyum öğütme süresi incelenmiştir. Öğütülmüş tozların mikroyapıları SEM ile karakterize edilmiştir. Sonuçlara bakıldığında alkali çözelti konsantrasyonu, sıcaklık, NaCl ilavesi oranı ve öğütme süresi arttıkça hidrojen üretim hızında artış gözlemlenmiştir. En iyi hidrojen üretimi, 65oC, %15 NaCl, 15 h öğütme süresi ve 1 M NaOH çözeltisinde görülmüştür.

Kinetics of the precipitation reaction between aluminium and contaminant orthophosphate ions

ABSTRACT The removal of phosphorous from wastewater in metal-orthophosphate systems typically occurs by simultaneous adsorption on poorly soluble metal hydroxides and by precipitation reactions between metal ions and orthophosphates in solution. To understand the individual contribution of these mechanisms to the removal of phosphorus, the main aim of this study was to determine the kinetics of consumption of contaminant orthophosphates by the precipitation reaction with aluminium ions in a solution free of insoluble aluminium hydroxide. To define the amount of aluminium and phosphorous compounds to be dissolved in water to have this desired reacting condition at a given pH, the solubilities of KH2PO4(s), Al(OH)3(s) and AlPO4(s) were examined at 25 °C in the pH range ∼2.6 to 7.9. pH-solubility diagrams for these ionic solids were made by solving a system of nonlinear algebraic equations involving dissolution, dissociation and hydrolysis reactions at equilibrium. The kinetics of the reaction between aluminium and orthophosphate ions at a reacting condition free of solids except for the product AlPO4(s) was investigated in a well-stirred batch reactor at pH ∼3.1 and 3.5 at 25 °C. A detailed kinetic model involving ten species, seven reversible reactions of hydrolysis of soluble aluminium and orthophosphate species and one reversible precipitation reaction between aluminium and phosphate ions revealed a rate constant for the latter reaction of 5.968 × 1010 L mol−1 s−1 (p = 0.191). XRD, TGA/DTGA and EDX analyses of the filtered and dried reacting mixture confirmed that the only solid product of the precipitation reaction was hydrated AlPO4(s).

Optimization of aluminum hydrolysis reactions and reactor design for continuous hydrogen production using aluminum wire feeding

The depletion of fossil fuels and the issues caused by CO2 emissions are driving changes in global energy approaches. In this context, hydrogen emerges as a new and clean energy carrier for the near future. In this study, a system that can produce hydrogen with a constant flow rate for on-demand applications is developed. Hydrolysis reactions of aluminum are utilized for hydrogen generation. Aluminum in the form of wire is used and the feeding issues have been solved. The parameters of the hydrolysis such as the solution temperature (25–80 °C), catalyzer concentration (1–4 M NaOH), aluminum quantity and aluminum wire diameter (0.6–1 mm) were optimized by adopting the response method (RSM) and using laboratory scale experiments. Aluminum hydrolysis reactions and aluminum transformations during the reactions are investigated by performing surface analyzes of the wire. Using the optimized data, the continuous hydrolysis reactor and the aluminum feeding mechanism are designed. The aluminum wire feeding system is computer controlled using a microcontroller-based code. Hydrogen production rates up to 350 ml min−1 have been accomplished. A fuel-cell in the range of 5–30 W is fed by the hydrogen generated by the hydrolysis reactor system and the stability of the hydrogen generation rate and hence of the electricity generation is proven. One of the original aspects of this study is the development of a process that continuously produces hydrogen using commercially available aluminum.

Studies on Water–Aluminum Scrap Reaction Kinetics in Two Steps and the Efficiency of Green Hydrogen Production

This work aims to explain aluminum hydrolysis reaction kinetics based on a properly chosen theoretical model with machined aluminum waste chips as well as alkali solutions up to 1M as a promoter and to estimate the overall reaction profit. The purpose of this work is to assess the optimal alkali concentration in the production of small- and medium-scale green hydrogen. To obtain results with better accuracy, we worked with flat Al waste chips, because a flat surface is preferable to maximally increase the time for the created hydrogen bubbles to reach the critical gas pressure. Describing the reaction kinetics, a flat shape allows for the use of a planar one-dimensional shrinking core model instead of a much more complicated polydisperse spheric shrinking core model. We analyzed the surface chemical reaction and mass transfer rate steps to obtain the first-order rate constant for the surface reaction and the diffusion coefficient of the aqueous reactant in the byproduct layer, respectively. We noted that measurements of the diffusion coefficient in the byproduct layer performed and discussed in this paper are rare to find in publications at alkali concentrations below 1M. With our reactor, we achieved a H2 yield of 1145 mL per 1 g of Al with 1M NaOH, which is 92% of the theoretical maximum. In the estimation of profit, the authors’ novelty is in paying great attention to the loss in alkali and finding a crucial dependence on its price. Nevertheless, in terms of consumed and originated materials for sale, the conversion of aluminum waste material into green hydrogen with properly chosen reaction parameters has positive profit even when consuming an alkali of a chemical grade.

Hydrogen production using aluminum-water splitting: A combined experimental and theoretical approach

Hydrogen generation from aluminum hydrolysis with NaOH as an activator is investigated experimentally. A theoretical model is developed using the Density Functional Theory (DFT) and a one-dimensional transport model formalism. The effects of NaOH concentration and reaction temperature on hydrogen production rates are investigated. The kinetic parameters calculated by DFT are used in the COMSOL transport equations and compared. A transport model is implemented for a reaction-diffusion problem of water over the Al surface. The activation barrier increases as the reaction progresses and adsorption of H2O molecules is limited due to space constraints. The reaction rate constants depend on temperature, species convection, and vibrational frequency. The three chemical reaction steps have activation barriers ranging from 7.72 to 61.75 kJ/mol. The activation barrier of the first H2O dissociation step is Ea,1 = 7.72 kJ/mol, whereas the second and third steps have activation barriers of Ea,2 = 15.44 kJ/mol and Ea,3 = 61.75 kJ/mol, respectively. The estimated DFT harmonic vibrational frequency of H2O stretching mode is 3788 cm−1.

Ultrafiltration membrane fouling control by two-stage coagulant dosing with moderate pH adjustment

For the coagulation-ultrafiltration process, it has been recognized that coagulation under acidic condition could greatly alleviate membrane fouling, but the high chemical consumption for pH adjustment and the diminished alkalinity of effluent severely restrict the practical application of this operation. In this study, it was found that two-stage coagulant dosing (separate dosing during rapid mixing and medium speed mixing) with pH adjusted to 6.5 could alleviate membrane fouling as that by one-time coagulant dosing at pH 5.5, which could significantly lower the chemical consumption for pH adjustment. Both the favorable aluminum hydrolysis speciation on the floc surface and the reduced interface interaction between membrane and foulant at pH 6.5 contributed to the effectiveness of this method on membrane fouling control. Compared with the scenarios at pH 5.5 and 7.5, the two-stage dosing at pH 6.5 could promote more aluminum species transformation to amorphous Al(OH)3 on the surface of flocs, resulting in less residual Al in the effluent. The acid-base interaction between foulant and membrane dominated membrane fouling. The degree of membrane fouling by separate dosage ratio of 3:7 at pH 6.5 was as low as that by one-time dosing at pH 5.5 because of the similarly low acid-base interaction energy.

Antimony and boron support to aluminum's hydrolysis performance and an application of PEM fuel cell

In this study, Al-Sb-B (aluminum-antimony-boron) ternary alloys are designed to improve the hydrolysis performance in alkaline media through the corrosive effects of intermetallic Al-Sb and Al-B particles. The maximum hydrogen generation rate of an ASB1 (Al-2.97 wt% Sb-0.99 wt% B) alloy is 4.78 times higher than ASB0 (Al-3 wt% Sb) alloy and 8.36 times higher than pure Al at certain temperatures. While the average hydrogen generation rate (HR) of pure Al is 2.66 ml cm−2 min−1, ASB1 alloy's HR is reached up to 16.78 ml cm−2 min−1. This improvement is achieved by sweeping the Al surface with the convection effect of the secondary phase particles (Al-Sb and Al-B) caused by the temperature fluctuations during the exothermic reaction. At 323 K–343 K temperature range, the apparent activation energy (EA) is calculated as 50.2 kJ mol−1 for pure Al and the lowest EA is calculated as 33.7 kJ mol−1 in ASB0 alloy. A selected alloy is tested in a Proton Exchange Membrane (PEM) fuel cell to observe its system performance. ASB3 (Al-2.913 wt% Sb-0.913 wt% B) alloy is selected for the PEM fuel cell application experiments and 2.72 mW output power is obtained. Thanks to alloying Al with other metals, different power demands of a PEM fuel cell flow requirements may be optimized.

The Hydrolysis of Ball-Milled Aluminum–Bismuth–Nickel Composites for On-Demand Hydrogen Generation

The hydrolysis of aluminum (Al) is a promising method for on-demand hydrogen generation for low-power proton exchange membrane fuel cell (PEMFC) applications. In this study, Al composites were mechanochemically activated using bismuth (Bi) and nickel (Ni) as activation compounds. The main objective was to determine the effects of Bi and Ni on Al particles during mechanochemical processing, and the hydrolysis activity of the Al-Bi-Ni composites. Successfully formulated ternary Al-Bi-Ni composites were hydrolyzed with de-ionized water under standard ambient conditions to determine the reactivity of the composite (extent of hydrogen production). Scanning electron microscopy (SEM) showed that Bi and Ni were distributed relatively uniformly throughout the Al particles, resulting in numerous micro-galvanic interactions between the anodic Al and cathodic Bi/Ni during hydrolysis reaction. The addition of >1 wt% Ni resulted in incomplete activation of Al, and such composites were non-reactive. All successfully prepared composites had near-complete hydrogen yields. X-ray diffraction (XRD) showed that no mineralogical interaction occurred between Al, Bi, and/or Ni. The main phases detected were Al, Bi, and minute traces of Ni (ascribed to low Ni content). In addition, the effect of the mass ratio (mass Al:mass water) and water quality were also determined.

Structure-Function Correlations in the Mechanism of Action of Key Antiperspirant Agents Containing Al(III) and ZAG Salts.

Aluminum hydrolysis chemistry is an important part of modern society because of the dominance of Al(III) as a highly effective antiperspirant active. However, the century-old chemistry centered on aluminum chloride (ACL) is not comprehensive enough to address all of the in vivo events associated with current commercial antiperspirants and their mechanism of action. The present study aims to address the knowledge gap among extensively studied benchmark ACL, its modified version aluminum chlorohydrate (ACH), and a more complex but less explored group of aluminum zirconium chlorohydrate glycine complexes (ZAG salts) toward understanding the mechanism of action under consumer-relevant conditions. ACH, which is the Al source used in the manufacture of ZAG salts, provides a bridge between ACL and ZAG chemistry. High viscosity and gel formation driven by pH and a specific Al(III) salt upon hydrolysis are considered the criteria for building an in vivo occlusive mass to retard or stop the flow of sweat to the skin surface, thus providing an antiperspirant effect. Rheological studies indicated that ACL and aluminum zirconium tetrachlorohydrex glycine (TETRA) were the most efficacious salt actives. Spectroscopic studies, diffraction studies, and elemental analysis suggested that small metal oxide and hydroxide species with coparticipating glycine as well as various polynuclear and oligomeric species are the key to gel formation. At a given pH, the key ingredients (NaCl, urea, bovine serum albumin, and lactic acid) in artificial sweat were found to have little influence on Al(III) salt hydrolysis. The effects of the sweat components were mostly limited to local complex formation and kinetic modification. The in vitro comparative experiments with various Al(III) and ZAG salt systems offer unprecedented insights into the chemistry of different salt types, thus paving the way for engineering more efficacious antiperspirant systems.

Application of Gel Electrolytes to Validate Transient Models of Galvanic Corrosion Phenomenon

The present work focuses on studying the acidity generated in the electrolyte during the galvanic corrosion of an aluminum alloy (AA) in contact with carbon steel (CS). A bare galvanic system exposed to a thin NaCl electrolyte has been considered. In this work, a mathematical model solved by the finite element method (FEM) is presented. It considers both electrochemical and aluminum hydrolysis reactions in the electrolyte solution. The model allows predicting the propagation of acidic pH fronts along the AA surface. Subsequently, the results obtained were validated by employing an innovative experimental technique using agar films doped with a pH indicator. The experimentally measured acid fronts show a similar trend to the numerical predictions and have a reasonable correlation in the first few minutes of the corrosion process.

Aluminum Soil Chemistry: Influence on Soil Health and Forest Ecosystem Productivity

Soil aluminum phytotoxicity has been a major research area since the inception of modern soil science. Acid soils, which typically manifest plant aluminum toxicity, are frequently dedicated to food production, thus yield and quality reductions influence food security. This manuscript reviews our modern understanding of 1) soil aluminum hydrolysis and polymerization, 2) aluminum complexation with inorganic and organic anions, 3) aluminum interference with vital plant physiological processes, 4) aluminum and forest ecosystem productivity, and 5) demonstrates the software simulation of aluminum reactivity and its role in predicting soil behavior. The manuscript also provides a perspective for future soil-aluminum research critical to maintaining food security and food quality.

Physicochemical characterization and flocculation performance evaluation ofPAC/PMAPTACcomposite flocculant

AbstractA novel inorganic–organic composite flocculant was prepared with polyaluminum chloride (PAC) and poly(methacrylamido propyl trimethyl ammonium chloride) (PMAPTAC). To understand the physicochemical characterization of PAC/PMAPTAC and evaluate its flocculation efficiency, the interactions of PAC and cationic polymer were investigated, then the characterization and flocculation performance of PAC/PMAPTAC and PAC/Poly‐dimethyldiallylammonium chloride (PDMDAAC) were compared. The results showed that there were obvious interactions between PAC and cationic polymer in composite flocculant. The cationic polymer chain exhibited a coiled state in PAC solution, and the curly degree of PMAPTAC chain was lower than that of PDMDAAC due to the intermolecular association of methyl of PMAPTAC. The cationic polymer enhanced the charge neutralization ability of PAC and changed the aluminum hydrolysis polymerization species of PAC from low and medium polymeric species to high‐polymeric species. The flocculation sedimentation experiments turned out that the charge neutralization and bridging ability of PAC/PMAPTAC was higher than that of PAC/PDMDAAC, and the increase of molecular weight or content of PMAPTAC in PAC/PMAPTAC could enhance the charge neutralization and adsorption bridging ability simultaneously. The enhanced effects may come from the exist of polymer and the interactions between PAC and cationic polymer in composite flocculant.

Hydrogen generation from the hydrolysis of aluminum promoted by Ni–Li–B catalyst

In this study, the high activity Ni–Li–B catalysts were fabricated through wet chemical reduction method. Their morphological structures, crystallinity, surface area and composition were examined by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) method and energy-dispersive X-ray spectroscopy (EDS). The aluminum-water reaction tests were explored in the range of temperatures from 35–75 °C. It was found that water could react with aluminum to generate hydrogen gas. The yield and hydrogen generation rate were significantly increased when all prepared catalysts were added into the reaction. The Ni–Li–B (XLiCl = 0.1 g) catalyst exhibited the highest cumulative hydrogen volume of 201.3 ml with an average hydrogen production rate of 0.50 ml min−1 at 55 °C. This phenomenon could be pointed to the emergence of the micro galvanic cell formed by the Ni–Li–B, Li/Ni–Li–B, Li and Al, which accelerated aluminum to rapidly react with water.

On-demand hydrogen generation by the hydrolysis of ball-milled aluminum composites: A process overview

The hydrolysis of aluminum (Al) is a relatively simple method for on-demand hydrogen generation for niche (low-power, <1 kW) proton exchange membrane fuel cell applications. The hydrolysis of Al in neutral pH water and under standard ambient conditions is prevented by the presence of a thin surficial oxide layer. A promising method to enable Al's spontaneous hydrolysis is by its mechanochemical activation (ball milling) with certain metals (e.g., Bi, Sn, In, Ga). This overview presents several aspects relating to the changes occurring in Al particles during ball milling, e.g., the structural and morphological behavior of Al during ball milling procedures (with and without the presence of activation metals), and the distribution and homogenization of Al and various activation metals. The formation of galvanic cells between anodic Al and cathodic activation metals (relative to Al) is discussed. A summary of the existing Al composites for on-demand hydrogen generation is presented. The paper concludes with a discussion of activation metal recovery, and the effects thereof on the economic feasibility of Al composites for hydrogen generation.

Effect of low B addition on Al-Zn alloy's hydrogen production performance

Aluminium hydrolysis is a promising method for hydrogen generation due to its instant hydrogen production, simplicity, controllability, and safety properties. Moreover, Al is very common, recyclable, lightweight material and it has no degradation problem to supply hydrogen in energy conversion devices. Hydrogen produced by Al can be easily adapted to fuel cells to convert energy into higher efficiency. In this study, the effect of low B additions (0.1, 0.3, and 0.5 wt.%) to the Al-2wt.%Zn alloy's hydrogen generation performance is investigated. Different temperatures (25, 50, and 80 °C) and different concentrations of NaOH (1, 3, and 5 M) are studied to observe their effects on the hydrogen production and corrosion rate. At 80 °C and 5 M NaOH concentration, in Al-2wt.%Zn-0.5wt.%B alloy, around 83% higher hydrogen generation performance is obtained than Al-2wt.% Zn alloy. The hydrolysis reaction kinetics are investigated with the Arrhenius equation and by low B addition, activation energy of the Al-2wt.%Zn and Al-2wt.%Zn-0.5 wt.%B alloys are decreased from 26.717 kJ mol−1 to 23.526 kJ mol−1.

Numerical Study of Local pH Variations in a Galvanic Carbon Steel-Aluminum Alloy System Under Immersion Conditions

This work focused on developing a mathematical model to predict the transient distribution of chemical species generated in the galvanic corrosion process when an aluminum alloy and carbon steel are coupled. It was considered a bared galvanic system under immersion conditions. The 2D electrochemical model considers both the electrochemical and homogeneous reactions, which occur in a static and uniform sodium chloride solution. The model was solved by the finite element method (FEM), and the main contribution of the investigation is the prediction of the local pH variation due to galvanic corrosion. The calculated pH profiles on the surface of the aluminum alloy showed strong acidification of the electrolyte. This abrupt drop in pH has already been measured experimentally with innovative techniques and attributed to aluminum's hydrolysis reactions.