Aluminum Recovery from White Aluminum Dross by a Mechanically Activated Phase Separation and Remelting Process

The aluminum recovery from white aluminum dross by a mechanical treatment and sizing followed by remelting process was investigated. The dross was subjected to a ball mill, and the obtained particles were sized in different ranges. They were studied by advanced materials characterization techniques. It was found that the larger particles contain high metallic portions, and most non-metallic components of the dross are in the fine fraction < 1 mm. The Al-rich particles (> 1 mm) were remelted at 900°C to recover aluminum. It was found that the metal structure after remelting is homogeneous and consisted of a dominant metallic aluminum matrix, containing an average of > 96% Al with around 99% total metallic components. The results show that the applied method is a good economic alternative for the aluminum recovery from white dross, which is important for the valorization/recycling of industrial waste and circular economy.

REVIEW ON ADVANCED TECHNOLOGIES FOR ALUMINUM RECOVERY FROM CARTON PACKAGES WASTE USING PYROLYSIS

A pirólise é uma tecnologia verde que permite separar o alumínio do polietileno das embalagens Tetra Pak. Essa alternativa pode ser utilizada para reduzir o impacto ambiental decorrente da destinação inadequada desses resíduos modernos. Além disso, a reciclagem permite recuperar materiais de alto valor agregado. Para a recuperação de alumínio e óleos parafínicos de resíduos de embalagens cartonadas, este artigo de revisão visa destacar os avanços na ciência e na tecnologia para a recuperação de alumínio de embalagens cartonadas. Dentre os reatores analisados, os leitos de jorro e os leitos fluidizados podem ser apontados como novas oportunidades e grandes sucessos do setor nos próximos anos. Em relação ao potencial econômico, dois fatores apontam a pirólise de resíduos de embalagens cartonadas como uma técnica promissora: o valor agregado dos materiais reciclados e a economia de energia do processo. Com base na análise econômica, a pirólise tem um potencial econômico positivo de 190,5 US$/por tonelada de produto. Quando comparada ao processo tradicional de produção de alumínio, a pirólise pode economizar 0,745 MWh por cada tonelada de embalagem cartonada recuperada. No que diz respeito à rentabilidade do processo, a pirólise por plasma tem uma relação de caixa acumulada de 3,27 milhões e uma taxa de retorno do investimento de 2,04%, mostrando-se um investimento atraente.

Temperature-dependent kinetics of aluminum leaching from peat clay

The leaching kinetics of aluminum from peat clay using 4 M HCl at dissimilar leaching temperatures (30–90 °C) was investigated. The maximum of aluminum recovery was 91.27% after 60 min of leaching in agitated Pyrex reactor at 90 °C. The model involved the concept of shrinking core in order to describe aluminum that is located inside the core solid particle of peat clay that shrinks as the extracted solute, and it assumed the unchanged particle structure, a first-order leaching kinetics mechanism and a linear equilibrium at the interface of solid-liquid. The proposed model was corresponding to fit experimental data and to simulate the aluminum leaching from peat clay with four fitting parameters of temperature, which was confirmed with the mass transfer coefficient (kc, cm/s), diffusion coefficient (De, cm2/s), and reaction rate constants (k, cm/s) by following an increasing trend with increasing temperature. Moreover, it was validated by the correlation coefficient (ccoef ≥ 0.9794), the root means square error (RMSE ≤ 0.485), the mean relative deviation modulus (E ≤ 3.290%), and the activation energy value (Ea = 19.15 kJmol-1). This model could describe the aluminum leaching kinetics from peat clay that suitable with experiment parameters and statistical criteria, by giving useful information for optimization, scaling-up, and design.

Aluminum extraction technologies from high aluminum fly ash

Coal fly ash (CFA), an industrial by-product of high-temperature combustion of coal in coal-fired power plants, is one of the most complex and largest amounts of industrial solid wastes generated in China. It is widely recognized that CFA should be considered as a potential alumina resource to substitute bauxite. In this review, the features of high-alumina fly ash and aluminum recovery technologies are first described. Later, the merits and drawbacks of alumina extraction technologies in recovering more valuable materials are compared in terms of extraction mechanisms and equipment requirements. It is shown that “predesilicating-sodium carbonate (Na2CO3) activation-acid leaching” is currently a promising method in achieving multimetal synergistic extraction. Finally, the hydrochloric acid and sulfuric acid combination process is proposed as a sustainable development of the predesilicating-Na2CO3 activation-acid leaching process. The findings of this review provide theoretical guidance for novel developments and applications of aluminum extraction technologies.

Sintering Optimisation and Recovery of Aluminum and Sodium from Greek Bauxite Residue

Bauxite residue is treated for the recovery of aluminum and sodium by sintering with the addition of soda, metallurgical coke and other reagents such as CaO, MgO and BaO. A thorough thermodynamic analysis using Factsage 7.0™ software was completed together with XRD mineralogy of sinters with different fluxes and reagents additions. Through both thermodynamic interpretation and mineralogical confirmations, it was observed that the type of desilication product in bauxite residue influences the total aluminum recovery through the sintering process and formation of sodium aluminum silicate exists in equilibrium with sodium aluminate, unless silica is consumed by additives (such as CaO, MgO, BaO etc.) forming other more thermodynamically favorable species and liberating alumina. Addition of barium oxide improves the aluminum and sodium recovery to 75% and 94% respectively. Complex sinter product formation that are triggered due to high calcium content in the Greek bauxite residue reduces aluminum recovery efficiency. Optimised and feasible recovery of aluminum and sodium for Greek bauxite residue was proved to be 70% and 85% respectively, when sintered with 50% excess stoichiometric soda. It was observed that stoichiometric carbon addition in inert atmosphere only assisted recovery up to 75% of aluminum and 83% of sodium, though there are benefits gained from pre-reducing iron from hematite for downstream recovery.

Aluminum Recovery From Multimaterial Tetra-Pak Waste Pyrolysis

A constant growth of the multimaterial waste production can be observed in the recent years. The multimaterial waste that contain aluminum are especially hard to process due to the fact that multiple layers of various materials are bonded permanently. Tetra-Pak waste contain high amounts of paper (approx. 70%) and are usually processed in papermills in order to recover cellulose. The overview on the methods used to process waste as well as the characteristics of the produced waste are presented in the paper. The application of pyrolysis has many advantages: the products are characterized by a high calorific value and can be used as fuels, and the process itself is much more environmentally friendly than the chemical methods used currently. The tests were performed with a special focus on the minimization of the aluminum oxidation level, so that in can be further processed. In order to determine the decomposition temperature of the individual components of the examined materials, the tests started with a thermogravimetric analysis of the pyrolysis process performed with the application of argon. The next step were the pyrolysis tests on a laboratory scale installation aimed in the verification of the results obtained during the thermogravimetry.