Optimal control problems arising in the zinc sulphate electrolyte purification process

Before zinc electrolysis, zinc powder is added to the zinc sulphate electrolyte solution to facilitate the removal of harmful metallic ions. This purification process can be modeled by a time delay differential equation. Since some of the parameters in this model are unknown, zinc powder is normally added excessively. We use an optimization technique to estimate the unknown parameters from experimental data. Then, we formulate an optimal control problem to minimize the amount of zinc powder added. We solve this optimal control problem numerically by using the control parametrization method. The results indicate that the amount of zinc powder added can be decreased, on average, by approximately 7%

Electrodialytic processes in solid matrices. New insights into batteries recycling. A review.

Electrodialytic Remediation has been widely applied to the recovery of different contaminants from numerous solid matrices solving emerging issues of environmental concern. Results and conclusions reported in studies about real contaminated matrices are summarizes in this work. The influence of the pH value on the treatment effectiveness has been widely proved highlighting the phenomenon “water splitting” in the membrane surface. This dissociation of water molecules is related to the “limiting current” which is desirable to be exceed at the Anion Exchange Membrane in order to produce the entering of protons toward solid matrix. Other important parameters for the optimization of the technique, such as the current density and the liquid to solid ratio, are also discussed through the revision of studies using real solid matrices. This work also focusses on the pioneer proposal of electrokinetic technologies for the recycling of lithium ion batteries considering the relevance of waste properties in the design and optimization of the technique. From a thorough literature revision, it could be concluded that further experimental results are needed to allow an optimal application of the technique to the rising problem of residues from batteries. The main aim of this work is to take the first steps in the recovery of valuable metals from spent batteries, such as Li and Co, incorporating principles of green chemistry.The authors acknowledge the financial support from the “Plan Propio de Investigación de la Universidad de Málaga with Project numbers: PPIT.UMA.B1.2017/20 and PPIT.UMA.B5.2018/17 and the European project THROUGH H2020-MSCA-RISE- 2017-778045. The first author also acknowledge the postdoctoral contract obtained from University of Malaga

Recovery of metals from highly concentrated acid mine drainage by liquid-liquid extraction

The growing consciousness and anxiety about the environment have motivated in the recent years extensive research aiming to develop new efficient technologies for the acid mine drainage (AMD) remediation. Such type of pollution is considered of serious concern because of its acidic nature (pH ranges around 2–4), and high concentrations of metals and sulfate. The AMD collected from the inactive São Domingos mine, Portugal for this work has the following concentrations of: 55.2 ± 0.4g/L Fe, 2.60 ± 0.03g/L Zn, 6.2 ± 0.1g/L Al, 4.60 ± 0.07g/L Cu and 123.9 ± 0.2mg/L Mn and 157.2 ± 3g/L of SO42-. The recovery of largely used metals such as, copper, zinc and iron, from this type of highly concentrated AMDs is still eco-unfriendly and expensive, thus new recovery strategies should be investigated. In this study, liquid-liquid extraction (LLE) process, involving commercial industrially known extractants and new extractants were tested for the recovery of copper, iron and zinc from the AMD collected at São Domingos mine. Accordingly, the extraction of copper by ACORGA M5640 and the subsequent stripping of the metal with H2SO4 solution were optimized. The results revealed that copper can be extracted from such AMD by 30% (v/v) ACORGA M5640 diluted in Shell GTL, making an 8/1 ratio of its active compound (5-nonyl-2-hydroxy-benzaldoxime) to copper ions, with an efficiency of 96 ± 3%. Copper was then efficiently stripped (95 ± 2%) from the metal loaded organic phase with a 2M H2SO4 solution. This organic phase has excellent reuse performance and can be recycled at least 5 times, according to this work and potentially much more times. Its maximum loading capacity of copper from AMD was determined to be 16.15 g/L and the accumulation of copper in the stripping solution in successive cycles reached 46 ± 3 g/L. After copper extraction, iron was successfully extracted from AMD 94 ± 2%) by an ionic liquid diluted in kerosene containing ions from Aliquat 336 and from Cyanex 272 (ALiCY) both in a 3/1 ratio to iron ions to prevent further iron co-extracted with zinc. Complete stripping of Fe (96 ± 2%) was achieved using also a 2M H2SO4 solution. As an alternative, it was confirmed that iron can be simply removed from AMD by adjusting the pH to values between 5 and 6. Concerning the subsequent recovery of zinc, 52 ± 2% was extracted using a synergistic mixture of 80% D2EHPA and 20% Cyanex 272 (with 18/1 and 4.5/1 ratios to zinc ions, respectively) diluted in kerosene with 3% Tributyl phosphate (TBP), and 99 ± 2% of this metal was then stripped from such organic phase once again with 2M H2SO4.A crescente consciencialização e preocupação acerca da poluição ambiental tem motivado um extenso esforço de investigação procurando o desenvolvimento de novas tecnologias de remediação de drenagem ácida de mina (DAM). Este tipo de poluição é considerado de grande preocupação devido à sua acidez (valores de pH entre 2 e 4) e elevadas concentrações de metais e sulfato. A DAM colhida para este trabalho na mina inativa de São Domingos, Portugal, tem as seguintes concentrações: 55.2 ± 0.4g/L Fe, 2.60 ± 0.03g/L Zn, 6.2 ± 0.1g/L Al, 4.60 ± 0.07g/L Cu and 123.9 ± 0.2 mg/L Mn and 157.2 g/L of SO42-. A recuperação de metais amplamente usados, como o cobre, o zinco e o ferro, deste tipo de DAMs altamente concentradas ainda é ecologicamente hostil e cara, sendo importante investigar novas estratégias de recuperação. Neste estudo foram testados processos de Extração Líquido-Líquido (ELL) com extratantes comerciais industrialmente conhecidos e com novos extratantes para a recuperação destes três metais da DAM colhida na mina de São Domingos. Assim, a extração de cobre com ACORGA M5640 e a subsequente reextração do metal com solução de H2SO4 foram otimizadas. Os resultados revelaram que o cobre pode ser extraído desta DAM com 30% (v/v) ACORGA M5640 diluído em Shell GTL, numa razão de 8/1 do seu composto ativo (5-nonyl-2-hydroxy-benzaldoxime) para iões de cobre, com uma eficiência de 96 ± 3%. O cobre foi depois eficientemente reextraído (95 ± 2%) da fase orgânica com uma solução de 2M H2SO4. De acordo com este trabalho, esta fase orgânica tem uma excelente capacidade de reutilização, podendo ser reciclada pelo menos 5 vezes e potencialmente muito mais vezes. A sua capacidade máxima de carregamento de cobre foi estimada em 16.15 g/L e a acumulação de cobre na solução de reextração em ciclos sucessivos chegou a 46 ± 3 g/L. Depois da extração de cobre, o ferro foi extraído da DAM com sucesso (94 ± 2%) com um líquido iónico diluído em querosene contendo iões provenientes de Aliquat 336 e Cyanex 272 (AliCy), ambos numa razão de 3/1 para os iões de ferro, para evitar posterior co-extração de ferro com o zinco. A reextração do ferro foi conseguida (96 ± 2%) também com uma solução de 2M H2SO4. Como alternativa confirmou-se que uma simples remoção do ferro da DAM é possível com um ajuste do pH para valores entre 5 a 6. No que respeita à subsequente recuperação do zinco, 52 ± 2% foram extraídos utilizando uma mistura sinérgica de 80% de D2EHPA e 20% de Cyanex 272 (com proporções de 18/1 e 4,5/1 para iões de zinco, respetivamente) diluídos em querosene com 3% de Fosfato de Tributilo (TBP), e em seguida 99 ± 2% deste metal foi reextraído desta fase orgânica mais uma vez com 2M H2SO4.I would like to thank European commission and, committee members and officials for the Master of Science program in Chemical Innovation and Regulation. The work was performed in the framework of project METALCHEMBIO (no. 29251) financed by national funds through the FCT – Foundation for Science and Technology and co-financed by the Algarve´s Regional Operational Program (CRESC Algarve 2020), through Portugal 2020 and European Regional Development Fund (FEDER

Supported liquid membrane process for nickel removal from electroplating wastewater

Supported liquid membrane (SLM) is one of the potential separation methods in treating wastewater loaded with toxic heavy metal ions owing to several advantages including simultaneous extraction and recovery processes, high separation factor, simple operation and it is easy to scale up. Right formulation, high stability and sustainable predominantly influence the success of the SLM process. Petroleum based diluents are hazardous whereas the single carrier is unable to efficiently extract nickel ion at lower pH. Liquid membrane loss leads to the SLM instability and short lifetime. In this study, a sustainable and stable SLM process using a mixture of carrier and cooking palm oil impregnated in composite membrane support was developed for the extraction and recovery of nickel ion from the electroplating wastewater. Electroplating wastewater was analyzed and SLM components such as carriers (di (2- ethylhexyl) phosphoric acid (D2EHPA), diisooctylthiophosphinic acid (Cyanex 302), tridodecylamine (TDA) and octanol), synergist carriers (Cyanex 302, TDA and octanol), diluents (kerosene and cooking palm oil) and stripping agents (sulfuric acid, hydrochloric acid and nitric acid) for nickel ion extraction were formulated via liquidliquid extraction process. The formulated liquid membrane containing D2EHPA and octanol in kerosene was impregnated in the membrane support pores of polyvinylidene fluoride (PVDF) with the features of 125µm thickness, 75% porosity and 0.22µm pore size. Parameters affecting SLM extraction of nickel such as carrier, synergist carrier and stripping agent concentrations as well as flow rate of feed and stripping phases were screened and optimized using the response surface methodology method. Several compositions of kerosene and cooking palm oil were studied to determine the feasibility of cooking palm oil in the extraction of nickel in SLM. The stability of SLM was investigated by developing a composite membrane support containing sulfonated poly (ether ether ketone) (SPEEK) and PVDF. Results showed that D2EHPA, octanol, cooking palm oil and sulfuric acid have potential as a carrier, synergist carrier, diluent and stripping agent, respectively. About 90 and 95% of nickel ions were successfully extracted and recovered, respectively under optimized conditions of 1.25M D2EHPA, 15% (v/v) octanol and 1.75M sulfuric acid. Upon applying 100% cooking palm oil as diluent, around 91% of nickel ions were extracted and 65% were recovered. The developed composite membrane support (SPEEK-PVDF) is capable of improving the SLM stability by reducing the liquid membrane loss from 47 to 23% upon applying the SPEEK layer at the feed side of the PVDF membrane support. High permeability (9.26 x 10-4 cms-1) and flux (6.48 x 10-7 molcm-2s-1) of nickel were achieved as the thickness of SPEEK was increased from 0.025 to 0.055mm. Recycling of the composite membrane support was found to be satisfactory until the ninth cycles with low weight loss percentage of the impregnated composite membrane support (8%). The findings of this study revealed that a sustainable and stable SLM process was successfully developed for the removal and recovery of nickel ion from the electroplating wastewater

Optimization of titanium recovery from drinking water treatment plant residue as potential photocatalyst

Titanium dioxide (TiO2) is known for its excellent photocatalytic activity and many industries have now shifted their efforts to recover TiO2 from secondary sources. Hydrometallurgy techniques which comprise of leaching, purification and precipitation have been commonly used to recover TiO2. However, this technique involves many processes and further work is needed to improve the laboratory process. This study aims to optimize the titanium leaching from drinking water treatment plant (DWTP) residue using response surface methodology (RSM). The parameters studied were acid concentration, temperature and solid to liquid ratio. The purification work was carried out using solvent extraction and the percentage recovery of titanium using Cyanex 272 and Cyanex 301 were investigated. The final product of TiO2 was obtained via precipitation using magnesium oxide. The performance of TiO2 as photocatalyst was evaluated using methylene blue and fungi under UV light irradiation. From the characterization study, it was found that the DWTP residue was poorly crystalline and predominantly consists of kaolinite and quartz with minor constituent of hematite, illite and anatase. Experimental results showed that a maximum leaching of titanium was obtained at 66% with optimum condition were found to be at 5.5 M acid concentration, 62˚C heating temperature and 10 g/L solid to liquid ratio. In solvent extraction, the best titanium recovery was achieved at 86% using Cyanex 272 with low extraction of aluminium and iron. In contrast, Cyanex 301 showed 60% titanium recovery with 54% of aluminium was extracted into the organic phase. The X-ray Fluorescence (XRF) analysis indicated that 71% of TiO2 was produced. In addition, X-ray Diffraction (XRD) confirmed the formation of TiO2 with the crystalline anatase phase detected at 2θ values of 25.3º, 37.8º, 48.0º. FESEM micrograph of TiO2 showed that the aggregates were present in the form of uniform spherical shape with considerable variation of particle size. The photocatalytic activity of the final product TiO2 under UV light irradiation showed maximum degradation (84%) with 0.5 g/L TiO2 loaded in methylene blue solution. At similar amount of loaded TiO2, the findings indicated that almost 50% of the fungi growth was inhibited within 14 days. Additionally, zero inhibition of fungi growth was observed without the presence of TiO2. In summary, the photocatalyst TiO2 had been successfully recovered from DWTP residue using an optimized leaching process, hence contributes to the improvement of hydrometallurgy technique

Magnetic Separation of Impurities from Hydrometallurgy Solutions and Waste Water Using Magnetic Iron Ore Seeding

The removal of iron ion from leaching solution is critical for the recovery of value metals, with the method of choice commonly being crystallization (precipitation). This paper summarized the new improvements in iron removal by precipitation methods in recent years and proposed a novel process, magnetic seeding and separation. The new process can promote iron precipitate aggregation and growth on the surface of the magnetic iron ore seeds. A core-shell structure was formed of iron precipitate and magnetic iron ore seeds, which can be magnetized and coalesced in magnetic field, accelerating the solid-liquid separation. The efficient magnetic flocculation and separation offset the poor settleability and filterability of the residues, contributing to the development of the hydrometallurgy process. Moreover, magnetic seeding and separation was also used for the removal of organic and inorganic contaminants from wastewater, significantly improving the purification efficiency. Therefore, iron ore not only played an important role in mining and steel manufacture, but also can be used to solve some problems in crossing fields

Development of hydrometallurgical processes for zinc recovery from steelmaking waste

257 p.La tesis defendida estudia el diseño y desarrollo de dos procesoshidrometalúrgicos para el tratamiento de los residuos producidos por laindustria del acero con el fin de obtener nuevos producto de zinc. Por lotanto, se ha estudiado la posibilidad de tratar residuos peligrosos, comoson los polvos filtrados de los hornos de producción de acero,inertizándolos y a su vez dándoles un segundo uso comercial. Para ello, seha diseñado un proceso hidrometalúrgico para producir óxido de zinc dealta pureza y por otro lado se ha desarrollado la purificación del óxidoWaelz para ser empleado como materia prima en la industria defabricación de zinc metálico por electrolisis. Es por ello que el propósito deesta tesis ha sido aumentar el ciclo de vida del zinc y a su vez favorecer lareducción de impacto ambiental de acerías de horno de arco eléctrico altratar los residuos generados por las mismas

Recovery and Recycling of Valuable Metals

Metals have always played a significant role in human life, and the current global growth and prosperity are directly dependent on these materials. With the rapidly growing global demand for metals, their extraction from natural minerals (as their primary sources) has been enhanced, causing a significant reduction in the grade and quality of the ores in ore deposits and leading to the production of huge amounts of waste, which requires management. In light of this, new proposals to develop more advanced metal recovery technologies from minerals are needed. Additionally, the huge quantity of waste generated through all steps of metal production is known to be a source of environmental pollution, while its valorization can create value via recycling metals or even though use in the production of other valuable materials. Such waste valorization is also in line with the United Nations’ Sustainable Development Goals (SDGs), as well as the implementation of the Paris Agreement. In this regard, the recycling of end-user products in order to reproduce valuable metals can also create significant value and reduce mining activities, and thus, their harmful consequences worldwide. Therefore, research and development in the state-of-the-art technologies for the recovery and recycling of metals are absolutely necessary. The aim of this Special Issue was to collect a range of articles on different aspects of valuable metal recovery and recycling from primary and secondary sources, as well as to decipher all new methods, processes, and knowledge in valuable metal production. We hope that this open access Special Issue will provide a great opportunity to demonstrate the work of researchers working in this area all around the world and help to provide new ideas for researchers who are working in the areas of hydrometallurgy, mineral processing, and waste recycling and valorization