Facoltà di Ingegneria Civile e Industriale

Dottorato di ricerca in Ingegneria Elettrica, dei Materiali e delle Nanotecnologie (EMNE)

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Dottorato di Ricerca in Ingegneria Elettrica, dei Materiali e delle Nanotecnologie

Relazione annuale A.A.:

2019 - 2020

Ciclo di Dottorato:

34

Curriculum:

Materiali

Dottorando/a:

Erwin Ciro Zuleta

Supervisore:

Professor Carla Lupi

TITOLO DELLA RICERCA: Indium recovery from ITO by electrowinning

1. Sintesi dell’attività di ricerca svolta

The increase of the indium demand has been mainly driven to indium-tin-oxide (ITO) production. ITO is widely required to carry out a proper optoelectrical performance in audiovisual technologies, optoelectronic systems, semiconductors and photovoltaic solar cells [1,2]. The current excessive demand and the restricted availability of indium have caused a serious disbalanced supply ratio. In fact, indium is usually obtained by primary extraction from mineral aggregates or by-products in sulfide ores of zinc, copper, tin and lead causing a higher environmental impact as proceeds [3]. Recently, WEEE (waste of electrical and electronic equipment) exhibits an evident potentiality to recover strategical metals from the scared devices. Indium metal is one of those strategical metals, which is widely found in end-of-life liquid-crystal display (LCD) due to large overproduction and short lifespan. Several advantages have been indicated to develop indium recovery from secondary resources such as processing in large volume of technological waste, less intervention in soils and water sources by ore mining and higher economical profiting. Furthermore, the WEEE processing has been widely carried out via electrowinning, where both nitric and chloride electrolytes were initially used [4-7]. Although chloride electrolytes have been diffusively used for indium electrowinning with high current efficiency (CE) and low specific energy consumption (SEC), wet corrosive chlorine gas emission represents a poisoning threat, demanding the implementation of hermetically sealed cells to recollect it at the anodic compartment. These sophisticated configurations imply higher investments to carry out the indium electrowinning and preserve workers safety. Therefore, the most remarkable challenges in the indium electrowinning comprise of stablishing optimized operating conditions with high CE and low SEC by using electrolytes with a lower environmental impact.

The first doctoral year has allowed to demonstrate the effectiveness of the indium electrowinning on several metal cathodes by using a sulfate solution (70 g/L In3+, 5 g/L H3BO3, 30 g/L Na2SO4 and 20 g/L Al2(SO4)3) at the same operating conditions (25 A/m2, 2.3 pH and 40 °C) [8]. The obtained findings showed different behaviors on each cathode for indium electrowinning indicating high CE and low SEC on stainless steel (SS) and Ni, while partially on Ti cathode. The optimization of SS cathode was carried out determining the most suitable operating conditions (current density (CD), temperature, composition electrolyte and pH) as can be seen in [9]. This investigation also indicated that electrolyte requires H3BO3, Na2SO4 and Al2(SO4)3 presence in order to favor the aspect of indium deposits. In the case of CD, it has been determined that at values higher than 25 A/m2 cause both the hydrogen evolution with bubbles presence, and undesirable dendritic structures that negatively affect the indium electrowinning. In Figure 1, it is possible to observe the effect of different current densities on indium deposits on SS cathode. The increase of current density causes the indium deposits disproportionally follow current lines, which tend to be concentrated around edges forming irregular structures. These irregular structures correspond to the dendrite formation due to the “edge effect”, where one of the main issues is the subsequent eventual short-circuits in the system.

Furthermore, the second doctoral year aimed to evaluate the influence of above-mentioned operating conditions on Ni cathode. This study gave rise to outputs in CE and SEC for indium electrowinning with 98% and 1.7 kWh/kg, respectively. By comparing the current results on Ni cathode with those obtained on SS cathode [8, 9], the indium electrowinning on Ni cathode can be achieved at high CE and low SEC by using more than three times the CD value used on the SS cathode, indicating a larger productivity as shown in Table 1. The indium deposits obtained on Ni cathode at the optimal conditions were evaluated by SEM micrographs and compared with those obtained for SS cathode. In Figure 2, it is also possible to observe a comparison between the deposits obtained on both Ni and SS cathode, where there is a clear difference on grain size and their distribution. The indium deposit on Ni cathode shows grains higher than 80 µm with a lamellar microstructure formation. Instead, the deposit on SS cathode presents like-rounded grains around 40 µm with a less compact morphology. The indium deposit shows typical defects because of the hydrogen evolution for both Ni and SS cathode. Figure 3a-b illustrates the presence of hydrogen evolution on the indium deposit. Initially, the formed hydrogen as bubbles remains both cathode and indium deposit surface until the bubble size becomes large enough to detach or collapse. Then during the growth phase, the bubble adsorbed on the surface isolates the underlying metal hindering the indium deposition and leaving a cavity. This previous behavior is observed both on the SS and Ni cathode, leaving more rounded cavities on deposits obtained by using SS cathode, while the deposit on Ni cathode suggests a higher compact microstructure due to closer cavities presence.

On the other hand, the electrochemical response of each support near the metal surface represent an important point to be considered. In this regards, electrochemical analyses were initially performed on different metal support (Cu, Ti and Al). The initial electrochemical findings, by using cyclic voltammetry (CV) to determine main electrochemical features, indicate that on each metal support occurs: indium reduction reaction (In3+/In0), indium stripping reaction (In0/In3+) and hydrogen evolution reaction (HER, H+/H2(g)). The characteristic stretching of each curve and the numerical treatment have allowed to determine the irreversible features of the indium discharge on each studied metal. Both Al and Ti cathode show an irreversible behavior, while Cu cathode highlights its quasi-reversible behavior for indium reduction reaction. Based on the current results, it is necessary to focus on the kinetic features considering the hydrogen evolution effect on the indium reduction reaction for metal with low hydrogen overpotential such as nickel and stainless steel. This study also will be part of the aims for the next doctoral year.

Finally, due to the system complexity, the principle of metal electrodeposition has been used in the manufacture of a Cu coating on FBG (Fiber Bragg Grating) sensor, before testing it with Indium. The application has been utilized for the temperature and mechanical stresses measuring on the overhead contact wire (OCW). The measuring system is composed of the Cu-coated fiber bonded two modified clamps which can be attached on the current electrical infrastructure in railway network. Figure 4 shows the aspect of the copper coated fiber in different view and scales. It is possible to observe that suitable electrodeposition operating conditions have allowed to obtain concentrical and compact coating without internal defects, which could affect the sensing response under thermal and mechanical stresses.

References

[1]K.J. Schulz, J.H. DeYoung, J.R.R. Seal II, and D.C. Bradley, Chapter I. Germanium and Indium, in: Crit. Miner. Resour. United States — Econ. Environ. Geol. Prospect. Futur. Supply, Reston, Virginia, 2017: pp. I2–I27.

[2]C. Lupi, D. Pilone, In(III) hydrometallurgical recovery from secondary materials by solvent extraction, J. Environ. Chem. Eng. 2 (2014) 100–104.

[3]B. Swain, C.G. Lee, Commercial indium recovery processes development from various e-(industry) waste through the insightful integration of valorization processes : A perspective, Waste Manag. 87 (2019) 597–611.

[4]Alfantazi, A.M., Moskalyk, R.R., 2003. Processing of indium: a review. Miner. Eng. 16, 687–694.

[5]Chou, W.L., Huang, Y.H., 2009. Electrochemical removal of indium ions from aqueous solution using iron electrodes. J. Hazard. Mate. 172, 46–53

[6]Lee, S., Lee, S-Y., Swain, B., Cho, S-S. and Lee. C.G., 2016, A validation experiment on indium recovery by electrowinning of aqueous electrolytes: Optimization of electrolyte composition. Mater. Test. 58 (11-12) 1001-1004.

[7]W. Chou, Y. Huang, Electrochemical removal of indium ions from aqueous solution using iron electrodes, J. Hazard. Mater. 172 (2009) 46–53.

[8] Ciro, E., Dell’Era, A., Pasquali, M., & Lupi, C. (2020). Indium electrowinning study from sulfate aqueous solution using different metal cathodes. Journal of Environmental Chemical Engineering, 8(2), 103688.

[9] Dell’Era, A., Ciro Zuleta, E., Pasquali, M., & Lupi, C. (2020). Process parameters affecting the efficiency of indium electrowinning results from sulfate baths. Hydrometallurgy, 193.

2. Seminari, Corsi, Workshop e Scuole

· Disaster mitigation and sustainable engineering – Recent progress and future direction. Horishi Asanuma, Chiba University.

· An Overview and Future Development of Robust and Smart Materials/Structures. Horishi Asanuma, Chiba University.

· Strengthening and toughening mechanisms for nano-composite materials. “Meccanismi di rinforzo e tenacizzazione nei materiali nano-compositi” Ph.D Laura Paglia, Sapienza-University of Rome.

· Effect of xanthan gum and psd on permeability of mud-cake produced during drilling operation. Prof. Jose Angel Sorrentino, University of Caracas.

· Waste to fuel.Prof. Giacomo Rispoli.

· “An alternative recovery of indium by electrowinning and some applications” Erwin Ciro, Sapienza-University of Rome.

· “An introduction to NMR spectroscopy for the study of biomacromolecules” Part 1 Dott.ssa Mariapina D'Onofrio, University of Verona.

· “An introduction to NMR spectroscopy for the study of biomacromolecules” Part 2 Dott.ssa Mariapina D'Onofrio, University of Verona

· “Sviluppo e fabbricazione di strutture aerospaziali in materiale (nano)composito” Dott.ssa Susanna Laurenzi, Sapienza-University of Rome.

3. Periodi trascorsi all’estero

None

4. Partecipazione a Congressi Nazionali e Internazionali

NanoInnovation 2020 Conference and exhibition - September 15 – 18.

5. Pubblicazioni su atti di convegno (prodotte o in corso di pubblicazione)

None

6. Pubblicazioni su riviste (prodotte o in corso di pubblicazione)

· Published paper: Process parameters affecting the goodness of indium electrowinning results from sulfate baths – Hydrometallurgy. Doi: 10.1016/j.hydromet.2020.105296

· Published paper: Indium electrowinning study from sulfate aqueous solution using different metal cathodes – Journal of Environmental Chemical Engineering. Doi: 10.1016/j.jece.2020.103688

· Published paper: Static and dynamic weighing of rolling stocks by mean of a customized FBG-sensorized-patch. 2019. SAFE 2019. International Journal of Safety and Security Engineering. Doi: https://doi.org/10.18280/ijsse.100111

· Submitted - Operating condition monitoring system of railway overhead contact wire, by means of FBG sensors: design, development and analysis – Sensors and Actuators A: Physical. (under review)

· Submitted - Comparing indium electrowinning on AISI 316L stainless steel and nickel cathodes from sulfate solutions. Minerals engineering (under review)

· To be presented - Indium electrowinning kinetics from sulfate solution on titanium, aluminum and copper supports.

Allegati (Figure e tabelle)

Figure 1. Current density effect on indium electrowinning process at: 25 A/m2, 100 A/m2, 200 A/m2 and 300 A/m2.

Table 1. CE and SEC for the indium electrowinning using SS cathodes.

Cathode

Cell voltage (V)

% CE

SEC (kWh/kg)

CD

[A/m2]

Ni

2.26

~98

1.7

80

SS

2.27

~95

1.7

25

Figure 2. Indium deposits micrographs at the optimized conditions for: a) Ni and b) SS cathode.

Figure 3. Hydrogen cavities on the indium deposit surface on: a) SS and b) Ni cathode.

Figure 3. Aspect of the copper coated fiber at: (a) optical general view, (b) SEM micrograph general view, (c) cross section and (d) surface morphology