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The technological progress and consumerism trend stimulate electric and electronic equipment replacing, inducing the generation of huge amounts of wastes, many of them containing dangerous (but valuable) waste printed circuit boards (WPCBs). A promising technology for their recycling is based on the electrochemically regenerable Br-/Br2 leaching system, for which the raw materials can be produced and recycled by electrochemical ways. In this context, the present work presents our research concerning the feasibility to produce by electrodialysis, on-site, HBr and KOH, which are required for the electro-hydrometallurgical recovery of metals from WPCBs. For this purpose, a four-compartment filter-press electrochemical reactor, divided by two cation and one anion exchange membranes, was used. The obtained results demonstrate that the proposed process can produce, at a current density of 4 kA/m², target solutions with concentrations over the required value (of 0.5 M), with average current efficiencies over 73% and 82%, and average specific energy consumptions around 40 and 25 kWh/kg for HBr and KOH, respectively. Moreover, several preliminary measurements performed simultaneously with the electrodialysis tests revealed that, by acquiring rigorous temperature data, the concentrations of the target solutions can be easily and rapidly evaluated and monitored on-line using simple electrochemical sensors for pH and conductivity, but more accurate and exhaustive calibration data is required. [ABSTRACT FROM AUTHOR]

Recycling Li-ion batteries (LIBs) is a globally discussed issue in relation with waste management and environmental protection. This review reports the recent research and industrial progresses in LIBs recycling. After a brief introduction concerning the importance of LIBs recycling, and their structure and applications, the main aspects dedicated to LIBs recycling (pre-treatment, pyrometallurgical and hydrometallurgical processes) are presented. Greater attention has been paid to the hydrometallurgical processes due to their complexity but also because they can lead to the production of valuable products without a high ecological impact (compared to pyrometallurgical ones). Given that today, worldwide, only about 5% of spent LIBs are recycled, the data presented in our review can inspire the design and implementation of competitive technologies that fit into a sustainable circular economy that preserves the primary resources and ensures the environmental protection. [ABSTRACT FROM AUTHOR]

This paper presents our results concerning the feasibility of selective potentiostatic electroextraction of copper, tin and lead from leaching solutions obtained during the recycling of base metals from waste printed circuit boards. Applying this protocol, in a first stage, the concentration of Cu ions from the leaching solutions can be lowered, with acceptable efficiency, below 0.5 g/L. To avoid the contamination of Sn-Pb alloys with Cu, an intermediary step of Cu cementation on metallic Sn were proposed and tested. Finally, the potentiostatic selective electrodeposition protocol was successfully applied for the electroextraction Sn-Pb alloys. The experiments were performed in real leaching samples, using a Fisher type electrode as cathode. The obtained experimental results demonstrate that, controlling rigorously the imposed potential and corelating them with the solution composition, high purity Cu and Sn-Pb alloys deposits can be obtained, maximum contents of 99.96%, 99.83% and 82.62% being evaluated for Cu, Sn and Pb, respectively. [ABSTRACT FROM AUTHOR]

This article presents our results concerning the feasibility of selective electroextraction of copper from leaching solutions obtained during base metals recycling from waste printed circuit boards. The researches were focused on the intensive copper electrodeposition as a potential parallel paired process for the electrochemical regeneration of the leaching solutions. Preliminary tests, performed by cyclic voltammetry on 316 stainless steel disc electrode in synthetic solutions of CuBr2, SnBr2 and PbBr2, indicate the possibility of selective electroextraction of Cu if the electrodeposition potentials of Sn and Pb are not exceeded. Therefore, selective and intensive Cu electrodeposition tests were accomplished in galvanostatic mode, in a real sample of leaching solution, using also 316 stainless steel sheets cathodes. The experimental results demonstrate that the selective electrodeposition of Cu is possible in a wide range of current densities, between 200 and 600 A/m², if the concentration of Cu in solution of at least 12 g/L is maintained. Under these conditions, the purity of the obtained Cu deposits can attain 99.6%. [ABSTRACT FROM AUTHOR]

Nowadays there is increasing interest in using various electrochemical methods as alternative to the energy consuming physico - mechanical, hydrometallurgical and pyrometallurgical techniques for metals recovery from waste printed circuit boards (WPCBs). Thus, cyclic voltammetry (CV) and cyclic square-wave voltammetry (CSWV) methods were used for studying the electrochemistry of some metals (Cu, Sn, Pb, Fe, Zn) on glassy carbon electrode from synthetic leaching solutions containing known concentrations of metallic ions and in real solution obtained from dissolving 10 WPCBs. A good linear correlation was obtained between the parameters evaluated by ICP-OES and cyclic voltammetry. The influence of pH and oxidation/reduction potential (ORP) on the corrosion rate of the mentioned metals was studied gravimetrically. Based on the obtained results, a complex sensors array (amperometric, pH, temperature and ORP) was proposed to assure the accurate monitoring and control of the electrochemical process for metals recovery from WPCBs. [ABSTRACT FROM AUTHOR]

Even if the mobile devices gain more popularity comparing to the desktop personal computers (DPCs), the last ones are still intensively used where highly computing or storage capabilities are required. Because the replacing rate of DPCs are very high, the amount of obsolete equipments is also huge, reclaiming adequate efficient and ecological recycling techniques. In this field, the main efforts are focused on the DPCs motherboards (DPCMBs) recycling because, even if they represent only 5 to 10% from the DPCs weight, they concentrate up to 80% from the recoverable value. By accounting the DPCMBs' traditional and incipient recycling technologies, it is obvious that none of them can solve alone the problem of this waste type. In this context, during the present work, the composition evolution of 10 DPCMBs released between 1998 and 2008 was evaluated and analyzed, the obtained results being used to design a feasible and eco-friendly combined strategy for integral DPCMBs recycling. [ABSTRACT FROM AUTHOR]

In this paper, an optimal artificial neural network determined by a self‐adaptive differential evolution approach is applied to model and optimize the removal of copper from wastewater by an ion‐exchange process. The Purolite S930+ resin with iminodiacetic group was used in batch mode for Cu(II) removal from synthetic aqueous solutions in different working conditions (initial solution pH, stirring rate, initial concentration of copper, temperature, contact time and resin amount). The obtained results indicated that the used methodology was able to provide good models for the studied process, the mean squared error in the testing phase obtained by the best network being 0.0034. In addition, the optimal combination of parameters leading to the maximization of removal efficiency determined with the proposed approach was experimentally validated, the prediction being in correlation with the observed data. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 605–612, 2018 [ABSTRACT FROM AUTHOR]

In the context of the large and increasing interest for an efficient and ecological recycling of the Waste Electrical and Electronic Equipments (WEEEs), we decide to evaluate the feasibility of an electrochemical recycling process for waste printed circuit boards (WPCBs) based on bromine-bromide leaching system. For this preliminary study, a perforated rotating drum chemical reactor (RDCR), interconnected with a divided electrochemical reactor (DER) in a closed hydraulic loop, was successfully used to dismantle consecutively three computer motherboards (CMB) after a minimal mechanical pre-treatment. Essentially, the base metals were leached at the RDCR level and the bromine-bromide system was regenerated at the DER level, simultaneously with the partial electrodeposition of dissolved metals. Even if the operating parameters were not optimized, each CMB was completely dismantled in around 18 h, with cathodic and anodic mean current efficiencies of 43.6% and 58.4%, respectively. Notably, grace to the proposed process, the remaining undissolved parts (fiberglass reinforced epoxy boards, electronic components, plastics, etc.) preserve their original shape and structure, allowing an easier consequent separation-classification and a more efficient and profitable recycling. [ABSTRACT FROM AUTHOR]

The increase of the graphite electrocatalytic activity toward hydrogen peroxide (HP) electrosynthesis (HPE) by the partial electroreduction of O2 can be achieved by in-situ electroactivation (EA). Our previous studies completed in strong alkaline media (1 M NaOH) by galvanostatic multisequence EA techniques (MSETs) revealed that an adequate graphite EA can improve HPE current efficiency (CE) up to 35 % compared to the unmodified graphite. In order to implement the optimised operational parameters to a micro-pilot scale electrochemical reactor, in a first step, several systems for the on-line HP concentration monitoring were designed and tested. Unfortunately, the preliminary test, even in moderate alkaline media (0.1 M NaOH) revealed that, at concentrations greater that 50 ppm, the HP decomposes intensively in contact with the setup components, disallowing the HP accumulation. As a consequence, for all further experiments, the alkaline supporting electrolyte was replaced with 0.1 M Na2SO4. In these new conditions, two models of HP on-line detectors (spectrophotometrical and amperometrical) were designed and tested, presenting adequate limit of detection (L.O.D. = 10 ppm and L.O.D. = 0.23 ppm, respectively). Also, the HPE process was studied in sulphate media, using a Pt/graphite wall-jet ring disk electrode system, revealed that the CE can reach a 46 % value for the unmodified electrode and increases up to 52 % when the auto-adaptive galvanostatic MSETs protocol is used. [ABSTRACT FROM AUTHOR]

The ability of unmodified or PbO2 coated spectral graphite (SG), to act as positive electrode in an all vanadium redox flow battery was tested. Our results showed that the unmodified SG requires simple pretreatment and is efficient in terms of current due to a large active area, 4 time greater that the geometrical one. The PbO2 deposits were grown on surfaces that previously received only basic treatment, but present a poor stability. In all experiments, large separations of anodic and cathodic peak potentials (between 118 and 1015 mV) were observed, proving the irreversibility of the VV to VIV redox couple on all studied materials. [ABSTRACT FROM AUTHOR]

Electrochemical oxidation/reduction of carbonaceous electrodes represents a simple and inexpensive way for in-situ electroactivation (EA), increasing the electrocatalytic activity toward hydrogen peroxide electrosynthesis (HPE). In this context, our previous results obtained by cyclic hydrodynamic voltammetry (CHV) and an original potentiostatic multi-sequence electroactivation technique (MSET) revealed that the graphite anodization followed by the surface partial reduction has a positive effect upon the HPE efficiency. Unfortunately, CHV is not suitable for industrial approaches and the use of MSETs in potentiostatic mode induces prohibitive electrical energy consumptions during the EA steps. In order to overcome these drawbacks, in this work, new galvanostatic MSETs were designed and tested in hydrodynamic controlled conditions using a Pt/graphite wall-jet ring disk electrode system. The galvanostatic approach diminished significantly the electrical energy used for graphite EA (under 30 % from the global consumption) and improved HPE efficiency up to 35 % compared to the unmodified graphite. The best results were obtained when original auto-adaptive protocols were used. Finally, in the attempt to eliminate the energy waste during the EA steps, we proposed the use of a symmetrical divided reactor with periodic inversion of the electrodes function and the feasibility of this idea was also tested with very promising results. [ABSTRACT FROM AUTHOR]

Lithium-ions batteries are widely used in many domains, from small dimensions gadgets to electric vehicles. For this type of batteries, an essential problem is strictly related to the achievement of an electrodic structure that will allow the reversible insertion/extraction of Li+ ions. In this context, LiMn2O4 can be a promising material. In the present paper, nanosized LiMn2O4 particles were synthesized and physically characterized and the obtained powder was embedded in carbon-paste electrodes and electrochemical characterized by cyclic voltammetry. The obtained results prove that the synthesized powder present a spinel structure and a reversible redox activity. The best electrochemical behaviour was recorded for a mass ratio between spinel and graphite powder of 1:2. [ABSTRACT FROM AUTHOR]

Studies concerning the hydrogen peroxide electrosynthesis carried out by cyclic hydrodynamic voltammetry (CHV), revealed that graphite anodisation followed by a sequence of surface partial reduction has a positive effect upon the HPE efficiency. In order to improve the promising results obtained by CHV a set of original multi-sequences techniques for repetitive potentiostatic graphite electroactivation for HPE efficiency improvement was designed. The new electroactivation protocols were tested in hydrodynamic controlled conditions using a Pt-graphite wall-jet ring disk electrode. The potentiostatic measurements using different shapes of the applied signal allowed us to identify the possible processes involved in the electroactivation and production sequences. Experimental optimisation of the original potentiostatic electroactivation technique of the graphite cathode was carried out leading to a decrease of the electrical energy consumption. [ABSTRACT FROM AUTHOR]

The hydrogen peroxide electrosynthesis by partial reduction of oxygen represents an attractive alternative to the anthraquinone process. The result presented in this paper show that the two steps electro-activation of a graphite electrode, consisting in the oxidizing of the surface followed by the partial reduction of the active sites generated upon oxidation, induces an improvement of hydrogen peroxide electrosynthesis efficiency. Because the stability of the generated active sites is limited, a special programmable cyclic multi-step technique was used and the experimental parameters were optimized for a rectangular shape applied potential. In order to understand the electrosynthesis mechanism and to optimize the electro-activation potentials, cyclic hydrodynamic voltammetry studies were performed. For all the measurements, a wall-jet ring disk electrode was used. [ABSTRACT FROM AUTHOR]

Nowadays, the damage of the environment quality has reached alarming levels requiring severe measures for stopping this process. In order to harmonise with the maximum admitted concentrations of nitrate in the discharged effluents, the electrochemical procedures represent a clean, flexible and efficient alternative of decontamination. Electrochemical reduction of nitrate/nitrite (ERNN) can be advantageously applied to the treatment of industrial waste water, whereby this species can be transformed into harmless products. In this context, the present paper describes the results of our researches concerning the design of an original technique for on-line detection of electroactive products resulted from ERNN in alkaline media. The obtained results shows that, using an adequate pH value, at least three electroactive species generated from the NO3 - reduction (NO2 -, NH2- OH and NH4 +) could be electrochemically detected at different applied potentials on the Pt-ring electrode. [ABSTRACT FROM AUTHOR]

This work presents the results concerning the copper recovery by electrodeposition from a synthetic solution simulating the dissolution of metallic part of electronic wastes in H2SO4. Batch electrolyses were carried out on graphite rotation disc electrode, at cathodic potentials between -100 and -300 mV vs. Ag/AgCl reference electrode and rotation rate from 100 to 700 rpm. The purity of cathodic deposit was evaluated by ICP-MS spectroscopy. The copper recovery efficiency from the synthetic solutions depends on applied cathodic potential. At more negative values (-300 mV), the electrodeposition rate increases, but the current efficiency and the deposit quality decrease. The electrodeposition tests confirm the possibility of copper recovery from a synthetic solution simulating the dissolution of the metallic part of electronic wastes in H2SO4, and the purity of the copper deposits are greater than 99 % in all of the tests. [ABSTRACT FROM AUTHOR]

An experimental study concerning the copper removal from a simulated wastewater containing 10 ppm of Cu2+ ions was performed in a continuous flow electrochemical reactor equipped with a rectangular threedimensional (3D) cathode made of reticulated vitreous carbon (RVC) with 100 ppi porosity. The influence of low supporting electrolyte concentrations and of the electrode polarisation potential was investigated. The reactor performance was evaluated considering the residual copper concentration and the specific energy consumption. After 90 min of electrolysis, the copper ion concentration was reduced to less than 0.1 ppm, permitting the discharge of the treated solutions to the drain system. With an operating cell voltage around 1.8 V, specific energy consumptions close to 0.18 kWh per cubic meter of treated wastewater was calculated. [ABSTRACT FROM AUTHOR]