Box–Behnken factorial design study of the variables affecting metal electrodeposition in membraneless fluidized bed electrodes

Abstract

BACKGROUND: Heavy metal removal from industrial wastewaters has been studied intensively since it is well known that they can cause severe problems to human health and aquatic life, even at very low concentrations. Traditional precipitation or adsorption technologies only transfer the problem to the solid phase, therefore new technologies, such as electrodeposition using fluidized bed electrodes (FBE), have been considered to avoid contamination. RESULTS: Copper electrodeposition from diluted solutions was carried out using a membraneless FBE. The supporting electrolyte concentration (Cs) was the main variable affecting the current efficiency (CE), energy consumption (EC), and space‐time yield (Y). Although it does not change the response surface morphology, increasing Cs there was an important improvement of CE, Y, and EC. The effects of current and bed expansion are much more complex, since an interaction effect between these two variables was verified. Considering only the region of active kinetic control, copper can be optimally recovered with CE > 90%, Y ∼93 kg h−1 m−3, and EC ∼3.2 kWh kg−1 by applying the highest levels of the independent variables. CONCLUSIONS: The results suggest that electrodeposition using a membraneless FBE is an excellent method for the treatment of effluents contaminated with copper or other metals. © 2012 Society of Chemical Industry

Heavy metal removal from simulated wastewater using electrochemical technology: optimization of copper electrodeposition in a membraneless fluidized bed electrode

“…3a that the operational conditions (I and E) and C s had main influence on the value of CE act , while C 0 influenced ACE since the initial concentration determines the relative contribution of the activated control and the mass transfer control to the overall reaction. The role of I, E, and C s on CE act was already studied in a previous work (Tonini et al 2013), but in order to optimize the process as Heavy metal removal from simulated wastewater… a whole, in this study the influence of mass transfer and C 0 on the average process responses were also considered. The values of IEC were inversely proportional to ICE [Eq.…”

“…The variables affecting cadmium removal using a rectangular spouted bed reactor were described by Baghban et al (2014). Although there have been several reports concerning the use of fixed bed electrodes, studies of fluidized bed reactors are lacking (with the exception of our own work, reported by Tonini et al 2013). The most recent article concerning the use of a FBE for metal recovery was published by Thilakavathi et al (2012), who used a theoretical model to predict the bed thickness and hydrodynamic behavior of the conducting particles in an expanded bed reactor.…”

“…One of the main drawbacks of using FBEs is that the cathodic and anodic compartments are separated by a membrane, which (in addition to perturbation of the fluid dynamics) makes the system unstable due to uneven electrical contact and current distribution. Tonini et al (2013) described the use of a new membraneless FBE for the removal of copper from dilute aqueous solutions. The membraneless reactor is a onecompartment reactor that does not require the use of an expensive membrane to separate the cathodic and anodic reactions.…”

“…The advantages of this type of reactor are that it is simpler, cheaper, and easier to maintain. Tonini et al (2013) studied the effects of three important operational parameters that affect the electrodeposition performance of membraneless FBE. Current, bed expansion, and supporting electrolyte concentration were investigated, since these factors influence the charge and mass transfer, as well as the conductivity of the solid phase.…”

“…Different to the earlier work (Tonini et al 2013), both the activated and mass transfer control regions of the concentration-time curve were used to calculate the average values of the response variables. The effects of four process variables (current, bed expansion, supporting electrolyte concentration, and initial copper concentration) were systematically investigated according to a Box-Behnken experimental design, in order to determine the main and interaction effects of the independent variables.…”