Emulsion Pertraction Technology Research Articles

Selective Recovery of Zinc over Iron from Spent Pickling Wastes by Different Membrane-based Solvent Extraction Process Configurations

This paper reports the selective separation of zinc over iron from spent pickling wastes or effluents using two different membrane-based solvent extraction process configurations, Nondispersive solvent extraction (NDSX) and emulsion pertraction technology (EPT). The process aims to obtain a highly concentrated zinc solution with a negligible content of iron to allow for Zn electrowinning. The effect of the following process variables on the kinetics and selectivity of zinc separation has been evaluated: (i) process configuration NDSX and EPT, (ii) extractant concentration, tributylphosphate (TBP) in the range of 20–100% v/v and (iii) stripping phase/feed phase volume ratio in the range Vs/Va 0.2–2. The transport of iron, chloride and free acid has been also monitored to gain insight into the separation fundamentals. EPT configuration overcame NDSX in terms of zinc and iron separation kinetics, although separation selectivity (at 30 min) was higher for NDSX configuration, αZn/Fe = 22, compared to EPT proce...

Improvement of the electrochemical behaviour of Zn-electroplated steel using regenerated Cr (III) passivation baths

Conversion coatings based on trivalent chromium are more sensitive to the presence of zinc and iron impurities than the chromate formulations. This fact contributes to a decrease in the quality of passivation and to the generation of a significant amount of hazardous liquid waste. Recently, a new eco-innovative process based on Emulsion Pertraction Technology (EPT) is being implemented at industrial scale for selectively removing Zn and Fe from spent passivation baths in order to enhance the lifetime of the Cr (III) baths. In this study, the effect of Zn and Fe removal on the electrochemical behaviour of Zn-electroplated steel samples was evaluated by means of polarisation curves and electrochemical impedance spectroscopy measurements at open circuit potential conditions in 3.5g/L NaCl solutions. The main objective was to assess the benefits brought by EPT using electrochemical methods. Cr (III) passivation baths regenerated using the EPT process have been compared to the bath used in a local industry as well as to fresh and spent baths. According to the results, the samples passivated in the EPT regenerated bath showed a significant improvement in their electrochemical behaviour compared to the samples passivated in the spent baths. This study concluded the suitability of EPT for regenerating Cr (III) passivation baths.

Implementation of an eco-innovative separation process for a cleaner chromium passivation in the galvanic industry

Abstract This paper reports the development and implementation of the eco-innovative process Emulsion Pertraction Technology (EPT) for the selective separation of zinc and iron impurities from used trivalent chromium passivation baths. The main goal was to purify the passivating formulations in order to extend their lifetime. Commercial hollow fibre membrane modules were used to provide the non-dispersive contact between the passivation bath and the emulsion extractant phase. Two passivation baths employed at two industrial facilities with initial concentration of metals in the range 3000 0 0 0 2 . The results showed that the effectiveness of EPT was enhanced by the countercurrent operational mode and high flow rates of the emulsion and passivation phases. The performance of the technology for purifying different commercial formulations of chromium (III) baths was proved to be comparable. The best experimental conditions resulted in a decrease of the feed concentration of Zn and Fe of 95% and 98%, respectively, and in a stripping solution enriched in Zn and Fe: 160,000 mg/L of Zn and 49 mg/L of Fe. The process scale-up was evaluated at industrial scale using an EPT unit with a membrane area of 40 m 2 . The mass transfer flux of Zn was 4.5 g/m 2 h, while the flux of Fe was 0.025 g/m 2 h. These values can be used as reference for the scale-up of the process. This work concludes that the implementation at industrial scale indicated the great prospects of EPT on applications in the surface treatment sector. Zinc recovery by electrowinning is recommended.

Environmental Sustainability Assessment of an Innovative Cr (III) Passivation Process

A life cycle assessment was conducted for the Zn-electroplating products passivated by different processes in a small and medium enterprise. The goal was to evaluate and to compare the environmental impact associated to the conventional and alternative passivation process from a “cradle to grave” analysis. The assessment was divided into “cradle to gate”, “gate to gate”, and “gate to grave” steps for natural resources usage and environmental burdens. The innovative process was based on the integration of emulsion pertraction technology to the passivation bath in order to extend its lifetime. Results showed that the transferred hazardous waste from the process to the landfill was the major contributor to the environmental impact of the conventional and innovative passivation. The manufacture of the sodium hydroxide needed in the wastewater treatment process had a main role in the impacts of the “cradle to gate” cycle. This work concluded that the innovative passivation decreased most of the generated waste (92%) during the manufacture cycle of the passivated product as a consequence of the extension of the lifetime of the passivation bath. A reduction of the total environmental burdens to air and to water and the resource usage during the whole manufacture cycle of the product was stated. The environmental burdens to air and to water were mainly connected to the environmental impacts: human health effects and ecotoxicity to aquatic life, respectively.

Temperature Enhancement of Zinc and Iron Separation from Chromium(III) Passivation Baths by Emulsion Pertraction Technology

This work reports the influence of the temperature on the selective removal of zinc and iron from a chromium(III) passivation bath by emulsion pertraction technology using Cyanex 272 as extractant and hollow fiber membrane contactors. The results indicate that the kinetics of the separation was largely influenced by the temperature in the range 10–40 °C. The viscosity of the organic liquid phase was measured at different temperatures and extractant concentrations, and the results were fitted to the Riedel and Grunberg and Nissan correlations. The improvement observed from 20 to 40 °C was explained by the increase in the diffusion coefficient of the zinc and iron organometallic complexes through the liquid membrane. However, the remarkably slower zinc and iron separation rates observed at 10 °C in comparison with those at 20–40 °C were attributed to a shift in the driving force due to an endothermic change of the interfacial extraction reaction. The equilibrium parameters at 10 and 20–40 °C were estimated by fitting the experimental kinetic results to the proposed mathematical model. Thus, this work addresses the thermal character of equilibrium and its relevant influence on the separation kinetics of reactive membrane systems.

The Use of Emulsion Pertraction Technology as an Eco–innovative Membrane Process for the Galvanic Industry

TIGI Project was financed by the 7th Framework Programme of the UE (contract number 218390-2). The collaboration of the SME company Zinper is specially acknowledged.

Zinc recovery and waste sludge minimization from chromium passivation baths

This work reports the feasibility of applying emulsion pertraction technology (EPT) aiming at zinc recovery and waste minimization in the zinc electroplating processes that include Cr (III) passivation. The assessment consists of firstly the lifetime extension of the passivation baths by selective removal of the tramp ions zinc and iron, and secondly, the recovery of zinc for further reuse. Spent passivation baths from a local industry were tested, being the major metallic content: Cr 3+ 9000 mg L −1, Zn 2+ 12,000 mg L −1, Fe 3+ 100 mg L −1. Working in a Liqui-Cel hollow fiber membrane contactor and using the extractant bis(2,4,4-trimethylpentyl) phosphinic acid, reduction of zinc and iron concentrations below 60 mg L −1 and 2 mg L −1, respectively were obtained, while trivalent chromium, the active metal that generates the passivation layer, was retained in the baths. Zinc was selectively transferred to an acidic stripping phase that in the experimental time reached a concentration of 157,000 mg L −1. Zinc recovery by electrowinning from the acidic stripping phase without any pretreatment of the electrolyte solution provided a purity of 98.5%, matching the lower commercial zinc grade. As a result of the extension of the life time of the passivation bath, significant environmental advantages are derived such as minimization of the volume of hazardous wastes and savings in the consumption of raw materials.

Development and validation of a dynamic model for regeneration of passivating baths using membrane contactors

This work aims at the development of a dynamic model for the mathematical description of facilitated transport separation processes carried out in membrane contactors where mass transport phenomena are coupled with chemical reactions. A general model that takes into account the description of all possible mass transport steps and interfacial chemical reactions is initially presented, allowing its application to a wide range of separation processes and operation conditions. The analysis of the specific system under study, regeneration of trivalent chromium spent passivating baths by removal of zinc using the emulsion pertraction technology, allowed to define several assumptions obtaining simplified models with minimum number of uncertain parameters and mathematical complexity. The final equations and parameters were validated with experimental data reported in a previous work ( Urtiaga, Bringas, Mediavilla, & Ortiz, 2010).

Selective extraction of zinc and iron from passivating baths

In this work, the viability study of the removal of zinc and iron from chromium (III) passivating baths is presented. The Emulsion Pertraction Technology (EPT), a liquid–liquid extraction process performed in membrane contactors has been applied. Real passivating baths with the following metal concentrations have been tested: Zn, 7000 mg/L; Fe, 30 mg/L and Cr, 5500 mg/L respectively. After the EPT treatment and at the applied experimental conditions, these concentrations were decreased to 2450 mg/L of Zn and 4 mg/L of Fe, while the chromium concentration was maintained approximately at the initial value. The EPT process allowed the simultaneous recovery of Zn in a concentrated stripping phase. The influence of the pH of the feed phase strongly affected the kinetics of metals removal. A value of pH = 2.5 allowed to attain the required high selectivity values of α Zn/Cr.

Influence of operation variables on the recovery of zinc from spent pickling effluents using the emulsion pertraction technology

Spent pickling effluents coming from hot-dip galvanizing processes contain high amounts of zinc and other metallic compounds in hydrochloric acid media. Thus, the effluent has a strong hazardous character and needs to be treated before disposal. Emulsion pertraction (EPT) with hollow fiber modules, can be considered as a clean alternative able to carry out the separation and recovery of zinc. After demonstrating the viability of EPT for the treatment of this kind of effluents in previous works using tributyl phosphate (TBP) as extractant agent and service water as back-extraction agent, several experiments were performed to analyse the influence on the extraction (EX) and back-extraction (BEX) kinetics of the main operation variables: (i) initial zinc concentration in the aqueous feed phase, (ii) organic phase/stripping phase volume ratio in the emulsion stream and (iii) emulsion volume.

Phenol recovery from phenolic resin manufacturing: Viability of the emulsion pertraction technology

In this paper, the viability of emulsion pertraction technology (EPT) for phenol recovery from the aqueous condensates obtained in the manufacturing of phenolic resins is described. This waste is highly concentrated in phenol (15–25 wt%) and formaldehyde (10–15 wt%). The experimental work was performed using real effluents of a phenolic resin producer. The simultaneous selective extraction and recovery of phenol from the condensate is performed in a single hollow fiber membrane contactor. Kerosene and its mixtures with a highly effective phenol extractant, Cyanex 923, were used as organic solvents. Phenol was transferred to the caustic stripping phase to give a final phenol concentration in the treated waste less than 0.5 wt%, whereas formaldehyde remained in the feed, thus providing the required selectivity. Phenol recovery was attained after acidification of the concentrated stripping phase.

Selective membrane alternative to the recovery of zinc from hot-dip galvanizing effluents

This work reports the study of the kinetics of zinc recovery from spent pickling solutions by means of emulsion pertraction technology (EPT) in order to reuse the metal in electrolytic processes. Tributyl phosphate (TBP) and service water were used as extraction (EX) and back-extraction (BEX) agents, respectively. Kinetic experiments were carried out in hollow fiber membrane contactors in order to analyse the influence of several operation variables on the rate of zinc recovery. A mathematical model that considers the mass transfer resistance shared between the organic liquid membrane and the organic phase boundary layer was developed; the mass transfer coefficients were estimated by means of the parameter estimation tool ASPEN CUSTOM MODELER (from ASPENTECH) to obtain the values k m = 2.68 × 10 −7 m/s and A V k o = 0.0125 s −1. Simulated results agreed satisfactorily well with experimental data. Consequently, the kinetic model and parameters were confirmed. Finally, a comparison between EPT and non-dispersive solvent extraction (NDSX) was carried out in order to evaluate the advantages and disadvantages of both membrane configurations.

Uphill permeation of Cr(VI) using Hostarex A327 as ionophore by membrane-solvent extraction processing

The transport of chromium by the emulsion pertraction technology (EPERT) using Hostarex A327 (tertiary amine) as a carrier has been investigated. The permeation of the metal is studied as a function of various experimental variables: hydrodynamic conditions, concentration of Cr(VI) and HCl in the source phase, carrier concentration and diluent in the organic phase, strippant concentration in the stripping phase and support characteristics of the membrane. The mass transfer coefficient and the thickness of the aqueous source boundary layer were estimated from the experimental data. Furthermore, the selectivity of the Hostarex A327-bases EPERT towards different metal ions and the behaviour of the system against other carriers are presented.

Optimal Groundwater Remediation Network Design Using Selective Membranes

This work deals with the optimal synthesis of groundwater remediation networks for the valorization of anionic pollutants by means of emulsion pertraction technology using hollow fiber modules (HFMs). Superstructures that incorporate all possible design alternatives are proposed. The aim of this work is to obtain a minimum cost groundwater remediation network that allows treatment of groundwater to required levels and, also, a contaminant rich solution that can be used for further processing. The optimization of the superstructure is initially formulated as a nonconvex nonlinear programming (NLP) problem. This rigorous NLP model is simplified using some assumptions to get a simplified model which is globally optimized using a Lagrangean decomposition algorithm. This globally optimal solution is used as an initialization point for optimizing the rigorous NLP problem. Three cases involving different numbers of HFMs are studied to determine a cost optimized network with an optimal number of modules.

Intensification of membrane processes. Remediation of groundwaters by emulsion pertraction as a case study

Membrane technology is strongly related tothe process intensification strategy, being thedesign of new operating modes one of the objec-tives, with the focus in the replacement of large,expensive and energy-intensive equipment withones that are less costly, more efficient or thatcombines multiple operations into a single appa-ratus [1]. Membrane contactors are expected toplay a decisive role in this scenario, based intwo principal characteristics: the ability to createa large exchange area for mass transfer and/orreaction and the independent fluid dynamics thatallow an easily controlled operation. Moreover,for the multiscale implementation of membranecontactors, effective computer aid processengineering is required [2]. The case study presented in this work is theremediation of polluted groundwaters containinghexavalent chromium coming from industrialeffluents leakages where other competitivespecies such as sulphate and chloride anions arealso present due to the reservoir location. Thedevelopment and implementation of the sustain-able technology that permits the recovery of thevaluable compounds and the effluent purifica-tion with minimum energy cost is of interest dueto the economical, environm ental and social bene-fits [3]. Membrane based solvent extractiontechnologies and in particular Emulsion Per-traction Technology (EPT) using hollow fibermodules, was the selected technology. In EPT,the aqueous phase with the target species is con-tacted in one hollow fiber module with an emul-sion formed by stripping phase dispersion intothe organic phase that contains a selectiveextractant. The chromium is transferred fromthe aqueous feed solution to the organic phase,and then it is transported to the internal back-extraction solution [4]. Thus, in the EPT technol-ogy, extraction and back-extraction operationsare efficiently combined in a single membranecontactor unit. The optimal emulsion pertraction processmust be able, with minimum cost, to obtaintreated effluent streams suitable of being dis-posed into the environment, and at the sametime a concentrated chromium stream that couldbe re-used in some industrial application. Thecosts evaluation in membrane processes can be

Separation and Recovery of Anionic Pollutants by the Emulsion Pertraction Technology. Remediation of Polluted Groundwaters with Cr(VI)

Polluted groundwaters with an average anionic composition of 9 mol Cr2O42-/m3, 64 mol SO42-/m3, and 9.2 mol Cl-/m3 were treated by the emulsion pertraction technology using Alamine 336 as the extractant and NaOH as the stripping agent, to reduce the concentration of chromate compounds and recover them in a concentrated solution. A careful experimental design was carried out to analyze the equilibrium and kinetic behavior of the separation system. The equilibrium parameters of the chemical reactions involved, Kiex, were calculated from the experimental data. A mathematical model that described the kinetics of the separation and concentration processes was developed, and the unknown model parameters, that is, the membrane and the organic phase mass transport coefficients, Km = 1.5 × 10-3 m/h and KoAv = 2.94 × 104 h-1, were estimated. Within experimental system the kinetic control is shared between the internal (feed phase) and the membrane mass transport resistances.

Use of membrane contactors as an efficient alternative to reduce effluent ecotoxicity

This works reports on the separation and recovery of copper cations from water streams from the wet peroxide oxidation process (WPO) using emulsion pertraction technology (EP) in hollow-fiber contactors as separation technology. The separation of the metal was enhanced by using LIX622N as a selective extractant, and its concentration took place in a sulphuric acid phase. The ecotoxicity characterization, according to the Vibrio fischeri bioassay of the waters coming from the WPO process, revealed that the presence of a residual copper catalyst gave the oxidized waters the character of being ecotoxic. Nevertheless, the subsequent removal of copper in the EP process produced non-ecotoxic oxidized water. Finally, the recovered copper catalyst obtained as concentrated copper sulphate solution in the emulsion pertraction process was recycled to the oxidation reactor, checking experimentally that the oxidation efficiency was maintained.

Modeling and Optimization of an Emulsion Pertraction Process for Removal and Concentration of Cr(VI)

This work reports the modeling and optimization of an emulsion pertraction process for the removal and concentration of Cr(VI) from aqueous effluents. The emulsion pertraction technology that combines the efficiency of emulsion liquid membranes with the advantages of using hollow-fiber modules as contactors has been applied to the removal of the Cr(VI) initially contained in aqueous effluents of defined composition together with its simultaneous concentration for reuse. A mathematical model that considered mass-transfer resistances in the aqueous feed film and in the membrane phase coupled to the kinetics of the back-extraction reaction described satisfactorily well the experimental results of Cr(VI) removal and concentration obtained after careful planning. Finally, the methodology leading to the determination of the optimal flow configuration that maximizes the effluent flowrate treated by the process is presented; a two-step process has been proposed, and its optimal operation has been found by solving...