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Recuperação da água de retenção do processo de eletrodeposição de ouro por eletrodiálise

by Roczanski, Airton Odilon

Abstract (Summary)
The aim of the present work is to evaluate the possibility of using an electrodialysis technique (ED) to recover rinsing water contaminated with the electrolyte during the processof gold electrodeposition. This arises from the rinsing of the components after electroplating with gold as performed within an alkaline bath containing gold and cyanide. This water iscalled retention water because its role is to retain as much gold as possible. During the rinsing process both the electrolyte, containing gold, silver and cyanide, and contaminants are removed from the bath. The more the rinsing water is used the more it becomes concentratedand therefore water replacement is necessary. Firstly: The electrolytic cells were constructed from laboratory bench electrodialysis cells containing two and three compartments. Two kinds of ion-selective membranes, a cationic one Nafion® 450 and an anionic one Selemion® AMV, were used in the construction. The total ?cell potential?, ?membrane potential? and ?polarization? as a function of appliedelectrical current behaviours were evaluated. The (retention water) rinsing water from the rinsing process and potassium hydroxide solutions (KOH) at concentrations of 0,01 M, 0,1 Mand 1,0 M were used within the cell assemblies. Polarization of the membranes was not observed until current densities of 35 mA.cm-2 were reached. Secondly: The electrolytic cells of two and three compartments were exchanged for a singlecell of five compartments in order to determine the fractions of gold, silver, cyanide (and other metals) within the ?retention water? in relation to current density and electrolysis time. The ?retention water?, potassium hydroxide solutions (KOH) 0,1 M and sodium sulphate solution (Na2SO4) 5% were used in these electrolytic cells. The results show that it is possible to remove more than 75% of all the metals and cyanide from the ?retention water? within 270 minutes of electrodialysis using a current density of 20 mA.cm-2. Increasing the current density to 30 mA.cm-2 results in the extraction of 56% of all metal and cyanide from the?retention water? within 190 minutes of electrodialysis. The ?retention water? used in the two different electrolytic cells show that after electrodialysis it is in a suitable condition to be returned and reused in the process
This document abstract is also available in Portuguese.
Bibliographical Information:

Advisor:Andréa Moura Bernardes; Marcos Rivail da Silva; Deyse Elisabeth Ortiz Suman Carpenter

School:Universidade Regional de Blumenau

School Location:Brazil

Source Type:Master's Thesis

Keywords:eletrodiálise electrodialysis ion-selective membranes electrodepositon of gold retention water recovery

ISBN:

Date of Publication:08/07/2006

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