Evaluation of the electrodialysis process for the treatment of metal finishing wastewater

Abstract

Neste trabalho estudou-se o tratamento, por eletrodiálise, de um efluente alcalino, oriundo de um processo de galvanoplastia, contendo íons de Zn, Ni, Cu, Fe e Al, bem como de Na e CN -. O estudo foi feito tanto em células de bancada quanto em uma planta piloto, utilizando-se membranas íon-seletivas Nafion e Selemion. Os resultados mostraram que os íons metálicos apresentam, em sua maioria, caráter aniônico devido à formação de complexos de coordenação. Cada tipo de íon metálico apresentou uma diferente taxa de extração da solução tratada, dependendo do controle do processo ser potenciostático ou galvanostático. Para Zn, Ni e Cu houve maior extração sob controle galvanostático. Já para o Al foi verificado uma maior remoção do efluente quando o controle era potenciostático. Observou-se um comportamento anômalo para os íons ferro, os quais não são removidos do mesmo modo que os demais íons metálicos. O rendimento da extração foi máximo em tempos de ensaio relativamente baixos (2-3 h).Metal finishing wastewater containing ions of Zn, Ni, Cu, Fe and Al, as well as of Na and CN -in alkaline pH was treated by electrodialysis. The treatment was conducted in a laboratory cell and in a pilot plant unity. The experiments were carried out using Nafion and Selemion membranes. Results showed most of the metallic ions to have an anionic nature, due to the formation of coordination complexes. Each metallic ion showed a different rate of extraction from the treated solution, depending on the galvanostatic or potentiostatic operation mode. Zn, Ni and Cu have shown higher extraction under galvanostatic control. For Al, higher extraction was observed when the experiment was conducted in a potentiostatic mode. Fe ions exhibited an unexpected behavior, not being removed in the same way as the other ions. The best extraction results were obtained within 2-3 h of treatment.

Biopolymeric Membrane Enriched with Chitosan and Silver for Metallic Ions Removal

“…where: C i and C f , were the initial and final iron (II) ions concentrations (g/L). The current efficiency (I E %) was calculated based on the concentrations of solutions using Equation (9) [15][16][17]:…”

“…Most of these methods generate the toxic residual metal sludge that must be treated because they affect the environmental if they are eliminated in the water [6]. The electrochemical methods involve the use of a membrane, most often prepared from the polymers, due to their chemical and physical properties [7][8][9][10][11][12][13][14][15][16][17]. The electrochemical methods have been successfully used at laboratory and industrial scale due to the many advantages, such as their technical maturity, low maintenance costs, feasibility, the ability to remove or recover metal ions, to remove organic or inorganic colloids, bacteria or other microorganisms, and lower energy consumption [10][11][12].…”

“…Electrodialysis (ED) is an electrochemical membrane process based on bipolar membranes or hybrid membranes, where ions are transported through ion selective membranes from one solution to another under the electric field influence [13][14][15][16][17]. The ED process was successfully applied for the removal of heavy metals from various wastewaters due to the high efficiency or operational feasibility.…”

“…Also, the process can simultaneously separate, enrich, and concentrate the investigated solutions. This membrane process operates without noise, does not require specialized equipment, has low chemical consumption, and the operation and maintenance are easy [13][14][15][16][17]. Sue et al [15] studied the efficiency of electrodialysis (ED) process to treat and reclaim wastewater that contains nano-scale slurry particles and metal residues from polishing a wafer.…”

“…The membranes based on natural biopolymers such as chitosan, cellulose, and its derivate were used in many applications (microfiltration, ultrafiltration, reverse osmosis, and nanofiltration membrane processes) due to the their advantages, such as low cost, availability, biodegradability, natural sources, being environmentally friendly, high flux and high rejection, good adsorption of liquids [12,[18][19][20][21][22][23][24][25]. Chitosan (CS), due to its advantages such as nontoxicity, being cheap, biocompatibility, and biodegradability [17][18][19][20][21][22][23] has been widely reported as an effective sorbent of heavy metals (e.g., Fe 2+ , Cu 2+ , Pb 2+ , Cr 3+ , Ni 2+ , Cd 2+ , Zn 2+ , Co 2+ , Mn 2+ , and Pd 2+ ) from aqueous systems. The ecological chitosan nanofibers produced by electrospinning technique has been successfully applied in the removal of Fe 3+ , Cd 2+ , and Cu 2+ from industrial effluents [5,7,10,18,26,27].…”