Pretreatment of Complexed Metal Wastewaters

Abstract

This study investigates the applicability of hydroxide precipitation to complexed metal wastewaters using inorganic cations that may function as ligand sharing agents. Within this context Ca2+, Fe2+, Fe3+, Mn2+ and Mg2+ cations with the metals Cd and Cu and EDTA and NTA as ligands are used to define the systems for which theoretical and experimental evaluations are made. Results indicate that calcium is the only cation that effectively binds the ligands that makes it possible to apply the hydroxide precipitation. Fe2+ and Mn2+ are not effective due to their rapid oxidation. Mg2+ is found partly effective but may not be adequate for pretreatment purposes.

Simultaneous destruction of Nickel (II)-EDTA with TiO2/Ti film anode and electrodeposition of nickel ions on the cathode

“…Ni(OH) + + e − → Ni(OH) ads (2) Ni(OH) ads + Ni 2+ + e − → Ni + Ni(OH) ads (3) Ni(OH) ads + e − → Ni + OH (4) Ni(OH) 2 precipitation at the electrode could substantially lower the effective adsorption of reactive intermediate Ni(OH)ads. In the present study, the electrodeposition of liberated nickel ions often does not proceed at high recovery efficiency.…”

“…It has been frequently detected in the environment [1]. And, EDTA can make it difficult to remove heavy metals in wastewaters by conventional chemical precipitation processes, including hydroxide and sulfide precipitation [2,3].…”

Treatment of the Processing Wastewaters Containing Heavy Metals with the Method Based on Flotation

“…Difficulty in pretreating and treating such wastewaters is usually connected with the level of concentrations and speciation forms of metals in wastewaters [3][4][5][6]. Several processes using different physico-chemical or mechanical methods of treatment of metal parts are related with the use of water and producing industrial effluents [7][8][9].…”

“…In processing effluents, heavy metals are found in different physicochemical forms: ionic, ionic-coordinative, emulsive (eg water-oily and suspensive) [3,8,9]. The treatment of such wastewaters is practically conducted by using different physicochemical methods [3,8,9,11]. The stage of basic, chemical treatment is mostly preceded by applying the systems of…”

“…The load of heavy metals in such sewages reaches different levels of concentration and is mostly affected by the processes of covering, detox bath residues, cleaning metal surfaces or washing production areas [7,8,10]. In processing effluents, heavy metals are found in different physicochemical forms: ionic, ionic-coordinative, emulsive (eg water-oily and suspensive) [3,8,9]. The treatment of such wastewaters is practically conducted by using different physicochemical methods [3,8,9,11].…”