Removal of heavy metals by electrocoagulation from hydrogenocarbonate-containing waters: Compared cases of divalent iron and zinc cations

Abstract

Divalent iron and zinc cations can be removed from water by electrocoagulation (EC) with aluminium electrodes in a discontinuous system: the effect of hydrocarbonate HCO3-ion often present in liquid waste and in groundwater on the EC process has been investigated. For the two ions, the presence of hydrocarbonate strongly limits the pH variations by its buffering properties and reduces the rates of Al dissolution by corrosion. Removal of the two cations was then shown to require longer treatment times and larger amounts of dissolved aluminium. Whereas the local pH gradients near the electrode surface with HCO3free water was previously shown to allow local formation of stable Zn and Fe hydroxides, which actively contribute to their elimination, the presence of hydrocarbonate nearly suppresses this positive phenomenon, resulting in far less efficient EC treatment. Whereas removal of zinc cations from carbonated water can be considered as their simple adsorption on the Al flocs, Fe 2+ ions are oxidized to Fe(OH)3 by air oxidation after their adsorption. Use of an overall adsorption model allowed quantitative comparison of the EC treatments, with very different adsorption parameters for the two metal studied.

Perspectives regarding metal/mineral-incorporating materials for water purification: with special focus on Cr(vi) removal

“…Several methods including physical, mechanical, chemical, thermal, and biological methodologies are applied to remove these polluters from water systems. Ion exchange, 34 precipitation, 35 flocculation/ coagulation, 36 photo oxidation, 37 phytoextraction, 38 electrocoagulation, 39 electrodialysis, 40 irradiation, 41 membrane separation, 42 ultrafiltration, 43 forward osmosis, 44 and microorganisms and plants [45][46][47] are applied to remove dyes and heavy metals from water bodies. Generally, wastewater treatment scenarios can be categorized into mechanical, chemical, physical, thermal, and biological methods as displayed in Fig.…”

Removal of Cadmium from Contaminated Water Using Coated Chicken Bones with Double-Layer Hydroxide (Mg/Fe-LDH)

“…The production rate of wastewater has increased due to the substantial rise in industrial output [4][5][6], while increasing water demand and climate change have limited the availability of freshwater [7,8]. Industrial wastewater is considered as the most serious source of water pollution as it contains a broad range of hazardous contaminants, such as biological pollutants [9,10], nutrients [11], geosmin [12], organic matter [13], dyes [14,15], and heavy metals [16,17]. Among these, heavy metals pollution is a grave concern for the water industry as heavy metals are toxic even at low concentrations [18][19][20], and their separation from wastewater is a significant problem [21,22].…”

Enhanced Adsorptive Bioremediation of Heavy Metals (Cd2+, Cr6+, Pb2+) by Methane-Oxidizing Epipelon

“…According to the US-EPA, lead (Pb), cadmium (Cd) and chromium (Cr) are designated as the top priority contaminants that are of major public concern [7]. Numerous studies have been focused on physico-chemical approaches, such as ion exchange, flocculation, membrane filtration, biosorbents, electrodialysis, reverse osmosis and precipitation, for heavy metal removal in recent decades [8][9][10]. Though some of these techniques are effective in the removal of heavy metals, practical applications are not easily employed on a large scale due to their high cost and the secondary contaminations by the chemicals used in the processes.…”