Chemical Leaching of Metals from Wastewater Sludge: Comparative Study by Use of Three Oxidizing Agents [H ₂O ₂, FeCl ₃, and Fe ₂(SO ₄) ₃]

Abstract

Chemical leaching of the toxic metals (cadmium, chromium, copper, nickel, lead, and zinc) and behavior of other elements (aluminum, calcium, iron, potassium, magnesium, manganese, sodium, phosphorus, and sulfur) in the wastewater sludge of the Montreal Urban Community wastewater treatment plant (Montreal, Quebec, Canada) were studied in 2‐L beakers using sulfuric acid and three oxidants [H 2O 2, FeCl 3, and Fe 2(SO 4) 3] and their association. Metal removal efficiencies of these oxidants were evaluated under different conditions of pH (2.0 and 2.5) and oxidation‐reduction potential (ORP) (350 to 500 mV). The solubilization of the different elements was linked to pH and/or ORP, and a period of 2 to 4 hours was required to obtain satisfactory metals removal yields. Sludge‐fertilizing properties generally were little affected by the decontamination process, especially for processes using a ferric salt. Finally, optimal conditions, for best metals solubilization, were established at pH 2.5 and ORP = 450 mV in a 4‐hour period.

Effectiveness of Electrooxidation Process for Stabilizing and Conditioning of Urban and Industrial Wastewater Sludge

“…Alternatively, agricultural spreading of wastewater sludge is hindered because of presence of pathogens (U.S. EPA, 1999), toxic metals (Bouda et al, 2009;Spinosa and Vesilind, 2001), emerging organic pollutants (Barnabé et al, 2009;Citulski and Farahbakhsh, 2010), and odor (Stuetz and Frechen, 2001).…”

“…Many conventional technologies (biological and physicochemical methods) are used for sludge treatment and management. The biological processes like aerobic and anaerobic digestion (Shanableh and Shimizu, 2000;Weemaes and Verstraete, 1998;Whipps and Whiting, 1999) (Metcalf and Eddy, 2003;Oleszkiewicz and Mavinic, 2001) require high energy consumption and long retention time, and their effectiveness is uncertain, especially during winter (Koers and Mavinic, 1977), and are incapable of providing a complete solution to the above problems (Bouda et al, 2009;U.S. EPA, 1999;Zheng et al, 2007).…”

An environmentally friendly process for the recovery of valuable metals from spent refinery catalysts

“…Within the bioleaching process ferric iron is often identified as the main compound involved in the indirect mechanism (Beolchini et al, 2012;Fomchenko and Biryukov, 2009). Some authors have developed leaching strategies using ferric ion on different matrices: pyrrhotite ore (Beolchini and Vegliò, 1999), silver sulfide (Dutrizac, 1994), chalcopyrite (Córdoba et al, 2008), high-arsenic refractory gold concentrate (Li et al, 2009), wastewater sludge (Bouda et al, 2009) and hydrotreating catalysts (Marafi et al, 1994). Furthermore, the environmental sustainability and the cheapness of the process are favoured by using either biologically produced ferric iron, by means of cyclic regeneration of such iron (Beolchini et al, 2010) or industrial wastewater that contains such element.…”