Removal of chromium (VI) from water by micro-alloyed aluminium composite (MAlC) under flow conditions

Abstract

This paper deals with Cr(VI) ion removal from water, by micro-alloyed aluminium composite (MAlC), under flow conditions. In a water environment the MAlC acts as a strong reducing agent. Dissolving it in water is accompanied by the generation of Al(III) ions and reduction of water to H 2 , with OHions. The final product is insoluble Al(OH) 3. A series of Cr(VI) model solutions, with initial pH ranging between 1 and 5, were treated in the original semi-flow system (SFS), which simulated flow conditions well. The results demonstrate a high MAlC efficacy, considering that at the end of the treatment, concentrations of Cr(VI) were below the maximal allowed concentrations for drinking water, in all model solutions. The MAlC mechanism of action is based mainly on processes of reduction and co-precipitation by Al(OH) 3 , because Cr(VI) is removed from the water phase as metal chromium and insoluble Cr(OH) 3. Behaviour of the composite in water is under significant influence of pH, which affects its efficacy and mechanism of action. Therefore, the rate of Cr(VI) removal is greater at the beginning, decreasing towards the end of the treatment. Additionally, the ratio of [metal chromium]/[Cr(OH) 3 ] in precipitate, at the end of the treatment, decreases with increasing initial pH of the model solution. Application of the SFS significantly enlarges efficacy of the MAlC, compared to work under stationary conditions.

Metallic iron for water treatment: leaving the valley of confusion

“…The work started by the ascertainment that Fe 0 should be a universal material for water treatment in deep bed filtration (Noubactep 2007(Noubactep , 2008(Noubactep , 2009a(Noubactep , 2010a(Noubactep , b, 2011aNoubactep et al 2009b). This ascertainment was based on, and supported by previous reports on the efficiency of Fe 0 for the quantitative removal several classes of biological and chemical contaminants (Bojic et al 2001;Richardson and Nicklow 2002;Bojic et al 2004;You et al 2005;Bojic et al 2007;Henderson and Demond 2007;Thiruvenkatachari et al 2008;Bojic et al 2009). Subsequent works demonstrated that chemical reduction was not a relevant removal mechanism (Noubactep 2011c) and that observed reductive transformations were not the cathodic reaction coupled to anodic iron dissolution (Ghauch 2015;Noubactep , 2016a.…”

Removal of Cu2+ and Zn2+ from model wastewaters by spontaneous reduction–coagulation process in flow conditions

“…Its mechanism of action is based on the several physico-chemical processes and the in situ formation of the coagulant, due to its spontaneous reaction with water [1,10]. The major processes are adsorption, reduction, hydrogenation, hydrolysis and coagulation, operating synergistically to degrade and remove variety of pollutants from water, similarly as in process of electrocoagulation [17,18].…”

Making Fe0-Based Filters a Universal Solution for Safe Drinking Water Provision

“…An established way to improve the efficiency of a BSF is to amend it with metallic elements (Al 0 , Fe 0 , Zn 0 ) [126,130,131,189,[193][194][195]. Depending on the intrinsic reactivity of the used Fe 0 , the extent of water contamination, the size of the filter, and water flow velocity, a relative small volumetric Fe 0 ratio (e.g., <10%) could yield efficient long-term water treatment.…”