Experimental studies on the durability and leaching properties of alkali-activated tailings subjected to different environmental conditions

Sustainable Alkali-Activated Mortars for the Immobilization of Heavy Metals from Copper Mine Tailings

“…The mean interval flux for selected elements (Al, Si, and S) was plotted on a log–log scale, as depicted in Figure S4. The flux over the exposed surface of the AAMs was estimated by dividing the interval mass release by the interval duration as follows: F i = M i t i − t i − 1 where F i is the interval flux, M i is the mass released during the current leaching interval that can be calculated via the element concentration of the leachate, and the specimen surface area and eluate volume, t i and t i –1 define the time of each interval. The mean interval flux varied but not so significantly with the solubility of each element in the different solutions.…”

“…Typically, AAM materials can release Si and Al ions into the surrounding solution when exposed to acidic conditions. 4 This happens because the amorphous silica and alumina framework within the matrix can dissolve when the protons (H + ) in the acid react with the Si−O−Si and Al−O−Si bonds in the structure. 36 Several factors, including the type and concentration of acid, temperature, composition, and structure of the AAMs, can affect the degree of leaching.…”

“…CMTs may contain heavy metals (e.g., Fe, Pb, Cd, As, Hg etc. ), sulfides, and other harmful chemical substances, which can leach into the surrounding environment due to natural weathering. − Leaching of heavy metals could contaminate local water sources that can cause long-lasting damage to aquatic ecosystems and pose a risk to human health . Thus, exploring methods for transforming massive amounts of CMTs can prevent this issue and be considered a progressive approach toward sustainable CMTs waste management.…”

“…The HMI (leaching) analysis showed that the resulting material was ineffective in immobilizing As, Si, and S elements. 4 However, some recent studies suggest that HMI in AAMs is possible when other additives such as blast furnace slag (BFS) or metakaolin (MK) are incorporated. Li et al used a mix of electrolytic manganese residue and lead−zinc smelting slag as a source of aluminosilicates along with BFS as supplementary cementitious material to immobilize Pb and Zn.…”

“…Considering that Pb, Mn, Cd, Co, Fe, Al, Si, and S are commonly present in CMTs, we used MK as an additive to support HMI along with KOH and sodium silicate activation of CMTs to produce AAMs. HMI in prepared mortars was performed through static monolithic leaching tests, 4 by submerging mortar (40 mm × 40 mm × 80 mm) specimens into deionized water, mild acid, and seawater (alkaline) solutions to mimic different environmental impacts. An assessment of the leaching kinetics of hazardous elements was conducted by analyzing their concentration over time using ICP-AES and a first-order reaction/diffusion model.…”