AbstractAlthough biosorption is an effective technique for removing potentially toxic elements (PTEs) from wastewater, it causes secondary pollution in the form of used adsorbents ending up in landfills, leading to PTE leaching into groundwater. This study used two kinds of adsorption process waste ash – adsorbed paper ash (APA) and adsorbed mulch ash (AMA)- as an additive to mortar, which added an environmental and economic value through energy recovery during the ashing process following the ideas of the waste to energy and circular economy, in addition to immobilizing the PTEs into a cement matrix aiming to close the loop of pollution. This study focused on investigating the leaching of PTEs (Cd, Zn, Cu, and Pb) at five different artificial adsorption initial concentrations (0.5, 1, 5, 10, and 50) mg/L and three different mixing weight proportions of ash with cement, as well as their pH-dependent behavior, to ensure environmental safety. To detect the release of PTEs from the mortar ash mixes, the ICP-OES technique was used. The study concluded that the used adsorbent ashes potentially could be environmentally acceptable as an additive for mortar because their ability to stabilize PTEs based on leaching values of (Pb, Zn, and Cu) was below the permissible limit under the nonhazardous waste category. Only Cd leached higher than the regulatory limit in the case of very low acidity when pH was lower than 0.