Disposal of wooden wastes used as heavy metal adsorbents as components of building bricks

Abstract

The recovery of wastes is the basis of the Circular Economy. In recent years, there is an increased interest in the use of agro-industrial wastes as simple and ?low-cost? adsorbents in the removal of heavy metals from wastewaters. However, the fate or reuse of such adsorbents saturated with pollutants has not been discussed deeply. The novelty of this paper is the valorization of pine sawdust waste and pine sawdust char, previously used as adsorbents for Ni(II), Zn(II), Cd(II) and their mixture, in the manufacture of porous fired clay bricks, which are an important kind of bricks due to their low weight and low thermal conductivity. Initially, both residues were evaluated as potential adsorbents for the heavy metals under study. The obtained results were much better for biochar with adsorption efficiencies close to 100%, both in individual and mixed systems, the later closer to real wastewater cases. Finally, 20% by volume of the contaminated biomass waste was incorporated into ceramic matrices, increasing the apparent porosity with respect to a brick of reference. The evaluation of the physical properties and their mechanical characterization, determined a decrease in the quality of these bricks even still within the current regulations for construction purposes. The s-s curves showed differences in the mechanical behavior associated with the type of waste material, being those obtained for bricks with biochar similar to those of the bricks of reference. Heavy metals immobilized in the clay matrix did not introduce significant changes in the physical and mechanical properties checked. Therefore, it is possible to take advantage of wood waste used as heavy metal adsorbents in wastewater treatment, with an option for its proper disposal.