Production of fired clay bricks as a safe removal method for spent adsorbents from sunflower and corn residues

Abstract

Significant research was done concerning the suitability of lignocellulosic wastes as heavy metal adsorbents. However, most of them do not focus on regeneration, environmental stability, or disposal of spent adsorbents, critical for commercial application. The scientific value of the current research is the production of fired clay bricks as a safe method for the removal of Ni(II), Zn(II), and Cd(II) adsorbents based on sunflower and corn residues, with retention efficiencies of more than 93.4%, 98.7%, and 98.5% for these contaminants, respectively. The bricks were molded by uniaxial compression and fired at 950 °C, and their performance as building bricks was evaluated, showing differences depending on biomass but no effect associated with heavy metals at the concentrations used. In the fired bricks, the biomasses served to form pores, increasing porosity to +46%, beneficial due to the low weight and hypothetical insulating capacity of the products. However, the bricks' quality and mechanical performance decreased compared to the control samples. Mechanical tests showed that bricks with corn were better than bricks with sunflower (compressive strength 7.96 MPa). The results presented here can be considered a starting point for the safe removal of spent lignocellulosic adsorbents using them as pore formers in building bricks.