Economical and Technological Aspects of Copper Removal from Water Using a Geopolymer and Natural Zeolite

This study reports the efficiency of a synthesized eco-friendly geopolymer (7.5 wt% of coal fly ash incorporated into its composition) as an adsorbent for the removal of Cu(II) from an aqueous solution and a real water matrix. The results obtained were compared with a commercial natural zeolite used as an adsorbent of toxic metals in Brazil. The effect of the operating conditions on the adsorption kinetics and equilibrium were studied in a finite bath and in a fixed bed column. The adsorption kinetics curves obey the pseudo-first-order model for both materials. The geopolymer presented higher adsorption capacity than zeolite, and values for the q max_geo / q max_zeo ratio were 1.13, 1.92, and 2.56 at temperatures of 25, 40, and 55 °C, respectively. The isotherms obtained in the thermodynamic study are favorable and spontaneous adsorption process. The adsorption processes are endothermic. The geopolymer showed higher adsorption efficiency than the zeolite in a fixed-bed column, and even with the presence of substances in the natural water sample, the Cu(II) removal capacity of the geopolymer is 3–4 times higher than that of the zeolite. A cost analysis was also performed, the geopolymer was found to be a more economical adsorbent than the commercial zeolite.