Red mud-fly ash-based geopolymers as an eco-friendly material for immobilization of toxic pollutants (Pb and Cu) from wastewater

Abstract

The use of waste materials as a precursor for synthesizing geopolymer materials is increasingly being utilized. This research aimed to examine the potential use of red mud-fly ash geopolymers to remove toxic pollutants such as copper and lead ions from wastewater. Samples of different ratios of red mud (RM) and fly ash (FA) were synthesized through alkaline activation. Based on compressive strength a geopolymer (RMFAGP1) with the highest value of 29.54 MPa, was chosen for further research. The physical-chemical characterization of RMFAGP1 in terms of mineral composition and structure was performed using XRD, DRIFT and SEM analysis. BET analysis was used to define porosity, as well as the specific surfaces necessary for efficient adsorption. The batch equilibration method was used to determine the PZC value, which serves as a guide for predicting the adsorption process. The best adsorption efficiency was achieved at pH =4 (88,5%) i.e. at pH=5 (99,4%) for Cu and Pb, respectively. The performed analyses indicate that waste materials, such as red mud and fly ash, can be used as raw materials for obtaining a geopolymer that can effectively immobilize Pb and Cu from wastewater, offering a low-cost and eco-friendly solution.