Removal of Heavy Metals from Wastewater Using Fly Ash Modified Basic Oxygen Furnace Slag Geopolymers

Abstract

In the current study, fly ash modified basic oxygen furnace slag geopolymers were synthesized and used as geofilters to remove heavy metals from wastewater. Batch experiment based on the removal of heavy metals from synthesized wastewater was conducted so as to investigate the influence of contact time and porosity on the metal removal efficiency and adsorption capacity of the geofilters. Adsorption kinetics was evaluated using Lagergren's pseudo-first-order model, Ho's pseudo-second order and Elovich models. Effect of contact time between geopolymer and wastewater was investigated within the first 15 minutes of adsorption with time interval of 3 minutes. The highest percentages for the removal of Fe2+, Cu2+, Al3+ and Ni2+ions with 1%H2O2 – FA-BOFS based geopolymer obtained after 15minutes were 100%, 86.87%, 84.64% and 84.63% respectively. The trend based on metal absorption capacities in an ascending order given as Fe >Cu>Ni>Al. The adsorption capacity of metal within the 15miniutes was relatively constant possibly due to sufficient number of sites upon which metal ion adsorption may have possibly occurred on the outer surface of geopolymers irrespective of H2O2 content. Metal ion adsorption rates in the current study strongly adhered to the Ho's pseudo-second-order model based on linear regression fitting method. The correlation coefficients R2 were 0.999. FA-BOFS based geopolymer can be considered as emergent and versatile material with inherent chemical microstructural property able to remove heavy metals from polluted effluent and metalliferous drainage.