Kinetics of Adsorption Competition of Pb-Cu and Pb-Methylene Blue in Aqueous Solution using Silica Gels from Coal Fly Ash

The present study investigates the removal of Pb2+ using silica gel (SG) in the presence of the Cu2+ (Pb-Cu) and methylene blue (Pb-MB) ion competitor. These pollutants are toxic and harmful to the ecosystem. The presence of the multicomponent pollutants causes more complications to remove from the water system. The adsorptions were examined in a batch system under certain experimental conditions (pH solution system and contact time). Meanwhile, the FTIR spectrophotometer determines the differences adsorption interaction in silica functional groups before and after adsorption. The results showed that the silanol group of silica gel acted as an adsorption site. In the single systems, the adsorption capacity of silica gel follows the order MB > Cu2+ > Pb2+ of around 84.03; 64.81; and 56.88 mg.L−1, respectively. The kinetic adsorptions of both single and binary systems were best fitted to pseudo-second-order models. In the binary solution systems, both adsorption capacity and adsorption rate of each component decreased compared to the single system. The results indicated that the cationic competitors influenced the Pb2+ adsorption, or vice versa, depending on the amount of charge and adsorption affinity.