Schiff Base Functionalized Adsorbent for Lead Removal from Contaminated Water and its Potential Regeneration Strategies for Re-Use

Abstract

The Schiff base functionalization successfully anchored organic acid-based adsorptive groups on a magnetic graphene oxide composite (GMNP). The effects of the polyamidoamine dendritic structure, GO (wt. %), and type of organic acid on the Pb (II) removal was investigated. Citric acid (CA) functionalized 40 wt. % GO composite exhibited the highest adsorption capacity of 548 mg/g, which was attributed to inner/ outer sphere complexation, electrostatic attraction, and van der Waal's forces between Pb (II) species and adsorbent. The effect of Pb (II) speciation in relation to the surface charge and available active sites of the composite was studied at various solution pH values. Piecewise linear regression was used to correctly identify and interpret the rate-limiting steps during the various stages of Pb (II) adsorption. The thermodynamic parameters were determined using van't Hoff's equation, which revealed the multimodal nature of Pb (II) adsorption. Selective Pb (II) adsorption from a multi-ion solution and its relationship with solution concentration was investigated. Four adsorbent regeneration strategies were employed, and a Pb (II) removal of up to 92% in the 10th cycle was achieved using the Na-EDTA method. A systematic investigation revealed that biocompatible composites have great utility in real wastewater applications.