Facile synthesis of Sn(II)-MOF using waste PET bottles as an organic precursor and its derivative SnO2 NPs: Role of surface charge reversal in adsorption of toxic ions

Abstract

A new Sn(II)-based metal-organic framework (MOF) has been solvothermally synthesized using post-consumer waste PET bottles as an organic linker source. The potential of the Sn(II)-MOF as an adsorbent material in the removal of arsenate (AsO43−) and phosphate (PO43−) from the aqueous medium was examined. The adsorption kinetics of the target anions followed the pseudo-second-order kinetic model, and the Langmuir isotherm best describes the adsorption profile. The adsorbent displayed a significant adsorption capacity of 90.90 mg g−1 and 126.58 mg g−1 for AsO43− and PO43−, respectively. The synthesized Sn(II)-MOF demonstrated promising anti-interference activity in the presence of co-existing anions, mainly F−, Cl−, NO3−, and SO42−. Besides, the synthesized Sn(II)-MOF exhibited remarkable removal efficiency (~ 99%) of AsO43− from actual water samples viz. tap water and lake water. Further, the work elucidates the role of surface charge regulation where the positively charged Sn(II)-MOF is converted to negatively charged tin oxide nanoparticles (SnO2 NPs) via a simple thermal decomposition route. The MOF derived highly crystalline SnO2 NPs (~ 25 nm) were explored in the adsorptive removal of toxic manganese (Mn2+) ions. The synthesized SnO2 NPs displayed excellent Mn2+ adsorption capacity (qm) of 52.63 mg g−1, which is in good agreement with the experimental value (qexp) of 56.96 mg g−1. Moreover, the SnO2 NPs displayed remarkable selectivity in Mn2+ adsorption despite the presence of other cations/anions. Notably, the present work can prove to be an economically viable method of recycling waste PET bottles into value-added adsorbent material for the decontamination of water.