Effective adsorption of cadmium and lead using SO₃H-functionalized Zr-MOFs in aqueous medium

Cadmium (Cd) and Lead (Pb) from industrial wastewater can bioaccumulate in the living organisms of water bodies, posing serious threats to human health. Therefore, efficient remediation of heavy metal ions of Cd (II) and Pb (II) in aqueous media is necessary for public health and environmental sustainability. In the present study, water stable Zirconium (Zr) based metal organic frameworks (MOFs) with SO₃H functionalization were synthesized by solvothermal method and used first time for the adsorption of Cd (II) and Pb (II). Synthesis of UiO-66-SO₃H, nano-sized (<100 nm) MOFs, was confirmed by FTIR, XRD, FESEM and BET. Effects of contact time, pH and temperature were investigated for adsorption of Cd (II) and Pb (II) onto SO₃H-functionalized Zr-MOFs. The UiO-66-SO₃H displayed notable rejections of 97% and 88% towards Cd (II) and Pb (II), respectively, after 160 min at 25 °C and pH (6) with an initial concentration of 1000 mg/L. Adsorption capacities of Cd (II) and Pb (II) were achieved as 194.9154 (mg/g) and 176.6879 (mg/g), respectively, at an initial concentration of 1000 mg/L. The Pseudo second-order kinetic model fitted well with linear regression (R²) of value 1. The mechanism was confirmed mainly as a chemisorption and coordination interaction between sulfone group (-SO₃H) and metal ions Cd (IIa) and Pb (II). These results may support effective adsorption and can be studied further to enrich and recycle other heavy metals from wastewater.