Cage-like octa(aminopropyl) silsesquioxane functionalized Ti3C2Tx for selective adsorption of Pb (II) ions by synergistic effect of coordination and oxidation

Abstract

Transition metal carbides or nitride (MXene) have attracted wide attention due to their unique properties and promising applications in batteries, sensors, and catalysis. Due to its good hydrophilicity and abundant groups, it is also favored in environmental remediation. In this work, a cage-like octa(aminopropyl) silsesquioxane (POSS-NH2) was chosen as the modifier to decorate the Ti3C2Tx and an amino-rich lamellar material, Ti3C2Tx/POSS-NH2, was prepared successfully via a dehydration condensation reaction. Ti3C2Tx/POSS-NH2 shows excellent adsorption capability toward Pb (II) ions within a wide pH range with an optimal adsorption capacity of 552.31 mg·g–1 at the pH value of 6. Even at strong acidic conditions (pH=2), the value is still as high as 283.65 mg·g–1. The Ti3C2Tx/POSS-NH2 also shows preferential selectivity for lead ions in lead-containing wastewaters containing Cu (II), Zn (II), Fe (II) and Mg (II) ions. The kinetics, isotherm, and thermodynamic analyses were also studied. It is found that the adsorption process is an endothermic one and complies with the Langmuir isothermal adsorption model. The experimental data of Pb (II） ions adsorption by Ti3C2Tx/POSS-NH2 can be well simulated with the pseudo-second-order kinetic model. XPS and FTIR results showed that the Pb (II) ions were captured by a synergistic effect of coordination of -NH2 on the Ti3C2Tx/POSS-NH2 surface and the oxidation of oxygenated moieties in the layered structure of Ti3C2Tx. The excellent properties of Ti3C2Tx/POSS-NH2 allow it to occupy an important position in the treatment of lead-containing wastewater.