Facile construction of coordination polymer sodium cobalt diphosphonate-based composite material with enhanced adsorption properties for lead ions

Abstract

A novel composite material (MWCNTs/NaCo-Pz) has been developed by integrating hydroxyl-functionalized multi-walled carbon nanotubes and sodium cobalt diphosphonate-based coordination polymer through a facile in situ hydrothermal synthesis method. The as-synthesized coordination polymer-based composite material has exhibited excellent adsorption properties of effective lead ions removal. The adsorption kinetics, adsorption isotherms, adsorption thermodynamics, adsorption selectivity, and adsorption mechanism of MWCNTs/NaCo-Pz for lead ions have been investigated. The corresponding kinetic results of lead ions adsorption by MWCNTs/NaCo-Pz followed the pseudo-second-order model and the Elovich kinetic model, and gave the highest coefficients of linear approximation R = 0.989 and 0.978, respectively. The experimental data fitted well with the Langmuir isotherm, and the predicted adsorption capacity of MWCNTs/NaCo-Pz for lead ions could reach 534.38 mg/g at 35 °C. The adsorption thermodynamic parameters ΔG, ΔH and ΔS of MWCNTs/NaCo-Pz were − 13.05 kJ mol^− 1 (35 °C), 26.84 kJ mol^− 1, and 96.94 J K^− 1 mol^− 1, respectively. Furthermore, the adsorption process parameters have been optimized using response surface methodology (RSM), and the maximum adsorption capacity (592.69 mg/g) for lead ions could be achieved under the optimum operating conditions. From this perspective, the extraordinary features of MWCNTs/NaCo-Pz for lead ions adsorption could ensure applicability and feasibility in environmental remediation.