Studies on copper (II) removal from aqueous solutions by poly (3,4-ethylene dioxythiophene) polystyrene/sulphonate Sn (IV)tungstatophosphate (PEDOT: PSS/STP) nanocomposite

Abstract

ABSTRACT To address the pollution of heavy metal ions in water resources, a new adsorbent poly (3,4-ethylene dioxythiophene) polystyrene/sulphonate Sn (IV)tungstatophosphate (PEDOT: PSS/STP), made of organic and inorganic materials, was effectively produced using a sol-gel bottom-up approach. The surface morphology, elemental composition and, structural features of the synthesised nanocomposite were investigated by various spectroscopic techniques such as XRD, TEM, FESEM, EDAX, and FTIR, whereas the surface charge measurement (Zeta potential) and ion exchange capacity (IEC) were determined by dynamic light scattering (DLS) analysis and standard column method, respectively. The batch experiment technique was utilised to determine the parameters for analysing the adsorption behaviour for the elimination of Cu (II) ions from aqueous solution. The kinetics of the adsorption process were investigated using pseudo-first-order and pseudo-second-order kinetic models, while the thermodynamics were assessed using Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin thermodynamic models. The Langmuir isotherm was best fit to experimental data for adsorption of Cu (II) ions from an aqueous solution with a maximum adsorption capacity of 85.05 mg g−1 at pH 7.0 at different temperatures, whereas kinetic adsorption characteristics were best suited to the pseudo-second-order model. The thermodynamic parameters ΔHo, ΔGo, and ΔSo were determined and represent Cu (II) adsorption onto PEDOT: PSS/STP is an endothermic, spontaneous, and chemisorption reaction. Furthermore, even after five adsorption-desorption cycles, the adsorption capacity of PEDOT: PSS/STP nanocomposite adsorbent was around 70%, demonstrating that the regeneration capability of PEDOT: PSS/STP nanocomposite adsorbent was excellent, which is the fundamental characteristic to select the proper adsorbent.