Pb (II) removal from water using surface-modified polythiophene-coated rice husk ash nanocomposite

In the present work, a novel nanocomposite adsorbent, polythiophene (PTh)/rice husk ash (RHA), has successfully been synthesized in the presence of hydroxypropyl cellulose (HPC) as the surfactant. The synthesized nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and thermal gravimetric analysis (TGA). The synthesized PTh/RHA/HPC nanocomposite adsorbent was applied as an efficient sorbent for lead ion [Pb (II)] removal from contaminated water. Concentration of Pb (II) ion before and after adsorption was measured using atomic absorption spectroscopy. Several variables affecting the extraction efficiency of the nanoadsorbent i.e., adsorbent dosage, metal ion concentration, extraction time, and adsorption conditions were investigated. The optimum pH value for Pb (II) ion adsorption on PTh/RHA/HPC nanocomposite was about four with maximum efficiency of about 96.58%. The highest efficiency of adsorption was 98.12% for sample with 0.05 g adsorbent in 50 mL of 10 mg/L Pb (II) solution. Equilibrium studies were also performed with known linear and non-linear adsorption isotherms including Langmuir, Freundlich, and Temkin from which the best result was achieved with Freundlich isotherm, with R-2 = 0.995 representing multilayer adsorption on heterogeneous structure of the adsorbent. The pseudo-first-order model and the pseudo-second-order model were adopted to analyze the adsorption kinetics of Pb (II) on PTh/RHA/HPC. The consistency of the experimental q(e) (9.92 mg/g) with q(e) (10 mg/g) calculated from the pseudo-second-order kinetic model illustrated that the adsorption of Pb (II) onto PTh/RHA/HPC at initial concentration of 50 mg/L was probably controlled by chemical adsorption.