A novel nanocomposite based on magnetic multiwalled carbon nanotubes coated with SiO2 and functionalized with 3-mercaptopropyltrimethoxysilane (3-MPTMS) was prepared for the efficient extraction and quantification of lead ions from water samples. The adsorption capacity of this adsorbent could reach 1.995 mg g-1 Pb2+ in an equilibrium time of 30 min. Under optimized conditions derived using the 25-1 fractional factorial design, a 45 mL aliquot of the sample was preconcentrated onto 90 mg of nanocomposite during 4 min. The lead ions adsorbed on the nanocomposite were eluted using 2 mol L-1 HNO3. The proposed method provided a preconcentration factor of 15.25 times, yielding limits of detection (LOD) and quantification (LOQ) of 0.56 and 1.86 μg L-1, respectively, and a linear range between 1.86 and 100.00 μg L-1. The relative standard deviations (RSD, n = 10), determined using solutions of Pb2+ at 10 and 120 μg L-1, were 2.3 and 2.1%, respectively. A high tolerance toward potentially foreign ions was observed. The proposed method was successfully applied to the rapid extraction of Pb2+ ions from different water samples, confirming good recovery values (90.33-109.53%); the accuracy of the method was evaluated through graphite furnace atomic absorption spectrometry (GF AAS) as a reference technique.
Improvement of Laccase Activity Via Covalent Immobilization over Mesoporous Silica Coated Magnetic Multiwalled Carbon Nanotubes for the Discoloration of Synthetic Dyes