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Anatase TiO2 nanoparticles with an average crystallite size of around 6.06 nm were successfully immobilized on the surface of polyaniline-coated kapok fiber (PANI-KpF) via hydrothermal reaction. The photocatalytic activity of the TiO2/PANI-KpF nanocomposite was studied under visible light using methyl orange (MO) and Cr(VI) as model pollutants. Photodegradation of MO was achieved using nanocomposites prepared with 0.5 and 1.0 mL titanium isopropoxide (TTIP) with removal efficiencies of about 87.4 and 76.8%, respectively. These are about 13 and 18% higher than the removal efficiencies under dark conditions. On the other hand, visible light-induced photo-reduction of Cr(VI) was carried out in the presence of isopropanol (IPA) as a hole scavenger, with 100% removal efficiency. Without IPA, Cr(VI) was removed by adsorption. The TiO2/PANI-KpF also showed antibacterial activity against E. coli bacteria under visible light. [ABSTRACT FROM AUTHOR]

Low value natural hollow kapok fibers (KpF) were utilized as support for the synthesis of highly efficient polyaniline (PANI)-based adsorbents for heavy metal and ionic dye pollutants. The PANI-kapok (PANI-KpF) nanocomposite was prepared via in situ polymerization of aniline monomer in acidic condition using ammonium persulfate (APS) as the oxidizing agent. The morphology, wetting property and adsorption capacity of the PANI-KpF nanocomposites were tailored by performing NaClO 2 pre-treatment and varying the APS to aniline ratio during coating. NaClO 2 pre-treatment was found to promote the adhesion of aniline monomer on the surface of kapok, leading to high quality coating. On the other hand, the nanocomposite with [APS]/[aniline] = 1.4 exhibited the highest adsorption capacity. The effects of adsorbent dosage, initial solution pH, contact time, initial dye and heavy metal concentrations, and temperature were investigated through batch adsorption experiments. Kinetic studies indicate that the adsorption of MO and Pb(II) onto the PANI-KpF nanocomposite agrees well with the pseudo-second order kinetic model. Equilibrium isotherm studies show that the adsorption of both model pollutants follows the Langmuir isotherm model, and the calculated monolayer adsorption capacities are 136.75 and 63.60 mg/g for MO and Pb(II), respectively. Thermodynamic studies reveal that the adsorption of MO and Pb(II) are both endothermic and spontaneous. Image 1 • PANI deposition on NaClO 2 -treated kapok fibers via in situ oxidative polymerization. • Effect of NaClO 2 treatment and APS to aniline molar ratio on PANI deposition was studied. • Kinetics, isotherm and thermodynamics of MO and Pb(II) adsorption were investigated. • Obtained adsorption capacities of 136.75 and 63.60 mg/g for MO and Pb(II), respectively. [ABSTRACT FROM AUTHOR]

In this study, hydrophilic kapok papers (KP) with grammage of 60 g m −2 were synthesized by treating naturally hydrophobic kapok fibers with chloroform and sodium chlorite. A hybrid nanocomposite consisting of zinc oxide (ZnO) and polyaniline (PANI) was successively deposited on the hand-made paper. SEM images show nano-size PANI and ZnO particles. XRD results revealed amorphous structure of the PANI with presence of peaks correlating to ZnO. FT-IR showed the change on kapok fibers upon chemical treatment and confirmed the presence of PANI on the synthesized paper. The KP-ZnO-PANI nanocomposite was further applied to test the photocatalytic removal of methyl orange (MO) from aqueous solution under UV irradiation. Results showed that the hybrid nanocomposite could be employed as an adsorbent of MO dye and was 10% more efficient when irradiated under UV light. [ABSTRACT FROM AUTHOR]