Nanomaterials with selective adsorption properties are in demand for environmental applications. Herein, acid etching and oxidative decomposition of melon units of graphitic carbon nitride (g-C3N4) was performed to obtain the oxidized graphitic carbon nitride (Ox-g-C3N4) nanosheets. Ox- g-C3N4 nanosheets were further decorated on the polyaniline nanofiber (Ox-g-C3N4/Pani-NF). Ox-g-C3N4/Pani-NF was well characterized and further applied for a selective removal of hexavalent chromium (Cr(VI)) form aqueous solution. The zeta potential analysis indicate that the surface of Ox-g-C3N4/Pani-NF was positively charged which could be beneficial to bind anionic Cr(VI) ions electrostatically. In addition, nitrogen and oxygen containing functional groups exist on the Ox-g-C3N4/Pani-NF were mainly responsible for adsorption of Cr(VI) ions from aqueous solution. Moreover, the adsorption of Cr(VI) ions was also dependent on solution pH, reaction temperature and initial concentration of Cr(VI) ions. The maximum monolayer adsorption capacity of Ox-g-C3N4/Pani-NF for Cr(VI), calculated from Langmuir isotherm was 178.57 mg/g at pH = 2 and 30 °C. The activation energy (Ea = −20.66 kJ/mol) and the enthalpy change (ΔH° = −22.055 kJ/mol) validate the role of physical forces in adsorption of Cr(VI). These results demonstrate that Ox-g-C3N4/Pani-NF can be used as a potential adsorbent for environmental remediation applications.

The combination of two or more semiconductor materials for the synthesis of new hybrid photocatalyst could be a good approach to enhance the visible light absorption, electron-hole (e − /h + ) pair separation rate and photocatalytic decomposition of the organic contaminants. Herein, a facile in situ oxidative polymerization method has been used for the synthesis of visible light active g-C 3 N 4 /TiO 2 @polyaniline (g-C 3 N 4 /TiO 2 @PANI) nanocomposite for the decomposition of the congo red (CR) under the solar light irradiation. Prior to making the composite of TiO 2 (P25) with g-C 3 N 4 and polyaniline, a lamellar structure was generated onto the TiO 2 brim by alkali hydrothermal treatment to enhance the surface area and adsorption properties. The PL and UV-visible analysis clearly showed the fast separation of the e − /h + pair, and reduction in the bandgap energy of the g-C 3 N 4 /TiO 2 @PANI nanocomposite. The results revealed TiO 2 , PANI and g-C 3 N 4 showed the synergestic behavior in the g-C 3 N 4 /TiO 2 @PANI nanocomposite and greatly enhanced the photocatalytic degradation of the CR. The photocatalytic decomposition of the CR was almost 100% for 20 mg/L at pH 5, 7 and 180 min. The reusability study of the spent catalyst showed the 90% degradation of CR after four consecutive cycles indicate that g-C 3 N 4 /TiO 2 @PANI nanocomposite is a stable and efficient catalyst. The high efficiency and reusability of the g-C 3 N 4 /TiO 2 @PANI nanocomposite could be attributed to the higher visible light absorption and sensitizing effect of the g-C 3 N 4 and PANI.

No abstract

No abstract