Functionalized MWCNTs-quartzite nanocomposite coated with Dacryodes edulis stem bark extract for the attenuation of hexavalent chromium.

Multiwalled carbon nanotubes/quartzite nanocomposite modified with the extract of Dacryodes edulis leaves was synthesized and designated as Q, which was applied for the removal of Cr(VI) from water. The adsorbents (PQ and Q) were characterized using the SEM, EDX, FTIR, TGA, XRD, and BET analyses. The XRD revealed the crystalline composition of the nanocomposite while the TGA indicated the incorporated extract as the primary component that degraded with an increase in temperature. The implication of the modifier was noticed to enhance the adsorption capacity of Q for Cr(VI) by the introduction of chemical functional groups. Optimum Cr(VI) removal was noticed at a pH of 2.0, adsorbent dose (50 mg), initial concentration (100 mg dm-3), and contact time (180 min). The kinetic adsorption data for both adsorbents was noticed to fit well to the pseudo-second-order model. The adsorption equilibrium data were best described by the Langmuir model. The uptake of Cr(VI) onto PQ and Q was feasible, endothermic (ΔH: PQ = 1.194 kJ mol-1 and Q = 34.64 kJ mol-1) and entropy-driven (ΔS : PQ = 64.89 J K-1 mol-1 and q = 189.7 J K-1 mol-1). Hence, the nanocomposite demonstrated potential for robust capacity to trap Cr(VI) from aqueous solution.