A core–shell structure of polyaniline coated protonic titanate nanobelt composites for both Cr(vi) and humic acid removal

Abstract

The current methods for chromium and natural organic matter decontamination from wastewater present limitations, such as high cost, poor reproducibility, and detrimental environmental effects as well as by secondary waste. Herein, we synthesized a core–shell structure of polyaniline/hydrogen-titanate nanobelt (PANI/H-TNB) composites through chemical oxidation in the presence of phytic acid, which played an important role in the formation and regeneration of PANI. The adsorption performance of PANI/H-TNB composites as an adsorbent of Cr(VI) and humic acid (HA) from aqueous solutions was tested. A batch technique was adopted to investigate the removal efficiency toward Cr(VI) and HA under various environmental conditions. The PANI/H-TNB composites exhibited excellent adsorption capacity toward Cr(VI) (156.94 mg g⁻¹) and HA (339.46 mg g⁻¹), outperforming that of PANI nanowires and many other materials. Large K_d values (>10⁴ mL g⁻¹) demonstrated the high affinity of the composites for both of Cr(VI) and HA. The analysis of Fourier transformed infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) showed that the removal of Cr(VI) was a combined effect of reduction Cr(VI) to Cr(III) and chemical sorption, while HA adsorption was mainly via surface complexation between the disassociated HA macromolecules and the positively charged PANI. The PANI/H-TNB composites presented satisfactory regeneration performance and reusability, which greatly reduced the wastewater disposal expenses. For the sake of industrial application, the PANI/H-TNB composites with high adsorption capacities can be applied as a suitable adsorbent for simultaneous removal of Cr(VI) and HA in wastewater cleanup.