Polyaniline decorated rooibos tea waste: An adsorbent for the removal of hexavalent chromium and its reuse as a photocatalyst for the degradation of tetracycline

Herein, the application of polyaniline-decorated rooibos tea waste (PANI-RBTW) as a composite adsorbent for the uptake of hexavalent chromium and its reuse as a photocatalyst for the abatement of tetracycline was explored. The polyaniline decorated rooibos tea waste composite adsorbent exhibited an excellent removal efficiency of 100 % for 20 mg/L Cr(VI) at a temperature of 45 °C, within 180 min, solution pH of 2, and 40 mg adsorbent dose. Also, the adsorption capacity of Cr(VI) by the composite adsorbent was estimated to be 293.72 mg/g. The removal of Cr(VI) ions by the polyaniline-decorated rooibos tea waste was endothermic and spontaneous. Furthermore, the heavy metal-loaded adsorbent was efficient for the abatement of 10 mg/L tetracycline and the degree of degradation as well as mineralisation was 80.4 % and 70 % respectively, after 150 min. Overall, the polyaniline decorated rooibos tea waste composite adsorbent presents itself as an alternative adsorbent for the elimination of noxious metal ions. In addition, the spent adsorbent offers itself as a viable photocatalyst in the remediation of water contaminated with organic pollutants. Future work shall be carried out to investigate the lifespan of the spent adsorbent for photocatalytic applications.