Biochar Derived from Curry Leaves for Cr(VI) Removal from Wastewater and Subsequent Use as a Supercapacitor Electrode

Addressing energy and environmental problems through sustainable routes is currently a vibrant field. This study focuses on achieving clean water by removing Cr(VI) using sustainable adsorbents, i. e., biochar derived from the fallen curry leaves. Intriguingly, the spent biochar is used as a supercapacitor electrode to find a sustainable solution for energy storage. Initially, biochar is prepared from fallen curry leaves by pyrolysis under an oxygen-deficient environment and characterised using multiple techniques. The prepared biochar could remove ~50 ppm of Cr(VI) from 50 mL of contaminated wastewater under optimized conditions. 1 g of CLB effectively removes 49.8 ppm of Cr(VI) from 140 ppm of the initial Cr(VI) concentration with 120 min residence time and simultaneously converts harmful Cr(VI) into harmless Cr(III). The structural, textural, and morphological properties of the prepared biochar are correlated to its adsorption capacity. Advantageously, the spent biochar, i. e., Cr(VI)-adsorbed biochar, is used as an electrode material that displays a remarkable specific capacitance of 188.44 F/g. The charged capacitors lighten the LED devices glowing brightly beyond 2.75 min. Notably, the prepared supercapacitor devices show the same efficiency during the multiple charging-discharging cycles. This work might add valuable insights into identifying sustainable solutions for achieving clean energy and a healthy environment.