Chromium (VI) remediation via biochar@polyaniline composite: advancing water treatment using biogas residue digestate

The demand for effective water treatment strategies has contributed for extensive research in materials chemistry, with great focus on advancing adsorbent technologies. This investigation centers on synthesizing and modifying carbonaceous materials, specifically biochar and its polyaniline composite (biochar@polyaniline: BC@PANI), to evaluate their effectiveness in eliminating hexavalent chromium Cr(VI) from aqueous solutions. The biochar composite was prepared using a straightforward in-situ chemical polymerization approach. The properties of biochar were modified by blending it with polyaniline at 25%, 50%, and 75% (w/w), successfully loaded into the biochar samples. For elucidating structural changes and functionalities introduced during modification, the synthesized materials were fully characterized using different techniques. The adsorption performance of BC@PANI50% was systematically evaluated through batch adsorption experiments. This PANI-modified biochar material exhibited exceptional adsorption capacity for Cr(VI) removal from aqueous samples, reaching 877.19 mg/g at 318.15 K, emphasizing its potential for water adsorption treatments. Our research in the kinetics of Cr(VI) removal showed that both pseudo-second-order and Langmuir models adequately described the adsorption process. Regeneration experiments demonstrated that, even after undergoing five cycles, BC@PANI showed 82.5% Cr(VI) removal indicating its exceptional reusability and stability. In summary, this study establishes the potential applicability of BC@PANI adsorption for the removal of Cr(VI) ions in water, providing a promising avenue for integrating such sorbents into water treatment engineering practices.