Synthesis of hierarchical porous carbon from rubber wastes by one-step molten salt method and its use in the modification of phenol biosensor for signal amplification

• Hierarchical porous carbon (HPC) from rubber waste was produced by an environmental-friendly Molten Salt method and recycled into a useful product. • HPC produced from rubber waste was used as a biosensor electrode for the first time. • The phenol biosensor presented an excellent measurement accuracy of 99.38 % ± 3.62. • HPC has amplified the biosensor signal by approximately twofold. This study presents the production of a hierarchical porous carbon material (HPC) from rubber wastes obtained from Cilas Rubber Company operating in Zonguldak-Devrek/Türkiye, and use of the HPC in operation of a phenol biosensor. Molten Salt method, which is an environmental-friendly progress, was utilized for the carbonization process. Chitosan polymer was modified with HPC to form a film on the glassy carbon electrode surface and laccase was chemically immobilized onto this film. The electrode was then tested for phenol detection at +0.44 V by using differential pulse voltammetry. Various pore sizes were formed due to salt aggregation with Molten Salt method in the carbon matrice. The biosensor presented a linear range from 30 µM (2.82 ppm) to 300 µM (28.2 ppm), a LOD of 10.45 µM, a measurement accuracy of 99.38 % ± 3.62 with the RSD of 4.46 %. %. The amounts of electroactive laccase for the HPC-modified and unmodified electrodes were calculated to be 116 µg and 32 µg, respectively. The biosensor accurately measured phenol in tap and stream water, achieving accuracies of 97.7 % and 92.3 %, respectively. HPC amplified the biosensor signal 1.83 times higher in comparison to unmodified electrode. Rubber wastes were evaluated as raw materials in a production process. A porous carbon material produced from rubber waste was used as a biosensor electrode for the first time.