UV degradation of cationic aromatic aryl dyes mixture by Cobalt nanoparticles doped coconut husk biochar (CoNPs@ChBc); A radical trapping study by a mechanistic approach

Textile industries release lots of synthetic dyes into wastewater without being treated. This wastewater causes water pollution and many problems related to aquatic life and human health. Therefore, the major challenge is to degrade the mixture of dyes from water. In this study, Cobalt nanoparticles doped coconut husk biochar (CoNPs@ChBc) are synthesized by the precipitation method. CoNPs@ChBc acts as a photocatalyst for the degradation of a mixture of cationic dyes, that is Rhodamine B and Malachite green, under the photocatalytic UV reactor. The surface functionalities and morphology of the prepared material were characterized by using FESEM, EDX, Mapping, FTIR, XRD, BET, and UV-visible spectroscopy. The results indicated that the highest degradation of a mixture of cationic dyes is 98.6 % with CoNPs@ChBc at a concentration of 20 mgL -1 in a 15-minute reaction time at room temperature. The effect of different parameters such as pH, initial dye concentration, light source, photocatalyst dose, and irradiation time was examined. The radical scavenging experiment confirms the involvement of hydroxyl (•OH) and superoxide radicals (• O 2 − ) in the photocatalytic degradation of a mixture of cationic dyes. Furthermore, a possible degradation mechanism for a mixture of cationic dyes under UV light exposure has been predicted based on these findings. The degradation of a mixture of cationic dyes is also confirmed with the help of the GC-MS technique. The reusability study of the CoNPs@ChBc demonstrated exceptional photostability and efficiency in every consecutive cycle. The CoNPs@ChBc catalyst has the potential to be reused for a maximum of eight cycles. Thus, CoNPs@ChBc exhibited excellent photocatalytic performance for the degradation of a mixture of cationic dyes.