The efficient degradation of halogenated organic compounds is a major challenge in advanced water treatment processes. This study reports the synthesis and evaluation of an asphaltene-tuned photocatalyst under two different photochemical reactors for degradation of 2,5-dichlorphenol, which is not only persistent and toxic but also declared as a pollutant of priority concern. Based on photocatalytic efficiency, graphitic carbon nitride was selected as a support material for immobilization of asphaltenes and for optimization of degradation parameters. Palladium-loaded graphitic carbon nitride (Pd/g-C₃N₄) nanocomposites were also synthesized. Photocatalytic performance of both synthesized photocatalytic materials was evaluated in two different photoreactor systems, i.e., an UV photoreactor and Xe-lamp photoreactor. Asphaltenes-tuned g-C₃N₄ exhibited significant photocatalytic activity under both irradiation sources which revealed the potential of asphaltenes as a promising and effective component of photocatalysts and highlighted the potential of transforming problematic petroleum fractions into functional materials that can be used for sustainable water treatment. The synergistic interactions between Pd nanoparticles with g-C₃N₄ matrix and effective generation of reactive species under irradiation accounts for a higher degradation rate for Pd/ g-C₃N₄ in both photoreactor systems. The comparative analysis revealed the role of loading metal on degradation kinetics. Overall, this study revealed that asphaltenes-tuned graphitic carbon nitride and palladium-loaded graphitic carbon nitride are efficient and promising photocatalysts for effective degradation and dehalogenation of halogenated phenols in diverse irradiation environments.