Carbon quantum dots modified Z and S–Scheme heterojunctions for pharmaceutical contaminants photodegradation: State–of–the–art, benefits, and limitations

In the last few years, the amount of wastewater–containing pharmaceutical contaminants that are released into the environment from hospitals, pharmaceutical industry, and aquaculture sector has significantly increased. In fact, it has become a real issue due to the excessive uses of pharmaceuticals and personal care products (PPCPs), fast urbanization, medical sector development, and the progress in the anthropogenic activities which directly polluted water. In this context, many efforts have been made in order to effectively remediate wastewater–containing pharmaceutical contaminants employing several processes (i.e., adsorption, biological remediation, membrane separation, electrochemical treatments, photocatalysis, flocculation, coagulation processes, etc.). Even though the mentioned processes present numerous benefits in the remediation of wastewater–containing active pharmaceutical ingredients, efficient feedstocks must be developed to achieve sustainability goals in wastewater remediation purposes. In order to attain such objectives, carbon quantum dots (CQDs) nanomaterials have attracted the attention of scientists and industrialists in pharmaceutical contaminants degradation due to their stronger fluorescence with high quantum yields in the low–energy region, synergetic effect, nontoxic, simple functionalization, tunable emission wavelength, etc. Herein, we review the recent developments made in CQDs–based Z/S–heterojunctions as high–efficient feedstocks for pharmaceutical contaminants degradation utilizing the photocatalysis process. The main sources of CQDs are also described. The limitations and benefits of the studied process are outlined. In the future research work, new sources of CQDs must be manufactured and advanced processes should be applied in the field of wastewater–containing active pharmaceutical ingredients remediation employing CQDs as organic feedstocks which present a new trend in nano–materials synthesis and their usages for pharmaceutical pollutants abatement.