A sustainable approach for heavy metal remediation from water using carbon dot based composites: A review

Cost-effective methods for the removal of water pollutants are emerging as an urgent need of the hour owing to the release of a huge number of toxic materials into the water bodies. Pollution from toxic synthetic chemicals, heavy metals, pesticides, herbicides, fertilizers, pharmaceutical substances etc. adversely affect aquatic ecosystem. It also make the polluted water unusable for human contact or consumption. Pollution from heavy metal namely, arsenic, cadmium, nickel, mercury, chromium, zinc, lead etc. is becoming a major health risk. Many diseases like gastrointestinal and kidney dysfunction, nervous system disorders, skin lesions, vascular damage, immune system dysfunction, birth defects, and cancer are associated with heavy metal poisoning. Adsorption-based methods are highly popular and advantageous because of their low cost, high retention time, and good recyclability. Carbon dots are emerging as green adsorbents of recent times for various categories of water contaminants including heavy metals. The use of bio sources as a green precursor to carbon dot synthesis is opening a huge opportunity to fabricate inexpensive materials for heavy metal remediation in the future. With very high surface functionalities and large speific surface area, the adsorption of heavy metals as high as 2000 mg g-1 is achievable. In this review, recent development about the use of carbon dot-composites with materials such as biopolymers, zeolites, layered double hydroxides, spinels and metal-organic frameworks has been discussed. Such matrix enhance the water stability of the carbon dots as well as synergistically improve the kinetics and thermodynamics of the interaction process making it an efficient material for heavy metal remediation. The review discusses the synthesis protocols of fabricating different carbon dot composites. It lists the various advantages of carbon dot-composite over other materials used for heavy metal remediation viz. low-cost as most of them are synthesized from biomass. Hence, they are biogenic, possessing many functional moieties making them efficient and eco-friendly in the removal of heavy metals. In addition, the review lists many advantages associated with green carbon dot based composites like methods of regeneration and reusability. In a nutshell, carbon dot based composites are wonderful sustainable material rendering an ideal approach for heavy metal remediation.

Automated summary

Cost-effective methods for removal of water pollutants are urgently needed due to the release of toxic materials into water bodies. Heavy metal pollution poses a major health risk and is associated with various diseases. Adsorption-based methods using carbon dots as green adsorbents have shown great potential for removing heavy metals from water. The use of bio sources as a green precursor for carbon dot synthesis offers opportunities for fabricating inexpensive materials for heavy metal remediation. Carbon dot composites with various materials have been discussed for their enhanced efficiency in heavy metal removal.