Abstract In this study, a carbon quantum dots composite was made from algal-cyanobacterial precursors using the oilothermal method. The performance of this composite as an adsorbent was evaluated in a model based on cadmium. The results showed that its optimal pH-dependent adsorption efficiency range is so broad that it covers pHs 5–10. The best correlations for adsorption isotherms and kinetics were observed with Langmuir and Elovich nonlinear models, respectively. The maximum cadmium adsorption capacity of 5.59882 ± 0.3276 mg/g and affinity constant of 2.66765 ± 0.56894 L/g were obtained in just 2 min of exposure time. The tolerance against ionic strength and co-existing cations was 5 ppm, and the recovery efficiency of cadmium from the natural sample was more than 95%. According to the findings of this research, it can be said that the algal-cyanobacterial origin carbon quantum dots composite, due to its unique properties, can be an efficient adsorbent for use in cadmium solid-phase extraction.
