CDs/HMS for removal of MB dye with highly adsorption capacity: isotherm, kinetic, and thermodynamic study

Pollution of water sources by industrial dyes is a priority concern around the world that the human health and the environment are being threatened by them. Therefore, efforts to remove them from wastewater are attracted considerable attention worldwide. For the first time, carbon dots (CDs) were synthesis from an l-histidine amino acid and citric acid with a 1:4 molar ratio, which quantum yield was obtained to be 39.34%. In the next step, the prepared CDs are embedded into hexagonal mesoporous silica (HMS) as an effective adsorbent to eliminate the Methylene Blue (MB) dye. The impact of operational adsorption parameters, including solution pH (3.0-11.0), contact time (10.0-180 min), adsorbent dosage (0.05-0.10 g), and initial concentrations of MB dye (10-100 mg/L) were investigated. The removal efficiency and equilibrium adsorption capacity have been determined at 97.0% and 47.0 mg/g, respectively, under optimum situations at 298 K and pH = 7.0. The isotherm of the adsorption was fitted with both Freundlich and Langmuir models, and the kinetics studies of MB dye removal pursued the pseudo-second-order model. In addition, thermodynamic evaluations indicated that the adsorption procedure had spontaneous and endothermic nature. Accordingly, this study demonstrates that CDs/HMS could be utilized as a promising adsorbent for the elimination of MB dye as a cationic dye model from an aqueous solution.

Automated summary

The pollution of water sources by industrial dyes is a global concern, and this study demonstrates the successful synthesis of carbon dots from l-histidine amino acid and citric acid for use as an effective adsorbent to remove Methlyene Blue dye. The removal efficiency reaches 97.0%, indicating the promising potential of CDs/HMS as an adsorbent for cationic dye removal.