Graphene quantum dots/persulfate boosted electro-oxidation for leachate degradation, carbon quantum dots extraction for anti-counterfeiting applications - a sustainable approach

Leachate management in an efficient way is still a challenge as it contains many emerging pollutants. This work activates the persulfate by defatted Moringa oleifera seeds waste-derived graphene quantum dots (M-GQDs) catalyst to degrade the matured leachate pollutants by electro-oxidation with scrap stainless steel as electrodes. At the optimized conditions with pH of 3, 4.5 V, 1 g/L of persulfate, 0.07 g/L of M-GQDs, 3 h of reaction time, the removal of UV254, chemical oxygen demand (COD), total organic carbon (TOC), and NH3-N is found to be 99 %, 97 %, 84 %, and 90 % respectively with less energy consumption of 0.44 kWh/kg COD. The 3D fluorescence excitation-emission spectrophotometer (3D EEM) and the Gas chromatography-mass spectroscopy (GC-MS) analysis results attune the degradation of dissolved organic matter and micropollutants in the leachate. From the above-mentioned electro-oxidation treatment generated sludge, the quantum dots (S-CQDs), have been synthesized and characterized. Both the M-GQDs and S-CQDs are green emissive, spherical, and hydrophilic, with an average particle size of 2 to 4 nm, a band gap of 4 eV, and a quantum yield of 3.91 %, & 6.73 % respectively. Both have shown good suitability for information encryption and anti-counterfeiting fingerprint enhancement without changing the latent shape. The work is innovative because it broadens the application of quantum dots to the purification of highly contaminated wastewater and the development of materials for industry from generated waste for a closed-loop sustainability system.