This study presents the preparation and use of nanostructured carbon dots derived from pawpaw (Carica papaya) peels to remove Total Suspended Solids (TSS) and Total Dissolved Solids (TDS) from petroleum-produced water during oil and gas extraction. Carbon dots were prepared via hydrothermal carbonization at 180°C for 6 hours, and subsequently functionalized with H₂O₂/NaOH to introduce oxygen-containing groups on the surface. Thorough characterization of carbon dots by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD). Process optimization was performed using Response Surface Methodology with Central Composite Design, implemented in Design-Expert Version 13, to evaluate the effects of contact time (30-150 minutes) and adsorbent dosage (0.5-2.5g/100mL) on removal efficiency. Fourier Transform Infrared Spectroscopy (FTIR), UV-Vis Spectroscopy, and Thermogravimetric Analysis (TGA) confirmed the successful synthesis of carbon dots with 67.20 wt% composition of carbon, having a graphitic structure with characteristic peaks at 2θ ≈ 28°, and thermal stability up to 285°C. TSS (100.2mg/l) and TDS (403.8mg/l) were maximally removed using the gravimetric method. Maximum removal efficiencies of 72.5% (TSS) and 67.3% (TDS) were achieved at a contact time of 150 minutes and a dosage of 2.5 g/100mL, with adsorption capacities of 2.88mg/g and 10.94mg/g, respectively. The statistical results showed that a significant linear model (F-values >640, p0.99) identified adsorbent dosage as the primary controlling variable. This study demonstrates that carbon dots produced from pawpaw peels offer an efficient, sustainable, and cost-effective approach to treating produced water while addressing agricultural waste valorization.
OHIMOR et al. (Sun,) studied this question.