Circular Resource Utilization of Waste-Derived Carbon Nano-Onions for Industry-Optimized Dye Removal via Response Surface Methodology

Abstract

Challenges persist in the low-cost, effective, and environmentally friendly elimination of diverse and complex contaminants from wastewater. Herein, green-synthesized carbon nano-onions (CNOs) are employed as a high-performance adsorbent to remove Rhodamine B from wastewater in a circular economy approach. CNOs are synthesized from waste cooking oil using a wick pyrolysis technique at room temperature without the need for sophisticated instruments and high-temperature processing. Response surface methodology is adopted to validate the stimulus of temperature, pH, and concentration change. Further, several batch experiments related to adsorption thermodynamics, isotherms, and kinetics were done for the validation of process practicability. The extremely good removal of Rhodamine B (∼99%) was obtained at a pH of 6.5. The practical applicability of CNOs was verified by Rhodamine B removal from various sources of water. In addition, the regeneration of the CNOs showed ∼97.19% RhB removal after five cycles, showing the sustainability and economic aspect of CNOs for applications in industrial wastewater treatment.