Ultra-fast microwave catalytic degradation of multiple dyes by waste derived carbon nano onions

Abstract

The industrial revolution gave rise to unmitigated pollution of water bodies, posing a significant pitfall to social well-being through the presence of harmful dye pollutants. To address this challenge, the utilization of waste frying oil derived carbon nano onions (CNOs) for the simultaneous and ultra-fast degradation of multiple organic dyes and their mixtures in wastewater under microwave exposure is reported herein. The unique structure of CNOs plays a crucial role to facilitate effective degradation of complex organic dyes. The microwave catalytic degradation by CNOs achieved rapid removal of cationic crystal violet (∼98% in 5 min), rhodamine B (∼99% in 6 min) and methylene blue (∼99% in 6 min). While degradation of anionic congo red took 9 min to achieve ∼98% removal. Remarkably, when dealing with a mixture of anionic and cationic dyes, CNOs exhibited exceptional degradation efficiency (∼99%) of mixture of dyes in just 3 min. The data acquired from the time study was most accurately fitted in pseudo-first-order kinetics. Based on observations during trapping, it was determined that superoxide and hydroxyl radicals are the most responsible agents for the microwave catalytic dye degradation. The plausible mechanism for the microwave assisted dye degradation with CNOs is also investigated. Remarkably, CNOs exhibited fairly good recycling and reusing efficiency with worthy structural and chemical stability. The total organic carbon (TOC) content in the treated water has been reduced to 87.35% as compared to mixed dye solution after the five cycles of treatment. The rapid removal activity, recyclability, reusability and cost-effective nature of CNOs exhibit remarkable potential for high-throughput environmental remediation in real-world wastewater applications, which is of great importance in the field.