Comparative efficiency of conventional and green functionalized carbon-based materials for the uptake of priority produced water contaminants

Abstract

Green chemistry has brought to the spotlight new sets of principles for reducing or eliminating hazardous substances in the synthesis and application of processes and products. Despite its noteworthy growth, this area still lacks studies that compare the potential of greener materials with those conventionally synthesized. Herein, novel materials based on chitosan and reduced graphene oxide were developed via the green (G-Fe/CS/rGO) and conventional routes (C–Fe/CS/rGO). Eucalyptus leaves extract and proanthocyanidin were used in the green approach as reducing/capping and crosslinking agents, respectively, replacing hydrazine and glutaraldehyde, commonly used in conventional synthesis. In addition, carbon nanotubes were also modified with plant extracts. The effect of different rGO contents was evaluated through adsorptive assays. Furthermore, the adsorption potential of C–Fe/CS/rGO, G-Fe/CS/rGO and green CNTs. Priority “Produced Water” contaminants of such as anthracene (ANT), fluoranthene (FLT), phenol (PE), and cyclohexane carboxylic acid (CHA) were used as target contaminants. The best materials were characterized by XRD, FTIR, SEM-EDS and Zeta potential analyses. C–Fe/CS/rGO-3% removed 86.6%, 89.3%, 13.4%, and 33.6%, G-Fe/CS/rGO-7% removed 83.2%, 83.9%, 6.7% and 30.3 % and CNT-E 82.9%, 97.6%, 10.7% and 12.4% of ANT, FLT, PE, and CHA, respectively. Green and conventional beads showed similar performance, indicating the promising use of green synthesis. CNT-E, which demonstrated the best adsorption capacity, was used in reuse assays to assess its feasibility. The material kept FLT removal above 85% after four consecutive adsorption-desorption cycles. Molecular modelling analysis indicated that CHA has greater stability, followed by PE, FLT and ANT, agreeing with the experimental results.