A novel graphene oxide-dicationic ionic liquid composite for Cr(VI) adsorption from aqueous solutions

A novel graphene oxide-dicationic ionic liquid composite (GO-DIL) was prepared by modifying graphene oxide (GO) with a dicationic ionic liquid (DIL), 3,3 '-(butane-1,4-diyl) bis (1-methyl-1H-imidazol-3-ium) chloride ([C4(MIM)2]Cl2). GO and GO-DIL were characterized by SEM, BET, FTIR, and XPS, and the materials were used for Cr(VI) adsorption. Batch adsorption studies showed that adsorption reached equilibrium within 40 min, and the optimal pH was 3, where the electrostatic attraction between GO-DIL and Cr(VI) was maximized. The maximum theoretical Cr(VI) adsorption capacity (qm) was 271.08 mg g+1, and qm remained above 228.00 mg g+1 after five cycles. The adsorption data were fitted well by both the pseudo-first-order kinetic model and the Langmuir model. Furthermore, thermodynamics calculations revealed that adsorption was a spontaneous endothermic process. Importantly, electrostatic attraction between Cr(VI) and the protonated imidazole N+ of GO-DIL played a critical role in Cr(VI) adsorption, and Cr(VI) was reduced to Cr(III). Thus, GO-DIL is predicted to be an effective adsorbent for Cr(VI) and other heavy metal ions in wastewater.

Automated summary

The novel graphene oxide-dicationic ionic liquid composite (GO-DIL) showed good adsorption performance for Cr(VI), with a high maximum adsorption capacity and maintained high adsorption capacity even after multiple cycles. The adsorption process fit well with pseudo-first-order kinetic model and Langmuir model, indicating that adsorption is a spontaneous endothermic process.