A high-performance 3D phosphorus-doped graphene oxide adsorbent for imipramine wastewater treatment

The presence of pharmaceutical wastes in the environment has adversely impacted the marine biodiversity due to their hazardous and bioaccumulation nature. This research focussed on the development of an effective phosphorus-doped 3D graphene oxide with bentonite and carboxymethylcellulose crosslinking (PG/BCC) for the removal of imipramine in wastewater. The impacts of single factor (adsorbent dosage, initial imipramine concentration, system temperature and contact time) on imipramine adsorption were examined by batch experiments while the interactive impacts of multiple factors and process optimisation were investigated by central composite design (CCD). The greatest adsorption capacity evaluated was 458.95 mg/g at the following CCD optimised operating parameters: 10 mg PG/BCC, 250 ppm initial concentration, 34 min contact time and 321 K temperature. The Langmuir model described well the equilibrium of imipramine adsorption whilst the pseudo-second-order model correlated closely to the kinetic data. The imipramine-PG/BCC system was spontaneous (-19.235 to −27.583 kJ/mol) and endothermic (1.230 to 14.562 kJ/mol) as evaluated from thermodynamic modelling. Characterisation of PG/BCC by various microscopy and spectroscopy analyses has validated the incorporation of imipramine in PG/BCC adsorbent. Regeneration of used PG/BCC was proven to be highly feasible with methanol eluent. Conclusively, the findings strongly advocate PG/BCC as a highly feasible and sustainable graphene-based adsorbent for imipramine separation from pharmaceutical wastewater.