Azo dye removal by acid pretreated biomass and its regeneration by visible light photocatalysis with incorporated CuO

ABSTRACT

In this work, we synthesized self-regenerative biosorbent BM-H₃PO₄-(CuO) by combining the photocatalyst CuO and acid pre-treated biomass (BM-H₃PO₄), the hybrid material BM-H₃PO₄-(CuO) was used for the removal of azo dye Direct Red 89 (DR-89). The morphology, texture phase, composition of the samples was characterized with scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, elemental diffraction analysis X-ray (EDAX). That confirms the presence of CuO into the pretreated biomass BM-H₃PO_4. The results reveal that when the biomass was loaded with a proper CuO/BM-H₃PO₄ weight ratio of 60%, the biosorption capacity was enhanced to 5.5 times compared to BM-H₃PO₄. The maximum adsorption capacity of BM-H₃PO₄-(CuO)_60% was 30.3 mg g⁻¹ determined from the Langmuir isotherm. The pseudo-second-order kinetic model was more appropriate for describing dye biosorption. The hybrid material BM-H₃PO₄-(CuO)_60% demonstrated a better photocatalytic activity under visible light irradiation then pure CuO. Incorporation of the CuO particles into the biosorbent, offers the possibility to harvest visible light for oxidative photodegradation. The prepared material also showed good reusability in the cyclic of biosorption–photocatalysis experiments and the biosorption efficiency was higher than 90% over four cycles. This study provides an eco-friendly way to fabricate self-regenerative biosorbents.

GRAPHICAL ABSTRACT

KEYWORDS:

• biosorption enhancement
• visible light photocatalysis
• copper oxide
• biosorbent reuse
• acid pretreatment

Acknowledgment

The authors wish to express their gratitude to the laboratory staff of Souk Ahras (Algeria) for their technical assistance in the spectroscopic analytical techniques (FTIR), and the national school of mines for EDAX analysis service.

Disclosure statement

No potential conflict of interest was reported by the author(s).