Effective separation of ciprofloxacin from aqueous solutions using BiOCl/Bi2S3/biochar hybrid structure fabricated via ultrafast solid-state reaction

Abstract

Developing a product that serves a dual purpose as an adsorbent/photocatalyst for ecological applications is a compelling study area. This article discusses a facile ultrafast synthesis of BiOCl/Bi₂S₃/biochar (BiOCl/Bi₂S₃/BC) by solid-state reaction with coupled roles as photocatalyst during sunlight exposure and adsorbent when there is no light. BiOCl/Bi₂S₃/BC was characterized by XRD, SEM, EDX, HR-TEM, XPS, FTIR, Raman, and DR/UV–Vis spectroscopy techniques. The adsorption efficiency and its parameters were explored using ciprofloxacin (CPF) as a contaminant model drug in the absence of light irradiation. The coupled role as adsorbent/photocatalyst was considered under direct sunlight irradiation. BiOCl/Bi₂S₃/BC₃₀ achieved removal of 81.25% in the dark and reached 90% during sunlight exposure within 1 h. BiOCl/Bi₂S₃/BC₃₀ exhibited a triplet initial adsorption rate, and doubled rate constant of photocatalysis (11.34 mg g⁻¹ min⁻¹, 0.642 min⁻¹) compared to BiOCl/Bi₂S₃ (3.88 mg g⁻¹ min⁻¹, 0.256 min⁻¹), respectively, indicating the adsorptive, catalytic, and cocatalytic role of BC. Mechanism studies indicated that BiOCl/Bi₂S₃/BC separated CPF by adsorption via electrostatic interaction, π–π conjunction, and hydrogen bonding while the photocatalysis occurred through the S-scheme mechanism where ^•O₂⁻ and h⁺ play the predominant role in the photocatalytic degradation. Besides, the BiOCl/Bi₂S₃/BC₃₀ hybrid was stable and revealed acceptable recyclability after four consecutive cycles for CPF removal from their aqueous solutions. This work provided an ultrafast, simple, economical, and efficient strategy for the application of BiOCl/Bi₂S₃/BC hybrid structure that has a dual function of adsorption and photocatalysis for the elimination of CPF from water.