Cu–ZrO2@GO scaffold: Visible spectrum triggered caffeine degradation and microbial inactivation

Abstract

Consumption of beverages with caffeine has increased in last decade and has led to increase in the concentration of caffeine in various water bodies, placing it in the category of emerging contaminants (ECs). Sewage treatment plants are incapable of completely removing ECs and therefore use of photocatalysis as tertiary treatment is the need of the hour. Reported is a visible light active Copper doped Zirconium oxide loaded Graphene oxide based (Cu–ZrO2@GO) composite using co-precipitation method for photocatalytic degradation of caffeine. The composite was characterized using physiochemical techniques such as FTIR, XPS, XRD, FE-SEM, HR-TEM, UV-DRS, PL, and BET for its successful synthesis confirming distribution of Cu–ZrO2 (5–40 nm) over GO matrix. With the band gap energy of 2.5 eV, Cu–ZrO2@GO could effectively degrade 81.18% for caffeine in 240 min (min) under optimum conditions (pH 3, dose 70 mg) due to its high surface area (80.57 m2 g−1) with pore diameter of 37.4 Ao mainly by the hydroxyl radical as reactive oxygen species (ROS). Proposed degradation mechanism for caffeine is supported by LC/MS analysis. Cu–ZrO2@GO could degrade 78% of caffeine in tea extract (real sample) as confirmed by HPLC studies. Reported composite also depicted antibacterial activity against Gram-positive staphylococcus aureus (S. Aureus) and Gram-negative Escherichia Coli (E. coli) bacteria and could be recycled upto four cycles. Cu–ZrO2@GO can effectively be used for wastewater remediation.