Ca-doped ZnO nanoparticles for MB dye degradation and adsorptive removal of tinidazole

Industrial dye degradation involves several processes by which dyes are broken down, ideally into innocuous products. Methylene blue (MB) is one of the most commonly employed dyes in the textile industry and is released into water in routine industry processes. These discharges lead to creating a nocuous nature for humans and animals. Drugs are also discharged into water bodies from various pharmaceutical industries. In these two contexts, in the present work, the green synthesis of calcium-doped zinc oxide nanoparticles (Ca-doped ZnO NPs) is achieved using the aqueous peel extract of Citrus limetta by the solution combustion technique. The structural, morphological, and optical properties of the synthesized Ca-doped ZnO NPs are investigated using XRD, FTIR, SEM, EDX, and UV-visible spectroscopy. The prepared NPs were subjected to photocatalytic degradation of MB dye under visible-light illumination, which shows ~ 95% dye degradation. The synthesized Ca-doped ZnO NPs were also employed to adsorb tinidazole (TDZ), a nitroimidazole antibiotic, from water samples. An excellent adsorptive capacity of the NPs was observed for selectively adsorbing the TDZ ~ 96.2%. The drug TDZ was found to have pseudo-second-order kinetics. The catalyst recycling proved its repeatability; removal of the dye reached up to 92% after three successive usages. Therefore, using waste Citrus limetta peel extract, the multifunctional Ca-doped ZnO NPs were synthesized, which maintained effective adsorption potential and photocatalytic abilities and could be used as an effective material for environmental remediation.