Synthesis and characterization of CaO nanoparticles from periwinkle shells for the treatment of tetracycline-contaminated water by adsorption and photocatalyzed degradation

Abstract

• Microporous CaO nanoparticles have been synthesized using periwinkle shell. • The nanoparticles showed 88% adsorption efficiency for tetracycline at pH of 10. • Photodegradation efficiency of 97% was achieved. • Adsorption was confirmed as the rate-limiting step for the degradation. • Results from computational calculation show agreement with experimental results. Due to the ever-increasing discharge of antibiotic residues into different water bodies, there is a significant need to improve existing water treatment methods. In this study, we synthesized calcium oxide nanoparticles from periwinkle shells using the sol-gel method for applications in the adsorption and photodegradation of tetracycline from wastewater. The nanoparticles were characterized using FTIR, UV-Visble spectroscopy, XRD, SEM-EDX, TEM, BET and TGA/DTA. The nanostructure produced showed strong crystalline, optical, structural and surface properties. With an average crystallite size of 25 nm, particle size of 2.09 nm, BET surface area of 582.68 m 2 /g, specific surface area of 90.08 m 2 /g, bandgap of 4.8 eV and other properties that supported their functionality as adsorbent and photocatalyst for the removal of tetracycline residue from water. The adsorption experiment gave a maximum efficiency of about 80% while the photodegradation catalysed by the nanoparticles indicated efficiency up to 97%. Both adsorption and photodegradation showed strong dependency on pH, tetracycline concentration, catalyst load and concentration of KI. Response surface analysis and subsequent experimental validation indicated that degradation approaching 100% for tetracycline is feasible under optimum conditions involving concentration = 500 ppm, time = 50 min, catalyst load = 1.25 g and KI concentration = 0.25 M. Computational calculations gave results that are in good match with experimental data and further proved that the degradation is limited by adsorption and is majorly controlled by oxidation facilitated by O 2 * .