Optimizing adsorption efficiency: synthesis and characterization of zinc-doped strontium titanate for highly effective removal of malachite green dye

The current study describes the use of an extremely effective adsorbent for the removal of dye from an aqueous solution. This work focuses on the prospective use of zinc-doped strontium titanate (Zn²⁺:ST) nano-powder to remove the malachite green (MG) from an aqueous medium. Optimization of experimental conditions to find the maximum dye adsorption is studied in detail. The Zn²⁺:ST nano-powder was synthesized using the low-temperature solution combustion method and extensively characterized using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), FTIR and UV–visible spectroscopy. PXRD analysis revealed a cubic structure of Zn²⁺:ST, closely matching ICDD card No. 35-734, indicating a space group of pm-3 m (No. 221). The average crystallite size was found to be 20–30 nm using the Scherrer formula. SEM images depicted the particles’ irregular shape. UV–visible spectroscopy showed the band gap of 3.1 eV and FTIR confirmed formation of M–O bond at 582 cm⁻¹ and 868 cm⁻¹ for SrO and ZnO, respectively. Optimal adsorption parameters were determined by varying dosage, stirring rate, and pH. Under these optimized conditions, for 10 ppm of stock solution, an impressive 98% adsorption efficiency was achieved with a 10 mg/L dose, 30-min contact time, and pH 10. Adsorption isotherms were fitted to the Langmuir model, showing a favorable correlation between experimental data and the model. This study provides valuable insights into the potential application of zinc-doped ST nano-powder for efficiently removing malachite green from water solutions.