Adsorptive potential of TiO<sub>2</sub> nanoparticles for the removal of Cr (VI) and Pb (II) metal ions from fertilizer wastewater

Titanium dioxide (TiO2) nanoparticles have emerged as promising adsorbents for the removal of heavy metal ions from wastewater due to their high surface area, chemical stability and adsorptive properties. The study evaluated the potential of TiO2 nanoparticles for removing Cr (VI) and Pb (II) from fertilizer wastewater. The TiO2 nanoparticles was synthesized via green method of synthesis with the highest crystallite size of 15.29 nm under the synthesis condition of a stirring time of 60 min. X-Ray Diffraction (XRD), High-Resolution Transmission Electron Microscopy (HRTEM), Dynamic Light Scattering (DLS), and Energy Dispersive X-Ray Spectroscopy (EDX) were used to characterise the synthesised TiO2 nanoparticles. HRTEM and XRD analyses of the TiO2 nanoparticles indicate the formation of spherical shapes and anatase phase crystallite size of 15.29 nm and 12.09 nm for 60 min and 30 min stirring time, respectively. The DLS results show an average particle distribution of 51.54 nm for both stirring time conditions. The EDX revealed the presence of titanium, oxygen and carbon in both stirring times. The synthesized TiO2 nanoparticles was used as an adsorbent for the removal of Cr (VI) and Pb (II) via batch adsorption. The results indicate that Cr (VI) had a higher adsorption removal efficiency of 52.87 % compared to 40.79 % for Pb (II) at a pH of 6.96, contact time of 30 minutes and a temperature of 30oC. The adsorption isotherm showed that the experimental data fitted best to the Langmuir isotherm as compared to the Freundlich and Dubinin-Radushkevich (D-R) isotherms, demonstrated by higher correlation coefficient values (R2). The research findings suggest that TiO2 nanoparticles can be utilized in fertilizer wastewater treatment.