Through converting the surface complex on TiO2 nanorods to generate superoxide and singlet oxygen to remove CN. J Environ Sci (China) 2023;124:300-309. [PMID: 36182139 DOI: 10.1016/j.jes.2021.08.054]

Cyanide Removal by ZnTiO3/TiO2/H2O2/UVB System: A Theoretical-Experimental Approach

Cyanide is a highly toxic substance present in wastewater from various industries. This study investigates the removal of cyanide species (CS) from aqueous solutions using the ZnTiO3/TiO2/H2O2/UVB system. ZnTiO3/TiO2 nanoparticles synthesized by the sol-gel method were characterized by powder X-ray diffractometry (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The adsorption capacity of nanoparticles was tested by varying the pH of the solution, adsorbent concentration, and contact time. The adsorption of CS on ZnTiO3 and TiO2 surfaces was verified by Density Functional Theory (DFT) calculations. Photocatalytic experiments were achieved under UVB irradiation (λ = 310 nm). The response surface methodology (RSM) was used to optimize the CS removal efficiency. The detoxification effect was evaluated by acute toxicity tests with brine shrimp. The theoretical results show that the adsorption of CS is energetically more favorable on the ZnTiO3 surface than on the TiO2 surface. The experimental results show that the system consisting of ZnTiO3/TiO2 (200 mg L-1), H2O2 (0.1%), and UVB light removes 99% of CS from aqueous solutions after 60 min and reduces the mortality of nauplii in 90% after 90 min. This system was reused in five consecutive cycles with a total loss of efficiency of 30%.

Effect of Doping TiO2 NPs with Lanthanides (La, Ce and Eu) on the Adsorption and Photodegradation of Cyanide-A Comparative Study

Free cyanide is a highly dangerous compound for health and the environment, so treatment of cyanide-contaminated water is extremely important. In the present study, TiO₂, La/TiO₂, Ce/TiO₂, and Eu/TiO₂ nanoparticles were synthesized to assess their ability to remove free cyanide from aqueous solutions. Nanoparticles synthesized through the sol-gel method were characterized by X-ray powder diffractometry (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transformed infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), and specific surface area (SSA). Langmuir and Freundlich isotherm models were utilized to fit the adsorption equilibrium experimental data, and pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to fit the adsorption kinetics experimental data. Cyanide photodegradation and the effect of reactive oxygen species (ROS) on the photocatalytic process were investigated under simulated solar light. Finally, reuse of the nanoparticles in five consecutive treatment cycles was determined. The results showed that La/TiO₂ has the highest percentage of cyanide removal (98%), followed by Ce/TiO₂ (92%), Eu/TiO₂ (90%), and TiO₂ (88%). From these results, it is suggested that La, Ce, and Eu dopants can improve the properties of TiO₂ as well as its ability to remove cyanide species from aqueous solutions.