Comparative Study of the Effect of Doping ZnTiO3 with Rare Earths (La and Ce) on the Adsorption and Photodegradation of Cyanide in Aqueous Systems

Abstract

Cyanide is a highly toxic compound that can pose serious health problems to both humans and aquatic organisms. Therefore, the present comparative study focuses on the removal of total cyanide from aqueous solutions by photocatalytic adsorption and degradation methods using ZnTiO3 (ZTO), La/ZnTiO3 (La/ZTO), and Ce/ZnTiO3 (Ce/ZTO). The nanoparticles were synthesized by the sol-gel method and characterized by X-ray powder diffractometry (XRD), Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), Diffuse reflectance spectroscopy (DRS), and Specific surface area (SSA). The adsorption equilibrium data were fitted to the Langmuir and Freundlich isotherm models. Adsorption kinetics were also evaluated using the pseudo-first-order and pseudo-second-order models and the intraparticle diffusion model. Likewise, the photodegradation of cyanide under simulated sunlight was investigated and the reusability of the synthesized nanoparticles for cyanide removal in aqueous systems was determined. The results demonstrated the effectiveness of doping with lanthanum (La) and cerium (Ce) to improve the adsorbent and photocatalytic properties of ZTO. In general, La/ZTO showed the maximum percentage of total cyanide removal (99.0%) followed by Ce/ZTO (97.0%) and ZTO (93.6%). Finally, based on the evidence of this study, a mechanism for the removal of total cyanide from aqueous solutions using the synthesized nanoparticles was proposed.

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

“…The maximum cyanide adsorption capacity was investigated by varying the concentration of 500 mL of KCN solution from 0.20 to 40 mg L −1 . The adsorption thermodynamics and kinetic behavior of cyanide adsorption were investigated using 500 mL of water containing 20 mg L −1 of KCN [ 38 ]. The alkaline picrate analytical method was used to quantify total cyanide in aqueous solutions [ 39 , 40 , 41 ].…”

“…The concentration of the solutions was determined based on the previously prepared calibration curve (R 2 = 0.9996) according to the Lambert–Beer Law. The tests were carried out in triplicate and the results were expressed as the average of three repetitions [ 38 ]. The amount of cyanide adsorbed (q e ) on the nanoparticles expressed in mg g −1 was estimated using the following equation [ 42 ]: where C 0 and C e are expressed in mg L −1 and correspond to the initial and equilibrium concentration, respectively.…”

“…The batch method was used, keeping the pH of the solution at 7.0 ± 0.1 by adding 0.1 M solutions of hydrochloric acid or sodium hydroxide. Typically, 0.2 g L −1 of nanoparticles were magnetically stirred in 500 mL of water containing 20 mg L −1 of KCN [ 38 ]. The photodegradation rate of cyanide species in the heterogeneous photocatalytic systems exposed to simulated solar light for the TO, La/TO, Ce/TO, and Eu/TO nanoparticles was followed by the Langmuir–Hinshelwood equation [ 47 ], which can be represented by the following equation [ 48 ]: where k (min −1 ) is the actual rate constant, K is the adsorption constant of the substrate on the nanoparticles, C 0 (mg L −1 ) represents the initial concentration of the substrate, and C t (mg L −1 ) represents the concentration at a specific time t (min), and k app (min −1 ) is the apparent rate constant.…”

“…In each treatment cycle, 100 mL of fresh KCN solution (20 mg L −1 ) was used. The amount of nanoparticles used in this experiment was 0.2 g L −1 [ 38 ].…”

Perovskite Nano-Powder and Nano-Film Catalysts in Mineralization of Aqueous Organic Contaminants through Solar Simulated Radiation

“…For the ZnTiO3 and MnTiO3 materials, the PZC values were ~7.80 and ~7.83. ZnTiO3 has a PZC value reported in the literature within the range of 7.00-7.60 [51,52], depending on the presence of TiO2. For MnTiO3, the present high values were due to the mixed phase with TiO2, as reported earlier [53].…”