Enhanced removal of crystal violet from aqueous solutions using BaTiO3@ZnO: isotherm, kinetic, and thermodynamic evaluation

Abstract

Crystal violet (CV), commonly utilized in various industries, presents risks to both the environment and human health because of its durability and harmful nature. This research discusses the synthesis of a BaTiO₃@ZnO composite for effectively eliminating CV from aqueous solutions. The composite was produced through a solid-state technique and characterized using XRD, FTIR, SEM-EDX, TEM, BET, and pH_pzc. The study of CV adsorption involves optimizing various parameters that influence the process, including pH, initial dye concentration, dosage of the adsorbent, contact time, temperature, and ionic strength. The BaTiO₃@ZnO composite displayed a mesoporous configuration with a surface area of 34.1 m² g⁻¹, a total pore volume of 0.0354 cm³ g⁻¹, and an average pore radius of 2.53 nm, along with an average crystallite size of 64.58 nm. The experimental data align most closely with the Langmuir isotherm and pseudo-second-order kinetic model, indicating that monolayer adsorption and chemisorption are the main processes involved. The Langmuir isotherm demonstrated a maximum monolayer adsorption capacity of 97.84 mg g⁻¹ for the BaTiO₃@ZnO composite. The thermodynamic studies suggest that the adsorption processes are spontaneous and endothermic. The BaTiO₃@ZnO composite can be effectively recycled and reused for up to ten cycles, maintaining relatively high adsorption capacity despite a gradual decline over successive cycles. This study exhibited the success of doping ZnO into BaTiO₃ to form a composite that possesses enhanced surface area, porosity, and surface charge, thereby making the BaTiO₃@ZnO composite a promising and efficient adsorbent for CV removal in industrial wastewater.