ADSORPTIVE AND PHOTOCATALYTIC PROPERTIES OF THE ZnO/BENTONITE/Ag HETEROJUNCTION

The degradation of organic wastewater pollutants from diverse sources represents a critical scientific challenge, particularly in light of the escalating demand for dyes across various industries. Addressing this challenge entails the exploration of efficient and eco-friendly methods to convert organic pollutants into benign and straightforward compounds, leveraging state-of-the-art photocatalysts. The synthesis was conducted via the novel sol-gel method. Structural, crystalline, elemental and phase parameters were analyzed using X-ray analysis, chemical surface characteristics investigated through infrared spectroscopy, band gap determination performed via diffuse reflectance spectroscopy, and evaluation of adsorption and photocatalytic activity carried out for the semiconductor photocatalyst ZnO and heterojunctions incorporating bentonite. The synthesized photocatalysts were employed for the removal of malachite green dye. Equilibrium studies for adsorption were conducted using Langmuir and Freundlich isotherms, revealing a superior fit with the Langmuir model. The maximum adsorption capacity was determined as 70.4 mg/g using the Langmuir equation. Kinetic parameters indicated that the adsorption of malachite green on bentonite followed a first-order kinetics model where k1=0,152 min-1. The photodegradation efficiency of ZnO, ZnO/bentonite, and Zn/bentonite/Ag was investigated by static experiment under ultraviolet irradiation. Within 60 minutes, a 99.4% photodegradation of the malachite green solution at a concentration of 100 mg/L was achieved using the ternary heterojunction photocatalyst. Remarkably, within just 10 minutes in the presence of the ternary composite, a degree of photocatalytic degradation reaching 72% was attained, which significantly exceeds the results of the binary heterojunction photocatalyst. Thus, the synthesized heterojunction exhibits notable photocatalytic activity, particularly evident within short time intervals. A proposed mechanism for the photocatalytic degradation of malachite green is outlined based on existing literature sources.