Insight into adsorption-desorption of methylene blue in water using zeolite NaY: Kinetic, isotherm and thermodynamic approaches

Removal of methylene blue from synthetic industrial wastewater by using geopolymer prepared from partially dealuminated metakaolin

Industrial wastewater frequently contains a huge of pollutants, such as heavy metals, dyes, and organic compounds, leading to considerable environmental discharge. Methylene Blue (MB), a cationic dye extensively utilized in the textile and pharmaceutical sectors, presents significant hazards to aquatic environments and human health. Exposure to MB may result in negative effects, including dermal irritation, stomach discomfort, and possible long-term ecological consequences. This research investigates the elimination of MB from synthetic industrial wastewater utilizing a geopolymer derived from Partially De-aluminated Metakaolin (PDK) by using adsorption technique it is a simple, low-cost, and effective method for removing a variety of pollutants. The geopolymeric materials were analysed using XRF, XRD, FTIR, SEM, EDX, and BET to confirm its structure then used for MB removal. The specific surface area of the geopolymer was determined to be 9.3 m2/g and a pore volume of 0.024 m3/g. Its kinetics and isotherms were investigated in the MB dye adsorption experiments. The adsorption was influenced by dose, initial dye concentration, pH, and contact time. According to the results, the maximum adsorption capacity (8 mg/g) was attained at 60 mg/L MB, 60 min of contact time, and pH 7-12 for one hour. The experimental data indicated that Freundlich isotherm model was the best-fit model to describe the sorption of MB on the synthesised geopolymer with higher determination coefficients R2 of 0.996. Value of n greater than unity indicates a favourable adsorption taking place. This indicated that the adsorption occurs under a multilayer and heterogeneous surface for MB. The adsorption kinetics of MB onto GP was investigated using pseudo first order, and pseudo second order models as shown in, using the experimental data at various initial concentrations. The calculated parameters values obtained from the application of three models are tabulated. By comparing R2 for each applied model and the compatibility between the estimated and observed qe values, the most favourable model may be identified. The pseudo 2nd order R2 value are greater than other models.

A Novel Approach to Waste Recycling and Dye Removal: Lithium-Functionalized Nanoparticle Zeolites

A zeolitic sample, named MT-ZLSH, was synthesized using mining tailings (MT) as the precursor material, resulting in a structure comprising: Linde type A (LTA) and sodalite-hydroxysodalite (ZLSH). This naming convention reflects the material's origin and its structural characteristics. The material was further modified by incorporating lithium, producing MT-ZLSH-Li+. Physicochemical characterizations were performed, and the material was evaluated for its potential to remove methylene blue (MB) from synthetic wastewater through adsorption and photocatalysis. Efficient adsorption was observed under typical wastewater pH conditions, with a maximum adsorption capacity of 23.4 mg·g-1, which fit well with the Langmuir isotherm model. The key mechanisms governing MB adsorption were identified as ion exchange, electrostatic attraction, and hydrogen bonding. The adsorption process was exothermic, with kinetic data fitting both the pseudo-second order and intraparticle diffusion models, achieving 82% removal and a maximum adsorption capacity of 40 mg·g-1 over 12 h. MB adsorption followed a two-step process, initially involving film diffusion, followed by intraparticle diffusion. Additionally, photocatalytic degradation of MB achieved 77% degradation within 180 min. However, a decrease in reusability was observed during a second cycle of MB adsorption and photodegradation, highlighting the need for further optimization to enhance the material's long-term performance.