Adsorption of methylene blue on lithium titanate and its composite with carbon dots: Optimization of parameters and adsorbent recovery

Porous lithium-titanium oxide (pLT) was produced by the combustion synthesis method. Based on the XRD pattern, the as-synthesized powder phase was Li۲TiO۳. The carbon dots were incorporated onto the lithium titanate sponge (pLT-CD) using the microwave method and natural precursors. Two synthesized structures were used to remove methylene blue from wastewater. A morphological comparison of pLT and pLT-CD was performed using field emission scanning electron microscopy. Elemental mapping of the pLT-CD composite was used to investigate the dispersion of CD on pLT and its stability in aqueous media. The experiments of methylene blue removal by adsorbents were designed using the Taguchi method. The effect of pH, time, temperature, and methylene blue concentration on the treatment process by pLT and pLT-CD was studied. The maximum removal percentage was observed at pH ۸, room temperature, ۱۰ min, and ۴۰ ppm dye concentration on the pLT-CD composite adsorbent. The adsorption equilibrium was better described by the Freundlich isotherm, indicating multilayer adsorption on heterogeneous surfaces. Kinetic results followed a pseudo-second-order model, with pLT-CD showing a higher adsorption rate due to enhanced surface interactions and increased active sites. Adsorbent recovery was performed by UV-Vis irradiation on the saturated adsorbent to decompose the adsorbed dye. An efficiency drop of about ۲۰ and ۱۳.۶۰ % was observed for pLT and pLT-CD, respectively, after four consecutive cycles

کلیدواژه ها:

Taguchi method ، Adsorbent recovery ، Carbon dots ، Porous lithium-titanium oxide ، dye removal