Microwave-modified coastal plant, casuarina equisetifolia seeds as adsorbents for adsorption of methylene blue dye

Abstract

An increasing use of dyes for product coloring has resulted in a huge volume of colored water. Casuarina equisetifolia seeds, an eco-friendly plant waste were used to develop a microwave and chemically treated adsorbent to remove methylene blue (MB) dye from aqueous solution. This study was conducted to determine the characteristics of adsorbent and effects of dosage of adsorbent on concentration of methylene blue dyes removed as well as applicability of Langmuir and Freundlich isotherms. The characteristics of adsorbent were investigated using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Brunaeur­ Emmet-Teller (BET) surface area analyzer, elemental analyzer and electro kinetic analyzer (EK.A). Adsorption experiments were performed based on adsorbent dosage parameter by using batch adsorption method. The Langmuir and Freundlich isotherms were employed to interpret the adsorption behavior. The adsorption of MB dye on C. equisetifolia seeds was confirmed by the presence of carboxylic acid and hydroxyl functional groups based on the FTIR spectrum. Other than that, morphology, surface area and surface charge analysis also supported the results of methylene blue dye adsorption. The best adsorbent dosage is 1 gram with 92.4% dye removal. Experimental data describes the adsorption behavior followed Langmuir isotherm model. The results imply that C. equisetifolia seeds are a potentially low-cost adsorbent for treating wastewater containing cationic dyes.