Sustainable adsorption of methylene blue (MB) dye using individual and combined ratios of Trigonella foenum-graecum (F) seed galactomannan and Linum usitatissimum (L) seed

This study explores the adsorption of methylene blue (MB) dye from aqueous solution using different forms of fenugreek galactomannan (F) and linseed (L) as an adsorbent. The characterization study of adsorbents reveals the involvement of carboxyl, hydroxyl, and amine groups in MB adsorption taking place on the amorphous, heterogeneous, and porous surface of the adsorbent. Different adsorption parameters were studied and optimized. The results of the study show 86.62, 86.94, 88.04, 88.24, 88.56, and 89.09 of MB dye adsorption with F, L, F + L (1:1), F + L (1:2), F + L (2:1), and F + L (2:2), respectively, under optimized conditions. The optimized conditions for the maximum dye removal include adsorbent dose of 1.2 g, dye concentration of 80 mg/l when contact time of 60 min was applied to the system at a temperature of 40 °C. The isothermal study shows the fitness of the experimental data to the Langmuir isotherm model. Kinetic modeling shows that both physical and chemical interactions are involved in the dye adsorption. The thermodynamic study confirms the spontaneity, endothermicity, and feasibility of the studied process. Overall, the current research involves use of low-cost raw materials for MB dye removal that aids not only in waste management but also in promoting sustainability and preservation of natural resources including air, water and land.