In This work the adsorption characteristics of methylene blue (MB) from aqueous solution by the new tri-azine-based adsorbent (TBDS) were compared with those of the pine leaves, soybean meal (SBM) and wheat bran as three natural adsorbents.The structure characteristics of the TBDS were studied using Fourier Transform Infrared Spectroscopy (FT-IR), Energy dispersive X-ray spectroscopy (EDX-mapping), Field-Emission scanning electron microscopy (FE-SEM), X-ray diffraction analysis (XRD), Thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) surface analysis. The effecting variables on the removal efficiency of MB by the mentioned adsorbents were optimized. The effects of pH (2-10), contact time (1-120 min), dose of adsorbents (0.005-0.02 g), concentration of MB (3-200 mg/l), temperature (8-40 °C) and electrolyte concentration were studied. The optimum conditions for TBDS were: temperature 25 ° C, pH=8, dose of adsorbent 0.01 g and contact time 15 min. The optimum conditions for natural adsorbents were: temperature 25 ° C, PH=7, dose of adsorbent 0.01 g for pine leaves and soybean meal (SBM) 0.015 g for wheat bran, contact time, 5 minutes for pine leaves and soybean meal (SBM), 15 minutes for wheat bran. The isotherm data of TBDS was well fitted to Langmuir isotherm. Pine leaves showed mix of Langmuir and Temkin isotherm characteristics. Soybean meal and wheat bran abbey Temkin isotherm. Pseudo-secound order kinetics characteristics were observed for all adsorbents. The natural adsorbents pine leaves and wheat bran were well recovered with distilled water and soybean meal with ethanol. The best recovering solvent for TBDS is water. The maximum adsorption capacity for TBDS and pine leaves were 15.3 32.1 mg/g respectively. The empirical adsorption capacity for soybean meal (SBM) and wheat bran were 71.6, 38.3 mg/g respectively. The detection limit of this work for measuring methylene blue by spectrophotometric method in linear range 1-10 mg/L, were 0.03 mg/L in pH=8 and 0.006 mg/L.in pH=7.
