The use of lignocellulosic waste of rice straw for AO7 and RBB dyes adsorption from water

In this research, rice straw was used as a low-cost and abundant lignocellulose material for adsorption of acidic and reactive dyes from aqueous solution and their adsorption efficiency has been investigated. Rice straw was used after grinding and extraction. The studied dyes were Orangan 7 (AO7) and Rimozol Black B (RBB) obtained from Alvand Sabet Co. in Hamadan. In this study, the effect of pH, temperature, adsorbent and dyes concentration, and adsorption time were investigated to determine the optimum adsorption conditions. Also the adsorption isotherm was studied for both dyes. The results of color adsorption by rice straw showed that the amount of adsorption depended largely on the pH of the solution, and in acidic pH the removal of the dye by rice straw was high. Also, the dye adsorption at the initial stages of treatment is very fast and more than 95% of the adsorption of dye takes place at the first 5 minutes. The adsorption rate was studied using well-known adsorption models, and the results indicated that the equilibrium data for both dyes were perfectly described by the Langmuir isotherm. The maximum adsorptions of rice straw were 16.5 mg/g and 27.3 mg/g for RBB and AO7, respectively. Due to low cost and abundance of rice straw, it could be a suitable material for removal of dyes pollutants from industrial and municipal wastewater.