Corn stalks (CS) were modified by a cationic surfactant, cetylpyridinium bromide (CPB), and used as an adsorbent (CS-CP) to remove anionic dyes [Acid Red (AR) and Acid Orange (AO)] from aqueous solutions. The FTIR analysis and the obtained calculations based on the determination of the adsorption capacity of CS towards CPB confirmed that the cationic surfactant had been adsorbed on the surface of corn stalks. Adsorption of the anionic dyes on modified corn stalks was investigated in a series of batch adsorption experiments at 303–328 K. The adsorption data were analyzed using Langmuir, Freundlich, and Temkin models. The Langmuir model was found to be more suitable for the experimental data of the anionic dyes on CS-CP than other adsorption models. Kinetic studies revealed that the pseudo-second order model showed the best fit to the experimental data. The thermodynamic parameters indicated that the adsorption process was spontaneous and exothermic. Mechanisms involving ion exchange and chemisorption might be responsible for the uptake of the anionic dyes on CS-CP. Obtained results imply that CS-CP could be applied as an effective adsorbent to remove anionic dyes from aqueous solutions.

The efficiency of unmodified and modified biosorbents (barley straw and Jerusalem artichoke stalks) in removing anionic (Acid Red) and cationic (Methylene Blue) dyes from their aqueous solutions has been studied. That the adsorption of dye onto unmodified and modified barley straw and Jerusalem artichoke stalks was found to be strongly affected by the pH value. The optimum pH is in the range of 6-10 for cationic dye and 2-3 for anionic one. The kinetic curves of cationic and anionic dye adsorption on barley straw and Jerusalem artichoke stalks are well described with the help of pseudo-second order kinetic equation. Studied biosorbents are natural, eco-friendly, and low-cost adsorbents and they can be an alternative to expensive activated carbons.

No abstract

as -29.6, -30.7, -32.6 for Acid 313, and 323 K, respectively,