I study the adsorption of a dye by lignocellulosic materials and when I carried out desorption studies by using different concentration of HNO3, I observed a decrease of desorption % with increasing of the nitric acid concentration. Could you please give me a possible explanation about that? After searching in the literature, I found two studies mentioned that: a) However, a higher concentration of HNO3 would dramatically increase the H+ concentration in solution and thus may enhance electrostatic repulsion among Ni(II) ions, inhibiting Ni(II) desorption( adapted from: Zhang, X., & Wang, X. (2015). Adsorption and desorption of nickel (II) ions from aqueous solution by a lignocellulose/montmorillonite nanocomposite. PloS one, 10(2), e0117077.)

b) It was also interesting to note that as the concentration of HCl was increased, the recovery was decreased from 88.3% to 80.2% for Cr3+ and 90% to 70.3% for Co2+ which might be due to the deterioration of Fe3O4@TSC surface functional groups at higher concentration of HCl solution. (Adapted from: Alqadami, A. A., Naushad, M., Abdalla, M. A., Ahamad, T., Alothman, Z. A., & Alshehri, S. M. (2016). Synthesis and characterization of Fe 3 O 4@ TSC nanocomposite: highly efficient removal of toxic metal ions from aqueous medium. RSC Advances, 6(27), 22679-22689.)

Speaking honestly I don’t agree with these reasons.

Thanks a lot in advanced

Best regards,

Ioannis