Regeneration of nonfunctional Macronet MN 200 loaded with metal complex dye using alcohols in batch and column experiments

Abstract

The conditions for reuse of the Macronet MN 200 by removing the metal complex dye Lanasyn Navy M-DNL (LnCr) from water solutions have been investigated. The Macronet MN 200 loaded with the LnCr dye has been regenerated using alcohols (methanol, ethanol and 2-propanol) in batch and column experiments. The FTIR spectrum of the Macronet MN 200 loaded with the LnCr dye confirmed physical interactions between the LnCr anion and Macronet MN 200 involving π–π and electrostatic bonds. In the batch experiments the desorption efficiency of LnCr dye depends on the solid/liquid ratio (S/L, g/mL), molecular mass of alcohol and duration of desorption. The LnCr dye has been desorbed most efficiently after 10 min at S/L = 0.033, while the desorption efficiency decreases with the increase of alcohol molecular weight: methanol > ethanol > 2-propanol. The rates of desorption were quantified using second-order (k₂), pore diffusion (D/r²) and intraparticle diffusion (k_i) models. The column test results showed that the regeneration efficiency of MN 200 loaded with the LnCr dye (R_e) using methanol with repeated adsorption/desorption cycles decreased but seems to be stabilized to 70% after 3 cycles. A very high LnCr dye concentration in methanol (about 4 g/L) has been obtained within the first 2 alcohol bed volumes and the LnCr dye has been completely desorbed back to the solution with 10 alcohol bed volumes.