Competitive Adsorption of Methylene Blue and Cu~(2+) onto Citric Acid Modified Pine Sawdust

摘要

Pine sawdust modified with citric acid (CA-PS) is used as an adsorbent for the removal of Cu2þ and methylene blue (MB) from the single and binary compound systems. The initial pH has a significant effect on Cu2þ adsorption, but a relatively little effect on MB adsorption. The kinetic and isotherm studies indicate that the pseudo-second-order model and the generalized model provide the best correlation of the experimental data in the single systems as well as in the binary systems. The adsorption capacities of CA-PS from Generalized isotherm model are 0.23 mmol/g for Cu2þ and 0.25 mmol/g for MB, which are higher than that of B-PS. In the binary systems, Cu2þ and MB exhibit competitive adsorption behaviors. The adsorption capacity of Cu2þ or MB is considerably reduced with an increase in the concentration of the other, and Cu2þ exhibits better competiveness than MB. However, the total adsorption capacity is higher compared with that in the single systems, which increases with an increase in the initial concentration of Cu2þ or MB and reaches a plateau value of 0.301 mmol/g.