The effect of the introduction order of the solutes(Napthol-2 and Calcium) on the adsorption of surfactants onto powder activated carbon F400
The effect of the introduction order of naphtol-2 and calcium (N-2 and ca) on the adsorption of surfactants by raw powdered activated carbon (PAC) F 400 has been studied in a static system, studied mixtures included the anionic surfactant: sodium dodecyl-sulfate (SDS) with N-2 or with N-2 + Ca, and the cationic surfactant beniyldodecyldimethylarnmoniurn bromide (BDDAB) with N-2, or with Ca. The experimental results demonstrate that whatever the order of solute introduction, the SDS concentrations at equilibrium are almost identical. Moreover, the adsorption kinetics of SDS and BDDAB increase in the presence of calcium ions. The adsorption kinetics of N-2 decrease in the presence of SDS, suggesting inhibition of N-2 adsorption by SDS. Concerning the adsorption of BDDAB the presence of N-2, for different introduction orders, plotting of the LANGMIIIR isotherms shows that the maximal BDDAB adsorption capacity Г∞, does not change but the LANGMUIR constant (K) decreases. For naphtol-2, however the maximal adsorption capacity Г∞, does vary slightly, going from l,67 to l.5 mmol/g for different BDDAB introduction orders. In the presence of increasing BDDAB concentrations, the maximum adsorption capacity of N-2 decreases from 1.67 to 0.8 mmol/g. The addition of N-2 after 3 hours of BDDAB/PAC contact does not lead to BDDAB desorption. similar behavior is observed on addition of N-2 after 3 hours of SDS/PAC contact, even though the addition of SDS to a N-2/PAC mixture leads to N-2 desorption.