Adsorption of 1,10-Phenanthroline and Sodium Naphthalene 2-Sulfonate onto Activated Charcoal from Mixed Solutions

Abstract

Abstract The adsorption (pH = 10) of single solution and binary mixtures of 1,10-phenanthroline (OP) and sodium naphthalene 2-sulfonate (SNS) on activated charcoal was studied. The maximum values for single solution adsorption were 1.811 mmol/g and 0.611 mmol/g for OP and SNS, respectively. Taking into account the total surface area of each molecule and the total maximum area of coverage on the charcoal, a specific area of 899.7 m2/g was determined for OP and 231.8 m2/g for SNS, indicating that orthophenanthroline molecules have a higher affinity for charcoal and that SNS adsorption occurs at specific sites. The results with binary mixtures show that OP hinders SNS adsorption, probably due to a steric impediment, and that adsorption of OP itself is independent of SNS, reaching comparable levels to the single solution. Using a competitive adsorption model it was shown that the two molecules do not compete for charcoal surface area. Application of the Langmuir two-surface adsorption model to the single solutions and binary mixtures indicates the existence of specific sites on charcoal with affinity for OP and SNS, respectively. In the case of the binary mixtures it was shown that the sum of the individual maximum quantities of adsorbed molecules lies within the same order of magnitude as the value determined by applying the Langmuir equation to each one individually.