Adsorption of organic molecules at the mercury-solution interface: effect of anion specific adsorption on double layer properties. [Benzyl alcohol]

Technical Report · Fri Aug 01 04:00:00 EDT 1980

DOI:https://doi.org/10.2172/5218754· OSTI ID:5218754

Buckfelder, III, J. J.

Adsorption of iso-pentanol, pentanoic acid, and benzyl alcohol at the mercury-solution interface was studied in HC1O/sub 4/, H/sub 2/SO/sub 4/, NaNO/sub 3/, and NaF electrolytes. The Frumkin isotherm equation Ba = (theta/(1-theta))exp(2..cap alpha..theta) together with the implied charge vs. surface excess relation: q = (1-theta)q/sub w/ + thetaQ were used to analyze the experimental data. Linear charge vs surface excess plots were obtained for the aliphatic compounds over the entire potential region studied; for benzyl alcohol, plots were linear only at anodic potentials. The slopes of these lines agreed with those predicted by the above equation, with Q = C/sub org/(V-V/sub n/), for cathodic potentials. At potentials anodic to the electrocapillary maximum, deviations between experimental and theoretical slopes appeared. In the model proposed, the double layer consists of two parts. The layer closest to the surface is restricted to water molecules and specifically adsorbed ions. The second layer contains organic molecules exclusively; any charge necessary to balance the surface charge is considered to be in a monolayer adjacent to the organic layer. From the slope of the charge vs surface excess plots, it is possible to calculate the charge on the covered portion of the surface and then calculate the amount of specific adsorption. The relative amounts of specific adsorption are in agreement with known strengths of adsorption of the anions of the electrolyte. Capacity curves were also calculated and were in good agreement with experimental curves.

• Research Organization: Ames Lab., IA (USA)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 5218754
• Report Number(s): IS-T-888
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ADSORPTION
ALCOHOLS
ALKALI METAL COMPOUNDS
AQUEOUS SOLUTIONS
CARBOXYLIC ACIDS
DISPERSIONS
ELECTROLYTES
ELEMENTS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
INORGANIC ACIDS
LAYERS
MERCURY
METALS
MIXTURES
MONOCARBOXYLIC ACIDS
NITRATES
NITROGEN COMPOUNDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PENTANOLS
PERCHLORIC ACID
SODIUM COMPOUNDS
SODIUM NITRATES
SOLUTIONS
SORPTION
SULFURIC ACID
SURFACES
VALERIC ACID