Adsorption Characteristics of Humic Acids on Imogolite and Contact Angle of Water on Imogolite-Humic Acids Complex Membrane

Abstract

Adsorption of humic acids (HA) on a synthesized imogolite with different pH was characterized. Adsorbed mass of HA on the imogolite was measured in a pH range of 4.5 to 11.0. The maximum adsorption mass was decreased with an increase of pH. This trend can be explained by an alternation of charge amounts of imogolite and HA as a result of pH change. Wetting of imogolite-HA complex membrane fabricated by a drying of retentate of imogolite-HA mixed solution with different pH was examined. Contact angle of water droplet on the membrane was increased with an increase of the adsorbed mass of HA. However, the higher the pH in the fabrication process, the smaller its increment. This difference can be attributed to a difference in a charging state of HA caused by solution condition when HA was adsorbed by surface of imogolite in the fabrication process.