Contribution of Electrostatic Interaction and Hydrophobic Interaction to the Adsorption Between Humic Acid and Chlorophenols

SHOJI Ryo, IWATA Kouki, SUZUKI Daisuke

doi:10.11353/sesj.31.252

<p>Chlorophenols are known as intermediate of dyestuff and insecticide arises on the process of bleaching paper pulp. They have strong toxicity to aquatic lives. In nature, it is known co-existing substances such as humic acid (HA) affects the toxicity of heavy metals and organic matters including cationic/anionic surfactants. The purpose of this study is to reveal the adsorption mechanism of HA and Chlorophenols. First, the chemical property of HA was examined with acid-base titration. This experiment shows HA has dominant sites of adsorption such as carboxyl group and phenolic hydroxyl group analyzed with NICA (Non Ideal Competitive Adsorption)-Donnan model. Then, adsorption between HA and chlorophenols including 2,4,6-trichlorophenol (2,4,6-TCP), 2,4-dichlorophenol (2,4-DCP), p-chlorophenol (p-CP) was examined by shaking experiment. The pka (acid dissociation constant) of each chlorophenols were within the range of 6 to 10. Amount of 2,4,6-TCP adsorbed onto HA was drastically decreased along with pH increase though 2,4-DCP was slightly decreased. No relationship between amount of p-CP adsorbed and pH of solution was found. 2,4,6-TCP is electronegatively charged because the proton dissociation generates repulsion between 2,4,6-TCP and HA. Moreover, a positive correlation between partition coefficient (logP) and amount of adsorption was suggested.</p>

Contribution of Electrostatic Interaction and Hydrophobic Interaction to the Adsorption Between Humic Acid and Chlorophenols

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