PH of solution greatly affects sorption of ionizable compounds into low-density polyethylene film

Hiroya Ishikawa, Toshiro Matsui, Takayoshi Ohtsu, Ken Ichi Watanabe, Keiko Matsumoto, Kiyoshi Matsumoto

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3 Citations (Scopus)

Abstract

Sorption of ionizable compounds of pyridines and aromatic carboxylic acids into low-density polyethylene (LDPE) film was investigated as a function of pH ranging from 4 to 7. The sorptions for pyridines were increased with increasing pH. Within the range examined, pH 7 was observed to promote the highest degree of sorption. When the pH increased by one unit from 6 to 7, the sorptions for 2-propylpyridine and 2,4,6-trimethylpyridine were both increased ∼3.8 and 10.5 times, respectively. At pH 4, the sorption for the pyridines entirely disappeared. In contrast, the sorptions for aromatic carboxylic acids increased with decreasing pH. Within the range examined, pH 4 was observed to promote the highest degree of sorption. The magnitude of sorption for pyridines and carboxylic acids apparently depended on the affinity (δC) of these compounds for LDPE film. Another factor affecting the sorption at various pHs was the pKa of these compounds; the sorption greatly decreased with the ionization degree of these compounds. To elucidate the phenomena, the following thermodynamic sorption equation was applied: S = Soy exp[V V{(δW - δV)2 - δc2)/RT}. The plots of In S for pyridines vs the term of the equation gave an insufficient relationship (r= 0.519). In contrast, taking into account the ratio (Χi) of concentration of un-ionized compound to total concentration, the improvement for the equation was made: S′ = S/χi= S0γ exp[Vv{(δ w - δv)2 - δc 2)/RT}. The plots of In S′ vs the term of the equation gave a better relationship (r = 0.884). Furthermore, the equation was also applicable for the sorption behavior of carboxylic acids into LDPE (r = 0.769).

Original languageEnglish
Pages (from-to)3488-3492
Number of pages5
JournalJournal of Agricultural and Food Chemistry
Volume53
Issue number9
DOIs
Publication statusPublished - May 4 2005

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Agricultural and Biological Sciences(all)

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