Nomogram for calculating percentage ionization of acids and bases

Hopgood, MF

doi:10.1016/0021-9673(70)80006-1

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“…Ionization degree, which is related to the electrostatic properties of organic compounds, was calculated by the ratio of dissociated ion [36], according to Eqs.…”

Section: Calculation Of the Adsorbate Ionization Degreesmentioning

confidence: 99%

Binding mechanisms and QSAR modeling of aromatic pollutant biosorption on Penicillium oxalicum biomass

Wei

Huang

Yang

et al. 2011

Chemical Engineering Journal

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a b s t r a c tThe biosorption of eight aromatic compounds with different functional groups by Penicillium oxalicum biomass were investigated. The affinity of the biomass for the eight compounds at pH 6.0 follows the following trend: 1-naphthalenamine > naphthol > benzoic acid > p-toluidine > p-cresol > p-toluic acid > phenol > p-toluenesulfonic acid. Biomass surface was characterized, and it was found that four discrete binding sites, corresponding to carboxyl (pK a = 4.0), phosphoric (pK a = 7.0), amine (pK a = 8.8), and hydroxyl groups (pK a = 10.0), were identified on the biomass surface by using the linear programming method (LPM) for the fitting of the titration data and FTIR analysis. The carboxyl and amine groups dominate the biomass surface sites, which might have played an important role in biosorption of organic compounds. Furthermore, the compounds were divided into two groups based on the calculation of ionization degree for toluene derivatives and the comparison on the number of benzene rings for barely ionized compounds. It was found that low ionization degree and high hydrophobicity favor the biosorption for the two groups, respectively. Moreover, a R 2 adj of 0.724 between the log of Freundlich coefficient (log K f ) and log Kow indicated that the hydrophobicity plays role in the sorption of eight organic compounds. The QSAR model with one variable was developed for the first time between log K f and polar surface area (PSA) to predict the biosorption behaviors of organic compounds (R 2 adj = 0.960) except for ptoluenesulfonic acid (with pK a < 0), which also supported the electrostatic attraction and hydrophobicity mechanisms.

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“…Ionization degree, which is related to the electrostatic properties of organic compounds, was calculated by the ratio of dissociated ion [36], according to Eqs.…”

Section: Calculation Of the Adsorbate Ionization Degreesmentioning

confidence: 99%