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For 1143 organic compounds comprising 580 oxygen acids and 563 nitrogen bases that cover more than 17 orders of experimental pK(a) (from -5.00 to 12.23), the pK(a) prediction performances of ACD, SPARC, and two calibrations of a semiempirical quantum chemical (QC) AM1 approach have been analyzed. The overall root-mean-square errors (rms) for the acids are(More)
A quantum chemical method has been developed to estimate the dissociation constant pK(a) of organic acids from their neutral molecular structures by employing electronic structure properties. The data set covers 219 phenols (including 29 phenols with intramolecular H-bonding), 150 aromatic carboxylic acids, 190 aliphatic carboxylic acids, and 138 alcohols,(More)
Big gap between experimental filtration resistance of cake layer formed on membrane surface and the hydraulic resistance calculated through the Carman-Kozeny equation, suggested the existence of a new membrane fouling mechanism: osmotic pressure during cake layer filtration in SMBR system. An osmotic pressure model based on chemical potential difference was(More)
A lab-scale membrane bioreactor (MBR) was continuously operated to investigate the membrane fouling. A new membrane fouling mechanism: osmotic pressure mechanism in cake layer filtration process was identified. Osmotic pressure was proposed to stem from the retention of counter-ions in the matrix of biopolymers in cake layer. Through Fourier transform(More)
The deterioration of water quality, especially organic pollution in Tai Lake and the Qiantang River, have recently received attention in China. The objectives of this study were to evaluate the formation of halonitromethanes (HNMs) using multiple regression models for chlorination and chloramination and to identify the key factors that influence the(More)
The dissociation constant pKa defines the ionization degree of organic compounds. It is an important parameter that affects their toxicity and environmental behavior and fate. Among the present approaches to predict pKa values of organic chemicals, increment methods show a good performance but are limited by missing values of special groups. The purpose of(More)
It is important to seek out plant species, high in phosphorus (P) uptake, for phytoremediation of P-enriched environments with a large amount of organic P (Po). P assimilation characteristics and the related mechanisms of Polygonum hydropiper were investigated in hydroponic media containing various concentrations of Po (1-8 mmol L(-1)) supplied as phytate.(More)
In this study, the effects of ionic strength on membrane fouling in a membrane bioreactor (MBR) were investigated. Ionic strength in range of 0.005-0.05mol/L exerted no apparent impacts on the resistance of virgin membrane, fouled membrane and pore clogging. Thermodynamic analysis showed existences of a secondary energy minimum and an energy barrier in the(More)
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