Surface Physical–Chemical Characteristics of Sludge Particulates
The surface physical–chemical characteristics, specifically surface acidity and surface electrical properties of sludge particulates, govern the fate and transport of heavy metals in wastewater treatment systems. Surface acidity (i.e., site density and acidity strength) and surface electrical properties such as pH at the zero point of charge (pHzpc) and surface charge of primary, secondary, and tertiary sludge particulates were investigated. Alkalimetric titration was used to determine the surface site density and acidity constant. Electrophoresis was used to determine the surface electrical characteristics. Results show that the sludge surface site can be treated as a weak monoprotic acid under neutral and low pH conditions. The site density (Λ m ) was determined to be 2.4 × 10−3 mol/g suspended solids (SS) for primary sludge and 1.7 × 10−3 mol/g SS for secondary and tertiary sludges. The acidity constant ( pKH ) was estimated to be 6.1 ± 0.5 for all sludge particulates studied. Results also showed that all sludge particulates have strong affinity toward metal ions, including potassium, sodium, and lithium ions. At the field ionic strength, the pHzpc value was approximately 2.9 ± 0.3 for all sludge particulates investigated. It was also revealed that the carboxyl moiety is the major surface functional group contributing the surface characteristics. The significance of surface physical– chemical characteristics of sludge particulates is exemplified by the metals uptake as effected by pH.
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Document Type: Research Article
Publication date: 2000-09-01
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Water Environment Research (WER) publishes peer-reviewed research papers, research notes, state-of-the-art and critical reviews on original, fundamental and applied research in all scientific and technical areas related to water quality, pollution control, and management. An annual Literature Review provides a review of published books and articles on water quality topics from the previous year. Published as: Sewage Works Journal, 1928 - 1949; Sewage and Industrial Wastes, 1950 - 1959; Journal Water Pollution Control Federation, 1959 - Oct 1989; Research Journal Water Pollution Control Federation, Nov 1989 - 1991; Water Environment Research, 1992 - present.
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