CHARACTERISTICS OF SLUDGE PARTICULATES IN RELATION TO HEAVY METAL UPTAKE
Abstract:The physical-chemical characteristics of sludge particulates determine the fate and transport of heavy metals in wastewater treatment systems. The surface site density, acidity constant, and electrical characteristics of primary, secondary, and tertiary sludge particulates were investigated. Alkalimetric titration was used to determine the surface site density and acidity constant. Results show that the sludge surface site can be treated as a weak monoprotic acid under neutral and low pH conditions. The site density (Γm) was determined to be 2.4 × 10−3 mol/g-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 primary, secondary, and tertiary sludge particulates. Results also showed that all sludge particulates have strong affinity toward cations, including K+, Na+, and Li+.
The surface site density and acidity constant were used for metal uptake modeling. The experimental results for the uptake of metals including Cu(II), Ni(II), Co(II), Cd(II), Zn(II), Pb(II), Cr(III), and Ag(I) were used. The stability constants (logK) of metal-sludge complexes can be determined from the curve fitting. They are, respectively, 5.85, 3.43, 3.41, 3.98, 5.28, 6.79, 6.57, and 6.57. Thus, the surface site density and acidity constant information are essential for metals uptake modeling.
Document Type: Research Article
Publication date: 2000-01-01
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