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Sorption and Release of Cadmium by Some Sewage Sludges
Author(s) -
Riffaldi R.,
LeviMinzi R.,
Saviozzi A.,
Tropea M.
Publication year - 1983
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1983.00472425001200020021x
Subject(s) - sorption , chemistry , cadmium , adsorption , sewage sludge , extraction (chemistry) , langmuir adsorption model , langmuir , ion exchange , environmental chemistry , nuclear chemistry , sewage , langmuir equation , chromatography , inorganic chemistry , ion , environmental engineering , organic chemistry , engineering
Sorption and release of Cd were determined in nine sewage sludges from Tuscany, Italy. The Cd adsorption data were in agreement with both the linear sorption isotherm and the Langmuir equation. The average of calculated adsorption maxima was about 50% of the mean CEC value, indicating that exchangeable cations present in the sludges were more effective in competing with the Cd ion for exchange sites. The calculated Langmuir adsorption maxima were found significantly correlated with fulvic acid C content and carboxyl and phenolic hydroxyl groups of fulvic acids. The release of Cd retained at two initial concentrations as a function of different extraction solutions was indagated. Extraction experiments showed that Cd may be held in sludges by more than one type of site and that the strength of bonding decreases as the total Cd increases. Cadmium was retained mainly by exchange and complexing sites, the former assuming a relatively more important role as cadmium adsorption increased. The effect of different exchangeable cations on the sorption of Cd by sludges was also studied. The amounts of Cd sorbed on the sludge surfaces decreased in the order: Ca‐sludge > untreated sludge > Fe‐sludge = Al‐sludge.