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Effect of temperature and salinity on Cd adsorption in a sandy coastal sediment

AuthorsBlasco, Julián ; Sáenz-Arreucoechea, Verónica; Gómez-Parra, Abelardo
Issue DateJun-2014
CitationXVII Seminario Ibérico de Química Marina (2014)
AbstractMetal adsorption in coastal sediments is a well studied process because sediments are the final repositoryof metal inputs which provokes a decrease in metal bioavailability and toxicity. The scientific literatureabout this process is wide and metals and sediments from different sources and nature have been studied.However, these studies are focused on sediment with high levels of clay and silt, and less attention hasbeen paid to sediments with coarse granulometry although they represent an elevated percentage in highenergy coastal areas, as estuary ecosystems, which are the main route for metal inputs in the oceans.In this work, Cd adsorption on sandy sediment (5.2% clay, 19.3% silt and 75.5% sand) and the influenceof temperature (20-30ºC) and salinity (20-35%o) on this process have been measured. Kinetic adsorptionhas been examined and the time to reach the equilibrium was less than 160 hours. The adsorptionthermodynamic constant and the variations of state funcions (∆Hº,∆Sº and∆Gº) were determined.Sediment sample was collected from the south area of Sancti-Petri Channel (Cadiz bay). This area showslow levels of metal contamination. Specific surface area was 8.6 m2g−2. Experiments were carried outin batch in Pyrex vessels with 0.6 g of sediment and 200 mL of Cd solutions in artificial seawater. TheCd concentration range was selected in logaritmic scale to include the whole range of Cd solubility inseawater. The analyses were carried out by GFAAS (Perkin Elmer 4100 ZL) and background correctionwith longitidunal Zeeman.In all cases, the results showed the best fit to Freundlich isotherm (C type). The constant values rangedbetween 148.80 and 454.36 L kg−1being the exponential term (n) lower than 1. The salinity effect on Cdadsorption is bigger than temperature. The adsorption process decreases with increasing salinity due tocompetence of alkaline and alkaline earth elements by adsorption sites. The∆Hº ranged between 24.91and 40.57 kJ mol−1,∆Sº between 106.64 and 230.34 J mol−1K−1and∆Gº between 6·104and 22.4·104kJ mol−1.
DescriptionTrabajo presentado en el XVII Seminario Ibérico de Química Marina (evento que une al IV Congreso de Ciencias del Mar, IV Simposio Internacional de Ciencias del Mar y al Encuentro de la Oceanografía Física), celebrado en Las Palmas de Gran Canaria del 11 al 13 de junio de 2014.
Appears in Collections:(ICMAN) Comunicaciones congresos
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