title: Nickel adsorption on chalk and calcite.
abstract: Nickel uptake from solution by two types of chalk and calcite was investigated in batch sorption studies. The goal was to understand the difference in sorption behavior between synthetic and biogenic calcite. Experiments at atmospheric partial pressure of CO2, in solutions equilibrated with calcite and chalk and pH ranging from 7.7 to 8.8, explored the influence of initial concentration and the amount and type of sorbent on Ni uptake. Adsorption increases with increased surface area and pH. A surface complexation model describes the data well. Stability constants for the Ni surface complex are log KNi=-1.12 on calcite and log KNi=-0.43 and -0.50 on the two chalk samples. The study confirms that synthetic calcite and chalk both take up nickel, but Ni binds more strongly on the biogenic calcite than on inorganically precipitated, synthetic powder, because of the presence of trace amounts of polysaccharides and clay nanoparticles on the chalk surface.
authors.affiliation: Nano-Science Center, Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark. Electronic address: db@nano.ku.dk.
authors.forename: D A
authors.initials: DA
authors.lastname: Belova
authors.affiliation: Nano-Science Center, Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark; Institute of Experimental Mineralogy, RAS, Academica Osypyana ul. 4, 142432 Chernogolovka, Russia.
authors.forename: L Z
authors.initials: LZ
authors.lastname: Lakshtanov
authors.affiliation: Departament of Geology, University of Oviedo, Campus de Llamaquique, Jesús Arias de Velasco, s/n, 33005 Oviedo, Spain.
authors.forename: J F
authors.initials: JF
authors.lastname: Carneiro
authors.affiliation: Nano-Science Center, Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark.
authors.forename: S L S
authors.initials: SL
authors.lastname: Stipp
mesh_terms: D000327:Adsorption; D002119:Calcium Carbonate / Q000737:chemistry*; D011232:Chemical Precipitation; D060766:Drinking Water / Q000032:analysis*; D009532:Nickel / Q000737:chemistry*; D013696:Temperature; D018508:Water Purification / Q000379:methods*
chemical_list: D060766:Drinking Water; D009532:Nickel; D002119:Calcium Carbonate
keywords: Calcite; Chalk; Nickel adsorption; Surface complexation model