TY - JOUR
T1 - Competitive sorption of tungstate, molybdate and phosphate mixtures onto goethite
AU - Xu, Nan
AU - Christodoulatos, Christos
AU - Koutsospyros, Agamemnon
AU - Braida, Washington
PY - 2009
Y1 - 2009
N2 - The interactions of MoO42- + WO4 2-, MoO42- + PO43-, WO42- + PO43- systems on goethite were studied to better understand the competitive adsorption/desorption of these anions in the natural environment. Tungstate has a strong adsorption affinity for goethite; molybdate adsorption onto goethite is reversible (as shown by the overlapping of adsorption and desorption isotherms), while tungstate and phosphate adsorption are irreversible. The activation energy needed by P, W and Mo to adsorb/desorb to/from goethite follows the order: P > W > Mo. The goethite surface contains adsorption sites that are specific to one anion, i.e. phosphate, molybdate and tungstate. For the binary system containing MoO 42- + PO43-, phosphate may react with molybdate to form phosphomolybdate, which strongly attaches to the goethite surface and becomes very difficult to remove. No such phenomenon was observed in the binary system containing MoO42- + WO 42- The Sheindorf-Rebuhn-Sheintuch (SRS) equation was applied to obtain coefficients accounting for the competitive adsorption interactions of tungstate, molybdate, and phosphate. The SRS equation shows that tungstate and phosphate have a comparable competitive effect; furthermore, both significantly compete with molybdate adsorption.
AB - The interactions of MoO42- + WO4 2-, MoO42- + PO43-, WO42- + PO43- systems on goethite were studied to better understand the competitive adsorption/desorption of these anions in the natural environment. Tungstate has a strong adsorption affinity for goethite; molybdate adsorption onto goethite is reversible (as shown by the overlapping of adsorption and desorption isotherms), while tungstate and phosphate adsorption are irreversible. The activation energy needed by P, W and Mo to adsorb/desorb to/from goethite follows the order: P > W > Mo. The goethite surface contains adsorption sites that are specific to one anion, i.e. phosphate, molybdate and tungstate. For the binary system containing MoO 42- + PO43-, phosphate may react with molybdate to form phosphomolybdate, which strongly attaches to the goethite surface and becomes very difficult to remove. No such phenomenon was observed in the binary system containing MoO42- + WO 42- The Sheindorf-Rebuhn-Sheintuch (SRS) equation was applied to obtain coefficients accounting for the competitive adsorption interactions of tungstate, molybdate, and phosphate. The SRS equation shows that tungstate and phosphate have a comparable competitive effect; furthermore, both significantly compete with molybdate adsorption.
KW - Adsorption
KW - Competition
KW - Desorption
KW - Molybdate
KW - Phosphate
KW - SRS
KW - Tungstate
UR - http://www.scopus.com/inward/record.url?scp=77955170399&partnerID=8YFLogxK
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U2 - 10.2462/09670513.925
DO - 10.2462/09670513.925
M3 - Article
AN - SCOPUS:77955170399
SN - 0967-0513
VL - 17
SP - 45
EP - 57
JO - Land Contamination and Reclamation
JF - Land Contamination and Reclamation
IS - 1
ER -