Heavy-metal extraction from sewage sludge using phosphorous-based salts: optimization process with Na2H2P2O7.
Land application is one of the important disposal alternatives for sewage sludge, but availability of potential toxic metals often restricts its uses. Three phosphorous-based salts (Na2H2P2O7, K4P2O7, KH2PO4) were studied as potential metal extractants. The conclusions of the research were that greater extractive efficiency is achieved through a 30-min process of vertical shaking with disodium diacid pyrophosphate - Na2H2P2O7- at a concentration of 0.2 M at pH 2. Alternatively, the optimized process with oscillating shaking equipment would require 60 min. In both cases the average of set of extracted metals is around 50%. A second extraction process with potassium pyrophosphate - K4P2O7at pH 6 achieved the reduction of further total amounts of metal, upper 65% with respect to the initial content. In this way the sludge could be used in land applications, with restrictions on each soil, according to the limit values specified in the future regulations.
a Chemistry Department , University of Burgos , Burgos , Spain.
Milagros
http://orcid.org/0000-0001-7012-1332
M
Navarro-González
b Civil Engineering Department , University of Burgos , Burgos , Spain.
Vanesa
http://orcid.org/0000-0003-0212-355X
V
Ortega-López
a Chemistry Department , University of Burgos , Burgos , Spain.
Juana I
JI
Lópéz-Fernández
c Mathematics Department , University of Castilla-La Mancha , Ciudad Real , Spain.
Mariano
http://orcid.org/0000-0002-0956-2531
M
Amo-Salas
a Chemistry Department , University of Burgos , Burgos , Spain.
Salvador
http://orcid.org/0000-0002-2000-8881
S
González-Carcedo
D019216:Metals, Heavy; D012492:Salts; D012722:Sewage; D012987:Soil; D012989:Soil Pollutants
D019216:Metals, Heavy; D012492:Salts; D012722:Sewage; D012987:Soil; D012989:Soil Pollutants
Heavy-metal extraction; disodium diacid pyrophosphate; land improvement; sewage sludge; treatment