Article

Characteristics and mechanisms of phosphate adsorption onto basic oxygen furnace slag.

School of Resource and Environment Science, Wuhan University, Hubei Wuhan, China.
Journal of Hazardous Materials (impact factor: 4.17). 08/2008; 162(2-3):973-80. DOI:10.1016/j.jhazmat.2008.05.131 pp.973-80
Source: PubMed

ABSTRACT The adsorption characteristics of phosphate adsorption on the basic oxygen furnace (BOF) slag were identified as a function of pH and ion strengths in solution. In addition, adsorption mechanisms were investigated by conducting batch tests on both the hydrolysis and phosphate adsorption process of the BOF slag, and making a comparative analysis to gain newer insights into understanding the adsorption process. Results show that the adsorption capacity from 4.97 to 3.71 mgP/g slag when the solution pH was increased from 2.0 to 13.0 and phosphate initial concentration was 50 mg/L, indicating that adsorption capacity is largely dependent upon the pH of the system. The results of the competitive adsorption between phosphate and typical anions found in wastewater, such as NO(3)(-), SO(4)(2-) and Cl(-), onto BOF slag reveal that BOF slag can selectively adsorb phosphate ions. The insignificant effect of NO(3)(-), SO(4)(2-) and Cl(-) on phosphate adsorption capacity indicates that phosphate adsorption is through a kind of inner-sphere complex reaction. During the adsorption process, the decrease of phosphate concentration in solution accompanied with an increase in pH values and concentrations of NO(3)(-), SO(4)(2-) and Cl(-) suggests that phosphate replaced the functional groups from the surface of BOF slag which infers that ligand exchange is the dominating mechanism for phosphate removal. At the same time, the simultaneous decreases in PO(4)(3-) and total calcium, magnesium and aluminum concentration in solution indicate that chemical reaction and precipitation are other mechanisms of phosphate removal.

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Keywords

adsorption characteristics
 
adsorption mechanisms
 
adsorption process
 
aluminum concentration
 
basic oxygen furnace
 
batch tests
 
chemical reaction
 
competitive adsorption
 
concentrations
 
dominating mechanism
 
functional groups
 
gain newer insights
 
inner-sphere complex reaction
 
phosphate adsorption
 
phosphate adsorption capacity
 
phosphate adsorption process
 
phosphate concentration
 
phosphate initial concentration
 
phosphate removal
 
solution pH
 

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