| Title |
Competitive Adsorption of Organic Acid and Phosphate in Goethite Suspension |
| Authors |
이승목(Seung Mok Lee),최봉종(Bong Jong Choi),이태우(Tae Woo Lee) |
| Abstract |
Competitive adsorption between phosphate and phthalic acid onto goethite was examined in single-sorbate and in binary-sorbate system to determine the extent of competition between phosphate and phthalic acid as a function of pH and ionic strength (0. 0l M NaCl). In order to compare the experimental data, MINTEQA2 program employing the diffuse layer model is used. This is important for a better understanding of the competitive binding of phosphate and phthalic acid in natural systems. Alkalimetric titration was used to characterize the surface acidity of the goethite. The surface acidity constants, pK^s_(a1) and pK^s_(a2), were 4.02 and 7.7, respectively. For phosphate and phthalic acid, typical anionic type of adsorption was noted, respectively. Also, in the binary-sorbate system, the amount adsorbed decreases with an increase in pH. In the experiments with simultaneous complexation of phosphate and phthalic acid, the complexation of phosphate was not influenced by the presence of phthalic acid. On the other hand, the complexation of phthalic acid was decreased by the presence of phosphate. These results suggest that phosphate can significantly influence the adsorption of simple organic acids in natural aquatic systems. Therefore less mobility of phthalic acid is expected than phthalic acid with complexation of phosphate in competitive condition. |