George Z. Pavlovich, R. Luthy
Mar 1, 1988
Citations
0
Influential Citations
20
Citations
Journal
Water Research
Abstract
Abstract This study characterized metal complexation reactions with 5,5-dimethylhydantoin. This compound is formed in certain coal gasification processes during gas quenching and tar separation. In such processes it can be the principal organic constituent in gas liquor following solvent extraction and gas stripping. 5, 5-Dimethylhydantoin is not biodegraded readily, and it has been demonstrated that this compound may be increased to the range of 0.1 mol 1 −1 through reuse of treated gas liquor as makeup water for evaporative cooling. The hydantoin may complex with various metals and thereby affect the equilibrium chemistry and speciation of calcium and heavy metals in gas liquors and in wastewater reuse systems. Stability constants were determined for 5, 5-dimethylhydantoin and metals by potentiometric titration, polarography, and specific ion electrode techniques. The hydantoin behaves as a weak acid (p K a ∼ 9.1), and it complexes with metals as an anion. For transition series metals the overall concentration stability constants were in the range: log β1 = 2.4–4.5, log β2 = 4.2–9.3 and log β3 = 5.2–11. Calcium showed log β1 ∼ 1.8. In general, the most utilitarian of the experimental data reduction techniques was a nonlinear parameter optimization program (FITEQL). The results of the study are useful for incorporation with chemical equilibrium models for evaluation of the speciation and the reactions of metals in hydantoinladen wastewaters, particularly certain coal gas liquors.