Langmuir-type Equations Research Articles

The effect of adsorption isotherms and flow rates on separation performance in multicomponent continuous separation.

Adsorption isotherms of a ternary mixture containing dimethyl phthalate, diethyl phthalate and di-n-butyl phthalate were measured by the step-pulse method in a wide range of concentration. They were expressed by Langmuir-type equations with weak interaction between components. The applicability of the proposed process to multicomponent continuous separation was confirmed by coupling the results of single-column experiments and simulation of the total process based on the isotherms obtained. It was found that non-linearity in adsorption isotherms had a positive effect on the separation. Separation performance depends significantly on the flow rates of desorbent fed to the columns in the refining zone and the shift time. Their effects on the separation were examined and the characteristic features of the proposed process were clarified. It was found for the ternary mixture tested that the middle component (i.e. diethyl phthalate) was quite sensitive to separation performance

High temperature gravimetric study on nonstoichiometry and oxygen adsorption of SnO 2

Gravimetric studies on porous SnO 2 between 200 and 1150°C and for oxygen partial pressures, P(O 2), between 1 and 10 −6 atm showed that the mass change of below 900°C is essentially due to oxygen adsorption on the SnO 2 surface. The oxygen adsorption was interpreted in terms of three Langmuir-type equations with different heats of adsorption. Mass changes due to nonstoichiometry were observed above 1000°C. The degree of nonstoichiometry of SnO 2 was found to be very small: For example, d in SnO 2− d at 0.1 atm of P(O 2) was 7 = 10 −5 at 1000°C and 2 × 10 −4 at 1150°C. The nonstoichiometry arises from oxygen deficiencies present as oxygen vacancies, V O ··; d in SnO 2− d above 1000°C is proportional to P( O 2) − 1 6 .

COMPETITIVE INTERACTIONS OF PHOSPHATE AND MOLYBDATE ON ARSENATE ADSORPTION

The adsorption of arsenate by a Cecil clay was found to be suppressed by the competitive effects of phosphate and molybdate. Competitive Langmuir-type equations have been used in other studies to describe the adsorption data, but in this investigation the adsorption of arsenate alone and in binary mixtures followed a Freundlich-type of response. Competitive Freundlich-type isotherm equations have not been used extensively in soil chemistry studies. The usefulness of two competitive Freundlich-type equations that have been used to model the competitive interactions of dilute organic solutes by activated carbon was examined for application to arsenate adsorption by a Cecil clay as influenced by phosphate and molybdate. The equation of DiGiano et al. (1978) had the potential of being able to predict the effects of competition on adsorption based entirely on single-component data. The Sheindorf et al. (1981) equation required the collection of competitive data to derive a competitive coefficient. Both expressions were found to be useful, although there was no clear indication of which, if either, was the more accurate. The ability of both expressions to describe the data appeared to be limited to situations where the ratios of the equilibrium concentrations of As/P and As/Mo were greater than 20, i.e., when the equilibrium concentration of As was much greater than that of P or Mo. This limitation was partly attributed to the regression procedure used to calculate competitive coefficients.

COLLIDINE SORPTION ON A SILT LOAM SOIL AND A SPENT SHALE

A laboratory study was made to assess the sorption of collidine on a Ritzville silt loam soil and a retorted oil shale from the Laramie Energy Research Center. Collidine sorption was found to fit a Langmuir isotherm type sorption on both the soil and spent shale systems. In the case of the soil, two Langmuir type equations were resolved from the data, though only a single equation was resolved from the retorted shale data. Langmuir sorption capacity and bonding term parameters were determined for both systems by linear regression analysis.

The adsorption of di-n-butylphosphate from organic solutions on some metal oxides

The adsorption of DBP from kerosene, 30% TBP- kerosene, and 30% TBP -0.1 M HNO/sub 3/--kerosene was studied for Al/sub 2/O/sub 3/, ZrO/sub 2/, and SiO/sub 2/. The adsorption isotherms can be expressed by Langmuir-type equations. The amounts of adsorbed DBP at saturation for the above solvents are 0.70, 0.50, and 0.85 mmole/g Al/sub 2/O/sub 3//; 1.10, 0.80, and 0.78 mmole/g ZrO/sub 2/; and 0.65, < 0.01, and < 0.01 mmole/g SiO/sub 2/. (D.L.C.)