La diffusion intraparticulaire dans la clinoptilolite application aux ions Na+ et NH4+

Studies on NH₄⁺ removal by mean of a zeolite: clinoptilolite, previously realised have led the authors to examine the exchange mechanisms between cations on the clinoptilolite grains.The use of clinoptilolite as conventional ion exchange resin (1, 2, 3, 4, 5, 6) for elimination of ammonia ion from waste waters or drinking water (7, 8, 12) poses a great number of difficulties, principally during regeneration.This text presents a brief theorical presentation of the material and the ion-exchange, especially in the case of isotopic exchange, allowing the introduction of the fundamental equation (2) and its approximate expression:

$\text{U(t)}\text{1?exp}\text{?}\text{D}\text{tπ}{}^2\text{r}{}^2{}_0{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$

with U(t) the exchanged fraction at time t.The experimental study concerns the NH₄⁺ cation exchange with Na⁺ ions on clinoptilolite.In this case, the curve u(t) and ln(l ? u²) vs time shows the non-applicability of the above formula (Fig. 5).Our subject was to examine the divergence causes and to propose for our regeneration problem a semi-empiric law which form is:

$\text{U(t)}\text{1?exp}\text{?}\text{β}\text{D}\text{tπ}{}^2\text{r}{}^2{}_0{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$

with

$\text{β=1?U(t)]}\text{2}\text{3}$

.The validated relation (Fig. 7) for the Na⁺/NH₄⁺ exchanges lead us to find the D_Na⁺ and D_NH2⁺ coefficients consistent with the literature.Using the experimental results from AMES, we show that our formula can be applied to other exchange cases (e.g. Sr⁺/NH₄⁺) (Fig. 8). The form of the β relation seems coherent with the proposed film diffusion interpretation.