Evaluation of the strength of granular ion exchange resins and the relationship between the strength of gel-like anion exchange resins and osmotic stability

Abstract

The breaking load was evaluate in compression of granular gel-like AN-22, AV-17 anion exchange resins and AN-251 porous anion exchange resins. It was established that the average arithmetical value of the breaking load P av shows a linear dependence on diameter d = 0·4–0·9 mm for AN-251. For AN-22 linearity is disrupted with an increase of d of granules to 0·7 mm and higher. The non-linear dependence of P av ∥ d∥ is due to a variation of indices. It was shown that the type of distribution curves differs from the normal. To explain the effect of recycling on the strength of granules, the latter value was determined after 150, 300 and 600 test cycles and also using initial granules. After 150 cycles the distribution curves showed a contraction of the variation interval, compared with the initial curve. With an increase in the number of cycles to 600 the type of distribution curves remained unchanged. A comparison of osmotic stability with breaking load showed that AN-22 granules swollen in water and characterized in the initial state by a value of P av > 1·2 kg do not break down by the action of osmotic forces. Apparently, there is a relation between breakdown by the action of mechanical load and osmotic forces. Osmotic forces and stress causing failure in compression were calculated. Using gel type anion exchange resins it was shown that when stress causing failure in swollen granules is at least 1·5 times higher than osmotic forces, granules do not break down by the action of osmotic forces.