A Comparative Study on Indigenously Available Synthetic Zeolites for Removal of Strontium from Solutions by Ion-Exchange

Abstract

Removal of Strontium ions from solutions by Sr-Na exchange, using indigenously available synthetic zeolites, has been studied. Batch tests indicated that the time required for equilibrium was 4 hours under stirred condition. The percent removal and the distribution coefficient {KJ) values for Sr were determined at different concentrations, ranging from traces of Sr (Solution of '°Sr-nitrate) to 50 mM Sr-nitrate. Two zeolites viz., 4A and 13X, were observed to provide high removal of Sr, while the other two, AR-1 (a synthetic mordenite) and ZSM-5, were not as effective. The nature of diffusion of Sr ions, Controlling the exchange reaction, was studied by drawing Bt-t plots (ß, diffusional frequency and t, time). Linear plots, obtained for 13X and 4A, at 50 mM Sr(N03)2 concentration, indicated that the process was controlled by diffusion through the particles. At lower concentrations of Sr and for the other two zeolites, the plots were non-linear and the process might be controlled by film diffusion.The equilibrium studies, carried out using isonormal solutions of Sr and Na ions at a total Sr+Na concentration of 0.1 N, indicated a marginal selectivity for Sr, in case of 4A and 13X. The corrected selectivity coefficient (K,) values were calculated and Kielland plots were drawn.Column trials with 1.5 ml beds of the granular zeolites and a simulated waste Solution containing ^'Sr, indicated that 4A and 13X could remove about 90-92% of Sr, at a flow rate of 60 bed volumes per hour (BV/h). The removal increased to 97%, when the flow rate was reduced to 12 BV/h. The third zeolite AR-1 provided lower removal of Sr in both the cases. When another simulated alkaline waste Solution, containing high sah content (3M NaNO,), in addition to '"Sr and '"Cs, was treated using a mixed zeolite column (4A + AR-1), the removal of both the Sr and Cs isotopes was about 55-65%.

Evaluation of zeolite A for the sorptive removal of Cs+ and Sr2+ ions from aqueous solutions using batch and fixed bed column operations

“…The critical bed depth (Z 0 ), which represent the theoretical depth of zeolite A material sufficient to prevent the Cs + and/or Sr 2+ concentrations from exceeding C b at t = 0, was estimated from Eq. (22). The obtained values of Z 0 (Table 7) were higher for the removal of Cs + ions than Sr 2+ ions and these values increased with increase in flow rate.…”

“…Ion exchange properties of zeolites have been received great attention, especially for application in radioactive liquid waste treatment [13][14][15][16][17][18][19][20][21][22][23][24]. The cationic radioisotopes, present in the liquid effluents of low and intermediate level liquid wastes, can be removed by the ion exchange with the Na + ions of the zeolites.…”

Modeling batch kinetics and thermodynamics of zinc and cadmium ions removal from waste solutions using synthetic zeolite A

“…A good correlation of the rate data in this model can justify the mechanism. Previous workers [26][27][28] in this direction reported diffusion coefficient 'D i ' values in the range of 10 −12 to 10 −13 m 2 /s for intraparticle diffusion to be the rate limiting step for the sorption of metal ions. As per this, the rate-limiting step appears to be particle diffusion since the D i values are in the order of 10 −12 m 2 /s.…”

Two-step method for preparation of NaA-X zeolite blend from fly ash for removal of cesium ions

“…Ion exchange properties of zeolites have been received a great attention in radioactive waste treatment [3][4][5][6][7][8][9][10][11][12][13][14][15]. Fly ash (FA) is a microspherical, particulate by-product of coal combustion and is generated from power generation stations.…”