The kinetics of sorption of Sr, Ni, Zn from surface waters by the method of «thin layer» on natural zeolite CLT and organozeolite PEI–CLT
Abstract
The solution of the problem of purification of surface waters from heavy metals is associated with the selection and use of the most effective sorbents. To predict the process of purification from pollution with the help of selected sorbents, it is necessary to obtain appropriate sorption characteristics (equilibrium and kinetic). The aim of this work is to study the kinetics of the sorption of heavy metals Sr, Ni, Zn in the region of low concentrations (1.0-0.3 mg/l) from surface water with pH 6-8 by the “ thin layer” method on the natural clinoptilolite of the Kholinsky deposit (CLT) and modified clinoptilolite (PEI- CLT). The sorption time continued from 0.5 hour to 2.5 months. Approximately 10 samples were taken at different sorption tine for every sorbents and values of рН solution. XRF method was used for analysis the concentrations of metals in initial and used samples of sorbents.
The kinetic curves of the sorption of Ni, Zn, Sr and the macrocomponent Ca were obtained by the «thin layer» method with their joint presence from surface water. It was shown that the internal diffusion is the limiting factor of the sorption kinetics in a "thin layer". The coefficients of internal diffusion of Sr, Zn, Ni and Ca on CLT (D) and the effective coefficients of internal diffusion at PEI-CLT (Deff.) at pH 6, 7, and 8 were calculated. For CLT the values of particle diffusions coefficients felt down in order: – Са > Sr> Zn> Ni; for PEI-CLT the values of Deff were less, then for CLT with the exception of Ni and felt down in order: - Са > Sr > Ni > Zn.
The dependence of the metal distribution coefficients (G) on solution pH was shown. So it was established that for Sr at all pH GSr is higher than for PEI-CLT, GZn - at pH 7.8 for both sorbents are close, and GNi for CLT is lower than for PEI-CLT. Using the example of a solution with pH 7 and 8, a comparison was made of the distribution coefficients of heavy metals obtained and Ca on the sorbent on CLT and PEI-CLT with the corresponding data of the sorption dynamics.
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References
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