Removal of strontium (Sr2+) from aqueous solutions with titanosilicates obtained by the sol–gel method

• TiSi synthesized by the sol–gel method for Sr2+ adsorption is characterized.
• The effect of precursors on TiSi adsorption capacity is investigated.
• The best sorption capacity is attributed to TiSi synthesized from a pure precursor.
• Correlations are found between porosity and sorption ability.
• The mechanism of Sr2+ sorption on titanosilicates is suggested.

Titanosilicates (TiSis) were synthesized from pure and technical precursors by the sol–gel method. X-ray diffraction (XRD) studies of TiSi identified amorphous phases. The Brunauer, Emmett and Teller (BET) surface area of TiSis obtained from pure and technical precursors measured using the low-temperature nitrogen adsorption/desorption technique were 270.3 and 158.7 m2 g−1, respectively. Micro-mesopore and micro- meso- macropore structures were attributed to TiSi prepared from pure and technical precursors, correspondingly. TiSis mass, solution pH, contact time, initial Sr2+ concentration, temperature and background solution were investigated for their effect on sorption properties. TiSis were observed to have a high affinity for strontium in the pH range of 4–12. Strontium adsorption isotherms were established and fitted to the Langmuir, Freundlich, Redlich–Peterson, Sips and Toth models. Pseudo-first and pseudo-second models were used to describe experimental kinetic data. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM–EDX) data for TiSis were collected before and after adsorption. Heterophase was observed on the surfaces of both types of TiSi material after Sr2+ uptake. The mechanism of Sr2+ sorption on titanosilicates was suggested.

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