Evaporation induced self assembled microstructures of silica nanoparticles and Streptococcus lactis cells as sorbent for uranium (VI)

• Different morphologies of silica and S. lactis microstructures were applied for U (VI) uptake.
• Spray dried doughnut shaped microstructure (SDSM) showed maximum U (VI) uptake.
• The maximum adsorption capacity 169.5 mg U/g was determined for SDSM at pH 5.0.
• Sorption is an endothermic spontaneous process that kinetically followed second-order model.

An assembled microstructure of silica nanoparticles and Streptococcus lactis (S. lactis) cells has been synthesized by evaporation induced self assembly, with the objective of its application in bioremediation. Different morphologies have been realized by tuning the physico-chemical conditions of the assembly process. The potential of these microstructures in removal of uranium (VI) has been evaluated. Morphology dependent uptake has been demonstrated and maximum uptake was seen for the spray dried doughnut shaped microstructure (SDSM). For a fixed morphology, the variation in uptake varies with solution pH, contact time, temperature and initial uranium (VI) concentration. The U (VI) removal was significantly rapid, with more than 85 ± 2% of total uptake in 10 min. The maximum sorption capacity (qmax) of U (VI) at pH 5.0 and temperature 298 K was 169.5 mg/g using SDSM as sorbent. The kinetic data of adsorption of U (VI) are best described by a pseudo-second-order kinetic model. Calculated thermodynamic parameters reveal an endothermic and a spontaneous adsorption process. The present work opens up the possibility of a means for the functionalization of silica microstructures through the incorporation of micro-organism and the potential for the use of these functionalized materials for bioremediation.

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