M. V. Pimple

Highly efficient removal of TiO2 nanoparticles from aquatic bodies by silica microsphere impregnated Ca-alginate

A novel material, “calcium-alginate–silica microsphere” (Cal-Alg–SM) beads, was developed by impregnating silica microspheres in calcium alginate. These beads were highly efficient in the removal of TiO2 nanoparticles from aquatic bodies without disturbing their physicochemical characteristics. The optimum composition of the beads was 10% loading of silica microspheres into a 4% Ca-alginate matrix. They were formed by the controlled addition of a homogenised mixture of SMs and Na-alginate solution into 0.4 M CaCl2 solution. Cal-Alg–SM beads were characterized by measuring zeta potential, recording Fourier Transform infrared spectra and scanning electron microscopy coupled with energy dispersive spectrometry mapping both before and after the uptake. Uptake studies carried out in batch mode showed that Cal-Alg–SM beads are very effective for the removal of TiO2 nanoparticles in the pH range of 3–5 and the sorption was more than 90% in the concentration range of 10–500 μg mL−1. Beads were successfully tested with lake and groundwater samples spiked with TiO2 nanoparticles. The sorption isotherm was seen to follow the Langmuir model and the uptake capacity evaluated was 29.9 mg g−1. The mechanism of sorption was proposed based on the zeta potential values of SMs and TiO2 nanoparticles at different pH values.

Ammonium molybdate phosphate functionalized silicon dioxide impregnated in calcium alginate for highly efficient removal of 137Cs from aquatic bodies

In this study, silica functionalized with ammonium molybdate phosphate (AMP) impregnated in calcium alginate (SiO2-AMP–Cal-Alg) was developed for the highly efficient removal of radioactive cesium from aquatic media. During the synthesis, a compact protective interlayer of silica was deliberately constructed to stabilize the AMP. The optimum composition of the SiO2-AMP–Cal-Alg beads was evaluated as 6% AMP modified SiO2 loaded into 4% calcium alginate. Because of high ion exchange capacity of the AMP functional layer, the SiO2-AMP–Cal-Alg has high removal efficiency (>91%) of radioactive cesium from 137Cs spiked solutions (3000–35 000 Bq L−1) and contaminated seawater. Batch experiments revealed that adsorption equilibrium was rapidly achieved within 30 min and the maximum sorption capacity was up to 37.52 mg g−1. Kinetic models and adsorption isotherm equations (Langmuir/Freundlich) were used to fit the experiment data for describing the sorption process. These SiO2-AMP–Cal-Alg beads are proposed to hold great promise for the clean-up of radiocesium contaminated water around nuclear facilities after nuclear accidents.

Association and migration behavior of trace metals with humus colloidal particles in aquatic subsurface medium

In this study, we investigate the influence of humic acid on the migration of trace metals (Fe, Ca, Mg, Cu, Sr, Zn) in the saturated subsurface medium. Migration study was carried out in a specially fabricated soil column. The results of this study demonstrate that presence of humic acid in the colloidal form play a key role in mobility of trace metals in aquatic subsurface medium. Migration of elements like Fe, Ca, Mg, Cu were facilitated by the presence of the humus colloids whereas presence of Zn, Sr in the hydrated form was evident from the experimental results. The observation was explained based on the linear attenuation coefficient (LAC).