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New functional ionic liquid (IL) capped graphene quantum dot (GQD) was synthesized as an adsorbent for the removal of toxic heavy metal chromium(VI) ion (Cr 6+ ). The physicochemical properties of the adsorbent (IL-GQD) were investigated by Fourier transform infrared, Xray diffraction, atomic force microscopy, Raman, scanning electron microscopy, energy dispersive X-rays, and transmission electron microscopy analyses. The adsorption parameters, namely equilibrium time, solution pH, competing co-ions, dosage, and initial chromium concentration, were optimized for maximum Cr 6+ adsorption. The maximum adsorption capacity reached 934.62 mg/g at 40 min in neutral pH; this is much better than most of the other adsorbents reported earlier. In addition, the effect of pH in solution was investigated in the range of 3.0−12.0. The result showed that the lower pH value was found to favor the adsorption. The adsorption kinetics and isotherms fitted well with Langmuir isotherm model and pseudo-second-order kinetic model. The thermodynamic studies indicated that the chromium adsorption process followed a spontaneous and endothermic model. This new functionalization of ionic liquid moieties into graphene quantum dot provides excellent results for the removal of toxic Cr 6+ . This can be utilized for field applications to reduce the chromium concentration to below the tolerance limit (>0.05 mg L −1 ).

Aim of this work is to synthesizing a new highly efficient adsorbent as of magnesium oxide (MgO 2 ) entrapped Polypyrrole (Ppy) nanocomposite preparation for toxic pollutant of fluoride removal form drinking water. The synthesized MgO 2 /Ppy hybrid nanocomposite shows an extraordinary defluoridation capacity of 4328 mg F − Kg −1 in the room temperature through batch adsorption technique. It was performed to know the effect of various parameters such as contact time, initial concentration, pH, competitor ions and temperature. The structural and morphological changes on the fluoride adsorbent in before and after were analyzed by using XRD, FTIR & SEM techniques. The adsorption isotherm of Freundlich, Langmuir, & Dubnin -Radushkevich isotherms were studied and the fluoride adsorption is well fixed with Langmuir isotherm model. The kinetic model studies were carried out by both diffusion and reaction based models. The mechanism of fluoride on the MgO 2 /Ppy nanocomposite is mainly influence the interaction of electrostatic adsorption and ion-exchange. The reusability and regeneration studies were performed for the reusability of the nanocomposite.

Mineral substituted hydroxyapatite (mHAp) nanocomposite was synthesized and it shows high fluoride adsorption capacity.