Hydrated cement: a promising adsorbent for the removal of fluoride from aqueous solution.

The present study was carried out to investigate the potential of cement hydrated at various time intervals for the removal of excess F- from aqueous solution by using batch adsorption studies. The influence of different adsorption parameters, viz. effect of adsorbent dose, initial concentration, pH, interfering ions and contact time were studied for their optimization. It was observed that the adsorbent exhibited reasonably significant F- removal over a wide range of pH. The presence of carbonate and bicarbonate ions in aqueous solution were found to affect the F- removal indicating that these anions compete with the sorption of F- on adsorbent. The equilibrium adsorption data were fitted well for both the Freundlich and Langmuir isotherms and the adsorption capacities were calculated. Comparative studies for F- removal in simulated and field water show relatively higher F- removal in simulated water. XRD and SEM patterns of the hydrated cement were recorded to get better insight into the mechanism of adsorption process. From the experimental results, it may be concluded that HC was an efficient and economical adsorbent for F- removal.

Study of the formation of perovskite type lanthanum ruthenates by heating their hydrous precursor.

Emanation thermal analysis (ETA), differential thermal analysis (DTA), thermogravimetry (TG), evolved gas analysis with mass spectrometric detection (EGA-MS), and X-ray diffraction (XRD) were used to investigate the formation of perovskite type lanthanum ruthenates on heating their hydroxide precursor in argon from 20 to 1200 degrees C. The co-precipitated lanthanum-ruthenium mixed hydroxide containing a small amount of carbonates was used as a precursor. The mass loss corresponding to the release of water and CO(2) from the precursor was determined by TG and EGA (MS), respectively. The ETA characterized the exposure of sample surface after release of water and CO(2), as well as microstructure development corresponding to the crystallization and structure ordering of LaRuO(3) and La(3.5)Ru(4.0)O(13) perovskite phases. The obtained information on formation of phases and their transformation is useful for optimizing their synthesis protocols for achieving the desired physical properties, and to estimate the thermal stability of these materials to be used as catalysts.