Yanhua Liu

Adsorption of malachite green and iodine on rice husk-based porous carbon

Abstract Adsorption isotherms of I2 and malachite green (MG) by rice husk-based porous carbons (RHCs) from aqueous medium have been studied. Three samples of carbons prepared by NaOH-activation, three samples prepared by KOH-activation and two samples of commercial carbons have been studied. And the adsorption isotherms have been determined after modifying the carbon surfaces by oxidation with nitric acid and hydrogen peroxide and after degassing at 800xa0°C. The results have been found to follow the Freundlich adsorption isotherm. Three samples of N series have larger capacity for removing I2 and MG from solution compared to that of the tested commercial carbons. The adsorption capacity of I2 is similar for K series and commercial carbons. And the capacity of commercial carbons for MG is larger than K series. The adsorption capacity of I2 on oxidation carbons has increased for hydrogen peroxide treatment and decreased for nitric acid, and that of MG is decreased. But the adsorption capacities of I2 and MG increase on degassing. On the other hand, the adsorption of I2 increases after modifying the carbon surfaces by HCl without oxidation. Suitable mechanisms have been proposed.

Preparation of rutile titania nanocrystals by liquid method at room temperature

Abstract Titania nanocrystals in rutile form were prepared in liquid phase at room temperature under normal pressure, avoiding the transformation of anatase-to-rutile. The process of preparation involves two stages: precipitating and peptizing. Precipitates of titanium(IV) obtained in the precipitation process were rearranged orientationaly, to form crystals during the process of peptizing. Results showed that lower peptizing temperatures were in favor of the formation of rutile TiO 2 , while anatase phase began to appear with the peptizing temperature higher than 70xa0°C. The phase and crystal size of the resulting titania crystals were also influenced by the conditions of the first stage (precipitation reaction). The mechanism of the formation of rutile titania in liquid system at room temperature can be confirmed by “growth unit” theory.