Tin oxide nanociystals with diameters smaller than 10 nm were synthesized using Na2SnO3 and CO2 as reactants and cetyltrimethylammonium bromide（CTAB） as stabilizer under mild conditions.As a mild acidic gas,CO2 is favorable for the accurate adjustment of pH value of Na2SnO3 solution.Stannate salt is stable,cheap and easy in operation.The effects of Na2SnO3concentration,CTAB concentration,aging temperature,and aging time on the nanociystals were studied.It was found that,with the increasing Na2SnO3 concentration,aging temperature and aging time,SnO2 nanociystals size decreases.The formation of SnO2nanociystals can be interpreted by electrostatic-interaction mechanism.SnO2 nanociystals show high photocatalytic activities in the degradation of Rhodamine B solution.The catalytic activity of small nanocrystals is higher than that of large ones.
Nanosized calcium carbonate particles were prepared with a continuous gas-liquid membrane contactor. The effects of Ca(OH)2 concentration, CO2 pressure and liquid flow velocity on the particles morphology, pressure drop and membrane fouling were studied. With rising Ca(OH)2 concentrations, the average size of the particles increased. The effects of Ca(OH)2 concentration and CO2 pressure on particles were not apparent under the experimental conditions. When the Ca(OH)2 concentration and liquid flow velocity were high, or the CO2 pressure was low, the fouling on the membrane external surface at the contactor entrance was serious due to liquid leakage, whereas the fouling was slight at exit. The fouling on the membrane inner-surface at entrance was apparent due to adsorption of raw materials. The membrane can be recovered by washing with dilute hydrochloric acid and reused for at least 6 times without performance deterioration.
Catalytic bubble-free hydrogenation reduction of azo dye by porous membranes loaded with palladium （Pd） nanoparticles was studied for the first time. The effects of Pd loading, dye concentration and reuse repetitions of membranes were investigated. In reduction, the dye concentration decreased whereas the pH rose gradually. An optimal Pd loading was found. The catalytic membranes were able to be reused more than 3 times.
