Li-Xiong Wen

Removal of Organic Matter and Ammonia Nitrogen in Azodicarbonamide Wastewater by a Combination of Power Ultrasound Radiation and Hydrogen Peroxide

Abstract A simple and efficient sonochemical method was developed for the degradation of organic matter and ammonia nitrogen in azodicarbonamide wastewater. The effects of initial pH, ultrasound format and peripheral water level on the sonolysis of hydrazine, urea, COD and ammonia nitrogen were investigated. It is found that the initial pH has a significant influence on the degradation of hydrazine and ammonia nitrogen, whereas this impact to urea is relatively small. It also shows that a noticeable enhancement of ammonia nitrogen removal could be achieved in a proper intermittent ultrasound operation mode, i.e ., 1/1 min on/off mode. The height difference between the peripheral water level and the inner water level of the flask affects the efficiency of ultrasonic treatment as well.

Modeling of the Precipitation Process in a Rotating Packed Bed and Its Experimental Validation

Abstract A mixing-precipitation model based on the modified coalescence-redispersion model was presented to describe the flow, mixing, nucleation and growth in a rotating packed bed (RPB). The model was coupled with population balance, mass balance and crystallization kinetics. It predicted well the influence of coalescence probability, which represents the mixing intensity among droplets, on the particle number density, supersaturation and mean particle size of the produced precipitates. The effects of the radial thickness of packing, liquid flow rate and rotating speed on the product particle size were also investigated. The results indicate that the needed radial length of packing is short for sparingly soluble substance precipitation (about 40-50 mm in this work), and the mean particle size of precipitates decreases with the increase of rotating speed and liquid flow rate, respectively. The validity of this model was verified by experiment on BaSO4 precipitation in RPB.

Improved biological effects of uniconazole using porous hollow silica nanoparticles as carriers.

BACKGROUNDnThe aim of this work is to prepare a controlled-release formulation of uniconazole using porous hollow silica nanoparticles (PHSNs) as carrier, and to investigate the biological effects on rice growth.nnnRESULTSnPHSNs with a shell thickness of ~15 nm and a particle size of 80-100 nm were synthesised through a sol-gel route using nanosized calcium carbonate particles as templates. Simple immersing (SI) and supercritical fluid drug loading (SFDL) technologies were employed to load uniconazole into PHSNs with loading efficiencies of ~22 and ~26% respectively. The prepared uniconazole-loaded PHSNs (UCZ-PHSNs) by SI and SFDL both demonstrated sustained release properties, and the latter showed better controlled release ability with a slower release rate. Compared with free uniconazole, UCZ-PHSNs exhibited a weaker growth retardation effect in the early stage but more significant retardation ability in later stages for agar-cultured rice seedlings. For the rice that grew in clay, UCZ-PHSNs demonstrated a weaker plant height retardation effect than free uniconazole at the early jointing stage by foliar spraying, but exhibited a stronger retardation capacity than free uniconazole by being applied into soil before seedling transplantation.nnnCONCLUSIONnThe results indicated that the prepared UCZ-PHSNs possessed good controlled-release properties and had improved retardation effects on rice growth. It is recommended that UCZ-PHSNs be applied into soil before seedling transplantation rather than administered by foliar spraying at the early jointing stage.