137Cs+/90Sr2+-containing radioactive wastewater is one of the most important problems that the world has been facing with. A by-product, activated porous calcium silicate, is generated at high levels by the pre-desiliconizing and soda-lime-sintering processes for producing Al2O3 from high-alumina fly ash. In order to examine if this by-product could be used as an absorbent for removal of 137Cs+/90Sr2+ from radioactive wastewater, various parameters, such as pH, adsorbent dose, contact time, and initial concentration, were discussed. Results indicated that the equilibrium reached in about 2 hr. Activated porous calcium silicate was highly pH sensitive and able to remove Cs+/Sr2+ in a near-neutral environment. The adsorption equilibrium was best described by Freundlich isotherm equations, and the adsorption of Cs+/Sr2+ was a physical process. The adsorption kinetic data could be better fitted by the pseudo-second-order model, and the adsorption was controlled by multidiffusion. Current study showed that activated porous calcium silicate has a good adsorption of Cs+/Sr2+ for their removal. However, other characteristics, such as selectivity because of coexisting cations, elution and regeneration, thermal stability, and acid resistance, should be discussed carefully before using it in an actual field.
Implications:Removing 137Cs+/90Sr2+ from radioactive wastewater is one of the tough issues that has been attracting more and more attention world widely, which is the same as fly ash. For recycling high-alumina fly ash, in which Al is extracted to produce Al2O3, a huge amount of activated porous calcium silicate is generated year by year. In this paper, this by-product was successfully used as an absorbent to remove 137Cs+/90Sr2+ from radioactive wastewater for the first time. Factors that affect the absorbability and the mechanisms were discussed in details, providing a possible choice for disposal of 137Cs+/90Sr2+-containing radioactive wastewater.相似文献
Objective: With increasing traffic volume and urban development, increasing numbers of underground tunnels have been constructed to relieve conflict between strained land and heavy traffic. However, as more long tunnels are constructed, tunnel traffic safety is becoming increasingly serious. Thus, it is necessary to acquire their implications and impacts. This study examined 4,539 traffic accidents that have occurred in 14 Shanghai river-crossing tunnels for the period 2011–2012 and analyze the correlation between potential factors and accident injury severity.
Methods: An ordered logit model was developed to examine the correlation between potential factors and accident injury severity.
Results: Results show that increased injury severity is associated with male drivers, drivers aged 65 years or older, accident time from midnight to dawn, weekends, wet road surface, goods vehicles, 3 or more vehicles, 4 or more lanes, middle speed limits (50–79 km/h), zone 3, extra-long tunnels (over 3,000 m), and maximum longitudinal gradient.
Conclusions: This article aims to provide useful information for engineers to develop interventions and countermeasures to improve tunnel safety in China. 相似文献