Removal of cyanide in aqueous solution by oxidation with hydrogen peroxide in presence of activated carbon prepared from olive stones

This work is dedicated to the removal of the very toxic free cyanide from aqueous solution by oxidation with hydrogen peroxide H₂O₂ in the presence of activated carbon prepared from olive stones. Effects of the initial molar ratio [H₂O₂]₀/[CN^?]₀, the initial cyanide concentration, the activated carbon concentration and the temperature on cyanide removal have been examined. The removal of free cyanide in absence of activated carbon showed very slow kinetics. The presence of activated carbon has increased the reaction rate showing thus a catalytic activity. The kinetics of cyanide removal has been found to be of pseudo-first-order with respect to cyanide and the rate constants have been determined for different values of the aforementioned parameters. The apparent activation energy has been determined from tests carried out at three different temperatures. It was found equal to 46.2 kJ/mol in the presence of activated carbon, which is about half of the 82.7 kJ/mol found for the oxidation in absence of the activated carbon.This process can be interesting for the cyanide removal from processed solutions because it does not use soluble metal catalyst and it consumes only hydrogen peroxide as chemical product.     

基于景观营造的城市雨水资源化探讨

随着水资源的日益紧张,雨水资源化以其处理成本经济、处理方法简单等优点,成为一种新的可利用水资源。雨水资已成为源应用于补充城市景观营造用水的途径和设计理念。以厦门市某工程为实例,介绍了城市雨水在城市景观水体建设中的应用技术,对缓解供水紧张和节约用水有着重大的社会效益、经济效益及生态前景。     

Three dimensional nonlinear model of beam tests for bond of near-surface mounted FRP rods in concrete

The use of near-surface mounted FRP reinforcement in reinforced concrete structures has seen a considerable increase in recent years as a strengthening method. Beam pull-out tests for near-surface reinforcement allow obtaining the local bond–slip behavior of a bonded joint. The current paper deals with the three-dimensional modeling of this kind of test with the purpose of suitably characterizing the mechanics of the bond between FRP rods and concrete. Different alternatives to represent the FRP bar – concrete interface have been evaluated. Furthermore, to do this modeling, a PID controller has also been designed to conduct the numerical tests correctly in order to properly capture the softening branch of the load-slip behavior. The numerical FE simulations were compared with previously published experimental measurements. Load-slip predictions compare well with the corresponding experimental data. The proposed model is also able to predict the failure mode at the FRP-concrete interface. Some parametric studies have also been carried out.     

Performance validation of a hybrid ventilation strategy comprising longitudinal and point ventilation by a fire experiment using a model-scale tunnel

We examined the exhaust performance of a hybrid ventilation strategy for maintaining a safe evacuation environment for tunnel users in a tunnel fire. The hybrid ventilation strategy combines the longitudinal ventilation strategy with the point ventilation strategy which is a type of transverse ventilation strategy. The model tunnel developed by this study was scaled to 1/5 the size of a full-scale tunnel. The model-scale experiment was performed taking into consideration Froude's law of similarity. Measurement items were the distribution of temperature and concentration of smoke inside the tunnel, longitudinal wind velocity, mass flow of smoke in the point ventilation duct, and the heat release rate of the fire source. The following main conclusions were obtained. The smoke height was constant even when varying the extraction rate of smoke from the ceiling vent. The backlayering length and critical velocity of the smoke flow in the hybrid strategy could be predicted by the methodology developed by using the longitudinal strategy. The hybrid strategy maintained a safe evacuation environment on both sides of the tunnel fire.     

Consistent data operations for multi-databases in extended possibility-based data models

This paper considers the data operation for multi-databases in an extended possibility-based data model. Owing to the complexity of the data model considered, inconsistent redundancy of tuples may occur when database relations being operated are associated with different resemblance relations on a given domain. This work first demonstrates the inconsistency problem, and then presents the notions of consistency constraints for multi-database design. Under the constraints, the extended possibility-based databases using different resemblance relations can preserve consistent redundancy.     

跌水曝气系统在污水处理工艺上的运用前景探讨

就重庆市某污水工程BT项目设计实例展开分析,结合国内外跌水曝气系统在实际工程上的运用,探讨在目前国情下,引入跌水曝气系统的可行性,并从生态环境保护和污水处理厂修建投资的经济性两个方面介绍跌水曝气系统特点,以及在氧化沟和其他污水处理工艺上的运用等。最后得出,跌水曝气系统可以作为一种独立的曝气方式设计使用,是适合中国中小型城镇水环境控制的污水处理改进技术;采用跌水曝气系统,可以使污水处理厂的运行费用得到降低,减少运行成本;可以很好的适应丘陵、山区的地形特点,进行因地制宜的设计,减少工程造价和人为对生态环境的破坏。     

Crystallization behavior of organo-nanoclay treated and untreated kraft fiber–HDPE composites

Both non-isothermal and isothermal crystallization behaviors of neat HDPE and organo-nanoclay treated and untreated kraft fiber–high density polyethylene (HDPE) or HDPE–maleic anhydride polyethylene (MAPE) composites were analyzed using differential scanning calorimetry (DSC). The isothermal crystallization process was studied by the Avrami model. The crystallization patterns and organo-nanoclay distribution was characterized by X-ray diffraction (XRD). It was found that both organo-nanoclay treated and untreated kraft fibers could act as nucleating agent for the HDPE polymer when the fiber length was comparatively small. All composites crystallized much faster than the neat HDPE, while their crystallinity levels were lower. The organo-nanoclay treatment of kraft fibers made the crystallinity level lower, but the nucleation rate increased in the composites compared to the untreated kraft fiber–HDPE composites. But both the crystallinity level and the nucleation rate of the composites were increased by adding MAPE compatibilizer to the composites. MAPE increased the d-spacing of the organo-nanoclay layers in the composites and resulted in exfoliated clay platelets when the fiber loading was as high as 40 wt%.     

Smoke and heat control for fires in large car parks: Lessons learnt from research?

This paper focuses on car park fire safety, more particularly on fire and smoke (and heat) dynamics. The first part deals with the choice of design fire, based on recent full-scale car fire experiments with modern cars and different set-ups. Different aspects of smoke and heat control (SHC) systems are then discussed from the perspective of smoke (and heat) dynamics. The focus is mainly on the effect of horizontal mechanical ventilation, a popular technique, on the smoke and heat generated by the fire source. Some fundamental differences from (longitudinal) mechanical ventilation in tunnels are described. Possible effects of water (sprinklers, water mist or from a fire brigade intervention), as well as some possible routes for further research, are briefly commented.     

Effect of NaOH activation on sulphate resistance of GGBFS and binary blend pastes

This paper presents an investigation into the observed enhanced performance that alkali activated ground granulated blast furnace slag (GGBFS) and binary blends offer against sulphate attack. X-ray diffraction (XRD) was carried out to identify and quantify the crystalline phases formed in a wide range of GGBFS and GGBFS-OPC (ordinary Portland cement) blends. Furthermore, specimens were exposed to a sulphate solution to examine the evolution of compressive strength along with identification of activation and/or hydration products. XRD demonstrated that ettringite was completely decomposed into its constituents in the presence of NaOH while quantification ascertained the formation of considerable amounts of hydrotalcite in the activated GGBFS and binary blends. Alkali activated GGBFS and binary blends specimens with higher GGBFS content offered enhanced resistance against aggressive sulphate ions and no significant degradation products were observed in these specimens after 6 months of exposure to sulphate solution. The results demonstrated that hydrotalcite formation may be a major reason for the improved sulphate resistance of alkali activated GGBFS and binary blend pastes with higher GGBFS content.