Filtration performances of HVAC filters for PM10 and microbial aerosols— Influence of management in a lab-scale air handling unit

Filtration performances of air handling unit (AHU) filters for particles and microbial aerosols were investigated. The influence of the AHU operational conditions on the behavior of microorganisms collected on the filters was also studied. A lab-scale AHU with two filtration stages was developed and validated for the study of downsized filters with industrial geometries. Three types of filters of different efficiency were considered: G4, F7, and F9, according to European standard EN 779. Two configurations of filters were studied: G4 pleated/F7 bag and F7/F9 bag. Filters were sequentially clogged by alumina particles, which provided a mineral fraction in the particulate cake, and then by micronized rice particles, which provided the fungus Penicillium chrysogenum and an organic fraction that acts as a substrate for microorganisms. Finally, a microbial aerosol composed of endospores of Bacillus subtilis and spores of Aspergillus niger was nebulized to contaminate filters. After clogging, periods of 5 days on and 2 day weekend stops with restarts of ventilation were simulated for 6 weeks. The results showed that the filter efficiency for particles was quite comparable to that for microbial aerosols expressed in cultivable concentration. The particulate cake composed of alumina and micronized rice particles enabled the growth of the endogenous species P. chrysogenum and the survival of exogenous species B. subtilis and A. niger on filters. During restarts of ventilation, low particle concentrations were detected downstream of the second filtration stages by release but the microbial concentration from the fraction of air sampled was below the detection limit.

© 2016 American Association for Aerosol Research     

Décontamination à l'échelle pilote de sédiments pollués en métaux toxiques par lixiviation chimique et biologique

Pilot studies were carried out to evaluate different options for metal‐polluted (Cd, Cr, Cu, Ni, Pb and Zn) sediment decontamination. Chemical and biological leaching tests were done in a 350‐L capacity stirredtank reactor. The use of short acidic sediment washing steps (pH 2.0–3.0) was not an efficient approach for metal removal. The addition of an oxidant agent during the first washing step resulted in a large increase of removal yields for Pb (53–76%), Cd (54–92%) and Zn (69–93%). However, other metals were not well leached from sediments: Cr (6–30%), Cu (0–34%) and Ni (1–16%). The bioleaching treatment, with or without chemical washing steps, allows very good removal yields for Cd (82–100%), Cu (44–70%) and Zn (80–87%). On the other hand, this method was not efficient to remove other metals like Cr (6–16%), Ni (12–21%) and Pb (14–33%). The metals solubilized by chemical and/or biological leaching techniques can be efficiently removed from solution by precipitation using lime.     

Comparative study of PCL-HAp and PCL-bioglass composite scaffolds for bone tissue engineering

The aim of this work is to compare the effect of hydroxyapatite (HAp) or bioglass (BG) nanoparticles in a polycaprolactone composite scaffold aimed to bone regeneration. To allow a comparison of the influence of both types of fillers, scaffolds made of PCL or composites containing up to 20 % by weight HAp or BG were obtained. Scaffolds showed acceptable mechanical properties for its use and high interconnected porosity apt for cellular colonization. To study the effect of the different materials on pre-osteoblast cells differentiation, samples with 5 % mineral reinforcement, were cultured for up to 28 days in osteogenic medium. Cells proliferated in all scaffolds. Nevertheless, differentiation levels for the selected markers were higher in pure PCL scaffolds than in the composites; inclusion of bioactive particles showed no positive effects on cell differentiation. In osteogenic culture conditions, the presence of bioactive particles is thus not necessary in order to observe good differentiation.     

Interaction mechanisms between caffeine and polyphenols in infusions of Camellia sinensis leaves

Black tea infusions of Camellia sinensis leaves were studied for the influence of water composition, especially calcium content, on the amount of extracted organic matter and on the interactions between caffeine and polyphenols. The higher the calcium content, the lower the extraction of caffeine and polyphenols in acidic media. In alkaline media, besides the calcium effect, polyphenols are oxidized. Caffeine NMR chemical shifts varied depending on the water used showing modified interactions. Using model solutions, polyphenols seem to be responsible for these changes in the case of ultra pure water, but in the case of alkaline solutions, the data in model solutions are different from tea infusions implying that other compounds should interact. Moreover, epigallocatechin gallate (EGCg) and epigallocatechin are the polyphenols interacting most strongly with caffeine in infusions and not EGCg and epicatechin gallate as thought before.     

Functionalisation of porous silica powders in a fluidised-bed reactor with glycidoxypropyltrimethoxysilane (GPTMS) and aminopropyltriethoxysilane (APTES)

This work deals with the use of a new solventless process for chemical grafting of solid particles. The process was previously used (Lazghab et al., 2008) to hydrophobise silica supports with conventional silanisation reagents such as octadecyltrichlorosilane (OCDTS) and trimethylchlorosilane (TMCS). The aim of the present work was to extend the applicability of this process to other types of surface functionalisation treatments in addition to hydrophobisation.Porous silica powder was treated using two commonly used coupling reagents: glycidoxypropyltrimethoxysilane (GPTMS) and aminopropyltriethoxysilane (APTES). The results showed that the chemical grafting can be performed successfully by the new process in the complete absence of any organic solvent. The two reagents were successfully anchored on a silica surface and achieved high surface coverage in only a few minutes. The hydrophobic effect provided by the treatment was also analysed and discussed.     

Metastability of heavy lanthanides in the ZnO wurtzite structure

The introduction and stability of the heavy lanthanide Er, into ZnO was studied by HRTEM, XRD and thermal treatments. The applied synthesis route allows introducing the Er atoms in the lattice in a metastable state. The stability depends on the Er concentration. ZnO with Er concentrations of less than 2% are stable up to 800 °C, while higher concentrations result in a phase segregation at T > 700 °C. Unit cell parameters obtained from the Rietveld refinement of XRD patterns provide a conclusive evidence of the incorporation of the Er ions in the host ZnO matrix.     

Modeling damage and load redistribution in composites under tension–tension fatigue loading

A fatigue model developed for composite laminates and based on the cycle-by-cycle probability of failure has been modified to account for damage creation and evolution and its effect on cycles to failure. The residual strength of different parts of the laminate is determined during cyclic loading and damage such as matrix cracking is quantified along with its effect on load redistribution and cycles to failure of different parts of the laminate. The model does not require any curve fitting or experimentally measured data other than basic material static strength values and their associated experimental scatter. The model is applied to uni-directional and cross-ply laminates. A stress-based approach using energy minimization and calculus of variations is used. The model predictions range from fair to excellent.     

Elevated levels of selenium in the typical diet of Amazonian riverside populations

Selenium (Se) intake is generally from food, whose Se content depends on soil Se and plant accumulation. For humans, adequate Se intake is essential for several selenoenzymes. In the Lower Tapajós region of the Brazilian Amazon, Se status is elevated with large inter-community variability. Se intake in this region, where Hg exposure is among the highest in the world, may be important to counteract mercury (Hg) toxicity.The present study was conducted in 2006 with 155 persons from four communities of the Lower Tapajós. The objectives were: i) to evaluate Se content in their typical diet and drinking water; ii) to compare food Se concentrations with respect to geographic location; and iii) to examine the contribution of consumption of different food items to blood Se.More than 400 local foods and 40 drinking water samples were collected. Participants responded to an interview-administered food frequency questionnaire and provided blood samples. Food, water and blood Se levels were assessed by ICP-MS. Since Brazil nuts may also contain significant levels of barium (Ba) and strontium (Sr), these elements were likewise analyzed in nuts.The highest Se concentrations were found in Brazil nuts, but concentrations were highly variable (median: 13.9 µg/g; range: 0.4-158.4 μg/g). Chicken, game meat, eggs and beef also contained considerable levels of Se, with median concentrations from 0.3 to 1.4 μg/g. There was no particular geographic distribution of food Se. Se concentration in drinking water was very low (< 1.4 µg/L). Blood Se covered a (103-1500 μg/L), and was positively related to regular consumption of Brazil nuts, domestic chicken and game meat. Brazil nuts were found to contain highly variable and often very high concentrations of Ba (88.0 µg/g, 1.9-1437 µg/g) and Sr (38.7 µg/g, 3.3-173 µg/g).Further studies should address multiple nutrient/toxic interactions in the diet and related effects on health.     

半沙漠地区中的生态住宅

项目地点:摩洛哥伊尔富德项目类型:建筑(住宅)开工日期:2006年元月该项目获2005年豪瑞可持续建筑大奖赛非洲中东地区提名奖     

Flocculation,Retention and Drainage in Papermaking: A Comparative Study of Polymeric Additives

Fibre and filler flocculation, filler retention and drainage, induced by several polymeric retention aids, were compared in laboratory experiments on mixtures of kraft fibres and two calcium carbonate fillers. Some experiments were also performed on thermomechanical pulp and de‐inked pulp fibres. Flocculation was measured by a focused beam reflectance measurement probe. It was found that flocs induced by polyethylene‐oxide (PEO) and cofactor broke up with time and shear and could not be reformed subsequently. Floc strength was the highest for PEO and the weakest for polyethylenimine and polyaluminium chloride. When comparing filler retention under optimal flocculation conditions, we found similar filler retention for all retention aids. Salt did not affect drainage for cationic retention aids, but reduced the drainage rate for PEO. Drainage with PEO was considerably slower than for other retention aids.