Contamination Control Technologies Research Articles

Removal of weed algal contamination in cultures of Botryococcus braunii with enlarged colonies using rotifers

We proposed a biological contamination control technology that preyed on and removed only invading weed algae by introducing rotifers into the culture ponds of Botryococcus braunii that had enlarged colonies. Botryococcus braunii strains Showa and Sanshiro belonging to race B were used, and the colonies were grown on a high-salt medium containing 3 g L−1 NaCl. Brachionus calyciflorus, a freshwater rotifer with large prey size, was used as the predator, and Westella sp. was used as the model weed algae. In the mixed culture of B. braunii and B. calyciflorus, the growth rate of B. braunii cultured in Chu13, a freshwater medium, was reduced due to predation by B. calyciflorus. However, enlarged B. braunii cultured in a high-salt concentration medium escaped predation and maintained a growth rate equivalent to or higher than that of the control. In the three trials combining B. braunii, B. calyciflorus, and Westella sp., B. calyciflorus was initially applied such that the ratio of the number of rotifers to the algal density of Westella sp. was 2.0 × 10−6. Under these conditions, the initial growth of Westella sp. was suppressed when using the Showa strain, which showed significant growth. The larger colony size of the Sanshiro strain showed greater proliferation of Westella sp. because its optical density was lower than that of the Showa strain. The growth of the Sanshiro strain was suppressed until day 6, when predation reduced Westella sp. density, but the growth rate recovered thereafter. A model for the optimum number of rotifer inputs, considering the optical density and the number of rotifers remaining in the future, and technology for outdoor cultivation must be developed in the future. We demonstrated the potential of an eco-friendly weed-algae-removal technology that uses a predation ecosystem without using special culture environments or pesticides.

Research on Adsorption Performance of Porous Materials Based on Ceramics to Organic Molecular Contamination

In the space environment, spacecraft on orbit released a series of organic gas molecules by means of material outgassing, vacuum outgassing, eliminating propellant, and so on. These gas molecules can deposit on sensitive surface by direct transportation, reflection, atmospheric-scattering transportation, self-scattering transportation, and thermalization atmospheric-scattering transportation, such as optical elements, thermal control coating, and solar cell, which can result in decrease of the property even out of work. Contamination control was the trend of long-life and high-reliability spacecraft. As a new type of contamination control technology, molecular adsorber based on ceramics with convenient measuring, lightweight, low power consumption is a useful way of controlling contamination of spacecraft-sensitive device. There is not any study on molecular adsorber, although the molecular contamination test and simulation analysis have been researched by many people in China. This article analyses the adsorption mechanism study of porous material to organic molecular contamination in vacuum and studies the adsorption property study of porous material to organ-molecular contamination in vacuum. Through the method study of molecular adsorber absorption capability, the development of molecular adsorber is suggested.

Dechlorination of Hexachloroethane in Water Using Iron Shavings and Amended Iron Shavings: Kinetics and Pathways

In contrast to previous studies which employed zero-valent iron powder, this paper investigated reductive dechlorination of hexachloroethane (HCA) using iron shavings and bimetallic iron shavings modified with Cu, Ag, or Pd. Results clearly show that iron shavings offer superior reductive dechlorination of HCA. In addition, surface-normalized pseudo first-order dechlorination rates of 0.0073 L·m−2·h−1, 0.0136 L·m−2·h−1, 0.0189 L·m−2·h−1, and 0.0084 L·m−2·h−1were observed in the presence of iron shavings (Fe0) and the bimetallic iron shavings Cu/Fe, Ag/Fe, and Pd/Fe, respectively. Bimetallic iron shavings consisting of Cu/Fe and Ag/Fe could greatly enhance the reductive reaction rate; Pd/Fe was used to achieve complete dechlorination of HCA within 5 hours. The additives of Ag and Pd shifted product distributions, and the reductive dechlorination of HCA occurred viaβreductive elimination and sequential hydrogenolysis in the presence of all iron shavings. This study consequently designed a reaction pathway diagram which reflected the reaction pathway and most prevalent dechlorination products. Iron shavings are a common byproduct of mechanical processing plants. While the purity of such Fe metals may be low, these shavings are readily available at low costs and could potentially be used in engineering applications such as contamination control technologies.

Contamination Control Technology in Semiconductor Manufacturing

Contamination Control Technology in Semiconductor Manufacturing

Contamination control — an indispensable factor in high-technology manufacturing tasks

Exacting manufacturing processes frequently require a clean environment, devoid of particulate contaminants, in order to meet quality and reliability specifications, to minimize reject rates and to guarantee product cleanliness. It is the objective of cleanroom technology to provide the required cleanliness level in working areas, in distinctive quality grades established by internationally recognized standards and guidelines. The necessary air cleanliness level is maintained through a combination of high-performance air filtration with appropriate airflow patterns in the protected areas, such as the principle of unidirectional displacement air-flow which is capable of meeting the most stringent cleanliness requirements. Providing a clean environment is, however, only the first step. Careful defect analysis, above all in microelectronics, has clearly demonstrated that an integral approach needs to be adopted, covering all aspects of contamination control. In the years to come, microelectronics will continue to be the main driving force for progress in contamination control technology. As the trend towards miniaturization of structures continues unabated, contamination control requirements will remain in the focus of interest. Thus, there will be no lack of challenges for scientists and engineers dedicating their professionalism to the ample and interdisciplinary area of total contamination control.