This paper presents details of a study that deals with determination of engineering properties, identification of phases of major hydration products, and microstructural characteristics of a zinc-c...

Engineering properties and microstructural characteristics of cement-stabilized zinc-contaminated kaolin

https://ir.nctu.edu.tw:443/bitstream/11536/9862/1/000255991200003.pdf

Recycling MSWI bottom and fly ash as raw materials for Portland cement

The past and future of sustainable concrete: A critical review and new strategies on cement-based materials

Photocatalyst-modified cements are discussed for various applications in building and environmental technology ranging from self-cleaning surfaces to solar-powered remediation devices for polluted waters. In this work, the photocatalytic atrazine degradation by white Portland cement samples modified with different semiconducting oxides (TiO 2 in form of Degussa P25, Hombikat UV 100, coarse-grained anatase, and ZnO) was used as a model reaction to investigate a possible application of modified cements for the degradation of pollutants on building surfaces. The cement mixtures were also characterised with respect to hydration kinetics and compressive strength which are relevant for possible construction applications. Particle suspensions containing 1 μg/l atrazine were irradiated with a sun simulator, and the atrazine degradation was monitored by ELISA (enzyme-linked immunosorbent assay). The atrazine degradation followed first-order kinetic and the obtained rate coefficients were compared with the degradation rate by unmodified cement samples. A significant enhancement of the photocatalytic activity due to the addition of 10 wt.% TiO 2 in the form of Degussa P25 and Hombikat UV 100 to Portland cement was observed, whereas addition of ZnO and coarse-grained anatase showed no effect. The primary crystal particle size of the semiconductor seems to have a significant influence on the photocatalytic efficiency of the semiconductor-modified cement samples. Additionally, modified cements were subjected to defined ageing conditions and carbonation was followed directly by laser Raman spectroscopy. Photocatalytic activity decreases during ageing of the hardened cement pastes. However, aged cement modified with Degussa P25 or Hombikat UV 100 exhibited at least threefold degradation efficiency compared to unmodified cement. Taking into account the sufficient radiation over a long time in the environment, degradation of harmful substances by modified cement samples could contribute considerably to the abiotic degradation of pollutants in the environment.

Photocatalytic activity of semiconductor-modified cement. Influence of semiconductor type and cement ageing

Water treatment technologies for arsenic removal from groundwater have been extensively studied due to widespread arsenic contamination of drinking water sources. Central to the successful application of arsenic water treatment systems is the consideration of appropriate disposal methods for arsenic-bearing wastes generated during treatment. However, specific recommendations for arsenic waste disposal are often lacking or mentioned as an area for future research and the proper disposal and stabilization of arsenic-bearing waste remains a barrier to the successful implementation of arsenic removal technologies. This review summarizes current disposal options for arsenic-bearing wastes, including landfilling, stabilization, cow dung mixing, passive aeration, pond disposal, and soil disposal. The findings from studies that simulate these disposal conditions are included and compared to results from shorter, regulatory tests. In many instances, short-term leaching tests do not adequately address the range of ...

Arsenic Waste Management: A Critical Review of Testing and Disposal of Arsenic-Bearing Solid Wastes Generated during Arsenic Removal from Drinking Water

E Chacon

Papers

Influence of lead, zinc, iron (III) and chromium (III) oxides on the setting time and strength development of Portland cement