Liséte Celina Lange

Effect of carbonation on properties of blended and non-blended cement solidified waste forms

Five types of cement and two pozzolans were used to investigate the influence of carbonation on the properties of solidified waste forms. The waste chosen was a commercially blended product which was mixed with cement and then cured in three different environments: nitrogen, air and carbon dioxide for 28 days. Samples were examined for strength development, setting time, microstructural development and leachate metal fixation. Samples cured in a carbon dioxide rich environment showed distinct changes in mechanical properties, microstructure and fixation of metal species. Carbonation was also found to play an important role in the hydration of the binder waste form mix. Carbonated solidified products were characterised by enhanced calcite contents, higher strength values and a significant reduction in leachable metals concentration for all the cement types examined when compared with samples cured in nitrogen. It is also shown that the type of cement or cement-blended system can be optimised to obtain maximum improvement in fixation of waste species in a carbonated product.

The effect of accelerated carbonation on the properties of cement-solidified waste forms

Ordinary Portland cement blended with blast furnace slag and pulverised fuel ash was used to solidify two industrial wastes containing large amounts of metals. The solidified mixes were carbonated using an accelerated regime previously established and compared for strength development, leaching characteristics and phase development against their non-carbonated analogues. A significant difference in the immobilisation of metals such as Zn, Ni and As was recorded for samples in which carbonation was optimised. The work has shown that by controlling mix parameters it is possible to improve the immobilisation of specific metals. Electron microanalysis showed that this is partly due to the precipitation of calcite in the solidified waste pore structure. Carbonation was also found to accelerate C3S hydration in all carbonated samples and to modify the morphology of residual cement grains through the formation of a calcite coating over de-calcified hydration rims. Some metals appear to be incorporated in both of these zones.

The influence of mix parameters and binder choice on the carbonation of cement solidified wastes

This paper explores the kinetics of carbonation of cement-based solidified hazardous waste. This study is part of a wide investigation into the effects of carbonation on solidified waste forms. Two commercially produced heavy metal wastes were solidified with three different types of Portland cement and two mineral admixtures and carbonated under controlled conditions. Measurements of the uptake of carbon dioxide were made for the different mixes and areas showing the degree of carbonation for each cement system were defined. The effects of water/binder ratio, waste and binder type on both total uptake of carbon dioxide and rate of carbonation were investigated and are discussed.

Estimativa do fluxo dos resíduos de equipamentos elétricos e eletrônicos no município de Belo Horizonte, Minas Gerais, Brasil

The aim of this study was to obtain an understanding of the flow of e-waste at the city of Belo Horizonte - Minas Gerais, Brazil. An estimative of the amount of e-waste generated and the domestic and second hand flow were investigated to achieve this goal. The results estimated approximately 153,000 tones of e-waste generated for the period of 2008 to 2023, and the main domestic disposal given by the consumers is donation. We concluded that the environmental management initiatives usually comes from the private sector and are applied to computers and mobile phones only. Other e-wastes are handled using improper tools, creating health and safety hazards for the workers, as well as those e-wastes have been arranged in an irregular way.

Characterization of landfill leachates by molecular size distribution, biodegradability, and inert chemical oxygen demand.

This work presents results from a detailed characterization of landfill leachates of different ages from a landfill in a major Brazilian city. This characterization consists of determining the molecular size distribution and the inert chemical oxygen demand (COD) and the biodegradability of both aerobic and anaerobic processes. Results show that leachate with a high COD concentration leachate has low biodegradability. A significant fraction of the COD is not characterized as protein, carbohydrate, or lipids, which reinforces the hypothesis that the remaining fraction was present in all leachate fractions (less than 1 kDa; between 1 and 10 kDa; between 10 and 100 kDa; and greater than 100 kDa) and is refractory. These results suggest that leachates with such characteristics require treatment systems that use physical-chemical processes as a pre- or post-treatment step to biological processes.