solidification
Dotaz
Zobrazit nápovědu
The aim of solidification of ashes is to reduce the bioavailability of toxic heavy metals. The review focuses on comparison of water leachability of raw ashes and ashes solidified with cement. The leachates of raw ashes were toxic due to increased concentrations of trace elements, in particular Cd, As, and Se. On solidification leachability of most of the toxic metals significantly decreased, but their ecotoxicity did not decrease to the expected extent.
Landfilling of waste is inseparably linked to the production of landfill leachate, which is treated and processed by different procedures. One of the options according to technical and economic development is the application of pressure-driven membrane processes, where landfill leachate concentrate (LLC) is produced. This may be further subjected to a stabilisation/solidification process (S/S) as one of its possible processing methods that leads to limited re-introduction of undesirable substances into the landfill body. This paper presents the research of the S/S of LLC, investigates the effect of the waste/binder ratio, the influence of Portland cement substitution, the influence of the additional concentration of the concentrate by evaporation at different levels from the original LLC, and the use of an innovative special highly absorbing binder based on specifically treated fly ash for selected leachate characteristics and compressive strength of the test specimen. The S/S process in most cases met the legislative requirements for water leachate characteristics for non-hazardous waste. Additionally, the comparison of indicative expense for selected solidificate compositions and scenarios is involved. The results of the study serve as necessary basement for further development of treatment of LLC.
Fused deposition modelling (FDM) is a process of additive manufacturing allowing creating of highly precise complex three-dimensional objects for a large range of applications. The principle of FDM is an extrusion of the molten filament and gradual deposition of layers and their solidification. Potential applications in pharmaceutical and medical fields require the development of biodegradable and biocompatible thermoplastics for the processing of filaments. In this work, the potential of production of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) filaments for FDM was investigated in respect to its thermal stability. Copolymer P(3HB-co-4HB) was biosynthesised by Cupriavidus malaysiensis. Rheological and mechanical properties of the copolymer were modified by the addition of plasticizers or blending with poly(lactic acid). Thermal stability of mixtures was studied employing thermogravimetric analysis and rheological analyses by monitoring the time-dependent changes in the complex viscosity of melt samples. The plasticization of P(3HB-co-4HB) slightly hindered its thermal degradation but the best stabilization effect was found in case of the copolymer blended with poly(lactic acid). Overall, rheological, thermal and mechanical properties demonstrated that the plasticized P(3HB-co-4HB) is a potential candidate of biodegradable polymer for FDM processes.
The freezing process consists of dissipating heat from the product until the final temperature is lower than the temperature of crystallisation of that product. Freezing can be used for numerous applications, including for disruption of waste-activated sludge (WAS). The aim of this study was to calculate the estimated amount of heat conveyed between the solidified carbon dioxide and the WAS, in the following ratios: 0.25:1; 0.5:1; 0.75:1 and 1:1. In heat of phase transformations, dry ice sublimation, water solidification, the amount of heat transferred by other substances and heat transferred from the sludge (dry sludge) were taken into account during the process of WAS freezing. Heat changes on the surface of WAS were registered using a thermovision camera. The effectiveness of WAS disintegration was confirmed by several biochemical parameters such as soluble chemical oxygen demand (increase over 14 times), degree of disintegration (48%), proteins (increase over 5 times), carbohydrates (increase almost 7 times), RNA (increase by 2.23 mg L-1), ammonia nitrogen (increase over 23 times), phosphates (increase almost 27 times) and turbidity (increased over 7 times). It was found that dry ice pretreatment of WAS can be an intriguing alternative for the conventional methods used.
