Hydrothermal treatment of MSWI fly ash for simultaneous dioxins decomposition and heavy metal stabilization

Researches on the hydrothermal treatment of municipal solid waste incineration(MSWI)fly ash were conducted to eliminate dioxins and stabilize heavy metals.In order to enhance decomposing polychlorinated dibenzodioxins(PCDDs)and polychlorinated dibenzo-furans(PCDFs)during hydrothermal process,a strong reductant carbohydrazide(CHZ)is introduced.A hydrothermal reactor was set up by mixing raw MSWI fly ash or the pre-treated fly ash with water and then heated to a pre-set temperature;CHZ was spiked into solution according to specially defined dosage.Experimental results showed that under the temperatures of 518 K and 533 K,the decomposition rates of PCDDs/PCDFs were over 80%and 90%,respectively,by total concentration.However,their toxic equivalent(TEQ)decreased only slightly or even increased due to the rising in concentration of congeners 2,3,7,8-TCDD/TCDF,which might be resulted from the highly chlorinated congeners losing their chlorine atoms and being degraded during the hydrothermal process.Better results of TEQ reduction were also obtained under the higher tested temperature of 533 K and reactor with addition of 0.1%wt CHZ was corresponded to the best results.Good stabilization of heavy metals was also obtained in the same hydrothermal process especially when ferrous sulphate was added as auxiliary agent.

Studies on the sound absorption and transmission loss performances of wood-based, natural and wastematerials

The sound absorption and sound transmission loss performances of the natural woods,hard and soft processed woods with attachment of the various natural orwastematerials were investigated in the present study using impedance tube with American Society for Testing Material(ASTM)standards.The sound absorption performances of all natural and all hard processed woods were very poor.It was found that filter mat made by the coconut fibre was the best material for sound absorption improvement of the hard processed woods.The sound absorption performance of the soft processed wood(cork)was better than all natural and all hard processed woods.Among all tested woods,it was found that the cork with attached tea bag made by corn fibre is the best selection for sound absorption application.The transmission loss performances of all natural woods were good.The effects of various materials on the transmission loss performances of all hard processed woods were not very significant.For cork with and without attachment of various materials,their transmission loss performances were not as good as the hard processed woods.Among all tested woods,it was found that Pterocarpus soyauxii and Quercus spp.(natural woods)are the best woods to be used in those applications when prevention of sound transmission is needed.It is recommended that cork is the best wood to be used in those applications where sound absorption and prevention of sound transmission are needed at the same time due to its good sound absorption performance while its ability on prevention of the sound transmission is also acceptable.