A Novel Hydrothermal Process To Stabilize Heavy Metals From Both Fly Ash And Waste Water

In this context, the hydrothermal process has been applied to deal with heavy metals from both waste incineration fly ash and waste water. Experimental studies of the hydrothermal synthesis and stabilization mechanism of heavy metals, and the stabilization effect of hydrothermal conditions have been determined. XRD analyzer, SEM-EDS, ICP-MS, the BET nitrogen adsorption instrument and other equipment applied to discover the effects of hydrothermal treatments on treated fly ash and wastewater characteristics, such as the element content, surface morphology, specific surface area, and heavy metal concentration of leachate.Fly ash used in experiments from municipal solid waste incineration and medical waste incineration was investigated experimentally, using the SEM-EDS and XRD to analyze the characteristics of their elemental composition, surface morphology and crystalline structure characteristics, and take advantage of solid particulate matter standards for heavy metals leaching toxicity formulated and implemented by the State Environmental Protection Department to identify the heavy metal leaching characteristics of fly ash. Among various concentrations of different heavy metals, Zn leaching concentration is the greatest, but as a highly toxic heavy metals, Pb and Cd leaching concentration have exceed the standard value.The increasing Al, Si element contents, reaction temperature and reaction time have been found play a positive role Fly ash treatment hydrothermal stability experiments and found that, increase the effects of heavy metals in stabilization and eventually stabilized. While the effects of liquid-solid ratio, dosage of alkaline substances, and initial concentrations of heavy metals in wastewater for the stabilization of heavy metals are volatile. Emerging from the study through experiments, liquid-solid ratio and dosage of sodium carbonate treatment have a greater impact on stabilized effect and secondary pollution. The results showed that, liquid-solid ratio of 10/1, sodium carbonate dosage (to 20 g dry mass of ash) for 4-5 g is more reasonable.In heavy metals co-disposal hydrothermal process, NaOH additions contribute to the formation of aluminosilicate, and the increasing reaction temperature helps to increase the crystals rate of aluminosilicate. The heavy metals removal efficiency of MWI fly ash affects by the reaction temperature, NaOH dosage and the initial heavy metal concentration. Removal efficiency increased with the reaction temperature and higher initial concentration, but too much addition of NaOH will lead to Zn (II) and Pb (II) removal efficiency dropped drastically.In the hydrothermal process, heavy metals were not only removed from the wastewater, and further transformed into a stable mineral structure and stability in the fly ash. Leaching toxicity test results showed that heavy metals leachability of fly ash greatly reduced as the effect of hydrothermal reaction. The reaction conditions have also affect heavy metals leachability of treated fly ash. Higher reaction temperature and a reasonable amount of NaOH addition, moderate concentrations of heavy metals in waste water can make lower heavy metals leachability of treated fly ash.Via the study of this paper, a relatively cost-effective treatment process for dealing with the waste incineration fly ash, heavy metals containing waste water and dioxins in fly ash, and has done an effective supplement for the realization of municipal solid waste and medical waste incineration pollution "zero emission" technology.