Papers by Keyword: Leaching Toxicity

Abstract: Select the e-waste in the PC board as the research object, and through microwave-assisted digestion and flip Preparation leaching solution, respectively, using inductively coupled plasma atomic emission spectrometry (ICP-AES) and gas chromatography - mass spectrometry (GC-MS) analysis of the circuit board test results with HJ/T299 set forth in the various elements and organic matter concentration limits comparison shows that a computer circuit board has a leaching toxicity, is hazardous waste for the computer circuit boards harmless and resource provide a reliable theoretical basis.

Abstract: APC fly ash requires safe handling due to existence of heavy metals which pose potential threat to peoples health and the environment. In this work, heavy metal characterization was performed by means of ICP analysis and leaching toxicity analysis. It is found that 14 minor elements are detected and content of them follows sequence of Zn > Pb > Cu > Ni > Cr > Hg > Cd > As. In addition, leaching toxicity of Hg, Cd, Zn and Pb exceeds the limit in accordance with the HVEP and ALT standards.

Abstract: This study aims to develop a methodology for thermal characterization of APC (air pollution control)fly ash using XRD (X-ray diffraction). It performed XRD analysis as a function of temperature between room temperature and 1200 °C. It is found that major mineralogical components of fly ash involve SiO₂, CaCl₂, Ca₃Si₂O₇, Ca₂SiO₄–0.35H₂O, Ca₉Si₆O₂₁–H₂O, K₂Al₂Si₂O₈–3.8H₂O and AlCl₃–4Al(OH)₃–4H₂O. Glass phases account for around 57%, which is conducive to reduction of energy in recycling of the ash. Salts decompose firstly with increase of temperature and then oxides derived from the decomposition process react with SiO₂, forming silicates, calcium-silicates and aluminosilicates.

Abstract: The disposal of acid wastewater generated by a copper-nickel smelting enterprise by using abandoned tailings mortar combined with sulfide precipitation and coagulation indicated that this method has demonstrated good results: the effluent can acheive “Emmission standard of pollutants for copper, nickel, cobalt industry” (GB 25476-2010); the heavy metals in the sediment is not apt to experience dissolution, thus less possible for secondary pollution of soil and groundwater. The optimal combination conditions of this process for sludge/wastewater mass ratio is 14:1; sodium sulfide’s dosing is 20 ml, reaction time is 20 min; FeSO4 and acid waste water volum ratio is 0.05, the reaction time is 30 min.

Abstract: The characteristics and leaching behavior of heavy metals in fly ash, sampled from one MSWI (municipal solid waste incineration) plant in Shanghai China, were investigated. The results indicated that the main elements of fly ash were Fe, K, Na, Cl, Si, Ca, Al, and the total fraction of heavy metals was in the range of 0.8 % - 2.0%. Hence, MSWI fly ash was considered to be one kind of hazardous waste due to its potential environmental risk. Leaching toxicity was performed on fly ash samples from the MSWI plant in Shanghai China. Leaching toxicity of the heavy metals by the ALT (available leaching toxicity) procedure exceeded that by the HVEP (horizontal vibration extraction procedure) standard. Leaching concentrations of Ni, Zn, Cd and Pb exceeded the limit of hazardous waste identification standard. Hence, fly ash is a hazardous waste.

Abstract: Solidification / stabilization (S/S) is a popular method for treating solid wastes containing heavy metals. In recent years, it shows positive results of magnesium potassium phosphate cement as stabilizing agent. In the work, the influence of heavy metal Cu、Zn and Pb on magnesium phosphate cement and the leaching behavior of magnesium phosphate cement were studied. Two proportions of cements were employed with hard burned magnesia and potassium phosphate. The hydration products were analyzed by XRD showing that: Cu、Zn and Pb would not take on obvious effect during magnesium phosphate cement hydration process. Leaching toxicity tests showed that: Cu、Zn and Pb were immobilized within cement hydration products through physical fixation, adsorption mechanisms, and the results were far lower than that of the National Standard in China.

Abstract: Series of experimental tests on the forming technique, sintering technique, performance and effectiveness of a new fired brick by mixing municipal sewage sludge and shale are carried out. Test results show that adding sludge properly in the process of manufacture shale fired common brick is feasible. Along with increase of sludge content, the compacting of uniformity of unburned brick decreased and its porosity increased. When shale-sludge mixtures were calcined, the heavy metal solidified, the ignition lost and organic substance volatilized that reduced the unconfined compressive strength (UCS) of the brick and improve its thermal insulation ability. The phase composition and leaching toxicity of sewage sludge-shale baked brick can be up to national standard. Good quality brick can be produced by blending mixture with the optimum moisture content (OMC) 18.0%-20.0%, drying at 105°C and sintering at 960°C. With all being considered in manufacturing brick, the content of sewage sludge shall be controlled within 9.0% that can make UCS of the new brick reach MU10 criterion and it has a superior heat preservation effect to normal brick from clay or shale alone.

Abstract: This work was done to develop a methodology for analysis of heavy metals in municipal solid waste incineration (MSWI) slag. It performed analysis of heavy metal content, leaching concentration as a function of pH and vibration time. It was found that content of heavy metals followed the decreasing sequence of Zn > Pb > Cu > Cd. Proper vibration time period was 1.0 h for extraction of theses metals, and their leaching concentrations increased with increasing pH from 1 to 11. Hence, an acidic environment could enhance leaching of the four heavy metals.

Abstract: Fly ash from the municipal solid waste incineration (MSWI) which contains a small amount of heavy metals becomes a threat to human health and other living organisms once emitted into the environment, and has to be treated before disposal. This study focuses on the characteristics of the MSWI fly ash, which involve mineral composing, granularity distributing, specific surface area, pore diameter and pore volume of fly ash, leaching toxicity and chemical species of heavy metals. The experiment results confirm that the fly ashes are mainly composed of sylvite, halite, portlandite and calcium sulfate hydrate, with the the average particle diameter of 15.082 μm and the specific surface area of 4.290 m²/g, and the heavy metals such as Pb, Cu, Cr in the MSWI fly ash are mobile except Hg. This research provides critical information for appropriate MSWI fly ash treatment technology.