Chemical states of arsenic contained in sewage sludge incineration ash and insolubilized material

Journal of Material Cycles and Waste Management - The chemical states of arsenic contained in 4 kinds of sewage sludge incineration ash and insolubilized materials are analyzed using a leaching...     

Evaluation of a recycling process for printed circuit board by physical separation and heat treatment

Printed circuit boards (PCBs) from discarded personal computer (PC) and hard disk drive were crushed by explosion in water or mechanical comminution in order to disintegrate the attached parts. More parts were stripped from PCB of PC, composed of epoxy resin; than from PCB of household appliance, composed of phenol resin.In an attempt to raise the copper grade of PCB by removing other components, a carbonization treatment was investigated. The crushed PCB without surface-mounted parts was carbonized under a nitrogen atmosphere at 873–1073 K. After screening, the char was classified by size into oversized pieces, undersized pieces and powder. The copper foil and glass fiber pieces were liberated and collected in undersized fraction. The copper foil was liberated easily from glass fiber by stamping treatment.As one of the mounted parts, the multi-layered ceramic capacitors (MLCCs), which contain nickel, were carbonized at 873 K. The magnetic separation is carried out at a lower magnetic field strength of 0.1 T and then at 0.8 T. In the +0.5 mm size fraction the nickel grade in magnetic product was increased from 0.16% to 6.7% and the nickel recovery is 74%.The other useful mounted parts are tantalum capacitors. The tantalum capacitors were collected from mounted parts. The tantalum-sintered bodies were separated from molded resins by heat treatment at 723–773 K in air atmosphere and screening of 0.5 mm. Silica was removed and 70% of tantalum grade was obtained after more than 823 K heating and separation.Next, the evaluation of Cu recycling in PCB is estimated. Energy consumption of new process increased and the treatment cost becomes 3 times higher comparing the conventional process, while the environmental burden of new process decreased comparing conventional process.The nickel recovery process in fine ground particles increased energy and energy cost comparing those of the conventional process. However, the environmental burden decreased than the conventional one.The process for recovering tantalum used more heat for the treatment and therefore the energy consumption increased by 50%, when comparing with conventional process. However, the market price for tantalum is very large; the profit for tantalum recovery is added. Also the environmental burden decreased by the recycling of tantalum recovery. Therefore, the tantalum recovery is very important step in the PCB recycling. If there is no tantalum, the consumed energy and treatment cost increase in the new process, though the environmental burden decreases.     

Crystallization Behavior and Dynamic Mechanical Properties of Poly(l-Lactic Acid) with Poly(Ethylene Glycol) Terminated by Benzoate

Effect of the addition of poly(ethylene glycol) terminated by benzoate (PEG-BA) on the crystallization behavior and dynamic mechanical properties of poly(l-lactic acid) PLLA is studied as compared with poly(ethylene glycol) (PEG-OH). It is found that PEG-BA is miscible with PLLA and shows good plasticizing effect. Because PEG-OH having the same degree of polymerization is immiscible with PLLA, the end group in PEG-BA, i.e., benzoate, plays an important role in the miscibility. Furthermore, PEG-BA does not induce the PLLA degradation at melt-processing, whereas PEG-OH leads to the hydrolysis degradation. Finally, the addition of PEG-BA pronounces the crystallization rate of PLLA at low crystallization temperatures and thus enhances the degree of crystallinity at conventional processing. Consequently, the temperature dependence of dynamic mechanical properties are similar to that for isotactic polypropylene.     

Inorganic iodine incorporation into soil organic matter: evidence from iodine K-edge X-ray absorption near-edge structure

The transformation of inorganic iodine (I⁻ and IO₃⁻) incubated in soils with varying amounts of organic matter (Andosols from the surface layer of an upland field and forest, as well as Acrisols from surface and subsurface layers of an upland field) was investigated by using the iodine K-edge X-ray absorption near-edge structure (XANES). After 60 d of reaction, both I⁻ and IO₃⁻ were transformed into organoiodine in surface soils containing sufficient amounts of organic matter, whereas IO₃⁻ remained unchanged in the subsurface soil of Acrisols with low organic matter contents. Transformation of IO₃⁻ into organoiodine was not retarded when the microbial activity in soil was reduced by γ-ray irradiation, suggesting that microbial activity was not essential for the transformation of inorganic iodine into organoiodine. Soil organic matter has the ability to transform inorganic iodine into organoiodine.     

Reduction in toxicity and generation of slag in secondary lead process

This paper focuses on the improvement of a secondary lead recycling processing plant, giving special attention to the generation of lead slag. The study was conducted using two different industrial rotary furnaces that together produce three different slag types, which depend on charge composition and lead-containing raw material obtained from a lead-acid battery recycling process. First, characterization of three slag types from different batches was performed, and such characterization included chemical, mineralogical, and structural analyses. By analyzing these data and the operational conditions of the process, it was possible to identify certain deficiencies in the recycling process and implement modifications in order to improve it. A reduction of up to 25% in the quantity of slag generated could be achieved with certain charges. In addition to this process improvement, it was possible to reduce the toxicity of the slag produced when processing a charge containing the same proportion of paste and grid as the lead-acid battery. This improvement lessens the overall environmental impact of the process. By applying this methodology, it was possible to determine some principles of cleaner production in the lead recycling process. So, waste generation could be reduced via improvements in the process and slag characteristics were modified to decrease its toxicity (as determined by lead content in leaching tests).