Advanced Materials Research Vol. 878

Abstract: Semi-aerobic method is a standard type of landfill currently used in Japan. Semi-aerobic landfill system enables to enhance the stabilization of landfilled solid waste utilizing the self-purification capacity inherent in nature. Although semi-aerobic method has been developed for about 20 years, the mechanism has not widely understood in many countries. The objective of this study is to make clear the influence of the laying condition (pipe diameter, pipe placement distance) of leachate collection pipe on the stabilization of landfill through numerical simulation, by use of landfill model constructed in this study with consideration of the interactions of microbial activity and the transport process such as gas transport, heat transport and material transfer between gas and liquid phases.

Abstract: Plenty of construction waste comes into being while the economic developing with a high speed, which brings tremendous harm to human beings and the environment. How to resolve this problem is being an awkward job. This paper builds a structure equation model to analyze the factors affected path and affected degree on the basis of theoretical analysis of the factors from every related subjects, so that we can find effectual measures to resolve the problem of construction wastes management.

Abstract: A copper dressing plant in Jiangxi province of China deals with raw ore in the capacity of 185,000 t/a, and its copper recovery is 86.5% while 13.5% copper still remained in tailings, and a considerable amount of copper is lost in coarse particles tailings. Coarse particles with large size and big mass are very easily detached from bubbles in flotation process, so it is difficult for the plant to use original flotation process and equipments to deal with copper ore. To recycle copper from tailings produced by original flotation circuit, laboratorial experiments were carried out, and then recycle system for that tailing was established and two steps beneficiation process was determined. The first step beneficiation only include one rougher bank, and two sets of CGF-40 flotation cells specially designed by BGRIMM(Beijing General Research of Mining and Metallurgy) for coarse mineral particles were used. The second step beneficiation consisted of one rougher bank, one scavenger bank and two cleaner banks, which is designed to further process froth product from step one. Based on that recycle system, the effect of the reagent and the operation parameters on flotation results was also investigated. The industrial test result shows that the copper recovery of entire recycle system is above 20% while the copper grade of 0.3% (equivalent to copper grade of raw ore). It is estimated that 3,000 tons of copper would be recycled per year using this flotation technique.

Abstract: In past years, the exploitation of mineral resource in our country was stressed on capacity and the solid waste recycle and innocent treatment was ignored. Much valuable metal is associated and coexist with waste, it is in difficult position for present technology to recycle valuable composition in that waste, which leads to valuable component loss and environment pollution. Therefore, the development and utilization of copper refining slag is in significance. In this paper, the advantages and difficulties to process refining slag by flotation method are discussed based on property analysis of copper refining slag. The refining slag is featured by high specific gravity, high concentration, and its particles distributing at both ends of small and large size. A flotation cell with special structure of barrier grid plate and multi-loop channel is developed for refining slag processing, which provides a proper way to solve the sediment problem during refining slag flotation. The application of CLF-40(effective volume,40m3) flotation cell for processing slag mixture from flash furnace and converter is expounded, the production index shows that the Cu grade is up to 27.18% at recovery of 83.93% when slurry concentrate being 70%

Abstract: Present day lead pollution is an environmental hazard of global proportions. A correct determination of natural lead levels is very important in order to evaluate anthropogenic lead contributions. In this paper, the impact of mining and smelting of lead metal ores on environmental quality is described. Globally mines produce large amounts of waste because the ore is only a small fraction of the total volume of the mined material. In the metal industry, production of lead, causes the greatest degradation of the environment. Lead smelters release large quantities of Cd and Pb into the environment as well as smelting and refining produce gaseous (CO₂, SO₂, NOx, etc.) and particulate matter emissions, sewage waters, and solid wastes; however, these pollutants take a lead to effects human health. A quantitative evaluation of the environmental health effects of lead mining and smelting is difficult because of the complexity of factors involved and lack of consistent methodology. Nevertheless, the investigation indicates that negative health effects could arise from lead mining and smelting.

Abstract: Gold ore is processed by all-sliming cyanidation CIP (carbon in pulp) at a gold mine in Gansu province of China. The leaching residue (tailing) Au grade is about 0.52 g/t, which is much valuable to be recovered. Mineralogical analysis shows that the loss of gold in leaching residue is mainly organic carbon adsorption gold and inclusion gold, accounting for 45.55% and 54.45% respectively. The inclusion gold is mostly wrapped by gangue and metallic mineral separately, accounting for 35.56% and 18.89%. Excluding the gold in gangue, both the gold adsorbed by organic carbon and wrapped in metallic mineral could be recycled by flotation process. Study has been carried out for recovering gold in cyanide residue by solely column flotation apparatus. During the semi-industrial test, B and E type sparger were adopted in flotation columns to evaluate their influence on process performance. To further improve metallurgy technology the ultrasonic device was introduced into flotation column tank. The results showed that ultrasonic pretreatment is negative influence, and the E type sparger is better than B type sparger. The concentrate Au grade is up to 10.14g/t, and34.3% of Au lost in tailing was recovered while feed grade being 0.52g/t. The column flotation process was proven being a proper way to recycle gold from the tailing of all-sliming cyanidation CIP.

Abstract: Electronic waste (E-waste) is recognized as a new emerging and fast-growing waste stream, and may be considered as a secondary ore for the recovery of some precious metals (such as gold). A number of control technologies have been conducted for gold recovery, and in which, cyanidation is widely used. In recent years, an alternate approach to the gold cyanidation process is being considered, in which the aim is to replace with the microorganism, specifically cyanogenic bacteria such as Chromobacterium violaceum, Pseudomonas fluorescens, Pseudomonas aeruginosa and Escherichia coli. All these species can produce cyanide ions and dissolve gold in their metabolic processes. The mechanism is a combination of chemical knowledge (interaction of metals and cyanide) with microbiological principles (biological cyanide formation) regarding metal solubilization from waste printed circuit boards and the formation of water-soluble cyanide complexes. And the activity of cyanogenic bacteria is affected by many factors, such as pH, dissolved oxygen pulp density and nutriment, especially several metal ions, which can serve as the catalyst in the metabolism. Now researchers are devoting themselves to looking for the proper conditions, not only from the bacteria themselves, but also the combination of many methods, which can reinforce the cyanide generation and improve gold leaching efficiency. At present the reported leaching efficiency of gold with cyanogenic is approximately 70%. As the continuous optimization of conditions, the industrial application can be expected soon.

Abstract: Vacuum metallurgy method is an economically viable and environmentally friendly way for recycling toxic heavy metals from e-waste. For the mixed metallic metals (MMP) obtained from waste printed circuit boards, the vacuum separating steps and related parameters are different and massive. This paper designs the front panel and the related block diagram programming based on Labview software. The explored human-machine interface realizes the convenient and intuitive guiding for vacuum separating metals from various kinds of MMP.

Abstract: In the present study, a green process for cuprous chloride synthesis from waste printed circuit boards (PCBs) was developed. High value-added cuprous chloride (98.7% purity) was obtained by treating metallic particles of waste PCBs with solution of cupric sulfate and sodium chloride. Typical noble metal (Pd) was dissolved by forming a stable chloride complex during the synthesis process as Cu²⁺ played the role of oxidant or concentrated in the residue. Under the optimum condition (V_NaCl/m_CuSO4 ratio = 6, [C/[Cu²⁺] mole ratio = 1.05, treatment time = 30 min, operation temperature = 60 °C), yield of cuprous chloride was 74.0% and approximately 98.5% of the copper could be recovered. It is believed that the process proposed is effective and practical for Cu recovery from waste PCBs.

Abstract: This article discusses relationship between environmentally sound management (ESM) and transboundary movements (TBM) of hazardous wastes, in particular E-waste. ESM and TBM are the main pillars of the Basel Convention; however, the issues on TBM had only been discussed intensively at early stage of the Basel Convention. ESM had been become a main agenda of international discussion of the Basel Convention after several years since entry into force of the Basel Convention. The article introduces a new concept to identify ESM level by using ESM benchmarks and standards.