Use of diffuse reflectance spectrometry in spot test reactions for quantitative determination of cations in water

Diffuse reflectance spectroscopy can be successfully used for the quantitative determination of small amounts of pollutants like metals. The remission function was found to be linearly proportional to the concentration, when we applied the Kubelka–Munk equation. The color reactions of Cu(II), Co(II), and Ni(II) with dithiooxamide, were realised on filter paper. Reaction between Fe(III) and ammonium thiocyanate was realized on filter paper and gelatine matrix. All measurements were accomplished with a laboratory-constructed reflectometer. We have obtained a calibration curve by plotting the optical density of reflectance A_R vs log of the mol l⁻¹ concentration. Limits of detection at the 10⁻⁴ M level were estimated for all the compounds. Linear dynamic range extend over one order of magnitude and shows the potential of device for the quantitative analysis of environmental pollutants.     

Mechanical treatment of automobile shredder residue for its application as a fuel

Enforcement of the Automobile Recycling Law in Japan requires utilization of automobile shredder residue (ASR). However, the high contents of copper (∼5%) and chlorine (∼1%) in ASR stand in the way of practical application. We studied methods for the removal of copper and chlorine from ASR so that it could be utilized as a fuel. By compression of the ASR for solidification with an extruder, the polyvinylchloride (PVC) that covered electrical cables was softened and stripped from the copper wire. The solidified ASR was comminuted with cutter mills and classified by dry density separation. The copper content of the obtained light products was 0.2%–0.5%. Furthermore, we studied the possibility of dechlorination of the ASR by mechanochemical (MC) activation. The light product of the ASR was milled with CaO or CaCO₃. The chlorine content decreased to about one-tenth of the original value after MC activation over 8 h. Therefore, the combined processing of softening–stripping and comminution liberated the PVC-covered cables and decreased the copper content of the ASR. In addition, dechlorination of the ASR was also possible by MC activation with the addition of calcium compounds.     

利用粉煤灰改进含铜酸性废水硫化法处理工艺

用粉煤灰对硫化沉淀法处理含铜酸性废水工艺进行改进试验,试验表明粉煤灰有吸附和絮凝沉降的作用,可显著改善单一硫化法沉降速度慢和脱水困难的缺陷。     

An advanced study on the hydrometallurgical processing of waste computer printed circuit boards to extract their valuable content of metals

This study refers to two chemical leaching systems for the base and precious metals extraction from waste printed circuit boards (WPCBs); sulfuric acid with hydrogen peroxide have been used for the first group of metals, meantime thiourea with the ferric ion in sulfuric acid medium were employed for the second one. The cementation process with zinc, copper and iron metal powders was attempted for solutions purification. The effects of hydrogen peroxide volume in rapport with sulfuric acid concentration and temperature were evaluated for oxidative leaching process. 2 M H₂SO₄ (98% w/v), 5% H₂O_2, 25 °C, 1/10 S/L ratio and 200 rpm were founded as optimal conditions for Cu extraction. Thiourea acid leaching process, performed on the solid filtrate obtained after three oxidative leaching steps, was carried out with 20 g/L of CS(NH₂)₂, 6 g/L of Fe³⁺, 0.5 M H₂SO₄, The cross-leaching method was applied by reusing of thiourea liquid suspension and immersing 5 g/L of this reagent for each other experiment material of leaching. This procedure has lead to the doubling and, respectively, tripling, of gold and silver concentrations into solution. These results reveal a very efficient, promising and environmental friendly method for WPCBs processing.     

Generation of copper rich metallic phases from waste printed circuit boards

The rapid consumption and obsolescence of electronics have resulted in e-waste being one of the fastest growing waste streams worldwide. Printed circuit boards (PCBs) are among the most complex e-waste, containing significant quantities of hazardous and toxic materials leading to high levels of pollution if landfilled or processed inappropriately. However, PCBs are also an important resource of metals including copper, tin, lead and precious metals; their recycling is appealing especially as the concentration of these metals in PCBs is considerably higher than in their ores. This article is focused on a novel approach to recover copper rich phases from waste PCBs. Crushed PCBs were heat treated at 1150 °C under argon gas flowing at 1 L/min into a horizontal tube furnace. Samples were placed into an alumina crucible and positioned in the cold zone of the furnace for 5 min to avoid thermal shock, and then pushed into the hot zone, with specimens exposed to high temperatures for 10 and 20 min. After treatment, residues were pulled back to the cold zone and kept there for 5 min to avoid thermal cracking and re-oxidation. This process resulted in the generation of a metallic phase in the form of droplets and a carbonaceous residue. The metallic phase was formed of copper-rich red droplets and tin-rich white droplets along with the presence of several precious metals. The carbonaceous residue was found to consist of slag and ～30% carbon. The process conditions led to the segregation of hazardous lead and tin clusters in the metallic phase. The heat treatment temperature was chosen to be above the melting point of copper; molten copper helped to concentrate metallic constituents and their separation from the carbonaceous residue and the slag. Inert atmosphere prevented the re-oxidation of metals and the loss of carbon in the gaseous fraction. Recycling e-waste is expected to lead to enhanced metal recovery, conserving natural resources and providing an environmentally sustainable solution to the management of waste products.     

Study on the mechanism of copper–ammonia complex decomposition in struvite formation process and enhanced ammonia and copper removal

Heavy metals and ammonia are difficult to remove from wastewater, as they easily combine into refractory complexes. The struvite formation method (SFM) was applied for the complex decomposition and simultaneous removal of heavy metal and ammonia. The results indicated that ammonia deprivation by SFM was the key factor leading to the decomposition of the copper–ammonia complex ion. Ammonia was separated from solution as crystalline struvite, and the copper mainly co-precipitated as copper hydroxide together with struvite. Hydrogen bonding and electrostatic attraction were considered to be the main surface interactions between struvite and copper hydroxide. Hydrogen bonding was concluded to be the key factor leading to the co-precipitation. In addition, incorporation of copper ions into the struvite crystal also occurred during the treatment process.     

Market efficiency,filter rules and buffer stock profitability

This paper uses a model of the optimum buffer stock as a ‘filter rule’ together with a financial model that can be used to assess the efficiency of international commodity markets. The approach is simpler to apply than many other methods which have hitherto been used and yields an economy in theoretical and computational effort. The arguments are applied as a case study to the international copper market. The main conclusion is that private storage is not under-provided for and that a public buffer stock agency would be unlikely to be self-financing.     

Copper in India: Present and future outlook

The availability of mineral resources plays an important role in India's national economy. Copper, one of the important non-ferrous metals, has various industrial uses and demand for it is increasing in India where the inventory and production of copper, though not comparable with developed countries, shows an impressive growth rate, particularly during the last decade. With an increasing rate of industrial production envisaged in future plans copper consumption is expected to rise. Logistic curves have been used to study the potential long-term production capability under the dynamic concept of reserves and resources, with curves drawn for various estimates of total available resources. The production figures shown are not final and are subject to change due to a number of factors. This approach merely provides a method for projecting trends in future production.     

污泥土地利用中重金属铜在土壤中的迁移行为

研究通过模拟土柱淋溶实验来研究污泥土地利用中重金属铜在土壤中的迁移行为。结果表明污泥土地利用会明显增加土壤中铜的总量,但大部分集中在40 cm以上的土壤中。通过BCR连续提取法发现,经淋溶后耕作层（0 cm~30 cm）土壤中的铜仍然以残渣态为主（占50%以上）,但能被植物利用的酸溶/可交换态和可还原态铜有了明显的增加。与去离子水相比,模拟酸雨（pH=4.5）会使土壤中铜的淋溶强度增加,并更能促使其向下迁移。     

仪器法与化学法测定防毒面具滤毒罐苯蒸气防护时间研究*

为研究仪器法和化学法对滤毒罐苯防护时间结果的一致性以及对防护时间判定的影响因素,参照强制性国家标准《呼吸防护 自吸过滤式防毒面具》（GB 2890—2009）,通过选择不同的实验条件,测试4种不同滤毒罐对苯的防护时间,并对实验结果进行显著性差异检验和分析。结果表明:仪器法测定的防护时间小于化学法测定的防护时间;2种检测方法所测定的防护时间结果有显著性差异;测试浓度越高、气流流量越大、采样流量越大,2种方法测定防护时间的绝对差值越小。从防毒面具的安全性和与国外标准一致性考虑,建议采用仪器法判定防护时间。