Copper removal from aqueous solution is necessary from the stances of both environmental protection and copper resource recycling. It is important to develop a new chemical precipitation method ...suitable for removing copper particularly at low concentration as the case of waste mine water, with regards to the various problems related to the current precipitation methods by using strong alkalis or soluble sulfides. In this research, we studied a possible chemical precipitation of copper ions at concentration around 60 mg/L or lower by cogrinding copper sulfate in water with calcium carbonate (CaCO3) using wet stirred ball milling. With the aid of ball milling, copper precipitation as a basic sulfate (posnjakite: Cu4 (SO4) (OH)6·H2O) occurred at a very high copper removal rate of 99.76%, to reduce the residual copper concentration in the solution less than 0.5 mg/L, reaching the discharge limit, even with the addition amount of CaCO3 as a stoichiometric ratio of CaCO3/Cu2+at 1:1. It is more interesting to notice that, at the same conditions, other heavy metals such as Ni, Mn, Zn and Cd do not precipitate obviously just with CaCO3 addition at CaCO3/M2+at 1:1 so that the precipitate without the impurities can be processed as good source to recover copper. This newly proposed concept can be further developed to treat wastewaters with other metals to serve both purposes of environmental purification and resource recovery in a similar way.
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•Ball milling to activate CaCO3 for chemical precipitation of wastewater.•High efficiency of copper removal even at low concentration.•Selective copper precipitation from other heavy metals.•Easy operation without pH etc. adjustment.
The disposal of scrap cathode ray tube (CRT) funnel glass has become a global environmental problem due to the rapid shrinkage of new CRT monitor demand, which greatly reduces the reuse for ...remanufacturing. To detoxificate CRT funnel glass by lead recovery with traditional metallurgical methods, mechanical activation by ball milling was introduced to pretreat the funnel glass. As a result, substantial physicochemical changes have been observed after mechanical activation including chemical breakage and defects formation in glass inner structure. These changes contribute to the easy dissolution of the activated sample in solution. High yield of 92.5% of lead from activated CRT funnel glass by diluted nitric acid leaching and successful formation of lead sulfide by sulfur sulfidization in water have also been achieved. All the results indicate that the application of mechanical activation on recovering lead from CRT funnel glass is efficient and promising, which is also probably appropriate to detoxificate any other kind of leaded glass.
China is among the countries facing the most serious pollution effects of e-waste. Many studies have focused on e-waste recycling laws and regulations, recycling technologies, and the pollution ...situation in China. However, there is a lack of case studies from the perspective of the residents’ attitudes and opinions about e-waste recycling. Based on 474 families surveyed by questionnaire, this study, taking Zhuhai City as one example, investigated residents’ behaviors and attitudes toward e-waste disposal, and their willingness to pay (WTP) for e-waste recycling. A majority (76.4%) of respondents realized that the improper treatment of e-waste would cause serious threats to the environment and human health. Only 38.2% of respondents were willing to pay for e-waste recycling. Most respondents believed that the fee should be borne by government and manufacturers. These results imply that income level and satisfaction with management will promote WTP significantly, whereas the recovery price is a negative influence on the respondents’ WTP. The WTP values were positively correlated with environmental awareness and income at 5% and 10%, respectively. Finally, the estimated average monthly WTP value per household in Zhuhai City is 10.2 RMB ($1.6).
In this paper, a novel method for copper removal was introduced, in which serpentine, a hydrated magnesium silicate, was activated by mechanical force to raise its reactivity as high as Mg hydroxide ...to remove Cu (II) from wastewater. Copper precipitation occurred easily when agitating the activated serpentine in copper sulfate solution. Characterizations of the activated samples and the samples after treatment of Cu (II) were also performed by X-ray diffraction (XRD), Thermogravimetry & Differential Scanning Calorimetry (TG-DSC). Chemical precipitation with wroewolfeite (CuSO4·3Cu(OH)2·2H2O), a basic copper sulfate, rather than the well known general adsorption by the raw mineral without activation, was formed and gave a very high capacity up to 538.8mg/g for copper removal, comparable with the precipitation by alkaline neutralization of Mg/Ca hydroxide. One more important advantage of using the activated serpentine allowed a selective copper removal from the solution with other metals as Ni (II), Mn (II), Zn (II) and Cd (II) remaining in the solution. The copper precipitate without coexistence of other metals may serve as a good source for copper recycling. The process based on using activated serpentine exhibits the merits for both environmental purification and copper recovery from secondary source/waste, providing a usable method for waste serpentine source as well.
The serpentine is a kind of layered silicate minerals, when the raw material of serpentine activated by the grinding operation, it would change to be amorphous gradually. After the treatment of copper(II) solution by the activated serpentine, the formation of wroewolfeite phase as the copper precipitate confirms that a chemical precipitation has occurred during the copper removal from the solution, explaining the higher capacity of the activated serpentine than the raw material. Display omitted
•Serpentine activated by mechanical force•Activated serpentine for removing Cu (II) from wastewater•Selective Cu (II) precipitation from other heavy metals•Easy Cu (II) recovery from the precipitate by weak acid leaching
Non-metallic fractions (NMFs), which make up almost three fourths (by weight) of waste printed circuit boards, have become a matter of great concern for e-waste recyclers, because most of them ...contain hazardous substances with low utilization value. This study used an advanced Sales Obsolescence Model approach to quantify the generation and flows of non-metallic fractions in China, and to examine the potential environmental impacts associated with both the fractions themselves, and their end-of-life processing activities: disposal into landfills or incineration, and recycling via physical or chemical methods. The results show that approximately 201,000 tons (one time standard deviation: 67,000) of scrap non-metallic fractions were expected to be generated in 2015, and that this amount could increase to 279,000 tons by 2020. Both our own analysis and a systematic review of existing studies on the hazardous characterization of printed circuit boards waste, non-metallic fractions, and their recycling and disposal activities, indicate the threat of environmental pollution, from heavy metals, brominated flame retardants and secondary persistent organic pollutants, particularly dioxins.
Currently, increasing amounts of end-of-life （EoL） electronic products are being generated due to their reduced life spans and the unavailability of suitable recycling technologies. In particular, ...waste printed circuit boards （PCBs） have become of global concern with regard to environmental issues because of their high metal and toxic material contents, which are pollutants. There are many environmental threats owed to the disposal of electronic waste; off-gasses, such as dioxins, furans, polybrominated organic pollutants, and polycyclic aromatic hydrocarbons, can be generated during thermal treatments. which can cause serious health problems if effective off=gas cleaning systems are not developed and improved. Moreover, heavy metals will dissolve, and release into the ground water from the landfill sites. Such waste PCBs contain precious metals which are of monetary value. Therefore, it is beneficial to recover the metal content and protect the environment from pollution. Hydrometallurgy is a successful technique used worldwide for the recovery of precious metals （especially gold and silver） from ores, concentrates, and waste materials. It is generally preferred over other methods because it can offer high recovery rates at a relatively low cost. This article reviews the recent trends and developments with regard to the recycling of precious metals from waste PCBs through hydrometallurgical techniques, such as leaching and recovery.
Polycyclic aromatic hydrocarbons (PAHs) are considered to be persistent organic pollutants, which pose a great threat to human health and the surrounding environment. In order to explore the ...influence of informal electronic waste (e-waste) dismantling activities on inhabitants who live nearby, soil samples were collected from informal e-waste dismantling areas in Xinqiao, China and analysed for 16 United States Environmental Protection Agency (USEPA) priority PAHs. Results indicated that the 16 USEPA priority PAHs were found at all seven sampling locations. Sampling location 3, which was only 10 m away from a residential area, had 1053.69 μg kg−1 of PAHs and seriously exceeded the standard value specified by the Netherlands. The total percents of 4-ring and 5-ring PAHs accounted for 61.74 and 71.70%, respectively, indicating that most of the detected PAHs belonged to high-ring PAHs. The informal e-waste dismantling activities are the major sources of soil PAHs in Xinqiao. Furthermore, the concentration of seven carcinogenic PAHs was 114.76 μg kg−1 and represented a potential health risk to humans. Thereinto, benzoapyrene contributed the most, accounting for more than 50% in these locations. Our results may provide a reference about the influence of informal e-waste dismantling activities on the surrounding inhabitants and suggest that e-waste dismantling activities must be conducted in a formal enterprise which is far away from residential areas.
Cold cathode fluorescent lamps (CCFLs), with mercury as their essential component, were widely used as backlight in liquid crystal display (LCD) appliances before 2008. Since 2008, the mercury-free ...light emitting diode started to be used as a substitute for CCFLs and the replacement finished in about 2014. Nowadays, CCFLs are obsolete products from the viewpoint of manufacture but they are important as waste. In recent years, large amounts of CCFLs are flowing to waste phase for treatment and this has become a major issue in most countries. To better understand and control the risk of CCFLs, the stock of mercury in CCFLs, its flow to waste phase and mercury emission with the life cycle of CCFLs in mainland China were estimated in this study. Results showed that there was 15.2 tons of mercury stocked in CCFLs in main LCD appliances (i.e., LCD televisions, LCD monitors, and laptop monitors) from 2003–2015. CCFLs and mercury started to flow to waste phase around the year 2007 and will likely peak in 2018 with an annual flow of 324.8 million units and 1.5 tons respectively, then will likely decline dramatically till 2030. Dismantling and production were the two main life stages of CCFLs with mercury vapor release, during which approximately 2.1 tons and 1.2 tons of mercury were released to the atmosphere respectively. The research also indicates that mercury recycling in specialized facilities was another life stage with high mercury emission risk in which the processes of shredding, separation, and residue disposal are inevitably accompanied by mercury release.
This study evaluates the efficiency of lead (Pb) extraction from lead bearing waste glass in strongly alkaline solution after mechanochemical reduction with iron. Less than 5% of the Pb can be ...leached directly by alkaline solution from the leaded glass. Compared with the non-activated leaded glass, the Pb extraction of leaded glass mechanically activated increased significantly. Around 67% of Pb was released after mechanical activation without iron, while more than 90% of Pb in the glass can be extracted after mechanochemical reduction with iron. The Pb-depleted solution can be recycled into the leaching step after Pb powder was obtained by electrowinning from the leaching solution. Thus, a novel hydrometallurgical process for recovering Pb from lead bearing waste glass in alkaline solution is proposed.
•It is very difficult to extract Pb from lead bearing waste glass as Pb atoms are fixed firmly in the glass network.•The Pb in leaded glass can be extracted in NaOH solution after mechanochemical reduction with metallic iron as additive.•The mechanochemical reduction process with iron follows the scheme: PbO3+Fe→Pbmod−O+FeO.•A novel hydrometallurgical process for recovering Pb from lead bearing waste glass in alkaline solution is proposed.
This study investigated a mechanochemical process for synthesizing slow-release potassium fertilizer by co-grinding starting materials of KOH, CaO and amorphous SiO2 in a planetary ball mill. X-ray ...diffraction (XRD), differential thermal analysis (DTA), Fourier transformation infrared spectrometry (FTIR) and ion chromatography (IC) were used to analyze the synthesized samples. The milled sample reached an amorphous glass phase of the K–Si–Ca–O system through the incorporation of K+ and Ca2+ into the SiO2 network. The release rate of nutrient K+ decreased with increases in the amount of added silica oxide and in the rotational milling speed. For a synthesized sample dispersed in water for 24h and milled at 400rpm, the release rate of K+ was approximately 25%. All the results indicate that mechanochemical synthesis using starting materials of hydroxides or oxides is a simple and feasible process for producing slow-release fertilizer.
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•Mechanochemical process was used to synthesize a slow-release potassium fertilizer.•KOH, CaO and amorphous SiO2 were directly as the starting materials for synthesis.•The synthesized fertilizer (K–Si–Ca–O system) was an amorphous glass phase.•K+ and Ca2+ were incorporated into the framework structure of SiO4 tetrahedron.•The release rate of nutrient K+ from the synthesized fertilizer was about 25%.
