Recycling of WEEE: characterization of spent printed circuit boards from mobile phones and computers

This paper presents a comparison between printed circuit boards from computers and mobile phones. Since printed circuits boards are becoming more complex and smaller, the amount of materials is constantly changing. The main objective of this work was to characterize spent printed circuit boards from computers and mobile phones applying mineral processing technique to separate the metal, ceramic, and polymer fractions. The processing was performed by comminution in a hammer mill, followed by particle size analysis, and by magnetic and electrostatic separation. Aqua regia leaching, loss-on-ignition and chemical analysis (inductively coupled plasma atomic emission spectroscopy - ICP-OES) were carried out to determine the composition of printed circuit boards and the metal rich fraction. The composition of the studied mobile phones printed circuit boards (PCB-MP) was 63 wt.% metals; 24 wt.% ceramics and 13 wt.% polymers; and of the printed circuit boards from studied personal computers (PCB-PC) was 45 wt.% metals; 27 wt.% polymers and ceramics 28 wt.% ceramics. The chemical analysis showed that copper concentration in printed circuit boards from personal computers was 20 wt.% and in printed circuit boards from mobile phones was 34.5 wt.%. According to the characteristics of each type of printed circuit board, the recovery of precious metals may be the main goal of the recycling process of printed circuit boards from personal computers and the recovery of copper should be the main goal of the recycling process of printed circuit boards from mobile phones. Hence, these printed circuit boards would not be mixed prior treatment. The results of this paper show that copper concentration is increasing in mobile phones and remaining constant in personal computers.     

Recycling glass-polishing sludge and aluminum anodising sludge in polyurethane and cement composites: fire performance and mechanical properties

Journal of Material Cycles and Waste Management - This article aims to study the mechanical strength and fire resistance of polyurethane/cement (PuCem) composites containing glass sludge and sludge...     

Recycling Expanded Polystyrene with a Biodegradable Solvent to Manufacture 3D Printed Prototypes and Finishing Materials for Construction

Journal of Polymers and the Environment - The amount of plastic waste generated is causing damage to the environment, such as sea and soil pollution, and one of the alternatives for disposing of...     

Recycling of Tannery (chrome) sludge into sludge biochar (SB) /TiO2 nanocomposite via chemical activation through hydrothermal pre-treatment

Journal of Material Cycles and Waste Management - The preparation of biochar from Tannery (chrome) sludge has gained recent attention among many scientists globally. Hydrothermal pre-treatment...     

The effects of using reprocessable material on the durability and mechanical properties of landfill leachate collection HDPE pipes

This paper investigated the durability and mechanical properties of landfill leachate collection HDPE pipes which had been made of different weight percent amounts of virgin and reprocessable HDPE compounds (VC and RC). Durability is reported base on the chemical properties, obtained through oxidative induction time (OIT) and melt flow index (MFI) measurements, at the temperature of 50 °C and over a period of 12 months immersion in a synthetic leachate. Mechanical properties are also described according to tensile and pressure tests which had been conducted on the pipes samples. All of the factors were examined had been affected by the addition of RC, but for the special combination the antioxidant depletion was significantly affected by the experimental aging condition and no important changes had been observed in the other pipe properties. The results from OIT tests indicate that the rate of antioxidant depletion is reduced by an increase in the weight percent amounts of RC, during the experimental aging condition. This reduction is probably attributed to the extraction of antioxidants from RC in their recovery process. Finally, although these results are related to the particular HDPE compound, antioxidant formulation and condition examined, but it can be said that the use of clean own reprocessable material for the production of landfill leachate pipes shall be permitted without limitations.     

Biodegradable municipal solid waste: characterization and potential use as animal feedstuffs

Five different fractions of the biodegradable municipal solid waste (BMSW) were evaluated as potential animal feedstuffs. For each source of waste (meat waste (MW), fish waste (FW), fruit and vegetables waste (FVW), restaurant waste (RW), household waste (HW)), samples were obtained from small shops (butchers, fishmongers, fruit and vegetable shops), restaurants and a MSW treatment plant (household waste). The chemical composition, microbiological characterization, dioxins, furans, PCB's and mineral content were determined for every type of waste fraction. The analysed biodegradable waste presented high moisture content (from 60% to 90%). Some fractions were dense in one nutrient: meat waste in ether extract, fish waste in crude protein, fruit and vegetable waste in nitrogen free extract. The other studied fractions (restaurant fraction and household fraction) presented a more balanced composition, but the presence of toxic concentrations of contaminants such as metals was higher than European legislation permitted values in animal feeding. From a microbiological standpoint, a heat treatment at 65 degrees C for 20 min was sufficient to ensure microbiological quality of the samples. This treatment was also advisable to reduce the moisture content: a lower moisture content facilitates the waste handling and processing and, therefore, the inclusion of these waste fractions in commercial animal diets. This paper presents a potential alternative for the recovery of organic matter content in municipal solid waste. The results obtained in this research and the feedstuffs legislation in force related to animal feed, indicated that some of the studied biodegradable waste fractions (meat waste, fruit and vegetable waste and fish waste) could be considered as alternatives to typical raw materials used in animal feeds.     

Determinants of waste characterization in Lebanon and material recovery potential

Journal of Material Cycles and Waste Management - Waste represents a largely untapped source of raw material in many countries, as resource recovery rates remain generally low despite most of the...     

Recycling potential of urban solid waste destined for sanitary landfills: the case of Indaiatuba, SP, Brazil.

The urban solid waste of the city of Indaiatuba (pop. 175 000), located in the state of S?o Paulo, was characterized, focusing on the recycling potential. For this purpose, collected waste was subdivided into 27 items, classified by mass and volume. About 90% of this waste was found to be potentially recyclable and only 10% requiring landfilling. The compostable organic matter, in the form of food and garden waste, both with high moisture content (51 and 41%, respectively), represents 54% in mass and 21% in volume. The most common type of plastic in this waste is high density polyethylene, whose estimated disposal is about 5000kgday(-1). A socio-economic analysis of the waste generation indicates that low-income neighbourhoods discard relatively less packaging and more food waste, shoes and construction debris than middle and high income ones, which may be due to low purchasing power and schooling. Our findings indicate that more aluminium and uncoloured polyethylene terephthalate is discarded in the warmest months of the year, probably due to a greater consumption of canned and bottled drinks.     

Physical separation,mechanical enrichment and recycling-oriented characterization of spent NiMH batteries

Nickel–metal hydride (NiMH) batteries contain high amount of industrial metals, especially iron, nickel, cobalt and rare earth elements. Although the battery waste is a considerable secondary source for metal and chemical industries, a recycling process requires a suitable pretreatment method before proceeding with recovery step to reclaim all valuable elements. In this study, AA- and AAA-type spent NiMH batteries were ground and then sieved for size measurement and classification. Chemical composition of the ground battery black mass and sorted six different size fractions were determined by an analytical technique. Crystal structures of the samples were analyzed by X-ray diffraction. Results show that after mechanical treatment, almost 87 wt% of the spent NiMH batteries are suitable for further recycling steps. Size classification by sieving enriched the iron content of the samples in the coarse fraction which is bigger than 0.25 mm. On the other hand, the amounts of nickel and rare earth elements increased by decreasing sample size, and concentrated in the finer fractions. Anode and cathode active materials that are hydrogen storage alloy and nickel hydroxide were mainly collected in finer size fraction of the battery black mass.     

CeO_2/三维石墨烯催化臭氧氧化降解刚果红

采用原位氧化还原法制备了三维石墨烯负载型CeO_2催化剂(CeO_2/3D GN),采用XRD、FTIR、SEM、比表面积和零电荷点测定等方法对其进行了表征,并考察了CeO_2/3D GN非均相催化臭氧氧化降解水中刚果红染料的影响因素。表征结果显示:CeO_2/3D GN具有相互连通的三维网络结构;CeO_2纳米颗粒均匀地分散在石墨烯片层中;比表面积为190.89 m~2/g;零电荷点pH_(zpc)为7.36。实验结果表明:CeO_2/3D GN非均相催化臭氧氧化体系比单独臭氧氧化体系对刚果红溶液的脱色率提高了60.56百分点;连续5次重复利用CeO_2/3D GN,刚果红溶液脱色率为96.50%~98.00%;在臭氧流量为20 mg/min、催化剂投加量为1.5 g/L、初始溶液pH为7.00的最佳工艺条件下反应15 min,刚果红溶液脱色率可高达94.65%。     

Recycling of construction and demolition waste materials: a chemical-mineralogical appraisal

Building activity is currently demanding remarkable amounts of inert materials (such as gravel and sand) that are usually provided by alluvial sediments. The EU directives and Italian Legislation are encouraging the re-use of construction and demolition waste provided by continuous urban redevelopment. The re-utilisation of building waste is a relatively new issue for Italy: unfortunately the employment of recycled inert materials is still limited to general bulk and drainage fills, while a more complete re-evaluation is generally hampered by the lack of suitable recycling plants. In this paper, chemical-mineralogical characterization of recycled inert materials was carried out after preliminary crushing and grain-size sorting. XRF and XRD analysis of the different grain-size classes allowed us to recognise particular granulometric classes that can be re-utilised as first-order material in the building activity. Specifically, the presented chemical-mineralogical appraisal indicates that the recycled grain-size fraction 0.6-0.125 mm could be directly re-employed in the preparation of new mortar and concrete, while finer fractions could be considered as components for industrial processing in the preparation of cements and bricks/tiles.     

MgO/SiO_2纳米复合材料同步吸附亚甲基蓝和Cu~(2+)

采用化学沉积法合成了MgO/SiO_2纳米复合材料,通过扫描电子显微镜和X射线能谱分析(SEM-EDX)、X射线衍射(XRD)、Zeta电位仪、FTIR等方法对其进行了表征。研究了MgO/SiO_2对亚甲基蓝(MB)和Cu~(2+)的吸附行为及同步吸附效果。表征结果表明:MgO/SiO_2为褶皱、凸起的球形形貌;MgO成功负载在SiO_2表面。实验结果表明:MgO/SiO_2对MB和Cu~(2+)的吸附符合准二级动力学模型和Langmuir等温吸附模型,MB和Cu~(2+)的饱和吸附量分别为83.72 mg/g和208.70 mg/g;MB和Cu~(2+)的同步吸附在MgO/SiO_2表面存在竞争关系;在溶液体积为30m L、MgO/SiO_2加入量为10 mg、MB质量浓度为10 mg/L或Cu~(2+)质量浓度为100 mg/L、吸附温度为25℃、吸附时间为24 h、初始溶液pH为4.00、解吸时间为4 h的条件下,MgO/SiO_2第1次吸附MB和Cu~(2+)的去除率分别为92.8%和90.1%,第5次吸附的去除率分别为59.6%和57.4%。     

Sensor-based sorting of waste digital devices by CNN-based image recognition using composite images created from mass and 2D/3D appearances

Journal of Material Cycles and Waste Management - To improve the recycling process of waste from electrical products, we developed a sensor-based sorting system using convolutional neural network...     

Life Cycle Assessment of Poly(Lactic Acid) (PLA): Comparison Between Chemical Recycling,Mechanical Recycling and Composting

This paper presents a life cycle assessment (LCA) comparing three forms of poly(lactic acid) (PLA) disposal: mechanical recycling, chemical recycling and composting. The LCA data was taken from lab scale experiments for composting and hydrolysis steps. Polymerization data in chemical recycling was obtained from computer simulation. Mechanical recycling data from lab scale were combined with the data from a plastics commercial mechanical recycling plant. The analysis considered two different product systems based on the input of the recycled PLA in the product system. Considering the categories: climate change, human toxicity and fossil depletion, the LCA showed that mechanical recycling presented the lowest environmental impact, followed by chemical recycling and composting. Among the forms of recycling, the most important input was the electricity consumption.     

Hydroreforming over Ni/H-beta of the thermal cracking products of LDPE, HDPE and PP for fuel production

The thermal cracking at 400?°C of pure polyolefins—low density polyethylene (LDPE), high density polyethylene (HDPE) and polypropylene (PP) and a standard polyolefin mixture (46?% LDPE?+?27?% HDPE?+?28?% PP)—was studied together with the catalytic hydroreforming of the obtained oils over Ni/h-beta at 310?°C under 20?bar of hydrogen. The oils obtained after the thermal cracking of PP contain the highest amount of gasoline (58?%), while those coming from HDPE the lowest (39?%). The bromine index of the oils was very high, ranging from 54.1 (LDPE) to 83.8 (PP), indicating a high olefinic content of the oils. Additionally, the thermal cracking of the mixture indicates the occurrence of a synergestic effect among plastics, with transfer of methyl groups from PP to polyethylenes. Ni/h-beta (Si/Al?=?25; Ni content?=?6.2?wt%) catalyst was used in the hydroreforming since it contains a bimodal pore size distribution (0.6/3.1?nm), which improves accessibility of the oil molecules to the catalytic sites. After the hydroreforming and regardless of the plastics used, the share of lighter products (gasoline and gases) increases, reaching a remarkable 68?% of gasolines with the oils coming from PP. Regardless of the starting feed, the amount of useful fuels (gasoline?+?light diesel) was within 80–85?%. Additionally, the oils were successfully hydrogenated since the bromine indexes dropped below 7, indicating that more than 90?% of the starting olefins were saturated. The usage of catalysts increased the amount of aromatics in the obtained oils within 13–20?%, depending on the starting plastic. Likewise, the isoparaffin content of the gasolines was within 35–40?%, except for PP, where it was enhanced to 62?%. However, the research octane number (RON) of the gasolines from LDPE and PP and the cetane indexes of the diesel from all the plastics were promising for their application as fuels.     

含铁矿物与UV联合催化H2O2深度处理印染废水

分别以天然含铁矿物黄铜矿、磁铁矿、磁黄铁矿为催化剂,构建了UV-异相类Fenton体系处理实际印染废水生化出水,确定了最优反应条件,并对反应机理进行了初步探讨。实验结果表明:最佳条件下,以黄铜矿、磁铁矿、磁黄铁矿为催化剂的3种异相UV-类Fenton体系对废水的COD去除率分别可达58.83%、57.41%和60.57%,UV254去除率均大于94%;3种天然矿物在重复使用5次后对废水COD的去除率仍保持在50%以上,光催化活性稳定;该体系产生·OH的途径主要有催化剂表面的Fe(Ⅱ)催化H_2O_2分解、H_2O_2光解、溶出的Fe~(2+)催化H_2O_2分解3种,以前两种方式为主。     

Recycling of printed circuit boards: ultrasound-assisted comminution and leaching for metals recovery

Journal of Material Cycles and Waste Management - The increase of electronic equipment consumption associated makes the recycling process crucial worldwide. Use of emerging technologies for...     

Recycling and valorization of distilled grape marc through vermicomposting: a pilot-scale study

The present study sought to evaluate the effectiveness of vermicomposting for the valorization of distilled grape marc, one of the main solid by-products of the winery sector during a 56-day pilot-scale trial. The increase in the density and biomass of earthworms (Eisenia andrei) during the earlier stages of the process reflected the suitability of the distilled marc (Vitis vinifera L. cv. Mencía) as feedstock in order to sustain large earthworm populations on a pilot-scale level. Supporting this, from 14 days onwards the pH of Mencía distilled marc fell within weak-alkaline levels and the electrical conductivity was between 0.21 and 0.11 mS cm⁻² providing optimum conditions for earthworm growth. A rapid decrease in microbial activity as well as in the content of total polyphenols, both indicative of stabilized materials was also recorded after 14 days of vermicomposting. Moreover, the content of macro- and micronutrients in the end product matched with those considered to have the quality criteria of a good vermicompost with respect to plant health and safe agricultural use. Altogether, it underlines the feasibility of vermicomposting as an environment-friendly approach for the biological stabilization of distilled grape marc fulfilling both environmental protection and fertilizer production.

     

复合顺序对三维花状TiO_2-FeOOH复合材料吸附及光催化性能的影响

以TiCl_4为钛源、Fe(NO_3)3·9H_2O为铁源,采用分子自组装法在活性炭表面制备了不同复合顺序的TiO_2-FeOOH复合材料,研究了其对甲基橙的吸附和光催化性能。实验结果表明,TiO_2-FeOOH复合材料由锐钛矿TiO_2和α-针铁矿复合层组成,并呈直径为200~300 nm的三维花状多级结构,这种独特的多级结构有利于实现吸附与光催化的协同作用。UV-Vis吸收光谱显示TiO_2与FeOOH的复合减小了TiO_2的禁带宽度,但TiO_2/FeOOH/AC、TiO_2/FeOOH/AC和TiO_2/AC对质量浓度为10 mg/L的甲基橙溶液处理6 h后,溶液脱色率分别为78.8%,33.9%,57.5%,表明复合顺序对TiO_2-FeOOH复合材料的界面电子传递过程及光催化性能有重大影响。