Recycling, Volume 2, Issue 4 (December 2017) – 8 articles

This study aims to provide an updated survey of the main thermoplastic polymers in order to obtain recyclable materials for various industrial and indoor applications. The synthesis approach significantly impacts the properties of such materials and these properties in turn have a significant impact on their applications. Due to the ideal properties of the thermoplastic polymers such as corrosion resistance, low density or user-friendly design, the production of plastics has increased markedly over the last 60 years, becoming more used than aluminum or other metals. Also, recycling is one of the most important actions currently available to reduce these impacts and represents one of the most dynamic areas in the plastics industry today. Full article

Environmental governance is commonly performed through recycling, but its effects are often difficult to predict. Studies have covered the environmental impacts and organizational structures of recycling and other circular economy governance, but only to a small degree related organization to environmental performance. We have therefore explored a methodological contribution for better understanding. We have applied and tested a hybrid, socio-material, approach, a product chain organization (PCO) study, in a comparison of governance of metal packaging product flows in Sweden and the Netherlands. A PCO study is a systematic and nuanced exploration of how nets of actions and actors shape environmental impacts. We identified that the policies in the two countries have focused on combined recycling rates, which has indicated superior Dutch governance. We, however, have discerned how various actions have been environmentally relevant, regarding inaccurate statistics, combining of waste streams, and consumption. We conclude that the test case on packaging shows how a PCO study can complement other approaches with a nuanced understanding of the environmental effects of governance toward a circular economy. Full article

Hydrogen decrepitation (HD) is an effective and environmentally friendly technique for recycling of neodymium-iron-boron (NdFeB) magnets. During the HD process, the NdFeB breaks down into a matrix phase (Nd₂Fe₁₄BH_x) and RE-rich grain boundary phase. The grain boundary phase in the HD powder is <2 μm in size. Recycled NdFeB material has a higher oxygen content compared to the primary source material. This additional oxygen mainly occurs at the Rare Earth (RE) rich grain boundary phase (GBP), because rare earth elements oxidise rapidly when exposed to air. This higher oxygen level in the material results in a drop in density, coercivity, and remanence of sintered NdFeB magnets. The particle size of the GBP is too small to separate by sieving or conventional screening technology. In this work, an attempt has been made to separate the GBP from the matrix phase using a hydrocyclone, and to optimise the separation process. HD powder, obtained from hard disk drive (HDD) scrap NdFeB sintered magnets, was used as a starting material and passed through a hydrocyclone a total number of six times. The X-ray fluorescence (XRF) analysis and sieve analysis of overflows showed the matrix phase had been directed to the underflow while the GBP was directed to the overflow. The optimum separation was achieved with three passes. Underflow and overflow samples were further analysed using an optical microscope and MagScan and matrix phase particles were found to be magnetic. Full article

Currently, about 25,500 large commercial aircraft are in use for passenger transport or as freighters, or in storage. As of today, the most prevalent metals in aircraft recycling are aluminium, as well as nickel and titanium super alloys, e.g., for the engines. The total fleet weight amounts to about 1.3 million metric tons of materials (not only metals). The aircraft engine material stock alone amounts to about 170,000 metric tons in the entire fleet. In the coming decade, more than 200,000 metric tons of obsolete aircraft structural materials can be expected for recycling. This article aims to quantify this flying stock in more detail. Full article

The recycling of valuable metals from spent lithium-ion batteries (LIBs) is becoming increasingly important due to the depletion of natural resources and potential pollution from the spent batteries. In this work, different types of acids (2 M citric (C₆H₈O₇), 1 M oxalic (C₂H₂O₄), 2 M sulfuric (H₂SO₄), 4 M hydrochloric (HCl), and 1 M nitric (HNO₃) acid)) and reducing agents (hydrogen peroxide (H₂O₂), glucose (C₆H₁₂O₆) and ascorbic acid (C₆H₈O₆)) were selected for investigating the recovery of valuable metals from waste LIBs. The crushed and sieved material contained on average 23% (w/w) cobalt, 3% (w/w) lithium, and 1–5% (w/w) nickel, copper, manganese, aluminum, and iron. Results indicated that mineral acids (4 M HCl and 2 M H₂SO₄ with 1% (v/v) H₂O₂) produced generally higher yields compared with organic acids, with a nearly complete dissolution of lithium, cobalt, and nickel at 25 °C with a slurry density of 5% (w/v). Further leaching experiments carried out with H₂SO₄ media and different reducing agents with a slurry density of 10% (w/v) show that nearly all of the cobalt and lithium can be leached out in sulfuric acid (2 M) when using C₆H₈O₆ as a reducing agent (10% g/g_scraps) at 80 °C. Full article

The primary production of sulfide concentrates includes smelting to copper matte or blister copper, conversion of matte to blister copper, and refining to copper. Smelting, converting, and fire-refining can use a limited amount of secondary materials. Molten copper can effectively dissolve many metals, from valuable noble metals to harmful impurities such as bismuth. However, some of the impurity metals in copper are valuable in other applications. In this paper, we outline the main material flows in copper smelting and electrorefining and describe how minor metals can be recovered from secondary raw materials using copper as a carrier material. We will use a system integrated approach to define the factors that affect the recovery of different metals and copper quality. Metals typical in copper production are used as examples, like noble metals, As, Bi, Se, and Te, including metals in the EU critical raw materials list like PGM and Sb. Full article

Improper handling of household solid waste causes problems that affect public health and the environment, as well as the aesthetic nature of cities. This paper aims to determine if the theory of planned behavior (TPB), and its extended version can be used to predict household recycling intention (RI), and whether perceived lack of facilitating conditions have a moderating role on households’ RI in Nigeria. Data from a sample of 393 households from Kano metropolis Nigeria were analyzed using structural equation modeling. The result reveals that the TPB Model predicts households RI in Nigeria and explains 42% of the variance in RI. Attitude is the most important predictor of RI in the TPB model (β = 0.593, p = 0.000). However, after personal norm (PN) was added into the model, the variance in RI increases to 58% and PN becomes the most important predictor of RI in the extended TPB model (β = 0.496, p = 0.000). Perceived lack of facilitating condition was found to have a significant moderating effect on households’ RI. Finally, our findings show that providing households with recycling facilities and local collections holds great promise for improving households’ intention to recycle. Full article

The tannery industry is renowned for the huge amount of toxic solid and liquid waste generated from the cleaning, fleshing, splitting, tanning, shaving and buffing of raw materials. Biomass briquettes are a proven way of generating energy from waste. This study investigates the development and characterization of biomass briquettes from tannery solid wastes (TSWs). TSWs, which comprise hair, flesh, chrome shavings and buffing dust, were collected from a tannery in Kano, Nigeria, to formulate and characterize six briquettes. Scanning electron microscopy and proximate analysis were carried out on the samples. The six briquettes, comprising varying ratios of hair, flesh, chrome shavings and buffing dust, were molded and characterized. Thermal efficiency, durability and compressive strength, among other properties, were determined for the six briquette formulations. The briquettes developed had calorific values between 18.632 and 24.101 MJ/kg. Durability of the briquettes ranged from 98.12% to 99.77%. The energy values were within the range of 17.462–24.101 MJ/kg, which was comparable to other fuel sources such as sub-bituminous coal (20.000–24.730 MJ/kg). This study shows that TSWs can be used for fuel briquette production, which is a source of sustainable energy generation. It is environmentally friendly, cost effective and affordable compared to fossil fuel. Full article