Experimental analysis of waste polyurethane from household appliances and its utilization possibilities

Elevated urinary levels of primary aromatic amines in residents from e-waste dismantling area: Associations with oxidative stress and kidney injury

Currently, the adverse effects of carcinogenic primary aromatic amines (PAAs) released from electronic waste (e-waste) dismantling activities on human health remain unclear. Therefore, this study examined the urinary concentrations of 28 PAAs in residents living in both e-waste dismantling and control areas, and the median concentrations (unit: μg/g Cre) of aniline (ANI) (1.06 vs. 0.49), meta-toluidine (m-TD) (0.41 vs. 0.06), 4-ethoxyaniline (4-EA) (1.66 vs. 0.13), 3,4-diaminoanisole (3,4-DAAS) (1.64 vs. 0.82), and Σ7PAAs (5.80 vs. 2.20) (the sum of 7 highly detectable PAAs) in residents living in the e-waste dismantling area were significantly higher (p < 0.01) than those in the control area. Our results indicate that e-waste dismantling activities contribute to human exposure to PAAs. Furthermore, urinary ANI, 4-EA, and m-TD concentrations were significantly positively correlated with oxidative stress biomarkers; additionally, significant positive associations were found between ANI, 4-EA, m-TD, ortho-toluidine (o-TD), and para-toluidine (p-TD) exposure and elevated NGAL levels, suggesting that these compounds may cause kidney damage. To our knowledge, this is the first study to examine the health risks of human exposure to PAAs in e-waste dismantling areas, providing a new perspective for assessing the health risks associated with PAAs in relation to e-waste dismantling activities.

Pollutant emission during pyrolysis of waste wind turbine blades: Nitrogen-containing components and polycyclic aromatic hydrocarbons

Serious attention was lacked for various pollutants formed in both gas and tar phase during pyrolysis recycling of waste wind turbine blades (WWTB), especially for components of carcinogenic bisphenol A (BPA) and potentially toxic polycyclic aromatic hydrocarbons (PAHs) in tar. Pyrolysis temperature within 400-600 °C would significantly impact pollutant formations. Additionally, CO2 had a potential to mitigate pollutants emission as an economic alternative for N2. This article investigated the influence of these factors on nitrogenous and PAHs components during WWTB pyrolysis through fixed bed and thermogravimetric experiments. The results showed that NO2 was dominated in nitrogen containing pollutants and was related to the evolution of pyrrole nitrogen oxides. It was found 550 °C as a turning temperature, at which the polycondensation reaction appeared significantly. This resulted in a markedly increase for toxic N-PAHs in tar. At this temperature, CO2 could be used to mitigate nitrogen pollutants. 25% CO2 reduced NOX emission about 26% and selectively promoted NH3 releasing to over 4.3 times and depressed HCN generating to 0.6 times. Moreover, the primary depolymerization product of organic pact in WWTB was BPA. Increasing residence time, temperature and CO2 concentration were beneficial for converting hazardous BPA to high valued P-Isopropenylphenol (IPP). The value of IPP:BPA could increase to over 2 in this experiment. It was aimed to provide not only an evaluation for the yield and migration of pollutants, but also an cleaner recycling solution through graded pyrolysis WWTB to mitigate pollution and maximize the value of by-products.

Distribution, migration, and removal of N-containing products during polyurethane pyrolysis: A review

Due to the wide applications of polyurethane (PU), production is constantly increasing, accounting for 8% of produced plastics. PU has been regarded as the 6th most used polymer in the world. Improper disposal of waste PU will result in serious environmental consequences. The pyrolysis of polymers is one of the most commonly used disposal methods, but PU pyrolysis easily produces toxic and harmful nitrogen-containing substances due to its high nitrogen content. This paper reviews the decomposition pathways, kinetic characteristics, and migration of N-element by product distribution during PU pyrolysis. PU ester bonds break to produce isocyanates and alcohols or decarboxylate to produce primary amines, which are then further decomposed to MDI, MAI, and MDA. The nitrogenous products, including NH3, HCN, and benzene derivatives, are released by the breakage of C-C and C-N bonds. The N-element migration mechanism is concluded. Meanwhile, this paper reviews the removal of gaseous pollution from PU pyrolysis and discusses the removal mechanism in depth. Among the catalysts for pollutant removal, CaO has the most superior catalytic performance and can convert fuel-N to N2 by adsorption and dehydrogenation reactions. At the end of the review, new challenges for the utilization and high-quality recycling of PU are presented.

One More Step towards a Circular Economy for Thermal Insulation Materials-Development of Composites Highly Filled with Waste Polyurethane (PU) Foam for Potential Use in the Building Industry

The rapid development of the building sector has created increased demand for novel materials and technologies, while on the other hand resulting in the generation of a severe amount of waste materials. Among these are polyurethane (PU) foams, which are commonly applied as thermal insulation materials. Their management is a serious industrial problem, due to, for example, their complex chemical composition. Although some chemical and thermochemical methods of PU foam recycling are known, their broader use is limited due to requirements related to the complexity and safety of their installation, thus implicating high costs. Therefore, material recycling poses a promising alternative. The incorporation of waste PU foams as fillers for polymer composites could make it possible to take advantage of their structure and performance. Herein, polypropylene-based composites that were highly filled with waste PU foam and modified using foaming agents were prepared and analyzed. Depending on the foam loading and the foaming agent applied, the apparent density of material was reduced by as much as 68%. The efficient development of a porous structure, confirmed by scanning electron microscopy and high-resolution computed micro-tomography, enabled a 64% decrease in the thermal conductivity coefficient. The foaming of the structure affected the mechanical performance of composites, resulting in a deterioration of their tensile and compressive performance. Therefore, developing samples of the analyzed composites with the desired performance would require identifying the proper balance between mechanical strength and economic, as well as ecological (share of waste material in composite, apparent density of material), considerations.

One-pot superhydrophilic surface modification of waste polyurethane foams for high-efficiency oil/water separation

Despite of the fact that polymers have brought tremendous convenience to human life, they have also inevitably caused considerable environmental pollution after their service life. Therefore, a feasible strategy that can effectively recycle waste polymers and endow them with high added value is much desired. Superwetting materials have shown great promise in oily wastewater treatment because of their high oil/water separation efficiency. However, most of these materials present some limitations, such as complex preparation procedures and poor salt tolerance, which hamper their practical applications. In this study, an iron hydroxide@polydopamine@waste polyurethane foam (Fe(OH)₃@PDA@WPU) was synthesized via a facile and mild "one-pot" reaction. During this process, polymerization of dopamine and in situ growth of Fe(OH)₃ were simultaneously realized, and the resultant PDA and Fe(OH)₃ nanoparticles were firmly attached to the surface of WPU. Due to the abundant hydrophilic groups from PDA and Fe(OH)₃ coupled with the surface roughness created by Fe(OH)₃ nanoparticles, the surface properties of the foam could be changed from hydrophobic to superhydrophilic. Remarkably, the Fe(OH)₃@PDA@WPU was capable of separating various oil/water mixtures even under some severe conditions (e.g. erosion in a saturated sodium chloride solution and longtime sonication), demonstrating high potential in marine oily sewage treatment. Moreover, this work also paved a new path for reducing the negative impact of waste polymer foams on our environment, and in the meantime realizing their high value utilization.

Promotion of Household Waste Utilization in China: Lessons Learnt from Three Case Studies

Household waste utilization has been regarded as an important pathway to promote the circular economy paradigm and sustainable development for a long time. However, relevant enterprises are facing dilemmas in terms of the backward disposal methods for food waste, inadequate recycling of low-value recyclable waste and the lack of leading enterprises, resulting in unsustainable expansion of the industry. To address these problems, we investigated governmental departments and 20 household waste utilization enterprises in China. From the investigation, three typical enterprises, representing the advanced technology for food waste, the recycling mode of recyclable waste and the cultivation mode of leading enterprises, were selected for case studies. The results indicate that applying the technology of bioconversion by maggots could improve the utilization of food waste and adopting the “online and offline” dual-channel mode could benefit the recycling of low-value recyclable waste. Additionally, leading enterprises can be cultivated by franchise mode, which can drive the utilization of household waste in China effectively. The findings enrich the theory of household waste utilization in terms of disposal methods, recycling modes and enterprise operation. Practically, this research should enlighten decision-makers to improve household waste utilization. Furthermore, the research results could be generalized in other countries, thereby advancing the household waste management worldwide.

Green development challenges within the environmental management framework

Green development of energy, water and environment systems is essential as these three systems represent the basic life needs of humankind. Therefore, environmental problems arising from each of these three systems need to be carefully addressed to preserve the energy, water and environment resources for future generations. This paper discusses some of the latest developments in three main areas of sustainability themes, namely energy, water and environment, that emerged from the 14th Sustainable Development of Energy, Water and Environment Systems (SDEWES) Conference held in 2019. As such, it acts as an editorial paper for the virtual special issue of the Journal of Environmental Management, dedicated to the SDEWES 2019 conference.

Environmental problems arising from the sustainable development of energy, water and environment system

Integration of energy, water and environment systems is essential in the multidisciplinary concept of sustainable development, as they represent the basic life needs of mankind. Therefore, problems arising from the sustainable development concept need to be carefully addressed to preserve the energy, water and environment resources for future generations. This article discusses some of the latest developments in three main areas of sustainability themes, namely energy, water and environment, that emerged from three Sustainable Development of Energy, Water and Environment Systems (SDEWES) conferences held in 2018. As such, it acts as an editorial paper for the virtual special issue of the Journal of Environmental Management, dedicated to the SDEWES2018 conferences.

A kinetic study of roadside grass pyrolysis and digestate from anaerobic mono-digestion

The aim of this research is to evaluate the thermogravimetric behaviour of roadside grass and its digestate obtained from mesophilic anaerobic mono-digestion by quantifying its impacts on biomass composition and properties. Thermogravimetric measurements were conducted in a laboratory furnace under nitrogen flowrate of 100 mL/min in the temperature range from 35 to 800 °C at five different heating rates of 2.5, 5, 10, 15 and 20 °C/min. Friedman and Kissinger-Akahira-Sunose differential and integral isoconversional models were applied to determine the distributions of activation energies and modified pre-exponential factors per reacted mass (degree of conversion). The investigation demonstrated that anaerobic digestion of roadside grass can be used to generate biochar-richer material (with significantly greater yield of final residues after pyrolysis) with less energy required for subsequent pyrolysis in comparison with raw roadside grass.