3D printing of various polymers has attracted great attention and developed rapidly in recent years. Digital light processing (DLP) has recently emerged as a fast growing 3D printing technique due to ...its high resolution and high speed. However, the lack of printable high-performance materials limits its broad applications. In addition, with the increasing adoption of DLP 3D printing, the efficient recycling of printed thermosetting materials is highly desired. Herein, we proposed a two-stage curing approach involving dynamic reactions by using the acrylate-epoxy hybrid resin for the recyclable DLP 3D printing of high-performance thermosetting polymers. Bond exchange reactions (BERs) could establish covalent bonds between the acrylate network and the epoxy network, thus partially triggering the copolymerization. The resulting new polymers exhibited excellent mechanical properties. A small-molecule assisted BER method was then used to efficiently depolymerize the thermosetting printed parts into soluble oligomers, which were formulated with fresh photopolymers for the next round of printing. The reprinted samples still showed good mechanical properties comparable to the virgin ones. In addition, the new polymers demonstrated potential applications in 4D printing of smart actuators. This work opens a novel avenue for green manufacturing technologies.
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•Digital light processing 3D printing of recyclable thermosetting polymers.•A two-stage curing approach involving dynamic reactions to improve performance.•Recycle printed parts by using small-molecule assisted bond exchange reactions.•Reprinted polymers exhibit comparable mechanical properties to the virgin ones.•4D printing of smart actuators by using the shape memory effect.
The removal of fluoride from wastewater is essential as the excess accumulation of fluoride in environment is harmful to the health of humans. In this study, the defluorination of water by aluminum ...hydroxide-coated zeolite (AHZ), which was synthesized from coal fly ash, was investigated in batches. The Langmuir maximum adsorption capacity of fluoride by AHZ reached 18.12 mg/g. Aluminum hydroxide was shown to be the major component that adsorbed fluoride. More than 92% removal of fluoride was achieved within 2 h, and the fluoride adsorption kinetics were well fitted to a pseudo-second-order model. The point of zero charge (pHpzc) of the AHZ was determined to be 5.52. Fluoride adsorption by AHZ depended greatly on pH, and maximum performance was obtained at pH 5.5–6.5. The AHZ showed good selectivity for the adsorption of fluoride in the presence of chloride, nitrate, sulfate, bicarbonate, and acetate ions, and the fluoride was nearly exhausted at a sufficiently high dose. The release of OH− due to fluoride adsorption was confirmed. FTIR and XPS studies further illustrated that the adsorption mechanism of fluoride adsorption on AHZ was ligand exchange with hydroxyl groups and the formation of F–Al bonds.
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•Aluminum hydroxide coated zeolite (AHZ) was synthesized from coal fly ash.•The maximum adsorption capacity of fluoride by AHZ reached 18.12 mg/g.•Optimal fluoride adsorption was within the pH range of 5.5–6.5.•Defluoridation by AHZ was fast and did not affect substantially by common anions.•The mechanism of fluoride adsorption was the exchange with hydroxyls on AHZ.
In a race to save the earth of its rapidly depleting natural resources, the use of Secondary Raw Materials (SMRs) as alternative replacements in several processes is currently intensively pursued. ...The valorization of SMRs is consistent with the sustainable circular economy, where resource efficiency is maximized for the benefit of both the economy and green environment. In line with this mandate, this article focuses on investigating recent studies on secondary zinc (Zn) resources and describing state-of-art Zn recycling technologies. Globally, some of the main Zn-containing secondary raw materials are mine/concentrator/smelter tailings, wastes, slags, scraps, dust, etc.
Although the pyrometallurgical process has been dominant in the secondary metal recycling processes, there has been growing interest and pressure to achieve sustainable and greener recycling methods to remediate the environmental problems caused by emissions of toxic heavy metals and sulfur oxides in the traditional smelting process. In the last decades, many sustainable and environmentally friendly novel hydrometallurgical processes for Zn extraction were developed to overcome tougher legislation and meet cost competitiveness. Secondary Zn recycling focuses on the development of selective Zn-rich but Pb, Fe, As-lean recovery processes.
•This paper reviews secondary Zn resources treatment and state-of-the art recycling technologies in the last decades.•Sustainable and environment friendly hydrometallurgical technologies for secondary Zn extraction overcome tougher legislations at lower costs.•Mineral acids, alkaline solutions and inorganic acids can be used at ambient conditions for secondary Zn extraction more than 90%.•Recycling Zn secondaries will be a green and lucrative solution.
Circular Economy (CE) and the adoption of its principles globally are more important than ever to sustain the rate of production of goods and services to meet the ever-increasing consumer demand that ...is burdening the environment and society. This study investigates the adoption of CE principles amongst emerging economies as the challenges faced by these economies are generally different in terms of resource availability, varying government policies and consumer behaviour from those of developed economies. This research presents an empirically validated CE adoption model using a sample of 183 consumer responses. The study highlights the strong influence of factors such as consumer behaviour on the acceptance of remanufactured products and using products as a service to encourage the adoption of CE practices in emerging economies. This research offers businesses, consumers and policy makers insights into measures that have been taken by emerging economies that are in line with CE principles.
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•Cyclodextrin-functionalized magnetic alginate microspheres (MSA-CDMW) are prepared.•The addition of MSA-CDMW significantly decreases the amounts of Pb and BPA in soil.•Ion exchange, ...complexation and electrostatic attraction convert Pb to stable species.•MSA-CDMW can capture BPA through host-guest interaction by hydrophobic cavity.•Eco-friendly MSA-CDMW microspheres can be easily collected and recovered from soil.
Currently, functional materials-based soil remediation focused on the stabilization of heavy metals and organics to inhibit their migration, however, the possible second release of these pollutants caused by soil condition variation attracts broad attention. Herein, β-cyclodextrin functionalized magnetic sodium alginate microspheres (MSA-CDMW) were fast and facilely synthesized through microwave-assisted one-pot method for synchronous detachment of Pb and BPA from contaminated soil. The obtained MSA-CDMW presented wide pH adaptability and fast capture for Pb(II)/BPA with superior adsorption capacity of 369.03/165.37 mg/g. Furthermore, the effects of material dosage and soil pH on the remediation ability of MSA-CDMW were explored in detail. After adding 5% MSA-CDMW into the contaminated soil for 3-round successive remediation (12 h for each round), the amount of extractable Pb and total BPA was simultaneously decreased by 56.30 and 0.78 mg/kg, respectively. Meanwhile, the quantity of exchangeable and carbonate bound Pb was significantly decreased to 7.13% with transformation into relatively stable fractions. A series of characterizations revealed that ion exchange, pore filling, complexation, and electrostatic attraction were responsible for Pb binding, while MSA-CDMW could capture BPA through host-guest interaction by the hydrophobic cavity of β-cyclodextrin. Additionally, recovery and floatation results revealed that the MSA-CDMW could be easily separated from the soil using magnets even at extreme drying and wetting conditions, thus providing a novel, fast, and eco-friendly strategy for effective remediation of heavy metals and organics contaminated soil.
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•A fully recyclable TIM with high thermal conductivity and conformability to the rough surface was prepared.•Filled BN could be oriented by hot-pressing and led to a thermal ...conductivity of 3.85 W·m−1·K−1, 4.3 times higher than the composite before hot-pressing treatment.•BN recovery rate of 96.2% and other organic raw materials recovery rate of 73.6% to 82.4% were achieved.•The electronic device made of the prepared composite exhibited a 20 °C lower core temperature than the commercial silicone material.
Thermal interface materials (TIMs) with excellent heat dissipation capacity are highly desired for the development of miniaturized, integrated, and dense electronic devices. In addition, with the increasing accumulation of e-waste, the recyclability of TIMs has also become an urgent concern. Herein, a fully recyclable TIM with high thermal conductivity and conformability to the rough surface was prepared based on the synthesized epoxy vitrimer and boron nitride (BN) nanosheet. Results revealed that only by simple hot-pressing, the filled BN could be easily oriented in the plane and led to a thermal conductivity of 3.85 W m−1 K−1 with the BN content of 40 wt%, which was 30 times higher than that of the pristine epoxy resin and 4.3 times higher than the composite before hot-pressing treatment. The electronic device made of the prepared composite exhibited a 20 °C lower core temperature than the commercial silicone material, due to the superior thermal conduction and mechanical compliance. Moreover, benefiting from the multistage degradation mechanism of the synthesized epoxy vitrimer, the fabricated composite could be efficiently chemically recovered under mild conditions, demonstrating the BN recovery rate of 96.2% and other organic raw materials recovery rate of 73.6% to 82.4%. This work provides us with a new strategy for the design of recyclable and high-performance TIMs.
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•MnCO3 roasting was more suitable for high chromium vanadium slag pretreatment.•89.37% vanadium, 0.10% chromium and 0.04% iron was leached.•Chromium-containing vanadium tailings was ...detoxified and prepared Fe-Cr alloy.•Three circulation routes were achieved during the whole process.
A novelty roasting method with manganese carbonate (MnCO3) as additive was carried out to separate and recover vanadium from high chromium vanadium slag (HCVS) efficiently. Vanadium tailings containing chromium was detoxified by carbon reduction and smelting to form Fe-Cr alloy. The whole process of HCVS utilization was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). 89.37% of vanadium and 0.10% of chromium was leached when MnCO3 was added to HCVS at the mole ratio of MnO in MnCO3 and V2O3 in HCVS (n(MnO)/n(V2O3)) of 2.0 and heating at 850 °C for 120 min, then leached under the pH value at 2.5. 99.19% of vanadium was precipitated by (NH4)2SO4 and V2O5 with a purity of 99.28% was prepared. More than 84% of manganese addictive was recovered after manganese precipitation by carbonization with CO2 discharged from manganese carbonate roasting, which could be used as the raw addictive for roasting. The wastewater after vanadium and manganese extraction could be circulated as leaching medium. Three circulation routes realized the closed-circuit circulation of raw materials and products, saving the production costs and avoiding the environmental pollution. Fe-Cr alloy with 67.35% of Fe and 13.28% of Cr was obtained from chromium-containing vanadium tailings, which could be returned to the steelmaking process.
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•Simultaneous removal of Cr(VI) and MB was achieved even in high saline medium.•The synergistic removal of Cr(VI) and MB was realized in coexisting system.•Cr(VI) and MB was ...classifiably recovered via electrochemically assisted desorption.
Heavy metal ions, dyes and high concentrations of salt are three kinds of representative compounds in the wastewater produced from dyeing processes. An integrated technical process with multifunctional adsorbents for the simultaneous removal of pollutants, e.g., inorganic heavy metal ions and organic dyes, is highly desired. Moreover, classification of the recycled adsorbates on the exhausted adsorbents is also important and necessary. Herein, we have developed a new strategy to synergistically remove and electrochemically classify the recycled Cr(VI) and dyes from synthetic dyeing wastewater. First, polyaniline (PANI) was used to decorate the spherical resin (PS) by one-step in situ polymerization, and the as-synthesized composite (PANI@PS) was used as an adsorbent for simultaneous removal of Cr(VI) and methylene blue (MB) in high saline medium mainly based on PANI and PS, respectively. The synergistic adsorption removal capacities of Cr(VI) and MB on PANI@PS reached 183.0 mg Cr(VI) g−1 PANI and 40.3 mg MB g−1 PANI@PS in a coexisting system, in contrast to 94.0 mg Cr(VI) g−1 PANI and 27.5 mg MB g−1 PANI@PS in a single-component system. These increases are attributed to the additional adsorption sites and electrostatic attractions between the adsorbed Cr(VI)(−) and MB(+). Noticeably, the adsorbed Cr(VI)(−) and MB(+) can be recovered and classified via electrochemically assisted desorption, with a maximum recovery ratio of 90.3% (Cr(VI)(−)) and 91.9% (MB(+)). This study is of great significance for introducing novel adsorbent composites for the simultaneous removal and classified recovery of specific coexisting pollutants.
The challenges of sustainable construction, industrial growth and importance of resource efficiency are clearly recognised by the UK government and are now at the forefront of strategy and policy. A ...critical component of the government’s sustainability strategies concerns way in which construction and demolition waste (C&DW) is managed. In this study a mixed method approach was adopted to investigate current practices of C&DW management and circular construction (re-use, recycle and recovery of materials) concept awareness in the UK. Relevant stakeholders from the construction industry (contracting, demolition and C&DW organisations) were selected and their views solicited on arguments about circular construction to help establish common visions and further encourage sustainable behaviour across the sector. The study revealed that legislation by the government on the re-use and recycling threshold for every new project can substantially improve circularity within the built environment. More specifically, focus should be on smart dismantling of buildings and ways of optimising cost effective processes. This will enable fair competition between stakeholders and eventually lead to investments in innovative approaches for resource recovery from C&DW. Further incentives and appreciations from government should also be given to stakeholders who are innovating and setting benchmarks in circular construction. This can lead to harmonised technological and non-technological solutions, closed-loop material processes and a circular economy.
Circular economy seems a vital enabler for sustainable use of natural resources which is also important for achieving the 2030 agenda for sustainable development goals. Therefore, a special session ...addressing issues of “sustainable solutions and remarkable practices in circular economy focusing materials downstream” was held at the 16th International Conference on Waste Management and Technology, where researchers and attendees worldwide were convened to share their experiences and visions. Presentations focusing on many key points such as new strategies, innovative technologies, management methods, and practical cases were discussed during the session. Accordingly, this article compiled all these distinctive presentations and gave insights into the pathway of circular economy towards the sustainable development goals. We summarized that the transition to circular economy can keep the value of resources and products at a high level and minimize waste production; the focus of governmental policies and plans with the involvement of public-private-partnership on 3Rs (reduce, reuse, and recycle) helps to improve the use of natural resources and take a step ahead to approach or achieve the sustainability.
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