Recycling Of Powder Research Articles

Production of Ni Fe alloy by combined recycling of waste nickel-metal hydride batteries and waste toner powder

Production of Ni Fe alloy by combined recycling of waste nickel-metal hydride batteries and waste toner powder

Influence of polyethylene terephthalate (PET) flakes coating on the microstructure and mechanical properties of alkali activated composites

The objective of this research is the improvement of the mechanical strengths of the alkali activated slag composites with polyethylene terephthalate (PET) flakes content. The main drawback when large PET flakes (2–9 mm) are used in these composites is reduced adhesion between plastic surface and binding matrix. Therefore, the PET flakes were coated with two types of adhesives – based on polyvinyl acetate or sodium silicate solution, and then covered with fly ash, waste glass or slag powders. The microstructure (assessed by scanning electron microscopy) of interfacial transition zone between the PET flakes coated with waste glass and slag powders is denser than for uncoated PET flakes; this explains the improvement of the compressive strength of these mortars especially after longer curing times (28 days). The flexural strengths of the mortars with PET flakes are higher than for reference mortar (with sand aggregate) and the apparent density of the alkali activated composites with PET flakes are in general smaller than for the reference mortar. Thus, the coating of PET flakes improves the mechanical behaviour of mortars, preserving also a low apparent density. These results can lead to a wider recycling of PET waste, slag and waste glass powder, promoting circular economy and reducing the CO2 footprint without compromising the critical mechanical strength of mortars.

Immobilization of Pb2+ and Cd2+ in water by sodium alginate magnet-biochar composite and LCA evaluation

Heavy metal pollution in water is one of the most pressing global environmental problems. In this research, two kinds of phosphorus-modified walnut shell biochar gel beads (P@WSBGB) and ferromagnetic gel beads (P@FWSBGB) were prepared by an environmentally friendly method to solve this problem. The maximum adsorption capacities for Pb2+ were 197 mg g−1 for P@WSBGB and 180 mg g−1 for P@FWSBGB, and for Cd2+, they were 125 mg g−1 and 108 mg g−1, respectively. Although Fe3O4 loading reduced adsorption capacity by approximately 10 %, life cycle assessment(LCA) showed that P@FWSBGB had a lower environmental impact than P@WSBGB when adsorbing the same amount of 1 mg of Pb2+. This indicates that a reasonable load of Fe3O4 can reduce the environmental impact. Conversely, when adsorbing Cd2+, the result was the opposite, demonstrating that unreasonable loading increased the environmental impact. To ensure that Fe3O4 loading did not lead to increased environmental impacts, we further analyzed the data to determine the optimal Fe3O4 loading level. The optimal Fe3O4 loading was determined to be 12.5 % for Pb2+ adsorption and <12.5 % for Cd2+. The main adsorption mechanism is that the -COOH and -OH groups on the surface of biochar form complexes with Pb2+ and Cd2+. Ion exchange, electrostatic attraction, co-precipitation of phosphate, and physical adsorption also contribute to the removal of Pb2+ and Cd2+. In summary, this research solved the challenge of difficult recycling of biochar powder and provides new insights for the synthesis and condition optimization of magnetic adsorbents.

Recycling of waste glass powder: Effects on microstructure, mechanical properties and sustainability of seashell powder calcined sludge cement

The massive accumulation of waste seashells, waste sludge and waste glass not only occupies a large amount of land resources, leading to a shortage of land resources, but also causes serious soil-water-air composite pollution over a long period of time with the role of the surrounding environment, which poses a serious hazard to the ecological environment and public health. In this study, the effect patterns of waste glass powder (WGP) on the workability, mechanical properties, microstructure and carbon emission of seashell powder calcined sludge cement (SCSC) slurries prepared using waste sludge and waste seashells as supplementary cementitious materials in place of part of the cement clinker were investigated. The hydration process and microstructure of the materials were characterized by heat of hydration tests, thermogravimetry (TG-DTG), infrared Fourier transform (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the addition of WGP improved the fluidity of SCSC slurries and reduced the shear stress of SCSC slurries without changing the flow pattern of SCSC slurries, and all the slurries conformed to the power law model. The compressive strength of SCSC slurries increased by 25.26 % with 5 % WGP addition. The CO2 emissions per cubic meter of SCSC slurries were reduced by 4.43 %, 8.81 %, 13.5 % and 18.23 % for WGP additions of 5 %, 10 %, 15 % and 20 %, respectively. These results can provide a new way for the efficient resource utilization of waste seashells, waste sludge and waste glass, and reduce the CO2 emission during the cement production process, promoting the clean production of cement.

Study on the basic properties of iron tailings powder-desulfurization ash mine filling cementitious material

Abstract To realize the recycling of iron tailings powder (IP) and desulfurization ash (DA) and reduce the high preparation cost of mine filling cementitious materials (MCs), this article adopts sodium carbonate (SC) as an activator to prepare iron tailings powder-desulfurization ash mine filling cementitious materials (IDMC). The effects of IP content, DA content, SC content, and mirabilite content on the mechanical properties and setting time are experimentally investigated. The micromorphology and phase compositions of the hydration products of IDMC are analyzed and characterized by scanning electron microscopy and X-ray diffraction. The results show that the initial setting time of the IDMC is reduced by 0.87 and 21.83% when the mirabilite content is increased from 0 to 1% and 2%, respectively, and the compressive and flexural strengths of the IDMC are increased by 24.01 and 86.25% when the IP content is increased from 0 to 20%, respectively. The IP not only participates in the hydration reaction but also plays an aggregate filling effect, significantly improving the mechanical properties of the IDMC. The pozzolanic effect is gradually enhanced with the increase of the DA content, and the hydration degree of the IDMC increases. The SC as an activator can moderately reduce the shrinkage rate of the IDMC. Based on the multi-index optimization analysis, the optimal mix proportion of the IDMC is obtained, which provides an effective reference for the preparation of the novel MC.

Concentration of Silver from Recycling of Fine Powder of Wasted Videogame Printed Circuit Boards through Reverse Froth Flotation and Magnetic Separation Processes

Electronic waste stream grows day by day; printed circuit boards are a kind of solid waste that accounts for 6% of electronic waste. When these are discarded, they can cause soil, water, and air contamination; however, if recycled, these can be considered as a secondary source of metals. Physical comminution of printed circuit boards generates particles with sizes smaller than 250 µm, which are typically not included in the recycling process because they are considered as dust and unvaluable; nevertheless, precious and base metals can be found in these particles. The concentration of metals like silver, among others, from these particles can be achieved by reverse froth flotation in a flotation column followed by magnetic separation of the tails products. A mass balance of the flotation column feed, concentrate, and tails indicates that using a pulp modified with 5 ppm methyl isobutyl carbinol plus 5 g/ton oleic acid (both biodegradable reagents), the concentration of the products improved, resulting in recoveries of 86.13 and 13.87% in the concentrate and tails zones, respectively, with a grade of 74.4% in the tails flow. Magnetic separation of the tails product increases slightly the concentration of silver, reaching a silver grade of 74.5%, a recovery amount similar to those obtained employing complex and environmentally unfriendly processes.

Recycling of waste silicon powder from the photovoltaic industry into high performance porous Si@void@carbon anodes for Li-ion battery

To enhance the performance of lithium-ion battery anodes, this study leverages recycled diamond wire-cut silicon particles, a byproduct of the photovoltaic sector. These particles undergo purification through acid wash and pyrolysis to eliminate contaminants, thereby serving as potential anode materials. The inherent challenge with silicon involves its significant volumetric expansion during lithiation and delithiation, which hampers its viability for commercial applications. Addressing this, the research introduces a facile approach by synthesizing porous silicon (pSi) via the Ag-assisted chemical etching method. Subsequently, a distinctive yolk-shell porous silicon@void@carbon (pSi@V@C) structure is created using a sacrificial template approach, ensuring the formation of voids between the porous silicon core and the carbon shell. This configuration mitigates the detrimental effects of silicon's volume expansion while enhancing electrical conductivity through the carbon shell. The pSi@V@C composite exhibits promising electrochemical performance, demonstrated by an initial discharge capacity of 1826 mAh g-1 and a Coulombic efficiency of 68.6% at 0.1 A g-1. Remarkably, it maintains a capacity of 821.8 mAh g-1 after 550 cycles at 1 A g-1, with a retention rate of 90.4%.

The effect of powder recycling on the mechanical performance of laser powder bed fused stainless steel 316L

Powder recycling refers to the reuse of unused powder feedstock in the laser powder bed fusion (PBF-LB/M) process. This approach is crucial for the economic viability and sustainability of PBF-LB/M, as powder accounts for a large proportion of the total production cost. However, through powder recycling, the physical and chemical properties of powder are liable to change. This variation in powder properties can subsequently lead to knock-on effects on the mechanical properties of a fully built component.This research has investigated the changes that occur to stainless steel 316L (SS316L) powder as a result of recycling. This includes changes to powder size distribution (PSD), flowability, chemistry and phase composition. Likewise, the impact that these changes have will also be assessed in PBF-LB/M SS316L components manufactured from powders after different levels of recycling and subjected to alternative post processing routes such as hot isostatic pressing (HIP). This comprehensive investigation involves a thorough examination of both macro- and microstructures, encompassing detailed analyses of chemical composition, microstructural features, and defects. The study aims to elucidate differences in mechanical behaviour through a series of experiments, including uniaxial tensile tests, Charpy impact assessments, and low cycle fatigue (LCF) experiments. Additionally, the investigation will be complemented by pitting potential tests, providing a holistic understanding of the material's performance and characteristics.Although moderate changes to powder were observed for both PSD and chemistry, this was found to be negligible and not enough to result in any adverse changes to part performance. In addition, the microstructure of SS316L remained stable across differing levels of powder recycling. Whereas the porosity content increased marginally as the fine particle content of powder was reduced, this was not found to be sufficient to affect the LCF performance of the material. After powder recycling, increases in ductility and Young’s modulus were attributed to a reduction in oxides present in the microstructure, which were sources of localised damage and deformation.

EFFECT OF DEEP EUTECTIC SOLVENT PRETREATMENT ON DEVULCANIZATION OF WASTE RUBBER POWDER

ABSTRACT The recycling of waste rubber is very important for environmental protection, but the compatibility problem restricts the recycling and application of waste rubber powder (WRP). Devulcanization of WRP has been proven to be an effective method to improve the solubilization effect. The use of environmentally friendly nontoxic solvents can not only improve the devulcanization effect but also avoid secondary pollution. Thus, in this article, an environmentally friendly deep eutectic solvent (DES) is first prepared and then applied to the devulcanization treatment of WRP. The results show that the prepared DES has a positive devulcanization effect, and the devulcanization rate can reach 50%. The devulcanization mechanism can be divided into two aspects: (1) adsorption and removal of sulfur-containing low-molecular compounds and (2) destruction of the crosslinking structure and improvement of fluidity. Observation of the microstructure showed that the rougher the surface of the desulfurized rubber powder, the more conducive to the crosslinking reaction with the matrix material to form a uniform whole. The devulcanization mechanism of DES is divided into destroying the sulfur-containing cross-linked structure and adsorbing the sulfur-containing low-molecular compounds. The surface of WRP after DES treatment is rougher and more porous, which is beneficial to the crosslinking reaction with the matrix material. Finally, the optimum process conditions for the de-crosslinking effect are determined by orthogonal test as follows: liquid-solid ratio 15∶1, temperature 120°C, time 0.5 h.

Continuous recycling of diamond wire sawing silicon powder – electron beam melting coupled with continuous feeding technology

Diamond Wire Sawing Silicon Powder (DWSSP), as the current major photovoltaic solid waste, how to achieve large-scale recycling has become the focus of the industry’s attention. In this work, a novel approach characterized by enhanced purification, reduced energy consumption, and large-scale recycling capacities was proposed. Focusing on the secondary oxidation of powder, which is difficult to be solved by traditional methods, it was proposed to utilize the electron beam melting technology to achieve rapid melting by its higher energy density and vacuum degree, and reduced the oxygen impurity by 98.4 %. Then, through the prefabricated molten pool and continuous feeding technology, substantially increased the yield of high-purity silicon (91 %) and reduced the energy consumption per unit of production (19.01 kW/kg). Finally, for the purified silicon ingot, the content of major metal impurities was reduced to less than 5 ppmw, and the content of some volatile metal impurities was reduced to less than 1 ppmw. This research demonstrate the feasibility of electron beam melting coupled with continuous feeding technology in realizing low-energy, large-scale and high-purity recycling of DWSSP.

Recycling of Spent CuCrZr Powder by Laser Powder Bed Fusion: Microstructure Evolution and Properties

Recycling of Spent CuCrZr Powder by Laser Powder Bed Fusion: Microstructure Evolution and Properties

Process development and techno-economic analysis for mechanochemical recycling of poly(ethylene terephthalate)

Chemical recycling of consumer plastics has garnered great attention recently towards achieving circular economy goals. Particularly in the case of PET waste, mechanochemical depolymerization in ball mill reactors has been identified as a very promising technology due to the high conversion rates achieved under mild conditions. While the absence of solvents in the reaction mixture reduces significant separation costs, mechanochemical depolymerization still presents challenges with respect to the efficient separation and purification of monomers. Thus, meticulous experiments, process modeling, and simulations are essential for demonstrating the separation and purification of monomers. In this study, we present the lab-scale separation process flow for the recovery of terephthalic acid (TPA) and ethylene glycol (EG) from mechanochemically depolymerized polyethylene terephthalate (PET). We additionally examine the use recycling of ideal PET powder and commercial samples (e.g., PET fibers, bottles, and food containers) as feedstocks. The process parameters are optimized to achieve 97 %+ of monomer recovery with 99 %+ purity. The complete recovery of EG, and recycling of process water enables a ‘zero-liquid discharge’ process design. Subsequently, we conduct a techno-economic analysis (TEA) to evaluate the economic potential of the proposed sequence, which resulted in a positive net present value (NPV) for the different scenarios and a minimum selling price (MSP) of $0.99/kg. Finally, we compare the economic potential of mechanochemical recycling of PET to fossil-based production and other recycling methodologies based on economic metrics.

Study on the recycling of 100Cr6 powder by plasma spheroidization for Laser Powder Bed Fusion

Additive Manufacturing (AM) of steel parts is crucial in various industries such as medical, energy and transport. Laser Powder Bed Fusion (L-PBF) is a commonly used technique for producing such parts, but it can alter the properties of the unconsumed powder. This study aims to investigate the recycling of oxidized 100Cr6 powder using a plasma spheroidization process, focusing on its physical and chemical properties. The experiments reveal that the powder feed rate during spheroidization has an impact on the physical properties of the recycled powder, an optimized powder feed rate is found. Different washing and drying conditions are applied to the spheroidized powder and their influence on the powder's chemical composition is analysed through oxygen measurement. One of the washing and drying condition led to oxygen content even lower than the commercial powder. Additionally, three different hydrogen ratios in the plasma during the spheroidization process are investigated and it is found that increasing the hydrogen ratio can reduce the oxygen content in the processed powders.

Recycling of clay brick powder to improve the microstructure and mechanical properties of oil well cement pastes at high temperature and high pressure conditions

In oil well cementing involving high temperature and high pressure (HTHP), silica sources are usually incorporated into oil well cement to prevent its strength retrogression. This paper aims to use recycled clay brick powder (CBP), a silica-enriched material, as an alternative to the use of silica flour (SF) to inhibit the strength retrogression of the cement pastes after thermal cycling curing at 300 °C/13.0 MPa. Pure pastes (G), blended pastes with 40 wt% SF (40SF) and blended pastes with 40 wt% CBP (40CBP) were prepared to comparative analysis. The results showed that 40CBP and 40SF exhibited lower compressive strength and poorer pore structure than the G samples at 50 °C. However, the incorporation of CBP could effectively improve the compressive strength of the cement at 300 °C/13.0 MPa compared to that of the G paste. Mineralogical analysis indicated that xonotlite phases were the main crystalline phases in 40CBP and 40SF after thermal cycling curing. Compared to reinhardbraunsite in G samples, xonotlite could improve the pore structure and make the microstructure denser. In addition, there are some hibschite phases in 40CBP, which may make its compressive strength slightly lower than 40SF. Nevertheless, the environmental impact and cost analysis showed that the energy intensity and CO2 emissions of 40CBP were significantly lower than those of G and 40SF, and it had great cost advantages. This study is expected to provide some help in the rational recycling of CBP and reducing the CO2 emissions in cement production.

Recycling of dolomite powder in clay bricks: Effects on characteristics and gas release

This paper evaluates the influence of dolomite industrial waste (dolomite powder (DP) on the properties, structure and durability of clay bricks. Four clay samples fired at 900 °C and 1000 °C containing 0 wt%, 10 wt%, 20 wt% and 30 wt% DP were prepared and investigated to measure their properties (shrinkage, bulk density, water absorption, thermal conductivity, apparent porosity, compressive strength), structure and durability (compressive strength after freeze thaw). The results showed a decrease in bulk density, compressive strength and an increase in apparent porosity and water absorption of the clay bricks produced by mixing 70–90 wt% clay and 10–30 wt% DP compared to the control bricks. Also, a significant improvement in the thermal conductivity of clay bricks produced by 70 wt% clay and 30 wt% DP (0.407–0.420 W/(m⋅K) compared to the control clay bricks (0.839–0.845 W/(m⋅K). As clay mixtures contain DP (chemical composition: CaO-49.68%, Loi-42.80%), CO2 emissions during the firing process are increased (decarbonation reactions). However, the thermal conductivity of the fired clay bricks is significantly reduced (to 50%). These results showed the potential of DP for the manufacturing of clay masonry units.

Research of synergistic effect of magnetic powder and biosurfactant in pollutants removal and membrane fouling alleviation

This study constructed a rhamnolipid-magnetic membrane reactor (RL-MMBR) coupled system to investigate the effects of RL and magnetic powder on membrane fouling alleviation and wastewater treatment efficiency. The optimal concentration was determined by comparing the effects of different concentrations of RL and magnetic powder as well as single and mixed injection on the operation performance. The effects of RL and magnetic powder on pollutant degradation and membrane fouling were investigated at the optimum concentration (300 mg/L RL + 120 mg/L Fe3O4). It was found that the time for TMP to reach 30 kpa in RL-MMBR was 7 days longer than that in CMBR. In the RL-MMBR, the concentration of SMP declined from 13.22 mg/L to 6.75 mg/L and the concentration of LB-EPS decreased from 14.37 mg/L to 7.95 mg/L, and their concentration in RL-MMBR was gradually lower than that in CMBR. But the concentration of TB-EPS in RL-MMBR was always greater than that of CMBR. The sludge particle size in RL-MMBR was gradually larger than that in CMBR. The overall COD removal rate of RL-MMBR (95 %-98 %) was better than that of CMBR (91 %-95 %). The synergistic effect increased the species abundance and diversity of microorganisms in the sludge mixture, but reduced the enrichment of microorganisms on the membrane, especially reduced the adhesion of high-viscosity microorganism Proteobacteria to the membrane. The RL-MMBR coupled system improved the degradation efficiency and alleviated the membrane fouling. In addition, the direct dosing of the agent increased the convenience of operation, the recycling of the magnetic powder reduced the operating cost, and the reaction had no secondary pollution. This provided new ideas and theoretical guidance for solving membrane fouling problems in MBR treatment of domestic sewage.

Recycling of waste magnesia refractory brick powder in preparing magnesium phosphate cement mortar: Hydration activity, mechanical properties and long-term performance

Waste magnesia refractory bricks (MRBs) that remain from industrial production are landfilled in large quantities or recovered to prepare recycled bricks with low added value. In consideration of the significant level of magnesia in waste bricks, this work proposes to extract and recover magnesia from spent bricks for manufacturing magnesium phosphate cement mortar (MPCM). The essential attributes of recycled magnesia (RM) and its influence on the workability, hydration temperature rise, mechanical properties, phase evolution, long-term performance and microstructure of MPCM were analyzed. The results reveal that RM significantly prolongs the setting time and reduces the overall hydration heat release, which is beneficial to the application in large-scale engineering. The compressive strength of MPCM prepared by RM (MPCMRM) initially grew and then decrease with the increase of magnesia to phosphate ratio (M/P ratio). The optimal performance was observed at M/P = 4, and the compressive strength cured for 3 h and 28 d were 39.1 MPa and 68.5 MPa respectively. While the mechanical properties of MPCMRM were marginally inferior to those of dead-burned magnesia (DM), it was found to satisfy the early and long-term strength requirements of engineering repair materials. In addition, MPCMRM did not generate new mineral phases, and the crystal morphology of hydration products (struvite) was worse than that of mortar prepared by DM. MPCMRM also exhibits excellent water resistance and volume stability due to the crystal characteristics of low-activity RM. It seems that RM can completely replace DM to prepare MPCM and achieve satisfactory performance, which not only reduces the cost of repair materials, but also provides a fresh approach for the recycling of waste MRBs.

A novel acid-free leaching route of recovering Li2CO3 and FePO4 from spent LiFePO4 black powder

With the rapid increase in the usage of lithium ion batteries, recovering Li2CO3 from LiFePO4 black powder has become an issue of public concern. Nowadays, the widely used acid leaching technology has some obvious disadvantages, such as complex recovery process, serious equipment corrosion and unavoidable secondary pollution. In this work, a novel acid-free leaching route of recovering Li2CO3 and FePO4 from LiFePO4 black powder is proposed. This novel route does not include inorganic or organic acid leaching, complex pH adjustment and wastewater treatment processes. After optimizing the technological conditions, Li2CO3 and FePO4 with high purity are recovered with high recovery rate of over 96%. Then, the recovered Li2CO3 and FePO4 are used as iron and lithium sources to regenerate LiFePO4 and the electrochemical performances are compared in detail. When the molar ratio of Li2CO3:FePO4:C6H12O6 (glucose) is 1.03:2:0.35, the regenerated LiFePO4 (R-LFP-0.35) cathode displays the optimal electrochemical performance with the discharge capacity of 163.9 mAh g−1 at 0.1 C, 120 mAh g−1 at 4 C and excellent capacity retention ratio of 98.0% after 100 cycles at 0.2 C. This work provides a new green and environmentally friendly strategy for the recycling of LiFePO4 black powder.

In situ monitoring the effects of Ti6Al4V powder oxidation during laser powder bed fusion additive manufacturing

Making laser powder bed fusion (L-PBF) additive manufacturing process sustainable requires effective powder recycling. Recycling of Ti6Al4V powder in L-PBF can lead to powder oxidation, however, such impact on laser-matter interactions, process, and defect dynamics during L-PBF are not well understood. This study reveals and quantifies the effects of processing Ti6Al4V powders with low (0.12 wt%) and high (0.40 wt%) oxygen content during multilayer thin-wall L-PBF using in situ high speed synchrotron X-ray imaging. Our results reveal that high oxygen content Ti6Al4V powder can reduce melt ejections, surface roughness, and defect population in the built parts. With increasing oxygen content in the part, there is an increase in microhardness due to solid solution strengthening and no significant change in the microstructure is evident.

Recycling of waste marble powder and waste colemanite in ternary-blended green geopolymer composites: Mechanical, durability and microstructural properties

The objective of this investigation was to identify the effects of curing temperature, cement clinker aggregate, waste colemanite (WCM) and waste marble powder (WMP), as well as their interaction, on the early physico-mechanical properties, microstructure, and high-temperature resistance of geopolymer composites (GC). Ground granulated blast furnace slag (GBFS), metakaolin (MK), and silica fume (SF) were employed as precursors for the production of GC. These materials were activated using a solution of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). In the fabrication of the GC, fillers such as WMP, WCM, and cement clinker aggregate (CCA) were employed. Four GC mixes were generated and cured for 8 h at curing temperatures of ambient (20 °C), 60 °C, and 90 °C. Investigations were conducted into how curing temperature, WMP, and CCA affected the GC's compressive, flexural strength, water absorption, dry unit weight, porosity, and sorptivity. The resulting mixes' performance at high temperatures was also assessed. Using SEM, microstructure investigations of GC mixes made for the study were also carried out. The obtained results indicated that the mixture M2 containing 100 kg/m3 of WMP and 750 kg/m3 of CCA exhibited the greatest compressive strength of 24.60, 55.60 and 68.80 MPa at ambient, 60 °C and 90 °C respectively compared the other GC mixtures. Moreover, the compressive strength of the M1 mixture enhanced by 190.65% and 239.56%, at 60 °C and 90 °C respectively compared to ambient-cured samples. Ambient cured mixture M4 that contains maximum WBM and minimum CCA content exhibited the strength enhancement of 54.01, 46.52 and 29.95% at 150, 350, and 550 °C respectively.