Journal of Material Cycles and Waste Management最新文献

Mining is a cornerstone of the productive system, particularly in sectors, such as renewable energy and electronic equipment production, where its significance is anticipated to grow in the coming years. Aligned with the principles of Nature-Based Solutions and Zero Waste policies, recycling mining waste as soil amendments could concurrently restore degraded areas and reduce the disposal of mining waste. In this context, we aimed to remediate a post-mining soil primarily impacted by heavy metal pollution using an alkaline waste generated in dunite exploitation, either in combination with compost or independently in field conditions. The objectives were to minimize heavy metal(loid)s mobility (As, Cu, Cd, Ni, Pb, and Se), to improve soil health, and stimulate plant growth (phytoremediation, Lolium perenne L. was used). Results revealed that the combination of dunite and compost successfully reduced the concentrations of available Cu and Ni in the soil by more than four times, significantly enhanced soil properties, and promoted the harvest of a greater biomass. Additionally, Lolium perenne L. demonstrated phytostabilizing capacity for Cu and Ni in the soil treated with the amendments. In conclusion, the utilization of combined dunite-based and organic amendments proves to be a favorable strategy for restoring polluted post-mining soils.

Geopolymers with the inclusion of waste materials, viz., fly ash and slag, have been considered for various applications as a substitute for non-eco-friendly conventional binder, i.e., cement. Nevertheless, none of the studies have focused on soil stabilization using novel alkali-activated precursors—fly ash and calcium-rich eggshell powder with different curing temperatures. The objective of the present study is to analyze the effect of alkali-activated fly ash and eggshell powder on the durability of reference soft soil mix. The sodium silicate and sodium hydroxide solution were used to activate the precursors. The specimens, with varying percentages of precursors (10%, 20%, 30%, 40%, and 50%), were heated for 7 days at 25 °C, 50 °C, and 80 °C before subjecting to 12 wetting–drying cycles. The outcomes of the investigation show that the residual strength increases with the increase in geopolymer concentration following a similar pattern of 7-day compressive strength. A decrease in the weight loss of geopolymer-treated clay was detected for the specimens earlier cured at 50 °C. Further, the cost analysis suggested that the eggshell powder–fly ash geopolymer is a much cheaper binder than conventional cement concrete.

Acid tar (AT) is a distinct black viscous waste from the petrochemical industry that retains hazardous characteristics decades after creation. It is defined as an emulsion of various organic compounds, sulfuric acid, and water. Due to specific chemical composition and physical properties, the best available technique for the treatment of AT is not determined. This paper investigates the treatment of AT by CaO, resulting in its complete physicochemical transformation into a dry powder with the characteristics of inorganic material. Waste characterization of AT and obtained powder (including metals, PAH, BTEX, total hydrocarbon content, and EN12457-4 leaching test), their comparative FT-IR and SEM–EDS analyses, and XRD analysis of the powder revealed that the transformation is a complex process involving Ca(OH)₂ formation, evaporation of water and BTEX, and degradation of aromatic and unsaturated hydrocarbons. The remained organic phase is encapsulated under Ca(OH)₂ and CaCO₃ layers forming “organic core—inorganic shell” micron-sized particles, rendering the powder suitable for further treatment. This was confirmed by solidification/stabilization treatment of AT and obtained powder using the same amount of cement and pozzolanic binder. In contrast to AT solidificates, the powder solidificates possess unconfined compressive strength above the required value and characteristics of inert waste.

The reuse of construction and demolition waste (CDW) is of great significance for the reasonable treatment of urban waste and the protection of soil. CDW fines less than 10 mm in size were used to explore the application in improving clay loam soil and as plant-growing media. Four sizes of CDW were mixed with clay loam soil in three mass proportions to plant 1-year-old Duranta repens seedlings with clay loam soil (C1) and 100% CDW fines (C2) as the controls. CDW fines application increased net carbon assimilation, leaf size, leaf nutrients, and plant growth with the best addition of 3–6 mm size and 35% mass proportion (T5) for clay loam. The branch number and leaf area in 3–6 mm group were 32.8% and 263.9% higher than those in C1, and 110.8% and 374.2% higher than those in C2. On average, the assimilation rate in T5 was 43.8% higher than that in the controls, while the respiration rate was 44.6% lower, indicating that plants in the T5 fixed more carbon. We suggest that CDW fines have the potential to be plant cultivation substrate and the addition ratio depends on the soil property. Our research provides an effective solution for the disposal of CDW fines.

In response to resource scarcity and environmental challenges, sustainable practices, particularly in recycling and reusing waste materials, have become crucial. This paper reviews the utilization of porous glass, particularly made from recycled waste glass, for manufacturing and environmental applications. Porous glass features a broad size range of tiny pores, offering advantages in recycling due to its inertness, sorption capabilities, and versatility. It can be produced through phase separation, sol–gel, hydrothermal methods, and the use of foaming agents, offering a large surface area and high sorption efficiency. The adsorption capacity, flexibility in enhancing material properties, and reusability of porous glass allow it to be applied in diverse environmental roles, such as contaminant removal from water and wastewater. The controlled release of phosphate from phosphate-porous glass adsorbent enables its use in fertilizing plants while minimizing excess phosphate release into the water bodies. Its unique physicochemical properties also make it suitable for use in construction sectors. Our findings highlight the porous glass's potential to significantly contribute to glass recycling, reduce landfill airspace, and support sustainable material usage. The study underscores the role of porous glass in advancing waste glass recycling and promoting sustainable environmental practices.

In this study, the characteristics of recycled aggregate concrete according to the mixing ratio of recycled coarse aggregate(RCA) were analyzed for different design strengths to explore the use of recycled materials in the production of ready-mixed concrete. The results show that, depending on the ratio of recycled aggregate, the compressive strength is similar to that of normal concrete and does not deteriorate. Therefore, it is possible to achieve a target design strength. Furthermore, if the ratio of recycled coarse aggregate for concrete is up to 25% of the total aggregate amount (50% of the total coarse aggregate), slump does not cause problems. Our findings show that the higher the design standard strength, the greater the amount of powder, and the more stringent the management of slump reduction, unit quantity, and performance necessary. The obtained results show that recycled aggregate can be used to produce ready-mixed concrete after adjusting its mixing ratio and concrete mix proportions.

In this study, polyethylene terephthalate (PET) bottles are transformed into filament for 3D printing using an open-source design. Three different strip widths (8 mm, 9 mm, and 10 mm) of thickness 0.25 mm were investigated and the 1.60 mm nozzle extruder produced filaments with a hollow cross section of mean diameter 1.80 mm and a tolerance of − 0.03 mm and + 0.04 mm at a temperature of 245 °C. The study revealed that the 10 mm strip width is best suited for bottles of 0.25 mm thickness for the production of 1.75 mm filaments of 100% high-quality and ethical standards. Test specimens were 3D printed at three different flow rates (100%, 125%, and 150%), and the tensile strengths were evaluated using the ASTM D638 test standard. The maximum tensile strength (31.92 MPa) was obtained from the 10 mm strip width filament at a flow rate of 150%, and the ductility of all the specimens was less than 5%. Further test revealed that PLA has a tensile strength nearly as twice as the PET filament. However, while there is currently no virgin PET filament on the market, the recycle PET filament is a suitable substitute for commercial filaments for 3D products with tensile strength in the range of 30 MPa.

Thermochemical conversion is a possible solution for effective disposal of sludge. In this paper, we report physico-chemical characterization and pyrolysis kinetics of three sludges, viz. biological (BS), chemical (CS), and oily sludge (OS). An attempt was made to deduce the chemical composition of sludges using XPS and FTIR analysis. Pyrolysis of sludges was studied using a Thermo-Gravimetric Analyzer (TGA). The TGA data was analysed using four isoconversional models (viz. OFW, KAS, Starink and Vyazovkin_AIC) for deduction of kinetic triplet, viz. activation energy, pre-exponential factors and reaction mechanism. For all sludges, the activation energy increased with conversion. The ranges of activation energies were: BS = 87.82–303.89, CS = 72.12–200.62, OS = 67.26–130.99 kJ/mol. The ranges of pre-exponential factors were BS = 2.09E + 09 to 1.79 E + 27, CS = 2.31E + 04 to 9.72E + 13, OS = 1.20E + 06 to 5.99E + 11. s^–1. High pre-exponential factors indicated high reactivity of sludges during thermal conversion. The predominant mechanism of thermal conversion of all sludges was an order-based reaction (F1/F2/F3). This indicated homology among the components present in the organic matter in sludge. In essence, pyrolysis shows high promise as a useful pretreatment for the safe disposal of sludges of different origins.

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Our goal was to explore the potential of bamboo as a solid biomass fuel through torrefaction and compare it with previous studies on unused forest biomass chips. The torrefaction process involved temperatures of 230–310 °C increased in 20 °C intervals, each lasting an hour. Significant differences in mass were evident between the 270 and 290 °C processing conditions during thermogravimetric analysis. Differential thermogravimetric analysis showed that both the initial and peak temperatures increased with higher processing temperatures. The mass yield ranged from 32.37 to 76.74%, and the calorific value varied from 19.50 MJ/kg to 28.68 MJ/kg. Compared to previous studies on the torrefaction of Liriodendron tulipifera and Pinus koraiensis, bamboo exhibited a relatively lower mass yield and calorific value; however, it was considered suitable compared to unused forest biomass wood chips. The optimal conditions for torrefaction were found to be 270 °C during processing.

Phosphogypsum (PG, CaSO₄·2H₂O), impure gypsum with phosphate residues, is a by-product of fertilizer industry. Due to calcium and phosphorus in its structure, PG can be evaluated for synthetic hydroxyapatite (HAp) production. This study provides a two-step reaction sequence for PG-derived synthetic HAp production. Synthesized HAp (s-HAp) particles were calcined at 900 °C for 4 h, followed by characterization studies with respect to commercial bone ash (CBA) sample to be evaluated as its substitute in bone china industry. Ca/P ratio (wt%) of the samples was investigated by microwave-assisted temperature-controlled acid digestion, followed by ICP-OES analysis. Crystallinity of the samples was analyzed by XRD, and morphological structure was investigated by SEM–EDS analyses. ICP–OES analyses revealed that s-HAp and CBA samples have similar Ca/P ratio, 2.0979 for s-HAp and 2.0917 for CBA samples, respectively. Low-intensity β-TCP phases in the XRD patterns of s-HAp samples revealed low crystalline structure. SEM images indicated a uniform distribution with spherical-like morphology in CBA samples, however, a layer-by-layer morphology and amorphous structure was observed in s-HAP samples. Structural and morphological differences indicate that PG-derived s-HAp samples require purification processes and reaction parameters should be further developed to increase yield. However, this study provides a high potential for a novel approach of an industrial scale valorization strategy for PG. Because the supply–demand cycle is price dependent, the availability of phosphorus in agriculture as a raw material has been a major concern for the usage of phosphate rock. Novel methods for substitute supplies of phosphorus in agricultural applications have been suggested. While HAp is a common ceramic material, its application as a substitute for phosphorus fertilizer is still in its infancy. PG has great potential as a raw material for the synthesis of hydroxyapatite and ammonium sulfate. Large-scale PG production in the phosphoric acid industry puts pressure on research to develop alternate methods for using PG aggregate resources in an economical and environmentally responsible way. The use of PG as a calcium and phosphorus precursor in the synthesis of HAp will result in an economical raw material and an effective waste management plan.