Journal of Material Cycles and Waste Management最新文献

Cement industries generate massive amounts of greenhouse gas (GHG) emissions. As a fast-growing economy in Southeast Asia, Indonesia consumed more than 62 Mtons of cement in 2020. To cut down the impacts from extensive resource extraction and GHG emissions from cement industries, utilizing secondary raw materials such as concrete is an option to simultaneously reduce the limestone requirement at cement plants. This study aims to estimate yearly concrete waste flow from residential building stocks and the environmental impacts of utilizing those concrete waste in a cement-producing region in West Java, Indonesia by combining dynamic material flow analysis, stock modeling, and life cycle assessment (LCA). We found Cirebon Regency’s residential buildings would accumulate 46.2 Mtons concrete stocks by 2050. The estimated concrete waste from demolished residential buildings in Cirebon would reach up to 2 Mtons by 2050 depending on building lifetimes. At the baseline scenario, environmental impacts per ton cement are 647.35 kg CO₂ eq. of Global Warming Potential (GWP), 90.25 kg C deficit of Land Use (LU), and 4,707.24 MJ of Cumulative Energy Demand (CED). By utilizing 1 Mtons of recycled concrete, the cement production facility would decrease those values by up to 5.42 kg CO₂ eq./ton cement, 0.09 kg C deficit/ton cement, and 0.43 MJ/ton cement, respectively. Our results help inform decision-makers to formulate policy options on utilizing concrete waste to reduce cement production environmental impacts.

Spent hydrodesulfurization catalyst (HDS) is considered as the important secondary resource for Mo and Ni. The separation of Mo from HDS was usually conducted by soda roasting and water leaching, while Ni remained in the leached residue. This study proposed a method to recover Ni from leached residue by H₂SO₄ leaching and solvent extraction, and Ni was recycled in the form of NiO. The results showed that the optimum Ni leaching process were conducted using 30% H₂SO₄ with liquid–solid ratio of 10 at 70 ℃ for 120 min. The optimal extraction was accomplished using 30% di-(2-ethylhexyl) phosphate (P204) saponification at pH value 6.0 with organic/aqueous (O/A ratio) of 1 for 1 min. Additionally, 20% H₂SO₄ could be used to strip Ni from organic phase with O/A ratio of 10. Finally, NiSO₄ was calcined at 850 ℃ for 1.0 h to obtain NiO. The Ni leaching kinetic analysis showed that the activation energy of Ni leaching process was 16.10 kJ/mol, which was accorded with the shrinkage unreacted kernel model controlled by internal diffusion. This study provided an alternative method to recycle Ni and given a deeper insight to the leaching mechanism during H₂SO₄ leaching Ni from spent catalyst.

Graphical abstract

Chlorine-containing Ti-extraction blast furnace slag (TEBFS) is a solid waste produced during titanium removal from high-titanium blast furnace slag. Large amounts of TEBFS affect the local environment and severely limit further process development. A lightweight calcium silicate board was successfully prepared via hydrothermal synthesis. When the mass ratio of TEBFS: Portland cement: diatomite: calcium hydroxide: quartz was 46∶15∶17∶13.9∶8.1, the bulk density, bending strength, and thermal conductivity of the sample were 1.23 g/cm³, 8.2 MPa, and 0.299 W/(m·K), respectively. The overall sample performance met the D1.3 category requirements in the national standard. After being immersed in water with stirring at 30 °C for 60 min, the sample exhibited a curing chlorine efficiency of 40.6%. Mechanical grinding increased slag activity and sample performance. Grinding for 3 min, the activity index of the slag was 72.74%, and the bending strength of the sample increased to 8.7 MPa. Increasing the pozzolanic activity of the slag and reducing the amount of aggregate produced between particles had a positive effect on optimizing sample performance. This paper provides a feasible method for the diversification and clean utilization of TEBFS.

Graphical Abstract

In the process of fly ash melting by plasma technology, additives are usually added to improve the melting characteristics of fly ash and reduce the leaching toxicity of heavy metals, thus reduce energy consumption and pollution risk. However, the effect of additives on the migration and transformation of chlorine salts in fly ash during the melting process is rarely reported. In this study, the effect of additives (SiO₂, Al, B₂O₃, bottom slag collected from the same incinerator) on the migration and transformation of chlorine was investigated by experiments and thermodynamic analysis, and the promotion mechanism of water vapor atmosphere on the migration and transformation of chlorine was also discussed. Soluble chloride is transformed into insoluble chloride during plasma melting of fly ash, B₂O₃ and Al play a role in solidification of the chloride in fly ash, SiO₂ promotes the volatilization of heavy metal chloride salts, the co-melting of fly ash and its homologous bottom ash significantly promotes the reduction of soluble chloride in fly ash, and the content of soluble chloride in fly ash is reduced from 22.39% to 2.2% with the addition of 20% bottom ash. Steam can be used as an inducer and vaporizer to further promote the chlorine volatilization.

Ferrochrome slag aggregate concrete (FCSAC) incorporated with fly ash offers multiple benefits over FCSAC alone and natural aggregate concrete (NAC) in terms of durability and environmental impacts, without sacrificing essential strength. However, structural behavior of fly ash-based FCSAC is poorly understood due to lack of investigations. This study examined shear performance of 16 full-scale reinforced concrete beams. FCSAC was prepared using 100% FCS coarse aggregate and fly ash as fractional cement replacement (0%, 20% and 30%). To completely comprehend the shear resistance mechanism of FCSAC, eight beams were built without shear reinforcement and eight with it. NAC and FCSAC (without fly ash) were considered as the reference beams. Existing design guidelines and fracture mechanics approaches were verified to predict shear capacity of FCSAC beams. The findings of the study revealed that fly ash incorporated FCSAC beam exhibited fewer cracks and higher shear capacity (about 7%) than NAC beam, but lower strength (about 8%) than FCSAC without fly ash beam. Shear provisions outlined in CSA provisions and fracture model by Gastebled and May could be adopted for FCSAC (with or without fly ash) beams without risk. This research demonstrates that fly ash-based FCSAC can be utilized safely for structural purposes.

The sugarcane bagasse (SCB) is the most abundant residue of the sugar and alcohol industry and its use is predominantly in these same industries as a source of energy through burning. This work aims to diversify the proposals for the use of this residue; thus, the use of SCB in the alumina-supported nickel catalysts synthesis was investigated. Two routes were researched using SCB: one, the SCB was used in the alumina (catalytic support) synthesis to obtain the dimensionally predetermined materials and another to get powder materials. The materials were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), N₂ physisorption at 77 K, energy-dispersive X-ray spectroscopy (EDX), and hydrogen temperature-programmed reduction (H₂-TPR). The presence of SCB in the synthesis of powder materials facilitated the incorporation of nickel particles into the crystalline lattice of the support, decreasing active nickel content for catalytic. On the other hand, the pre-dimensioned catalytic materials exhibited higher crystallinity, lower nickel oxide reduction temperature and greater disposal of active nickel, resulting in higher production of ordered carbon (carbon nanotubes) and H₂ COx-free under milder conditions in the methane decomposition reaction at 500 °C for 30 min.

Pressure to increase the renewable energy matrix motivates the search for new energy sources. Pulp and paper mills have been constantly expanding in Brazil, and to ensure their competitiveness, new processes should be established both in terms of reducing the waste discarded in landfills, as well as the substitution of fossil fuels used in the mills. The present work aims to evaluate the energy potential of primary sludge (PS), secondary sludge (SS), a mixture of primary and secondary sludge (MS) and tree bark (B) generated in a Brazilian TMP mill. Characterization of all biomasses was performed. Moisture content, higher, lower, and net heating value, elemental, structural, and immediate composition, thermogravimetric analysis and quantification of minerals and metals were determined The bark presented the highest higher heating value (HHV) (18.90 MJ kg⁻¹), while the secondary sludge had the lowest HHV (12.45 MJ kg⁻¹). The high concentration of ash in the sludges PS (26.58%), SS (40.46%) and MS (25.78%) negatively affected their heating value. The sludges also showed high moisture content, which made their burning without a previous drying stage unattractive. Nevertheless, the sludges and the bark are rich in carbon which makes them attractive for use as biomasses for energy generation.

Anaerobic digestion under hydrogen (H₂)/carbon dioxide (CO₂)-versus nitrogen (N₂)-purged conditions was examined for the potential for biogas enhancement in the presence of polylactic acid. With or without polylactic acid, H₂/CO₂ purging demonstrated a 25% higher methane (CH₄) production, reaching approximately 160 NmL CH₄/g VS_add compared to N₂ purging. When H₂/CO₂ was purged with polylactic acid, there was reduced dominance of Spirochaetales, resulting in fewer intermediates that caused a similar amount of CH₄ yield. Despite similar CH₄ yield to conditions without polylactic acid, verification through Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) confirmed extensive polylactic acid decomposition. DSC revealed double melting peaks at 151.8 °C and 156.1 °C, indicating increased crystallinity and vigorous polylactic acid decomposition, particularly in the amorphous region, under H₂/CO₂ purging. This aligned with the decrease in the FTIR carbonyl index, visually confirmed using SEM. Metagenome sequencing highlighted the prevalence of hydrogenotrophic methanogens, Anaerolineales, Bacteroidales, and Thermoanaerobacterales under H₂/CO₂ purging, demonstrating higher polylactic acid degradation compared to N₂ purging conditions. This study revealed a potential for biogas upgrading with waste management of polylactic acid.

Phosphogypsum backfill technology is an important way of backfill mining. However, phosphogypsum has problems such as poor water resistance and low strength. Therefore, in this study, phosphogypsum and carbide slag (CS) were mixed to form the phosphogypsum backfill (PB). The effects of the CS content on the workability, mechanical properties, and microstructure of PB were studied by means of pH value, bleeding rate, fluidity, strength, water resistance, SEM, and XRD. The results showed that the incorporation of CS significantly improved the working performance. The softening coefficient initially climbed and subsequently declined. Peak stress and MOE of PB showed a trend of rise-fall, reaching the peak when CS content was 10%. The damage evolution process of PB was revealed. The process of energy dissipation of PB during uniaxial compression showed a law of increasing and then decreasing with increasing CS dosage. The test group composed of 90% phosphogypsum and 10% CS was the best experimental scheme. These results were hoped to provide guidance for the comprehensive utilization of phosphogypsum and CS and the theoretical basis for the application of PB in backfill mining.

Rapid economic growth, urbanization, and shifting lifestyles have triggered a global plastic pollution crisis, threatening the environment. Understanding consumer behavior is crucial for implementing a circular economy (CE) for plastics aimed at minimizing waste, as psychological factors can hinder technical solutions. This paper aims to pinpoint the determinants influencing young consumer intentions in plastic waste minimization (PWM). An extended Theory of Planned Behavior (TPB) and Structural Equation Modeling were applied to explore antecedents of behavioral intention of 677 young consumers in Vietnam regarding PWM. The study reveals that attitude is the most significant positive factor influencing consumers' behavioral intention to lower plastic consumption, followed by perceived behavioral control and the effect of charges on plastic utensils. In contrast to the other TPB constructs, the subjective norm, which fails to meet the criteria for passing the hypothesis test, is determined to be an insignificant predictor of consumers' intention toward PWM. Furthermore, the study also confirms the significant correlations between consumer characteristics (gender, field of study, levels of education program, and the status of pedagogical training) and the attitude, subjective norm, perceived behavioral control, effect of charges on plastic utensils, and behavioral intention. This study thereby enriches the existing literature on PWM, offering insights that can assist governments and organizations in comprehending consumer intentions, contributing to the success of CE projects.