Utilization and life cycle assessment of low activity solid waste as cementitious materials: A case study of titanium slag and granulated blast furnace slag

The Synergistic Effect of Limestone Powder and Rice Husk Ash on the Mechanical Properties of Cement-Based Materials

Fully utilizing solid waste as supplementary cementitious materials (SCMs) while ensuring the mechanical properties of cement-based materials is one of the pathways for carbon reduction in the cement industry. Understanding the effects of the two solid wastes-limestone powder (LP) and rice husk ash (RHA) on the mechanical properties of cement-based materials is of great significance for their application in concrete. This study investigates the impact of LP and RHA on the strength of cement mortar at various ages and the microhardness of hardened cement paste. The results suggest that two materials have a certain synergistic effect on the mechanical properties of the cementitious materials. The addition of RHA effectively addresses the issues of slow strength development, insufficient late-stage strength of the cementitious material, and the low strength blended with a large amount of LP, while a suitable amount of LP can promote the strength increase in the cement-RHA system. Based on the comprehensive analysis of compressive strength and microhardness, the optimal solution for achieving high mechanical properties in composite cementitious materials is to use 10% each of LP and RHA, resulting in a 9.5% increase in 28 d strength compared to a pure cement system. The higher the content of LP, the greater the increase caused by 10% RHA in compressive strength of the composite system, which makes the strength growth rate of cementitious material mixed with 10% LP at 3-56 d 62.1%. When the LP content is 20% and 30%, the addition of 10% RHA increases the 28 d strength by 44.8% and 38.8%, respectively, with strength growth rates reaching 109.8% and 151.1% at 3-56 d.

Integrated assessment of environmental and economic impact of municipal solid waste incineration for power generation: A case study in China

Municipal solid waste incineration for power generation is significant for reducing and reusing solid waste. The study conducted an integrated assessment of environment and economy on municipal solid waste incineration in China, from a "cradle to grave" perspective using 1 tonne of municipal solid waste incineration as the functional unit. The environmental impacts of each month are also calculated to analyze the dynamic change throughout one year. The results indicate that the environmental impacts are mainly concentrated in marine ecotoxicity, freshwater ecotoxicity, human carcinogenic toxicity, and human non-carcinogenic toxicity. Flue gas purification, waste incineration and transportation are the key processes, which account for 65.61 %, 18.50 %, and 11.93 % of the overall environmental impact, respectively. Urea, activated carbon, chelating agent (EDTA) and diesel fuel for transportation are key factors. The life cycle cost (LCC) is 132.26 RMB/t of waste, of which the initial capital causes the largest economic cost. When considering power generated from municipal solid waste incineration to replace electricity supply from the power grid, it achieves significant environmental benefits and the normalized environmental impact value changes from 0.85 to -12.19. The findings provide references for municipal solid waste treatment to mitigate the environmental impact and reduce the economic burden across the entire life cycle.

A life cycle analysis approach to evaluate sustainable strategies in the furniture manufacturing industry

Life Cycle Assessment (LCA) plays a crucial role in sustainability evaluations and impact assessments, especially in the realm of eco-design and environmentally friendly manufacturing in the furniture sector. However, the existing research tends to focus on specific stages of the furniture life cycle and leaves a substantial portion of the environmental impact unaddressed, including resource consumption, waste generation, and emissions throughout the entire value chain. This research presents a comprehensive LCA of the production and distribution process of a Pinewood Table, aiming to evaluate and improve its environmental sustainability. Six different production and distribution models were analyzed, including a base model strategy and five alternative strategies incorporating various sustainable policies. The study assessed the environmental impacts at each stage, considering resource consumption, emissions, and waste generation. Additionally, a cost analysis was conducted to identify the most economically viable sustainable option among the alternative strategies. Among the six production and distribution models studied, Alternative Strategy 5 demonstrates the lowest Climate Change CO2 equivalent emissions, with Alternative Strategy 2 following closely. This outcome underscores the importance of reducing forklift usage and transitioning to photovoltaic cells, resulting in a 50 % reduction in carbon emissions during CNC machining processes. Results also indicated that the collaborated strategy exhibited the highest reduction in Climate Change CO2 eq which is 65.4 %, highlighting the significance of reducing forklift usage and transitioning to photovoltaic cells for electricity generation. Finally, a sustainable option where all the strategies were collaborated is recommended for practitioners, emphasizing the significance of implementing eco-friendly practices to enhance the overall sustainability of pinewood table production and distribution. This research contributes to literature by providing essential information and guidance for industry stakeholders and policymakers to make informed decision-making and promote sustainable practices within the furniture manufacturing sector.

Life cycle assessment and optimization scenario of solid wood composite doors: A case study in the east of China

The large scale of the Chinese wooden door market has resulted in a slew of environmental issues that must be addressed. This paper evaluated a solid wood composite door using life cycle assessment (LCA). Field research was used to obtain production data for the wooden door. The production stages were divided into the raw material stage, the transportation stage, the woodworking workshop stage, and the painting workshop stage in order to identify potential environmental improvements and analyze the underlying causes to offer some suggestions for improvement. Four service lives were considered in the use stage, and three disposal methods were considered in the disposal stage to explore their environmental impacts. The functional unit was defined as a solid wood composite door using the "cradle-to-grave" system boundary. Using a 20-year service life as an example, the results revealed that the production stage was the most crucial stage, with a contribution ratio of 49% to 72% to all impact categories, regardless of waste disposal method. The main reasons for this were the production of density boards and the consumption of electricity. By replacing straw-density boards and hydropower, the global warming potential (GWP) was reduced by 46% and 67%, respectively. If a wooden door can be used for 20 years, the use stage will account for 26% to 51% of the environmental impact contribution, owing primarily to wood wax oil. Recycling was recognized as the most environmentally friendly method of waste disposal. This research can be used as a reference for evaluating solid wood composite doors in China as well as providing optimization recommendations for production improvement.

Influences of Friedel's Salt Produced by CaO-Activated Titanium-Extracted Tailing Slag on Chloride Binding

Titanium-extracted tailing slag (TETS) has high activity, but the content of chloride ions is high. To effectively bind the chloride ions, CaO was used to activate the TETS, and the solidified cementitious material of CaO-activated TETS was prepared. The effects of CaO content and curing age on the strength of solidified samples, chloride binding capacity, and chloride binding mechanism were studied. By means of XRD, FTIR, SEM, and EDS, the hydration reaction products, microstructure, morphology, and micro-components of the solidified sample were characterized. The results show that the chloride ions can be effectively bound by using CaO to activate TETS with higher mechanical strength. When the CaO content is 10 wt%, the strength of the 28-day-cured body can reach more than 20 MPa, the chloride ion binding amount is 38.93 mg/g, and the chloride binding rate is as high as 68%. The new product phases of the solidified sample are mainly Friedel's salt (FS) and calcite, in which the amount of FS production and the degree of crystal development are affected by the CaO content and curing age. The chloride binding ions in the solidified sample are mainly the chemical binding by FS. The FS diffraction peak strength increases with the increase of CaO content and curing age, but the calcite diffraction peak strength is less affected by them. FS mainly accumulates and grows in the pores of the solidified sample. It can optimize the pore structure of the solidified sample and improve the strength of the solidified sample while binding chloride ions. The results can provide useful information for the resource utilization of chlorine-containing TETS, the improvement of durability of Marine concrete, and the application of sea sand in concrete.

Recent Developments on Processes for Recovery of Rhodium Metal from Spent Catalysts

Rhodium (Rh) catalyst has played an indispensable role in many important industrial and technological applications due to its unique and valuable properties. Currently, Rh is considered as a strategic or critical metal as the scarce high-quality purity can only be supplemented by refining coarse ores with low content (2–10 ppm) and is far from meeting the fast-growing market demand. Nowadays, exploring new prospects has already become an urgent issue because of the gradual depletion of Rh resources, incidental pressure on environmental protection, and high market prices. Since waste catalyst materials, industrial equipment, and electronic instruments contain Rh with a higher concentration than that of natural minerals, recovering Rh from scrap not only offers an additional source to satisfy market demand but also reduces the risk of ore over-exploitation. Therefore, the recovery of Rh-based catalysts from scrap is of great significance. This review provides an overview of the Rh metal recovery from spent catalysts. The characteristics, advantages and disadvantages of several current recovery processes, including pyrometallurgy, hydrometallurgy, and biosorption technology, are presented and compared. Among them, the hydrometallurgical process is commonly used for Rh recovery from auto catalysts due to its technological simplicity, low cost, and short processing time, but the overall recovery rate is low due to its high remnant Rh within the insoluble residue and the unstable leaching. In contrast, higher Rh recovery and less effluent discharge can be ensured by a pyrometallurgical process which therefore is widely employed in industry to extract precious metals from spent catalysts. However, the related procedure is quite complex, leading to an expensive hardware investment, high energy consumption, long recovery cycles, and inevitable difficulties in controlling contamination in practice. Compared to conventional recovery methods, the biosorption process is considered to be a cost-effective biological route for Rh recovery owing to its intrinsic merits, e.g., low operation costs, small volume, and low amount of chemicals and biological sludge to be treated. Finally, we summarize the challenges and prospect of these three recovery processes in the hope that the community can gain more meaningful and comprehensive insights into Rh recovery.