Alkali-activated foam: Understanding the relationship between rheology, activator-precursor interaction, and pore characteristics

The pore characteristics and stability of alkali-activated foams (AAFs) are crucial factors that determine their application and performance. These aspects are influenced by the material mix design and the foaming method employed. The interaction between the activator and precursor paste results in a change in the rheological properties which possess significant impacts on the behaviour of the foam and the stability of the pores in AAFs. Various raw materials and foaming methods have been utilised to develop AAFs. However, The combined influence of the activator-precursor interaction, foaming, and rheological properties on the pore structure and properties of AAFs is not well explored. Hence, the purpose of this study is to investigate this interrelationship. To develop AAFs, a combined mechanical and chemical foaming method was employed. Waste glass, fly ash, and slag were used as precursors and activated using activators with varying silica modulus. The rheological parameters of the paste and the hardened properties of the AAFs were investigated. The findings indicate that pastes with high viscosity and high yield stress have more stable and uniformly distributed pores. The presence of a viscous activator reduces the colloidal interaction between precursor particles, thereby lowering the yield stress of the activated paste. Furthermore, the early setting of slag and the partial dissolution of all precursors play a significant role in establishing stable networks and final pore stabilisation within the AAFs. Controlling these parameters, lightweight AAFs were developed using a high volume of waste glass with homogeneous pore distribution and moderate mechanical strength (up to 2.83 MPa)

Wettability of Carbonaceous Materials with Molten Iron at 1550°C

In the direct iron smelting process, interfacial reactions of carbonaceous materials with molten iron are among some of the key factors that dictate the rate of carbon transfer into molten iron and establish a carbon concentrated melt to reduce iron oxide in the slag phase. Detailed wettability investigations on a range of carbonaceous materials, e.g. synthetic graphite, natural graphite, coke, coal-chars, coke-polymer blends, waste plastics in contact with molten iron at 1550°C were carried out using the sessile drop method. Experimental results on dynamic contact angles are presented in this chapter and are discussed in terms of the basic characteristics of carbons and the changing composition of the interfacial region as a function of time

Influence of Wettability and Reactivity on Refractory Degradation – Interactions of Molten Iron and Slags with Steelmaking Refractories at 1550°C

Refractories, materials that can withstand high temperatures, play an important role in the iron and steel sector which alone accounts for ~70% of total refractories produced. In this chapter, detailed wettability and interfacial phenomena investigations on alumina-carbon and zirconia-carbon refractories at steelmaking temperatures. The wettability between refractory substrates and molten iron/slags was investigated at 1550°C using the sessile drop approach in a horizontal tube furnace equipped with a CCD camera. Detailed experimental results were obtained on alumina-carbon/molten iron system at high temperatures. Alumina is known to be non-wetting to molten iron while carbon can be easily wetted. Observed contact angles were found to depend strongly on the substrate composition and contact time. While the refractory substrates containing 50 and 60% carbon were found to be non-wetting to molten iron, the substrates containing higher amounts of C (≥ 70%) were found to become increasingly wetting. Molten iron droplets were seen to spread on these substrates

Waste battery disposal and recycling behavior: a study on the Australian perspective.

Consumer behavior is a critical consideration for the development of sustainable waste management systems, including waste batteries, which pose a serious threat to human health and the environment if disposed of improperly. This study investigates the consumers' perspective on the waste battery collection and recycling behaviors in Australia, and analyses their implications for the development of recycling schemes. The results show that, although general awareness exists among consumers about the negative impacts of improper disposal, this awareness was not reflected during the disposal of waste batteries among the participants. Insufficient knowledge about the waste battery collection points and convenience were the most important factors affecting the inappropriate disposal behavior from most of the consumers. Over 50% of participants were unaware of the collection points for waste batteries. The most-preferred battery collection systems involved a deposit return system similar to that used for bottle recycling in the state of New South Wales (NSW) or collection at supermarkets/retailers. The most preferred methods for providing an incentive to recycle batteries were "old-for-new" battery swaps, "vouchers that could be used for other items in a store," and "cash payments." Several policy implications have been highlighted from this pioneering study that could shape the future development of sustainable waste battery management systems in Australia

Recycled ZnO-fused macroporous 3D graphene oxide aerogel composites for high-performance asymmetric supercapacitors

First published: 06 August 2022In the arena of energy storage device, asymmetric supercapacitors (ASCs) are considered a key category due to its high-power density and energy densities. In this study, a novel macroporous microrecycled ZnO nanoparticles (mi-ZnO NPs) recovered from spent Zn–C battery-decorated three-dimensional graphene aerogel (GA) composite has been synthesized via simple eco-friendly synthetic method, which is used as a proficient anode material to fabricate ASC. The interconnected macroporous networks and ∼40-nm microrecycled ZnO NPs incorporated GA (mi-ZnO–GA) enhanced the surface area of anode materials, which lead to achieve a formation of high-performance ASC. Here, we composed ASCs from a microrecycled ZnO thin film (cathode) and mi-ZnO–GA composite (anode), which reveals fast charging/discharging characteristics, stable widen cell voltage, superior power, and energy densities (13.7 W h/kg, 13.2 kW/kg), and finally stable cyclability (76.8% retention after 5000 cycles). These outcomes open up the window for microrecycled ZnO NPs incorporated GA (mi-ZnO–GA) as a prominent anode material for high-performance energy storage devices.Kamrul Hassan, Rumana Hossain, Veena Sahajwall

Environmental Impact of Processing Electronic Waste – Key Issues and Challenges

Extensive utilization of electric and electronic equipment in a wide range of applications has resulted in the generation of huge volumes of electronic waste (e-waste) globally. Highly complex e-waste can contain metals, polymers and ceramics along with several hazardous and toxic constituents. There are presently no standard approaches for handling, dismantling, and the processing of e-waste to recover valuable resources. Inappropriate and unsafe practices produce additional hazardous compounds and highly toxic emissions as well. This chapter presents an overview of the environmental impact of processing e-waste with specific focus on toxic elements present initially in a variety of e-waste as well as hazardous compounds generated during e-waste processing. Hazardous constituents/ and contaminants were classified in three categories: primary contaminants, secondary contaminants, and tertiary contaminants. Primary contaminants represent hazardous substances present initially within various types of e-waste; these include heavy metals such as lead, mercury, nickel and cadmium, flame retardants presents in polymers etc. Secondary contaminants such as spent acids, volatile/toxic compounds, PAHs are the by-products or waste residues produced after inappropriate processing of e-waste and the tertiary contaminants include leftover reagents or compounds used during processing. A detailed report is presented on the environmental impact of processing e-waste and the detrimental impact on soil contamination, vegetation degradation, water and air quality along with implications for human health. Challenges and opportunities associated with appropriate e-waste management are also discussed

“Control-Alt-Delete”: Rebooting Solutions for the E-Waste Problem

A number of efforts have been launched to solve the global electronic waste (e-waste) problem. The efficiency of e-waste recycling is subject to variable national legislation, technical capacity, consumer participation, and even detoxification. E-waste management activities result in procedural irregularities and risk disparities across national boundaries. We review these variables to reveal opportunities for research and policy to reduce the risks from accumulating e-waste and ineffective recycling. Full regulation and consumer participation should be controlled and reinforced to improve local e-waste system. Aiming at standardizing best practice, we alter and identify modular recycling process and infrastructure in eco-industrial parks that will be expectantly effective in countries and regions to handle the similar e-waste stream. Toxicity can be deleted through material substitution and detoxification during the life cycle of electronics. Based on the idea of "Control-Alt-Delete", four patterns of the way forward for global e-waste recycling are proposed to meet a variety of local situations