Parallel Session 2B

The aim of this study is to assess the potential of Deep Eutectic Solvents (DES) to extract lithium and Rare Earth Elements (REEs) from E-waste (Electronic Waste) and spent batteries in Sri Lanka, in a sustainable way. Choline Chloride, Malonic Acid and Acetic Acid were synthesized to assist the metal dissolution at room temperature in three DES systems. The results of the experiments showed that, under the optimum experimental conditions (1:1:1.0 DES molar ratio and 1:20 solid-to-liquid ratio), the maximum lithium recovery was 37.41%. The highest recovery of rare earth elements (Nd, Pr, Dy) was 16.59% at higher acidity and a higher quantity of solvent. The optimum co-extraction condition, 1:1:1.0 DES composition at 1:20, solid-to-liquid ratio, was determined, which provided the most optimal recovery of both the critical metal groups. Through this approach, the circular economy is promoted as an alternative to conventional mineral acid leaching, reducing energy consumption and carbon emissions in urban mining.

The aim of this study is to assess the potential of Deep Eutectic Solvents (DES) to extract lithium and Rare Earth Elements (REEs) from E-waste (Electronic Waste) and spent batteries in Sri Lanka, in a sustainable way. Choline Chloride, Malonic Acid and Acetic Acid were synthesized to assist the metal dissolution at room temperature in three DES systems. The results of the experiments showed that, under the optimum experimental conditions (1:1:1.0 DES molar ratio and 1:20 solid-to-liquid ratio), the maximum lithium recovery was 37.41%. The highest recovery of rare earth elements (Nd, Pr, Dy) was 16.59% at higher acidity and a higher quantity of solvent. The optimum co-extraction condition, 1:1:1.0 DES composition at 1:20, solid-to-liquid ratio, was determined, which provided the most optimal recovery of both the critical metal groups. Through this approach, the circular economy is promoted as an alternative to conventional mineral acid leaching, reducing energy consumption and carbon emissions in urban mining.

Sri Lanka possesses abundant vein quartz deposits that are primarily utilized for low-value industrial applications due to a natural lack of gem-quality color and clarity. This study investigates the technical and economic viability of enhancing local vein quartz through controlled heat treatments using transition metal additives. Iterative experimental trials determined ideal thermodynamic conditions and application methods for ionic diffusion. Dopants including Cobalt, Copper, Iron, Chromium, Manganese, and Nickel were applied to quartz samples processed up to 1100°C. Results concluded that Cobalt and Chromium successfully act as chromophores. Using a direct evaporative bonding method, Cobalt diffused into the quartz lattice at 1000-1100°C, producing a vivid deep blue. Prolonged multi-cycle heating at 1000°C allowed Chromium to yield a slightly yellowish-green hue. Post-treatment testing confirmed these modifications exhibit high stability against chemical and photochemical degradation. Furthermore, thermal processing enhanced optical clarity by facilitating the release of natural fluid inclusions along pre-existing fracture planes. To preserve structural integrity without uncontrolled fragmentation at the 573°C transition point, programmable electric furnaces with incremental heating rates (<3°C/min) are required.

The production of manufactured sand (M-sand) generates substantial quantities of quarry wash fines (QWF), creating disposal challenges, increasing airborne dust levels, and causing sedimentation in surrounding ecosystems. This study investigates the utilization of QWF, for the development of geopolymer and alkali-activated bricks. Two binder systems incorporating 10% metakaolin (MK) and 10% ordinary Portland cement (OPC) were evaluated under different curing conditions using a 14 M NaOH and water glass alkaline activator. The influence of binder type and curing regime on mechanical performance and microstructural development was systematically assessed. Results indicate that both binder additions enhanced matrix formation through the development of amorphous sodium aluminosilicate and calcium aluminosilicate gels, leading to improved structural integrity. The developed composites exhibited compressive strengths ranging from 4.26 to 9.96 MPa and water absorption values between 1.2% and 8.3%. Among all formulations, water cured alkali-activated OPC bricks (C2) demonstrated the best overall performance, achieving superior strength development and durability compared to other curing conditions. These findings confirm that QWF can be effectively valued into low-energy masonry units suitable for sustainable construction applications, meeting the required industry standards.

Aqueous zinc-based energy-storage systems are gaining attention due to their low cost, safety and environmental advantages compared with conventional systems using non-aqueous electrolytes. This study evaluates a locally adaptable Zn graphite electrochemical cell using graphite-based composite electrodes, zinc plates and ZnSO₄ electrolyte. Graphite is important in this system because of its layered structure, good electrical conductivity, chemical stability, low cost and wide availability, making it suitable as a conductive carbon-based electrode material. The main aim was to assess the electrochemical behavior of the Zn graphite cell and identify the key factors affecting its performance. Graphite composite electrodes were prepared on glass substrates using an acrylic binder and compressed to improve particle contact. The cell was assembled with controlled electrode spacing and tested for electrical uniformity, electrolyte concentration effect, discharge behavior and cycling stability. The results indicate that the graphite composite electrode supported stable electron transport, while electrolyte concentration and electrode spacing strongly influenced voltage and current response. The discharge and cycling behavior showed gradual performance fading without sudden failure. Overall, the Zn graphite system demonstrates promising potential as a simple, refillable and low-cost aqueous energy-storage cell.

This final segment invites reflections from presenters and attendees, synthesizing key insights from the session. The session chair will conclude the discussion by summarizing thematic threads, highlighting interdisciplinary contributions, and outlining potential collaborative directions.