Lead waste glasses management: Chemical pretreatment for use in cementitious composites

Reuse of lead glass sludge in the fabrication of thermally insulating foamed glass with outstanding properties and high Pb-stabilization

This study represents the sustainable/safe consumption of lead glass sludge (LGS) in the fabrication of thermally insulating foamed glass via sintering (750-950º C) and chlorination processes. The impact of selected additives including calcium chloride (CaCl₂) and sodium hydroxide (NaOH) on the foaming efficiency and Pb-stabilization has been deeply investigated. LGS is mainly lead silicate material with considerable content of calcium carbonate, which acts as foaming agent during sintering process. The newly developed foamed-materials exhibited thermal conductivity of 0.054-0.136 W/m.K, density of 0.23-1.10 g/cm³, porosity of 63.3-92.6%, and compressive strength of 0.10-2.69 MPa. X-ray diffraction proved that the immobilization mechanism was attributed to the transformation of free Pb within LGS into insoluble ganomalite Pb₉Ca₅MnSi₉O₃₃ phase. Adding NaOH enhanced the foaming process accompanied by a significant reduction in Pb-leaching. Incorporating CaCl₂ has resulted in a retardation in Pb-leaching, which associated with Pb-stabilization and Pb-vaporization. In an attempt to reduce CO₂-emission, the potential use of alkali-rich-wastewater (AW) as eco-friendly alkali source in lieu of NaOH was studied. Regardless of the variation in Pb-concentrations in leachates, all samples recorded Pb-concentrations lower than the safe limit (≤ 5 mg/l), achieving Pb-immobilization of 95.98-99.87%. The significantly reduced thermal conductivity and enhanced Pb-immobilization efficiency along with the reasonable compressive strength summarize the major innovation presented in this study.

Properties of Cement-Based Materials Containing Cathode-Ray Tube (CRT) Glass Waste as Fine Aggregates—A Review

Among many alternatives to replace sand in cement-based materials, cathode-ray tube (CRT) glass emerges as a suitable replacement for many reasons. This paper provides a state-of-the-art review on the use of cathode-ray tube (CRT) glass waste in cement-based concrete and mortar in accordance with PRISMA guidelines. The new aspects of the research are the literature coverage up to 2021 which would make it distinct from other articles. This review would act as a catalyst to use CRT glass waste in concrete mixtures. A total of 61 papers from literature were analyzed with emphasis on the fresh, mechanical, and durability performance of cement-based materials containing CRT glass waste as fine aggregates. The analysis revealed that the majority of the studies agreed that replacing sand with CRT glass waste increased the consistency where the low permeability of the CRT glass caused this effect. Strength of cement-based materials, on the other hand, decreased due to the weaker bond between the cement paste and the aggregates. The low water absorption of the CRT glass defined its effect on the durability properties of cement-based materials, such as drying shrinkage and water absorption capacity, leading to an improved performance. In addition, CRT glass waste activated the alkali-silica reaction in cement-based materials causing undesirable expansion. Additionally, several investigations proposed solutions to mitigate the lead leaching associated with the lead content found in the CRT glass. In general, it was assessed that CRT glass waste could be a valid component in the production of sustainable cement-based materials, especially for radiation shielding applications. The recommendations for future research are also suggested.

Stabilization of hazardous lead glass sludge using reactive magnesia via the fabrication of lightweight building bricks

This study focused on the stabilization of lead glass sludge (LGS) using reactive magnesia (MgO) via the fabrication of lightweight building bricks. Two types of MgO with different reactivities were prepared by the thermal treatment of magnesium carbonate at 800 °C and 1200 °C (MgO-800 and MgO-1200, respectively). The fabrication of bricks and Pb stabilization were performed by wet mixing LGS with MgO followed by humidity incubation. Results showed that the Pb immobilization and performance of the produced bricks were strongly affected by MgO reactivity, curing time, and LGS-MgO weight ratios. Pb immobilization was performed by the transformation of soluble lead into an insoluble hydrocerussite phase, particularly in hydrated mixtures with high MgO content (> 25 wt%). Pb immobilization inside a magnesium silicate hydrate skeleton is the main mechanism in the hydrated samples containing 25 wt% MgO. To achieve "sustainability," we recommend the use of a hydrated mixture containing 75 wt% of LGS and 25 wt% of MgO-800 in the production of building bricks because this mixture exhibits high compressive strength, high Pb immobilization, low energy demand, and low environmental pollution.

Analytical framework for value added utilization of glass waste in concrete: Mechanical and environmental performance

This work was designed to incorporate glass waste as partial replacement of coarse aggregate in concrete through optimization of its amount by assessment of mechanical and environmental performances. Fresh and hardened properties of glass waste concrete were evaluated and compared with the conventional concrete. Moreover, compressive strength was evaluated experimentally as well as analytically at different ages. While, environmental performance was evaluated with an assessment of CO₂ footprint and volume utilization of raw materials for both types of concrete; conventional and glass waste concrete. Consequently, a sustainable concrete was selected that possesses high workability and mechanical performance, minimum CO₂ footprint and least utilization of conventional natural raw materials. For optimization, corresponding values of designed parameters were translated into a framework for glass waste management by application of analytical hierarchy process (AHP) and technique for order preference by similarity to ideal solution (TOPSIS). Similar prioritization for all types of mixtures was achieved through proposed framework by applying such multi criteria decision making techniques. Proposed framework may further be used for adjusting the priority weights for each criterion according to the requirement as well as for extended evaluation of additional criteria.

Gravimetric composition of the rejects coming from the segregation process of the municipal recyclable wastes

Rejects from selective collection are municipal solid waste (MSW) not used for recycling and are, therefore, destined for the landfill in Brazil. Knowledge of the composition and generation of this waste is important for strategically planning public policies that minimize its generation and its negative environmental impacts. However, this portion of MSW is not very well known. Therefore, the aim of this study was to analyze the rejects from the sorting process of the selective waste collection in the municipality of Blumenau, in the State of Santa Catarina, southern Brazil. The studied rejects came from the largest cooperative in the city, and its composition was sorted into 17 categories of 101 samples over the course of one year, with a total of 3893 kg of analyzed rejects. The waste collected by the selective collection of the municipality was evaluated monthly to determine which part of this quantity became rejects and to determine the composition and seasonality of these rejects. The study found that 30.5% of the waste sorted by the cooperative was rejected. Among these rejects, the presence of materials that could be marketed by the cooperative was verified. Hazardous and/or legally prohibited waste were also identified, as were organics, construction and demolition waste, health care waste, electronics, textiles, footwear, batteries, and bulbs. Seasonal analysis indicated a concerning constant generation of health care waste. Aside from that, there was an increase in the generation of waste from electrical and electronic equipment (EEE) during the Christmas period, when a large part of the population discards their EEE. This information is important for the enforcement of the MSW management structure as well as for educational campaigns aimed at the correct separation of waste that should be sent for selective collection.

Chemical extraction of trace elements from hazardous fine fraction at an old glasswork dump

Old glassworks sites have been always associated with contamination by different trace elements like Pb, Cd, As, Zn and others. The mixture of soil and waste glass of particle sizes <2 mm at one of the oldest Swedish glassworks (the Pukeberg) was studied by analyzing the trace elements content, organic content (3.6%) and pH (7.4). The results showed hazardous concentrations of Pb (1525 mg/kg), Ba (1312 mg/kg), Sb (128 mg/kg), Cd (36 mg/kg), As (118 mg/kg), Zn (1154 mg/kg) and Co (263 mg/kg) exceeded the Swedish guidelines of contaminated soil. Batch chemical extraction by the chelating agents EDTA, DTPA and the biodegradable NTA were performed to study the effect of chelating agent concentration and mixing time on the extraction efficiencies by following a Box-Wilson design of experiments. The results displayed good extraction efficiencies (less than 41%) of Pb, Cd, As and Zn by the EDTA, DTPA and NTA, which seemed depends on the type of chelator. In addition, high correlation between the extraction efficiencies, the chelators concentration and mixing time was found based on the statistical and experimental results.