Production of carbon negative precipitated calcium carbonate from waste concrete

Abstract

Mineral carbonation can contribute to climate change mitigation through the production of synthetic limestone (CaCO 3 ) from calcium silicate minerals and gaseous CO 2 . Some carbonates, such as Precipitated Calcium Carbonate (PCC), have industrial applications and may provide sufficient economic incentive for sequestering CO 2 should the product be a marketable commodity. Cement is a suitable source of calcium and can be recovered from waste concrete. The production of cement accounts for 9.5 % of global CO 2 emissions, however up to 50 % of the manufacturing emissions can be mitigated at the end of the materials service life through mineral carbonation.The objective here is to sequester CO 2 through the production of PCC via the recovery and carbonation of calcium from waste cement. The calcium is suitable for mineral carbonation and can be effectively leached using an acid (e.g. HCl). When calcium is completely leached, the solution will be slightly acidic and contain impurities such as iron and silica. The impurities can be removed by adding alkalinity prior to CaCO 3 precipitation, via reaction with Na 2 CO 3 in a separate reactor. The Na 2 CO 3 is produced by the absorption of CO 2 using NaOH, while the resulting NaCl solution is recycled via bipolar membrane electrodialysis. Overall transportation emissions and costs are reduced and the process could enhance current waste concrete recycling practices. Furthermore, the low carbon intensity of electricity generation in Eastern Canada allows for capture of 444 kg CO 2 per tonne of PCC.

Thermally Induced Aragonite–Calcite Transformation in Freshwater Pearl: A Mutual Relation with the Thermal Dehydration of Included Water

“…Calcium carbonate (CaCO 3 ) is a well-known inorganic raw material and historically used for a variety of applications including architectural materials and pigments. , There are many sources of CaCO 3 available in nature as minerals and those produced through the biomineralization of living organisms. Effective reuse of CaCO 3 , recovered from waste architectural materials and food processing wastes, is also a focus of materials recycling. − Therefore, novel potential applications of CaCO 3 have been continuously investigated to find additional value and establish cost-effective reuse of the material resource. Recently, the reversible reactions of the thermal decomposition of CaCO 3 to form calcium oxide (CaO) and carbon dioxide (CO 2 ) and the carbonation of CaO to form CaCO 3 , i.e., CaCO 3 ⇄ CaO + CO 2 , have attracted considerable attention once again − The absorption of CO 2 by the carbonation of CaO and recovery of the CaO absorbent by the thermal decomposition of CaCO 3 function as a CO 2 looping system to mitigate the greenhouse effect. − Because of the endothermic thermal decomposition of CaCO 3 and exothermic carbonation of CaO, the reversible reactions can be used for the thermal storage of solar energy. − For these potential applications of the reversible reactions, the physicochemical properties and morphological characteristics of CaCO 3 and CaO are recognized as important factors to determine the functionalities.…”

Utilization of Gaseous Carbon Dioxide and Industrial Ca-Rich Waste for Calcium Carbonate Precipitation: A Review

“…Therefore, possible technologies for its utilization or reuse are sought [73]. There is a lot of research regarding the use of waste concrete for the production of PCC [74]. The potential amount of calcium that can be recovered from waste concrete depends on the content of this element in cement.…”

“…Therefore, 88 kg of calcium can be recovered from a ton of Portland cement-based concrete [76]. Commonly used processes for the chemical recovery of calcium from waste concrete include three energy-intensive stages: crushing, milling, and leaching [74]. For the production of PCC from waste concrete, numerous studies have been conducted on various leaching agents.…”

“…Van der Zee and Zeman [74] proposed a method of producing precipitated CaCO 3 from waste concrete, where HCl was used as the leaching agent. Precipitation of calcium carbonate was carried out in a separate reactor by mixing the calcium-rich solution obtained by leaching and aqueous sodium carbonate solution.…”

Mitigating CO2 emissions of concrete manufacturing through CO2-enabled binder reduction

“…Expected supply limitations of FA and GGBS in the near future are encouraging researchers to explore additional options; other minerals and waste materials can be used as SCM [22][23][24][25][26][27][28]; optimized low-clinker system can be used as a binder [29]; clinker-free geopolymer can replace OPC [30]; self-healing concrete can mitigate CO 2 emissions from repair events [31,32]; and ductile engineered composites can reduce life cycle CO 2 emission with an extended service life [33,34]. Another area of active research includes so-called 'CO 2 utilization' in concrete where concrete is formulated with added CO 2 either in its constituents before casting, during batching and mixing, or in finished products.…”