Accelerated Weathering of Limestone for CO2 Mitigation

Abstract

Rock weatheringWeathering is a natural phenomenonPhenomenon which brings about several changes on the Earth’s landscape but it has one more useful functionFunction. It controls the CO2 concentrationConcentration in the atmosphereAtmosphere by precipitatingPrecipitating the magnesiumMagnesium and calcium carbonatesCalcium carbonate. The process is slow and takes place over a long period of time. However, if this process is accelerated, the atmospheric CO2 can be removed in sufficient volumes at a faster rate and converted to bicarbonatesBicarbonates thus mitigating the greenhouseGreenhouse effect. A geochemistryGeochemistry-based captureCapture and sequestrationSequestration process that reacts CO2 with water to produce a carbonic acid solution is one of the methods to understand this phenomenon. This carbonic acid solution is then reacted with carbonate rocks to precipitate bicarbonates. The rate of reactionReaction depends upon the temperatureTemperature, flowFlow rate and particle size. In the present study, the accelerated weathering of limestoneLimestone was carried out using different sizes of limestone cuttingsCuttings (4 mm, 500, 250, 100 and 50 µm) under different flow rates of carbonic acid (0.5, 1.0 and 1.5 L/min) for a duration of 2 h at a constant temperature of 80 °C. SEMScanning Electron Microscope (SEM) and elemental analysisAnalysis were done before and after the experiment. Results from the experiment showed that the highest flow rate (1.5 L/min) exhibits the greatest weight loss. This weight loss is brought about by the dissolutionDissolution of calcium to release bicarbonate and carbonate ionsIons. EDXEDX analysis shows a reduction in both calciteCalcite and dolomiteDolomite indicating dissolution of these two mineralsMinerals. Acid attack on the samplesSample forms dissolution patterns which are visible in SEM images. The principle mode of sequestration in limestone formationFormation is ionic trapping. CO2 trapped in this way in the form of bicarbonate solution can be safely discharged in aGlobal waterWeathering bodyLimestone or reservoir for storageStorage.