**Abstract**

Different feedstocks Dunite, Olivine and Lizardite are examined in this research using various measuring techniques such as TGA-MS, XRD and Quantitative XRD and EDS. Quantitative XRD results matched with TGA-MS results. Malvern Mastersizer, EDS and QXRD results also showed a good match regarding the individuality of results which are shown graphically. TGA-MS calibration curves example is provided. Matching the results of different measuring techniques is a key to fundamental research. Comparison of the reactivity of dunite, soaked dunite, heat-activated dunite and lizardite and raw dunite soaked has been performed. TGA-MS and QXRD results match each other. Malvern Mastersizer, EDS and QXRD results match with their individual results indicating the instrument's reliability. Semi-Quantitative XRD results authenticity is EXCELLENT. TGA-MS results match with QXRD is excellent. Mineral carbonation converts CO2 into stable mineral carbonates. This research explores the utilisation of serpentinised dunite (which is comprised of 61% lizardite) as a potential feedstock for mineral carbonation. Heat activation, *ex-situ* regrinding and concurrent grinding techniques were employed to enhance the reaction rate and yield, and to provide information on the carbonation reaction mechanism. Silica-rich layers that appeared during reference experiments were disrupted using concurrent grinding and significantly higher magnesite yields and Mg extractions were obtained.

**Keywords:** CCS (carbon capture and storage), CCSU (carbon capture, storage and utilisation), mineral carbonation (MC), carbon capture (CC), materials science

## **1. Introduction**

Greenhouse gases especially CO2 concentration in the atmosphere has increased to a level of 419 ppm compared to a value of 280 ppm from the preindustrial revolution (1975) [1]. Reduction in greenhouse gases is a need of time. Significant research has been published regarding mineral carbonation [2–15], geological carbon dioxide storage, oceanic storage [3], carbon dioxide conversion into chemicals, carbon dioxide fixation in polymers and carbon dioxide conversion into Urea [16, 17]. Mineral carbonation is one of the forefront technologies recently proposed. Although various publications have been done in this field [2], the basic need of time is to foresee how

the research efforts need to be oriented or centred on that technology [3, 4, 9–11, 13, 14, 18–20]. This article will indicate some directions for the utilisation of different feedstocks for CO2 utilisation and fixation. Geological storage poses a threat to nearby occupants as there were thousands of killings in the Crater Lake incident. ALOHA software can be used for the estimation of such leakages if CO2 is to be stored in geological formations. CO2 can cause asphyxiation; hence, safety measures are at most necessity. ALOHA can estimate CO2 vapours travelling distances and how far this gas can travel and how much concentration will be at a specified point. Oceanic storage pose threat to aquatic life and is expected to disrupt the ecosystem seriously. Increased concentration of CO2 in oceans [21] will reduce the pH of the oceanic water, rivers or canals making them undrinkable. Seawater is used in various industries. Reduced pH will cause serious corrosion issues and may result in materials damage and or stress corrosion cracking.

Greenhouse gases are uncontrollable. Each greenhouse gas concentration increases day by day. CO2 is recently converted to jet fuel using sunlight by Adele Peters from Fast Company [22]. Researches are not giving up. However, the Antarctic lake has disappeared in just 3 days [23]. More efforts need to be initiated. Extremism in climate shattering weather patterns is expected right now [23]. Europe has seen extreme flooding in 2021. Pakistan has seen extreme summers like what the Middle East has seen shooting of temperatures. Catalysts have been discovered to convert CO2 into fuel [24]. A single reason why CO2 is not controlled is that industries emit more than capture. Adam Vughan has indicated that atmosphere warming could not have been kept below 1.5°C [25]. Alas, more seriousness is required. No negative emissions drama. The cement industry is also one of the largest CO2 emitting industries. Novel modifications are proposed to overcome this threat [26]. Coal-burning emissions and their environmental effects are also highlighted [27].

## **2. Analytical instruments**

Dunite, different varieties of olivine and lizardite are used in this research. Proper functioning of analytical instruments is a fundamental to perform the highest level of research. Fundamental instruments operation and working is described here.

### **2.1 TGA-MS analysis**

Thermogravimetric analysis (TGA) measures the change in mass over time as the sample is heated. These measurements provide compositions of different feeds or carbonated products. TGA is suitable to characterise different materials that display mass loss or gain due to thermal decomposition and thus enable an estimate of magnesite yields of the carbonated products to be obtained. Feed materials or carbonated products were heated in TGA (**Figure 1**) from 25 to 1000°C and mass losses due to decomposition of different phases present are identified. To identify the evolving gases generated during heating, the TGA-DSC (Setsys Evolution 1200) was coupled with a mass spectrometer (Thermostar Quadrupole). The initial loss of mass observed between 25 and 280°C corresponds to physically bound moisture present in the sample, while the second mass loss from 280 to 430°C corresponds to brucite decomposition, while the third major mass loss in the range of 430–830°C corresponds to lizardite decomposition (**Figure 2**).

*Testing and Validating Instruments for Feedstocks of Mineral Carbonation DOI: http://dx.doi.org/10.5772/intechopen.101175*

### **Figure 1.**

*Photo of TGA-MS set up. A, autosampler and small sample crucibles; B,TGA furnace where the sample is being heated; C, mass spectrometer connected with TGA furnace to receive evolved gases from TGA; D, computer for data output; E, argon cylinder for argon gas flow; F, chiller to cool down TGA furnace.*

### **Figure 2.**

*Typical TGA-MS curve. The first significant loss of mass is due to moisture present in the sample. The second mass loss is due to brucite decomposition. The third mass loss is due to lizardite decomposition. All major changes in mass are due to the elimination of H2O vapour from the sample.*

Lizardite decomposes over the same temperature range (300–600°C) as the magnesite [6] and this can introduce a systematic error in magnesite yield estimation (leading to an over-estimation of the magnesite yield) unless the mass loss in this period can be quantitatively attributed to loss of H2O or CO2 from the sample. To distinguish between these species, the ion current from the m/z = 44 ion (CO2 + ) from mass spectrometer was calibrated using sodium bicarbonate samples and a calibration curve for CO2 concentration was obtained, which is used to quantify CO2 mass loss (distinguishing CO2 production from the loss of water vapour, which occurs simultaneously) and thus render more accurate estimation of the magnesite yield. CO2 peak areas were calculated using the mass spectrometer data and CO2 mass response is estimated based on the reaction (2NaHCO3 ➔ Na2CO3 + CO2 + H2O). The relationship between peak areas and CO2 mass loss was linear.

For carbonated samples, the CO2 peak areas were estimated using MS data and then these peak areas are used to determine CO2 mass loss applying the CO2


### **Table 1.**

*TGA calibration data for three runs.*

calibration curve. This CO2 mass loss was used in an equation to calculate magnesite yield. The equation is based on the Gadikota formula [28].

Three TGA runs (**Table 1**) were completed with calcium oxalate hydrate (99% pure) to calibrate the TGA response. Theoretical and measured mass loss shows good agreement (**Table 1**).
