Physicochemical comparison of precipitated calcium carbonate for different configurations of a biogas upgrading unit

Abstract

BACKGROUND:Thispaperpresentsaphysicochemicalcomparisonofthesolidproductsobtainedfromtwoalternativeprocessesthatrecyclewastesodiumcarbonate(Na2CO3)solution,whichisproducedfollowingtheabsorptionofCO2inabiogasupgradingunit.Chemicalregenerationprocessesofferanattractivealternativetotheenergeticallydemandingstandardphysicalmethods.In the first process, sodium hydroxide (NaOH) is regenerated as a precipitate from the chemical reaction of Na2CO3with calciumhydroxide (Ca(OH)2).Thesecondprocessshowsapathtoobtainavaluablesodiumchloride(NaCl)andcalciumcarbonate(CaCO3)rich brine from calcium chloride (CaCl2) acting as a precipitant agent. In both processes, precipitated calcium carbonate (PCC) isobtained as the most valuable by-product, but with varying properties owing to the different origin.RESULTS: The purpose of this work is to analyze physicochemically both variations of PCCs obtained and examine the differencesbetween these solid samples in order to determine which method produces more desirable characteristics in the final product.To this end, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD) and scanning electronmicroscopy (SEM) were employed as characterization methods. The results reflect that both PCCs have a calcite crystal structure,or morph, being as both PCC products originate from CaCl2that is more similar to commercial calcium carbonate calcite.CONCLUSION: These results confirmed that a pure CaCO3valuable by-product can be obtained from a biogas upgrading unitwith several industrial applications.