Effect Of The Types Of Surfactants On The Morphology And Phase Of Calcium Carbonate In Two Kinds Of Systems

Different sizes,phases,and morphologies of calcium carbonate have different applications in industry.In addition,calcium carbonate is one of the most common scale-forming substances in oil field production.Therefore,the study of the phase and morphology of calcium carbonate in different chemical environmentsand the influence of additives on the phase and morphology of calcium carbonate have a certain significance for the application of calcium carbonate and the knowledge of oil field scale.In this thesis,the effects of different types of surfactants?anionic,cationic and non-ionicsurfactants?and other additives on the phase,morphology,and growth of calcium carbonate in water system and 10% volume fraction oil-in-water kerosene emulsion system were investigated by using calcium chloride and sodium carbonate direct mixed precipitation method.The phase of the collected samples was characterized by FT-IR and XRD.The morphology of the samples was characterized by SEM.The study found that in the aqueous system,the anionic surfactants SDS,HABS and SDBS all promoted the transformation of the crystal form at the initial stage of the reaction,while inhibited the transformation of the crystal form at the late stage of the reaction.The cationic surfactant CTAB slightly inhibited the transformation of the crystal form in the early stage,but promoted the crystal in the later stage.The non-ionic surfactant OP-10 promotes the conversion of vaterite to calcite throughout the entire maturation process.Among them,the effect of morphology of calcium carbonate was small when regulated by OP-10,however,calcium carbonate particles have fuzzy boundaries,rough surfaces and defects inside the crystals when controlled by OP-10 and HPAM together.The inhibition of anionic surfactants HABS and SDBS was significantly greater than that of SDS in the later stage,which was due to the fact that the terminal positions in the HABS and SDBS structures contained a benzene ring with a large steric hindrance,thereby hindering the process of crystal transformation.Besides,unlike conventional cubic calcite,calcite calcium carbonate particles synthesized under the control of the additive SDS were irregular spheres composed of a large number of sharply-packed fragments.The water system co-regulated by HABS and SiO₂ could form peanut-like,irregular aggregates and wheat-like special morphologies.In the emulsion system,the effect of different types of surfactants on calcium carbonate was the same as that in the water system,and there were also different places.The emulsion system controlled by anionic surfactant SDS,cationic surfactant CTAB,and nonionic surfactant OP-10 together with HPAM all played an important role in promoting the conversion of calcium carbonate from vaterite to calcite.The SDS-emulsified kerosene emulsion medium inhibited the growth of crystals to well-defined morphology,and the formed calcium carbonate generally presented as defect spheres,irregular cubes and fragments.The emulsion systems controlled by non-ionic surfactant OP-10 and anionic surfactant SDBS played a inhibited role in the conversion of Ca CO3 from vaterite to calcite.The inhibition effect of SDBS-regulated emulsion system on the formation of crystalline forms of calcium carbonate was particularly evident,and it was a new system that can maintain nanoscale precursor amorphous calcium carbonate in the aging time of 0.5 h.At the same time,the mechanism of the different growth modes,morphology and phases of calcium carbonate caused by different additives in the two systems was investigated and explained in the form of mechanism diagram.This can predict the morphology,phase and properties of calcium carbonate under different system conditions,and has theoretical guiding significance for the work related to scaling in oil fields.