Study On The Modification Of Polyaspartic Acid And Polyepoxysuccinic Acid And Their Scale Inhibition Properties

Fouling and corrosion of industrial pipelines are serious problems that must be faced in industrial production.For example,in industrial circulating cooling water and seawater desalination processes,including multi-stage flash evaporation,membrane distillation,reverse osmosis and other processes,the concentration of calcium ions,magnesium ions and chloride ions will increase due to the excessive concentration of brine,and the concentration of calcium ions,magnesium ions and chloride ions will increase,thus calcium scale（Ca CO₃,Ca SO₄,Ca₃（PO₄）₂）is easily formed under weak alkaline conditions.The generated calcium scale is mainly deposited on the pipeline equipment or attached to the surface of the membrane,which is difficult to clean,causing blockage of the pipeline or membrane,and reducing the efficiency of heat and mass transfer.At the same time,during the operation of the equipment,corrosion of pipes and instruments will occur,and even if the corrosion is severe,the equipment must be replaced regularly.The presence of calcium scale and corrosion caused huge economic losses and severely affected industrial production efficiency.In this dissertation,modified polyaspartic acid and polyepoxysuccinic acid were synthesized and their chemical structures were characterized.The scale inhibition effect on calcium scale and the corrosion inhibition efficiency on carbon steel were discussed.The main research contents are as follows:（1）Polyaspartic acid（PASP）and polyepoxysuccinic acid（PESA）were prepared under mild conditions.The modified PASP was synthesized by arginine,histidine,and sulfamic acid under alkaline conditions at 40℃,and modified His-SA-PASP and Arg-SA-PASP were obtained.Through NMR and FTIR,His-SA-PASP and Arg-SA-PASP were successfully synthesized.Epoxy succinic acid（ESA）was prepared by maleic anhydride ring-opening modification,and calcium hydroxide was added as an initiator to carry out the polymerization of epoxy succinic acid to obtain polyepoxysuccinic acid（PESA）.Polyarginine was modified with arginine,and arginine was grafted to obtain Arg-PESA.The NMR and FTIR characterization also proved the successful synthesis of Arg-PESA.（2）Molecular Studio simulations were performed on His-SA-PASP and Arg-SA-PASP polymer molecules prepared by Materials Studio 8.0（MS）,and the polymer molecules were structurally optimized by Gauss 6.0.Simulation calculations show the possibility of the His-SA-PASP and Arg-SA-PASP polymer molecules interacting with calcium carbonate and calcium sulfate.The scale inhibition efficiency of these two modified polymer molecules was determined by the static scale inhibition method.The morphology of calcium carbonate and calcium sulfate obtained with or without the addition of His-SA-PASP and Arg-SA-PASP was analyzed by scanning electron microscopy（SEM）.The crystals of calcium carbonate and calcium sulfate obtained with or without the addition of scale inhibitor molecules were analyzed by XRD.The obtained calcium carbonate scale was analyzed by X-ray electron spectroscopy（XPS）.The corrosion inhibition effect of His-SA-PASP and Arg-SA-PASP on carbon steel surface was measured to determine the polarization curve and AC impedance spectrum of polymer molecules under different addition amounts.Experimental results show that His-SA-PASP and Arg-SA-PASP have better scale and corrosion inhibition performance.（3）Molecular dynamics simulation of the Arg-PESA and calcium carbonate interaction system was performed by MS.The negative interaction energy indicated the interaction between the scale inhibitor molecule and calcium carbonate.The scale inhibition efficiency of Arg-PESA on calcium carbonate and calcium phosphate was determined by static scale inhibition experiments.The morphology of the calcium carbonate scale crystals was analyzed by SEM.XRD analysis showed that the addition of Arg-PESA caused the transformation of calcium carbonate from aragonite to vaterite.The XPS analysis proved the interaction between Arg-PESA and calcium carbonate.The corrosion inhibition experiment of Arg-PESA on carbon steel was measured by the Electrochemical Workstation（CHI600E）.The corrosion inhibition efficiency of Arg-PESA was analyzed by polarization curve and AC impedance spectrum.The surface morphology of carbon steel was analyzed by scanning electron microscope and atomic force microscope.The experimental results show that Arg-PESA has a good scale and corrosion inhibition effect.