Synthesis Of Hydroxy And Heterocyclic Polyaspartic Acid And Its Scale And Corrosion Inhibition Performance

As a nontoxic,phosphorus-free and biodegradable scale and corrosion inhibitor,polyaspartic acid?PASP?possesses good inhibition performance against CaCO₃ and CaSO₄.However,its inhibition performance against Ca₃?PO₄?₂,dispersion performance for ferric oxide and corrosion inhibition performance are not satisfying.In this dissertation,several modified PASP with hydroxyl and heterocycle are designed and synthesized.It has been found that the comprehensive performance of the modified PASP are improved on the basis of maintaining the original scale and corrosion inhibition performance of the PASP.The main research contents and results of this dissertation are as follows:?1?Polysuccinimide?PSI?,the precursor of PASP,was synthesized by thermal polycondensation reaction with maleic anhydride and urea as raw materials.2-Amino-2-methyl-1-propanol,2-amino-1,3-propanediol,furfurylamine and 4-?2-aminoethyl?morpholine went through a ring-opening reaction with PSI under alkaline condition,and polyaspartic acid/2-amino-2-methyl-1-propanol?PASP/AMP?,polyaspartic acid/2-amino-1,3-propanediol?PASP/APD?,polyaspartic acid/furfurylamine?PASP/FA?and polyaspartic acid/4-?2-aminoethyl?morpholine?PASP/AEM?were synthesized,respectively.In addition,the structure of the synthetic products were characterized by ¹H NMR.?2?The static method was conducted to evaluate the scale inhibition and dispersion performance of modified PASP.Compared with PASP,the inhibition efficiency against CaCO₃ and CaSO₄ of PASP/AMP,PASP/APD and PASP/FA have been improved to a certain degree.The inhibition efficiency against Ca₃?PO₄?₂ of the four modified PASP were also greatly improved with respect to PASP.Especially,PASP/APD achieved 100%inhibition efficiency against CaCO₃ and CaSO₄ at dosages of 1 mg/L and 4mg/L,respectively.When the dosage was 10 mg/L,the inhibition efficiency against Ca₃?PO₄?₂ of PASP/AEM reached 100%.In addition,both PASP/FA and PASP/AEM exhibited good dispersion performance for ferric oxide at a dosage of 56 mg/L,corresponding to the transmittance of the test solution was 69%and 66%,respectively.The morphology of the scale crystals in the absence and presence of modified PASP were investigated by SEM and XRD.When modified PASP were added to water,the growth of scale crystals was severely inhibited,the surface of crystals became rough,and the structure became irregular and broken,so it was difficult to accumulate in large amounts.?3?The corrosion inhibition performance of modified PASP on carbon steel in 0.5 M H₂SO₄ was evaluated by weight loss method and electrochemical method.The corrosion inhibition efficiency of the four modified PASP on carbon steel have been improved to some extent compared to PASP.Especially,the corrosion inhibition efficiency of PASP/AEM at a dosage of 100 mg/L was as high as 90.3%.As a mixed-type corrosion inhibitor,PASP/AEM can prevent the dissolution of the metal anode and the hydrogen evolution reaction of the cathode simultaneously.When PASP/AEM was added to the H₂SO₄solution,a uniform and dense adsorption membrane can be formed on the surface of the carbon steel to prevent the contact of the acid solution with the metal.Hence,the corrosion of the metal was lessened.?4?The biodegradability of modified PASP was investigated.The biodegradation rates of PASP/AMP,PASP/APD,PASP/FA and PASP/AEM within 28 days were 65%,61%,58%and 55%,respectively.