Research On Synthesis And Performances Of Polyepoxysuccinic Acid

In water treatment industry, the latest research trend is to develop new environmentally-friendly water treatment agents. Developed in 1990's, polyepoxysuccinic acid (PESA) has been treated as a novel green water treatment agent at home and abroad for its excellent scale inhibition, corrosion inhibition, biodegradability and unique molecular structure having no hetero-atoms such as nitrogen and phosphorus.In this thesis, PESA was synthesized using two different methods: the conventional one-step method and the two-step method we have developed. The corresponding products obtained by the one-step method and the two-step method are named PESA I and PESA II, respectively. For the two-step method, highly pure sodium hydrogen cis-epoxysuccinate was firstly synthesized in an aqueous solution containing 75% by volume of alcohol, while sodium tungstate dihydrate was used as catalyst and epoxidation of maleic acid was obtained by hydrogen peroxide reagent, the yield of sodium hydrogen cis-epoxysuccinate was up to 97.8%. PESA II was obtained by polymerization of epoxysuccinate disodium salt in the presence of calcium hydroxide as an initiator . The structure of polyepoxysuccinic acid was characterized by IR and ¹3C NMR spectra. According to the ¹3C NMR spectra, the average polymeric degree of PESA I and PESA II are about 3 and 4, respectively.The scale and corrosion inhibition performances of polyepoxysuccinic acid synthesized were evaluated by static tests. The following conclusions can be deduced from the results of the tests: (1) PESA is an excellent scale inhibitor for CaCO₃ and CaSO₄ and can disperse ferric oxide effectively. The experimental results also show that PESA has poor performance of phosphate inhibition and zinc salt stabilization. The performance of scale inhibition of PESA II is better than that of PESA I .(2) The performance of inhibiting corrosion on Q235 carbon steel of PESA I is better than that of PESA II in neutro-water, the corrosion inhibition efficiency of PESA I is 60.5%, which is improved to 76.2% by adding tungstate sodium as synergestic reagent.The scale inhibition mechanism of PESA was proposed on the basis of characterization of transformation of calcium carbonate crystal by means of X-ray Diffraction (XRD) and scanning electron microscopy (SEM). The effect of temperature on corrosion inhibition efficiency of PESA was investigated and the Bockris substitution model is proposed to studythe thermodynamics of inhibiting process of PESA. The calculation results show the adsorption of PESA on carbon steel is a spontaneous exothermic process with the increase of entropy.