Study On The Synthesis Of AA-APEA₁₄and Its Scale Inhibition Performance

Antiscalant is a chemical agent that can prevent the formation of fouling or inhibit its deposition in industrial circulating water system.The development of scale inhibitors has successively changed from inorganic to organic and from phosphorus and nitrogen to green scale inhibitors.The organic scale inhibitor separates inorganic scale embryos from the circulating water through functional groups,and prevents or delays the further growth of inorganic scale embryos,thereby achieving the purpose of scale inhibition.Polyethylene glycol sodium monoacetate was synthesized through polyethylene glycol（PEG-600）,chloroacetic acid and sodium hydroxide as the materals,anhydrous ethanol used as solvent,and temperature controlled at 40-50°C.Then the generated sodium polyethylene glycol monoacetate,propylene chloride and sodium hydroxide were refluxed in absolute ethanol,and finally the p H value of the solution was adjusted with concentrated hydrochloric acid to obtain allyl polyethylene glycol monoacetic acid(APEA₁₄)monomer.APEA₁₄ was characterized by infrared spectroscopy（FT-IR）and nuclear magnetic resonance spectroscopy（¹H NMR）.A hydrophilic copolymer containing carboxylic acid and ethylene oxide groups AA-APEA₁₄ was synthesized in aqueous solution using acrylic acid and APEA14 as monomers,as well as ammonium persulfate as initiator.Taking the efficiency of the polymer to inhibit calcium carbonate scale as the object of investigation,the orthogonal experiment was used to explore the best synthesis conditions of the synthetic polymer.Finally,the polymer was characterized by infrared spectroscopy（FT-IR）and nuclear magnetic resonance spectroscopy（¹H NMR）.The effects of monomer ratio,temperature,heating time,Ca²⁺concentration,solution p H,addition amount,and relative content of COOˉ/EO in AA-APEA₁₄ molecule on the scale inhibition performance of polymer AA-APEA14 were studied by static experiments.Combined with scanning electron microscope（SEM）and X-ray diffraction（XRD）images,the scale inhibition mechanism of AA-APEA₁₄ was analyzed.The corrosion inhibition performance of AA-APEA₁₄ polymer was also investigated by hanging test,and its corrosion inhibition mechanism was preliminarily explored.The results were shown as following:（1）Static experiments show that the tendency of AA-APEA₁₄ polymer to inhibit Ca CO₃/Ca₃（PO₄）₂/Ca SO₄scale is linearly positively correlated with the increase in the amount of addition,and shows a certain threshold effect;for the same dosage,the scale inhibition efficiency increases with the increase of the relative content of COOˉ/EO in the polymer AA-APEA₁₄,which is related to the adsorption of COOˉon inorganic scale;in the experiment of heating time,AA-APEA₁₄ delays the nucleation time of fouling crystals,resulting in the reduction of scale inhibition efficiency with increasing temperature.However,with the increase of EO groups in AA-APEA₁₄ structure,the scale inhibition efficiency decreases.In the alkali resistance test,AA-APEA₁₄ can still have excellent scale inhibition performance within a certain alkalinity.In the calcium-dissolving ability experiment,due to the polyether structure（EO）in the AA-APEA14 molecule,the polymer has a certain calcium-dissolving ability,and the overall trend of the calcium-dissolving ability is gentle.（2）The scale inhibition mechanism of AA-APEA₁₄ mainly involves lattice distortion and electrostatic dispersion theory.On the one hand,Ca²⁺can complicate with carboxylate in AA-APEA₁₄.On the other hand,Ca²⁺weakly interacts with ether oxygen atoms in AA-APEA₁₄,and EO groups can form hydrogen bonds with water molecules bound on the surface of scale crystals,increasing the dispersion degree of the organism in the solution.AA-APEA₁₄ is adsorbed on the surface of particles or doped in the particle to consume their growth active points or their solution points and prevent the transformation of metastable particle to steady ones.The crystal microstructure shows fuzzy edges and corners,loose structure,rough surface concave and convex,uneven size distribution,and mostly exists in fine granular form.The study also found that the content of vaterite increased significantly with the relative content of COOˉ/EO in the AA-APEA₁₄ molecule,therefore the content of calcite decreased.In coupon corrosion test,at low dosage,the amount of AA-APEA₁₄ can not meet the corrosion inhibition requirements,which resulted in pitting corrosion on the surface of the hanging plates.However,with the increase of the addition amount of AA-APEA₁₄,the lamellar oxide covering layer on the hanging plates was significantly reduced,and the corrosion marks and pit damage were also significantly reduced.On the one hand,AA-APEA₁₄ can interact with the corrosion products of the hanging plate and metal ions to form a dense protective film,which hinders the continuous development of corrosion and dissolved oxygen reaction.On the other hand,AA-APEA₁₄ is adsorbed at the corrosion active point of carbon steel,which improves the activation energy of electrochemical corrosion reaction,affects the migration rate of charged particles,and reduces the corrosion current.