Synthesis And Performance Of Phosphono Carboxylic Acid

Phosphono carboxylic acid (POCA) was prepared by telomering of acrylic acid (AA)and 2-arylamido-2-methylpropane sulfonic acid (AMPS) with phosphorous acid used aschain transfer agent and ammonium persulfate as initiator. Taking scale inhibition of POCAon CaCO₃,Ca₃(PO₄)₂ and Zn(OH)₂ as the criterion, the optimum reaction conditionsobtained are m(AA):m(AMPS)=3:1, n(H₃PO₃):n(AA+AMPS)=1:5, n(Na₂S₂O₈):n(AA+AMPS)=1:10, the temperature 110℃, the catalyzer 5mg/L, the drop adding time ofmonomers 2.5hs and circumfluence for 1.5hs until the end.The scale inhibitions of POCA on CaCO₃, CaSO₄, Ca₃(PO₄)₂ and Zn(OH)₂ anddispersion on Fe₂O₃, Ca(SiO₃)₂ were evaluated. The abilities to endure calcite hardness,heat, press and to resist hydrolysis, gelation and oxidation were investigated. The resultsshowed that POCA is much better than the common scale inhibitors in general.The performance and mechanism of corrosion inhibitions of POCA were studied bymethods such as weight-loss, electrochemistry, EDS, XPS and quantum chemistry. It isfound that POCA is cathodic corrosion inhibitor, having synergistic effect with HEDP andZn²⁺. The P and O atoms of phosphono have important electron density contribution toHOMO orbital and the electron gross orbital population is bigger than 1, so it is easy toform absorbing location between phosphono and metal resulting in good corrosioninhibition on mild steel. POCA has corrosion effect on brass less than HEDP and hassynergistic effect with BTA, the corrosion of brass can be efficiently prevented by adding1mg/L BTA.The scale appearance and structure messages from XRD and SEM and TEM revealthat POCA has strong effect on dispersion and lattice distortion of scale. POCA is adsorbedon the growth sites of the scalent crystal restraining the growth of crystal or loosening anddispersing scale grains so as to prevent deposition of hard scale, the inhibition on CaSO₄ isstronger than CaCO₃.The related parameters were calculated by quantum chemistry method, thediscrepancy of scale inhibition capability of polymers was unpuzzled by matching model;The microcosmic scale inhibition mechanism was simulated by molecular dynamics (MD),the relationship between structure of polymers and effect was expounded, providing theoryguidance for molecular design of new multifunctional water treatment agents. With the practical use, it is proved that the chemicals, which take POCA as the maincomponent, would marvelously keep 35mmol/L～50mmol/L hardness and alkalinity withincirculating cooling water system in stable with about 30mg/L POCA dosage. The corrosionof brass were controlled owing to the consistency between POCA and BTA.