Determination Of The Content Of Nitrilotris(Methylenephosphonic Acid)N--Coxide And Quantum Chemistry Studies On Mechanism Of Scale And Corrosion Inhibition

In the paper, a novel direct method for the accurate determination of ATMPO was developed based on the application of ultraviolet spectrophotometer ultraviolet spectroscopy. The optional wave length and a number of key factors including H2O2, pH, ATMP and PO43- affecting on the determination of ATMPO absorbance are discussed. Test shows that there are nearly no effect on its determination at 204nm when conditions are as follows:pH being controlled in 2～9, H2O2<1%wt, ATMP<2%wt, PO43-<2%wt. Under the optimal experimental conditions, the change of absorbance was linearly proportional to the concentration of ATMPO. The method is simple, rapid, accurate, its detection limit is 3mg/L, and is appropriate to be an useful assay determination of ATMPO.The scale and corrosion inhibition efficiency of ATMPO,ATMP,HEDP and PBTCA in simulated circulating cooling water was investigated by means of static scale inhibition test and rotating corrosion inhibition test. In the performance measurement experiments, the scale inhibition ability of ATMPO,ATMP,HEDP and PBTCA improved significantly with the increase of concentration of scale inhibitor up to the constant value. The scale inhibition efficiency on calcite has the order of PBTCA> HEDP≈ATMP≈ATMPO. Meanwhile, ATMP、ATMPO、HEDP have similar corrosion inhibition ability, with PBTCA more.By the computational approach of quantum chemistry in the project of B3LYP/6-31G**, optimized configurations and quantum chemical parameters representing molecular characteristics of ATMPO、ATMP、HEDP、PBTCA were obtained. Quantitative structure-activity relationship between quantum chemical parameters and scale and corrosion inhibition was established. Interrelated analyses conclude that a positive correlation between scale inhibition and electric charge and electrophilic index of phosphorus atom was founded, as with electrophilic index of oxygen atom in phosphonic acid group by a double bond. Scale inhibition and energy of LUMO presented negative correlation,and the correlation coefficient was 0.9. Meanwhile, electric charge and nucleophilic index of phosphorus atom,and electrophilic index of oxygen atom in phosphonic acid group by a double bond showed positive correlations with corrosion inhibition. On the contrary were LUMO-HOMO gap and energy of LUMO.