Polyaspartate (PASP)’s application research

Modification application research

After modification, polyaspartate (PASP) contains multiple functional groups in its molecular structure, which improves the comprehensive scale inhibition ability and dispersibility and expands the scope of application.

In order to improve the corrosion inhibition efficiency of PASP, histamine was used as a modifier to synthesize polyaspartic acid/histamine compound (PASP/HA) through ring-opening polymerization. The corrosion inhibition performance of PASP/HA compound under different conditions (drug concentration, temperature, pH, heating time) was evaluated by rotating hanging plate mass loss method. The results showed that: with the increase of drug concentration, the corrosion inhibition rate of PASP/HA compound continued to increase; the corrosion inhibition effect of PASP/HA compound was better than that of PASP, and the temperature-resistant corrosion inhibition performance was excellent; the corrosion inhibition rate of PASP/HA compound decreased with the extension of immersion time, but it could still maintain more than 70% after immersion for 120 h; PASP/HA compound can show excellent corrosion inhibition performance in acidic medium.

The polyaspartic acid/3,5-diaminobenzoic acid (3,5-DMBA) graft copolymer (PASP/3,5-DMBA) was synthesized by the amino ring-opening method. The scale inhibition and corrosion inhibition performance of the copolymer were investigated by static scale inhibition and dynamic corrosion methods. The results showed that the introduction of 3,5-DMBA can effectively improve the scale inhibition and corrosion inhibition performance of PASP, especially at lower concentrations, the scale inhibition performance of CaSO4 and Ca3(PO4)2 was significantly improved. When the dosage of PASP/3,5-DMBA was 1.25 and 6 mg/L respectively, its scale inhibition efficiency for CaCO3 and CaSO4 was close to 100%; when the dosage was 18 mg/L, the scale inhibition efficiency for Ca3(PO4)2 could reach 75%.

Technical Expert Zhang Yuling et al. modified and synthesized a new product, aspartic acid-itaconic acid copolymer (PAI), to improve the performance of PASP in inhibiting CaCo3 scaling. The static scale inhibition method was used to investigate the effect of different water quality conditions on the scale inhibition performance of PAI, and compared with the modified product aspartic acid-lysine copolymer (PAL) and the commercially available PASP. The differences in scale inhibition effects of PAI, organic phosphine scale inhibitor 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) and PASP under specific conditions were investigated from a kinetic perspective. The results showed that under the same experimental conditions, the scale inhibition rate of PAI on CaCO3 scale could reach up to 90.12%, which was slightly better than PAL and significantly higher than PASP; the crystal growth rate constants () of CaCO3 under the action of different scale inhibitors were (PBTCA) = 30.39 < (PAI) = 34.806 < (PASP) = 40.557. This shows that PAI is a new modified product with excellent scale inhibition performance, suitable for water systems with unstable water quality conditions and long hydraulic retention time.

PASP/L-carnosine was synthesized by ring-opening reaction under alkaline conditions using L-carnosine as the ring-opening medium. The static scale inhibition method was used to investigate the scale inhibition performance of PASP/L-carnosine against CaCO3 scale and Ca3 (PO4) 2 scale. The results showed that when the scale inhibitor dosage was 1.25 mg/L, the scale inhibition rate of PASP/L-carnosine against CaCO3 scale could reach 100%; when the scale inhibitor dosage was 8 mg/L, the scale inhibition rate of PASP/L-carnosine against Ca3 (PO4) 2 scale could reach more than 90%, which was better than PASP. PASP/L-carnosine has strong tolerance to high temperature and high phosphate concentration.

Composite application research

Due to the structural characteristics, the scale inhibition and corrosion inhibition performance of unmodified PASP is not very ideal when used alone. When PASP is compounded with other water treatment agents such as corrosion inhibitors and scale inhibitors, the synergistic effect between the reagents can be fully utilized to improve the comprehensive performance, reduce the amount of reagents used, and improve the economic benefits of the enterprise.

The corrosion inhibition performance of three single-component corrosion inhibitors, polyepoxysuccinic acid (PESA), PASP and sodium gluconate (Glu), on carbon steel was studied by static mass loss method. Then, the three were orthogonally compounded to obtain a new type of phosphorus-free composite corrosion inhibitor PESA/PASP/Glu with excellent corrosion inhibition effect. The effects of different factors on its corrosion inhibition performance were investigated. The results showed that the optimal mass concentration of the composite corrosion inhibitor was 1 000 mg/L, at which the corrosion inhibition rate reached 94.6%; the corrosion inhibition rate gradually decreased with the extension of time, but it still maintained above 70% at 48 h; the corrosion inhibition rate slightly decreased with the increase of temperature, but it could still reach 86.5% at 80 ℃; the corrosion inhibition rate increased with the increase of pH, and it could reach 96.5% at pH 12, almost completely inhibiting the corrosion of carbon steel.

The synergistic performance and action mechanism of PASP with polyacrylic acid (PAA), ZnSO4 and PBTCA were studied. The results showed that when the mass concentrations of PASP, PAA, ZnSO4 and PBTCA were 40, 30, 4 and 8 mg/L respectively, the scale inhibition rate of the composite reagent for CaCO3 scale could reach 95.04%, and the corrosion inhibition rate could reach 90%, showing excellent synergistic performance.

After the static scale inhibition test, it was found that when PASP and hydroxyethylidene diphosphonic acid were mixed in a mass ratio of 1:1, the scale inhibition performance was better than that of any monomer; under the condition of PASP and PBTCA usage of 1:1 (mass ratio), the corrosion and scale inhibitor was prepared by compounding. When the dosage of the composite corrosion and scale inhibitor was 30 mg/L, the corrosion and scale inhibition effect was significant.

The four-component compounding of PASP, benzotriazole (BTA), sodium tungstate (Na2WO4) and sodium gluconate was studied, and the optimal ratio was obtained through orthogonal test: (PASP): (BTA): (Na2WO4): (sodium gluconate) is 10:0.5:20:10 (total mass concentration is 40.5 mg/L). The scale inhibition rate and corrosion inhibition rate of copper in this formula are 99.22% and 0.000 6 mm/a respectively, which has good scale inhibition and corrosion inhibition effect.

PASP, propylene tricarboxylic acid-acrylic acid copolymer, sodium gluconate and zinc salt were compounded into a multi-element phosphorus-free composite water treatment agent in a certain proportion, and its corrosion inhibition and biodegradability were evaluated. The results showed that when the PASP in the composite reagent was 4 mg/L, the propylene tricarboxylic acid-acrylic acid copolymer was 8 mg/L, the sodium gluconate was 20 mg/L, and the zinc salt was 2 mg/L, the corrosion rate of carbon steel was 0.018 0 mm/a, and the corrosion inhibition rate reached 98.01%. In a complex water system with high Cl- and SO42- contents, the corrosion inhibition rate can still reach more than 90%. After 28 days, the biodegradation rate reached 87.5%. The composite reagent is suitable for complex water systems with high hardness and high alkalinity.

The corrosion and scale inhibition performance of PASP and Na2WO4 on 304 stainless steel under high concentration rate circulating water conditions was studied by static hanging plate method, static scale inhibition method, orthogonal method and Tafel polarization curve method. The results showed that under high concentration rate circulating water conditions, zinc salt was used as an additive (2 mg/L), and when the total mass concentration of the corrosion inhibitor was 80 mg/L, the composite of PASP and Na2WO4 had a good corrosion and scale inhibition effect on stainless steel, and the best composite formula was 40 mg/L PASP+40 mg/L Na2WO4. The composite of the two had a significant synergistic effect on the corrosion inhibition of stainless steel.

The corrosion inhibition performance of PASP and its composite with sodium molybdate and sodium dodecyl sulfate on carbon steel in tap water was studied, and the results showed that the corrosion inhibition efficiency increased with the increase of PASP concentration. When the mass concentration of PASP is 1.0 g/L, the corrosion inhibition rate reaches 61.4%; when 0.1 g/L polyaspartic acid is used alone, the corrosion inhibition rate is only 25.8%; when 0.1 g/L PASP is added and compounded with 0.1 g/L sodium molybdate, the corrosion inhibition rate increases to 73.95%; when 0.1 g/L PASP is added and compounded with 0.05 g/L sodium dodecyl sulfate, the corrosion inhibition rate increases to 70.71%. The compounding of PASP with sodium molybdate and sodium dodecyl sulfate has a positive synergistic effect.

An efficient green scale and corrosion inhibitor, which consists of PASP, PAA and PBTCA, is tested for the scale inhibition performance of PASP and its compound by calcium carbonate precipitation method, and the optimal formula is (PASP)∶(PAA)∶(PBTCA)=6∶1∶1. Under the test conditions, the scale inhibition rate of the compound can reach 91.71%, and the corrosion inhibition rate for carbon steel can reach 92.23%. It is an excellent scale inhibitor and corrosion inhibitor.

The synergistic effect of the compound system of PASP and aminotrimethylphosphonic acid (ATMP) was studied by static scale inhibition method, and the effects of scale inhibitor addition, temperature, pH, Ca2+ concentration, and HCO3- concentration on scale inhibition performance were investigated. The results showed that the scale inhibition performance of the compound system was better than that of a single scale inhibitor. When (PASP) ∶ (ATMP) was 2∶3, the scale inhibition performance was optimal. When the dosage of the composite scale inhibitor PASP-ATMP was 5 mg/L, the scale inhibition rate was as high as 93.04%. Although the scale inhibition performance of the compound system decreased with the increase of temperature, pH, Ca2+ concentration, and HCO3-, it still showed a certain calcium tolerance and was suitable for use in high pH and high HCO3- environments.

With PASP as the main agent, it was compounded with hydrolyzed polymaleic anhydride (HPMA) to develop a new type of corrosion and scale inhibitor suitable for weak alkaline conditions. The scale and corrosion inhibition performance of the corrosion and scale inhibitor in weak alkaline media was studied by static scale inhibition experiments, Tafel polarization curve method, AC impedance method and static mass loss method. The results showed that the corrosion and scale inhibitor belongs to a mixed corrosion inhibitor and shows good scale and corrosion inhibition effects in weak alkaline media.