Font Size: a A A

Theoretical Study On The Operation Mechanism Of Scale And Corrosion Inhibitors

Posted on:2007-01-24Degree:DoctorType:Dissertation
Country:ChinaCandidate:S G ZhangFull Text:PDF
GTID:1101360185491852Subject:Applied Chemistry
Abstract/Summary:PDF Full Text Request
Quantum chemistry and molecular dynamics methods are used to study the operation mechanism of scale and corrosion inhibitors of circulating cooling water system in the dissertation. It can be divided mainly into two parts. Firstly, based on the experimental outcomes and theoretical simulation, we chose three kinds of ordinary scale crystals as substrates, including calcite, anhydrite and hydroxyapatite, to investigate systematically the scale and corrosion inhibition mechanism of carboxylate polymers, polyether polyamino methylene phosphonates, phosphonic acids. Secondly, the mechanism of pyridine, benzotriazole, imidazole and their respective derivatives as corrosion inhibitors of aluminum, copper and iron were also discussed by using theoretical calculation methods.The interactions between carboxylate polymers and three kinds of scale crystals were simulated dynamically by employing molecular dynamics method. The results show that the scale inhibition capacity order of polymers against calcite is: AA-MA>HPMA> AA-HPA>PAA>AA-MAE>PMAA, and the inhibition against (110) face is the dominant aspect, same conclusion was obtained by analyzing pair correlation functions of systems. The orders of scale inhibition capacity against anhydrite and hydroxyapatite are as follows respectively: AA-MA>HPMA>AA-HPA>AA-MAE>PMAA>PAA, AA-HPA>AA-MA> HPMA>PAA>AA-MAE>PMAA. The binding energies of carboxylate polymers and scale crystals are mainly come from the contribution of coulomb interaction. Polymers deformed violently during the binding process, electrovalent bonds formed between the calcium ions in scale crystals and the carbonyl oxygen atoms in carboxylate polymers. The middle carboxyls in polymers inhibit the growth of scale crystals more effectively than the end ones because they combine with scale crystals more firmly.The DFT study result of phosphonic acids indicates that the match degree between the atomic distances of functional groups in phosphonic acids and the distances of closed calcium ion pairs in calcite crystal surfaces determines the scale inhibition capacity of phosphonic acids. Under the periodic boundary condition, we obtained the order of binding energies for phosphonic acids with calcite (104) surface: ATMP>EDTMP>HEDP>GDMP >AEDP>MADMP. The strong electric interaction between the phosphonate, carboxyl oxygen atoms and calcium ions in crystal surfaces make them combined tightly. By analyzing molecular orbital energy gap, frontier orbital coefficient and orbital electron population of phosphonic acids, we obtain the order of corrosion inhibition capacity:...
Keywords/Search Tags:Scale and corrosion inhibitor, Scale crystal, Interaction mechanism, Quantum chemistry, Molecular dynamics, Binding energy, Pair correlation function, Solvent effect
PDF Full Text Request
Related items