Dissolution Kinetics and Mechanism of Pandermite Mineral in Acetic Acid Solutions

Abstract

Bu çalışmada, önemli bor minerallerden biri olan pandermitin asetik asit çözeltilerindeki çözünme kinetiği ve mekanizması incelendi.Çözünme kinetiği için, tane boyutu, asit konsantrasyonu, katı/sıvı oranı, reaksiyon sıcaklığı parametre olarak seçildi. Deneysel veriler ışığında pandermitin asetik asit çözeltilerindeki çözünme hızının, azalan tanecik boyutu, azalan katı/sıvı oranı, artan reaksiyon sıcaklığı ile arttığı ve artan asit konsantrasyonu ile 3 M' lık derişime kadar arttığı daha sonraki derişimlerde ise dönüşüm hızının artamasında azalma oduğu tespit edildi..Pandermit mineralinin asetik asit çözeltilerinde çözünme mekanizması incelendiğinde çözünme hızının artan asit konsantrasyonu ile sınırlandığı ve bununda mineralin yüzeyinde çözünen borik asitin belli bir doygunluğa ulaştıktan sonra çökmesi ve katı yüzeyine asit difüzlenmesini zorlaştırmasına bağlandı.Asetik asit çözeltilerinde pandermit mineralinin çözünme hızı homojen ve heterojen kimyasal reaksiyon modellerine göre incelendi. Grafiksel ve istatiksel veriler kullanarak reaksiyon kinetiğinin [-ln(1-X)] = kt şeklinde birinci dereceden yalancı homojen reaksiyon modeline uyduğu belirlendi. Çözünme prosesi için aktivasyon enerjisi 28.496 kj/mol olarak bulundu ve çözünme prosesini en iyi ifade eden model;[-ln(1-X)] = [6.68x103(Rp)-0,2933(CA)o0.3899(K/S)-0.2878 e3427.47/T.t] olarak belirlendi.Anahtar kelimeler: Asetik asit, Çözünme, Kinetik, Mekanizma, Pandermit.

In this present study, the dissolution kinetics and mechanism of pandermite, which is one of the most important mineral in boron reserves, was investigated in acetic acid solutions.For the dissolution kinetics; the effect of particle size, acid concentration , solid-to-liquid ratio and reaction temperature were chosen as parameters. In the light of the experimental data; it was determined that the dissolution rate of pandermite in acetic acid solutions was found to increase with decreasing particle size, decreasing solid-to-liquid ratio, increasing reaction temperature and increasing acid concentration up to 3 M then the increase of the dissolution rate decreased a further increse in acid concentrations.In the investigation dissolution mechanism of pandermite mineral in acetic acid solutions; it was observed that the dissolution rate was restricted by increasing acid concentration. When the acid concentration increased a certain value boric acid reaches one saturation value near the solid particle, it forms adifficult-soluble solid film layer around the particle,causes the system to have diffusional character, and results in slowing down the dissolution process.The dissolution rate of pandermite mineral in acetic acid solutions was examined according to homogeneous and hetereogeneous chemical rection model. It was determined by graphical and statistical methods that the reaction kinetics fitted to model in form of first order pseudo homogeneous model showed as [-ln(1-X)] = kt and activation energy for the dissolution process was found to be 28.496 kj/mol. The following mathematical model, which indicates very well the dissolution process, was established;[-ln(1-X)] = [6.68x103(Rp)-0,2933(CA)o0.3899(K/S)-0.2878 e3427.47/T.t]Key words: Asetic acid, Dissolution, Kinetics, Mechanism, Pandermite.