Study of the water state in chemically treated glauconite samples by thermal analysis

Abstract

Glauconite can be used to create new composite sorbents for water purification from oil. Methods for modifying and activating natural sorbents are used to improve their sorption properties. When oil is absorbed by the sorbent, water absorption takes place, which reduces its oil capacity. It is of interest how the moisture retention capacity of glauconite varies, after its chemical treatment. Glauconite was treated with solutions of sodium chloride, hydrochloric acid and sodium hydroxide. The process of dehydration of the initial and chemically treated glauconite samples was examined on a synchronous thermal analysis instrument (TG-DTA / DSC) of the model STA 449 F3 Jupiter, the company NETZSCH in a nitrogen atmosphere. The accuracy of temperature measurement is 0.1 °C using differential scanning calorimetry (DSC) and thermogravimetry (TG) methods. As a result of the study, thermograms were obtained, depending mainly on the chemical composition and structure of the test substance. On the DSC curves, one endothermic effect is observed, accompanied by a change in the mass of glauconite samples on the TG curves. The thermal effect corresponds to the removal of water from glauconite samples. The process of dehydration of glauconite samples treated with these reagents proceeds at lower temperatures than for the initial sample. A glauconite sample modified with sodium chloride is characterized by the lowest enthalpy of the dehydration process. The degree of conversion α (mass ratio at time “t” to the total change in mass at the end of the process) is calculated from the TG curves as a function of temperature. The obtained dependences are S-shaped, which indicates the complex nature of the interaction of water molecules with glauconite and suggests a different rate of water release at different stages of dehydration. From the graphical dependences (-lgα) on the value (103 / T), three stages of dehydration of the samples were determined, which correspond to the release of moisture with different shapes and energies. It is shown that the fraction of weakly bound water in glauconite samples decreases by 2.3 times, NaCl by 1.49 times, NaCl by 1.27 times in comparison with the initial sample. The proportion of medium bound water, on the contrary, increases when the HCl treatment is 1.29 times, NaCl is 1.34 times and NaOH is 1.58 times. The proportion of strongly bound water decreases by 1.44 times with glauconite modification by sodium chloride, by 1.09 times with NaOH activation and with acid activation practically does not change. The results of thermal analysis show that chemical modification with sodium chloride, acid and alkaline activation of glauconite, change the water content of different degrees of cohesion.