SURFACE CHARGES AND ZERO CHARGE POINTS OF NATURAL CLAYS OF ORENBURG REGION

Abstract

The values of surface charges and zero charge points in water-clay suspensions with pH equal to 5, 7 and 9 have been studied. Their changes under the influence of a microwave field and variations in particle dispersion have been determined. Powders of two fractions of montmorillonite, polymineral and kaolin clays of the Orenburg region were selected as objects of research. The determination of the TNZ of natural clays was carried out by the method of weight titration, based on the measurement of the pH limit value with an increase in the weight fractions of clay. Processing of clay powders in a microwave field was carried out according to the following mode: output power of 750 watts, operating frequency of 2.45 GHz, exposure time 600 s. The magnitude and sign of the charges formed at the interface of the surface of the electrolyte solution particles depend on the mineralogical compositions of the particles. The fine fractions of two clays – montmorillonite containing and polymineral – were sensitive to treatment in the microwave field; the pH values of TNZ shifted to the acidic region by 0.26 and 0.31 units, respectively (by 4 %). The pH values of the TNZ suspensions with kaolin clay after treatment in microwave radiation practically did not change. If the pH value of the solution surrounding the particle exceeds the pH of the TNZ, then the sorbent will be able to absorb cations if the pH value of the solution is lower than the pH of the TNZ – anions. The results obtained will allow the use of microwave exposure as a tool that expands the pH range, contributing to the effective sorption of anions and cations.