Characteristics and potential applications of coarse clay fractions from Puolanka, Finland

Abstract

Characterization of coarse fractions of kaolin clay from two locations in Puolanka (Pihlajavaara and Poskimäki) was performed in order to find potential applications for these materials in water and wastewater treatment as low-cost adsorbents or as a raw material for other uses. The effects of wet and dry fractionation methods and the annealing of the sample on the properties of the coarse fractions were studied. The coarse fractions contained mainly quartz, while the kaolinite content was considered low. The Poskimäki (PM) clay had a higher specific surface area (SSA) and cation exchange capacities (CEC) than the Pihlajavaara (PV) clay due to a higher amount of iron. Annealing (800°C) decreased the SSA and CEC. The fractionation method had only a minor effect on particle size distribution. PV and PM colloidal suspensions had a negative zeta potential at natural pH values. Very small amounts of contained elements (Al, Si, Ca, Mg, K, Cd, Co, Fe, Mn, Cr, Ni, Cu, Zn, Pb, Ba) were dissolved from samples at natural pH values. PM clay could be utilized in water treatment for example as a raw material in iron oxide-coated sands. For this purpose, the wet fractionated samples had a higher content of iron than the dry fractionated samples.