CHARACTERISATION OF ATTAPULGITE AND ITS COMPARISON WITH DIATOMACEOUS EARTH ON THE BASIS OF PHYSICOCHEMICAL PROPERTIES AND SORPTION BEHAVIOUR OF P AND NH4+

Attapulgite is a naturally occurring crystalline hydrated magnesium alumino-silicate that gives it unique colloidal and sorptive properties, whereas diatomaceous earth is a naturally soft, siliceous sedimentary mineral with a fine white to off-white powder. The main objective of the research is to characterize the physicochemical properties and sorption behaviour of attapulgite, and its comparison with that of diatomaceous earth. Both materials were analysed for physicochemical properties such as mineralogy by XRD, pH, electrical conductivity (EC), phosphorus retention index (PRI), Exchangeable cations (Ca2+, Mg2+, Na+ and K+), cation exchange capacity (CEC) and sorption studies (NH4+ and P sorption). Mineralogy results showed that attapulgite contain major palygorskite and kaolin with trace halite (NaCl), whereas diatomaceous earth contains major quartz, minor kaolinite and halite. The lower Ca/Mg ratio (< 1) suggests that both materials are Ca deficit. Due to higher individual base saturation percentage attapulgite is weakly leached, which suggests it may be able to prevent leaching of soluble cations from sandy soils of Western Australia. Both materials have good phosphorus sorption capacity compared to the NH4+ sorption and it can be improved by treating them with other cations/anions or organic matter addition. This preliminary investigation suggests that attapulgite can be used as slow release fertilizer after treating with phosphate for sandy soils of Western Australia but it needs further investigation to assess its effect on nutrient availability to plants and leachability.