Application of sequential extraction to determine the composition of zeolite for its safe use in agriculture

Zeolites are alumo-silicate minerals, commonly used industry, medicine and agriculture. Their application in agriculture is based on the fact that they can increase crop yield and promote nutrient use efficiency. In order to determine is zeolite (clinoptilolite) safe for use in agriculture, regarding its elemental analysis, sequential extraction followed by Inductively coupled plasma - optical emission spectrometry analysis is performed. Sequential extraction perrmited insight into elemental composition of clinoptilolite, through various extraction phases – exchagable, carbonate bounded, metals bound to Fe and Mn oxides, metals bound to organic matter and residual phase. The most abundant elements in first phase are Ca, K, Mg and Na (with a concentration greater than 100 ppm). Similar observation wa made for second phase of sequential extraction, but in this phase high content of Mn (232.6±0.7 ppm) was also noticed. In those two phases, that represents cations available to plants, no toxic elements exceeded permissible values prescribed by Serbian law. However, he content of Be (1.822±0.002 ppm) in sample obtained from third phase exceeds the concentration limit prescribed by Serbian law, which might be potentially dangerous, since Be could be adopted by plant and transferred to human through food chain. Concentration of toxic Cd was twice as higher compared to law limitations in residual phase. Bearing in mind obtained results, clinoptilolite analyzed in this study could be used in agriculture, but with continuous soil properties monitoring, since toxic elements could be mobile under various reducing and pH conditions.