SOME MINERALOGICAL AND CHEMICAL PROPERTIES OF NATURAL ZEOLITE IN INDONESIA AND ITS PROPOSED APPLICATIONS IN AGRICULTURE

Suwardi, Astiana Sastiono and Itsuo Goto (1995)

ABSTRAK

Eleven natural zeolite sample collected from various locations in Indonesia were investigated for the mineralogical composition and chemical properties. X-ray diffractogram of the sample showed that the sample contained mordenite and mixture of mordenite and clinoptilolite. The sample were also associated with other minerals such as quartz, feldspar, montmorillonite, and volcanic glass. The zeolite content of the sample showed wide differences from 26 to 80%. The pH values were considerably high with the average of 7,2, whereas the electrical conductivity (EC) values were low with the average of 0,06 dSm^-1. The cation exchange capacity (CEC) values of zeolite varied between 71,9 to 167,0 cmol (+) kg^-1 with the base saturation of about 100%. The exchangeable bases of zeolite were dominated by calcium and potassium with some sodium. The availability of micro nutrients was low except manganese. Although zeolite was rich in SIO₂ and AL₂O₃ (the average contents of 69,3 and 12,7 wt %, respectively), the availability of SiO₂ and solubility of Al₂O₃ was low. The mineralogical composition and chemical properties of the sample were vary with every deposit and even in different parts of the same deposit. The variation was caused by the presence in various ratio of zeolite minerals and of the impurities such and quartz, feldspar, and montmorillonite. There for, it is necessary to be thoroughly characterized with respect to mineralogical composition as well as chemical characterization before a particular zeolite is offered for a particular use. The result suggested that direct application of zeolite as soil amendment should be accompanied by high dosage of fertilizers or together with the other soil amendment. The other zeolite applications in agriculture are proposed such as for a cultural medium, for reducing odor of compost during process, and for a slowly released fertilizer material.

Keywords: Cation exchange capacity (CEC), chemical composition, mineral composition,

soil amendment, zeolite.