Uhlík P., Vajdová M. & Shiwa A., 2022: The use of the zeolite from Nižný Hrabovec for zeoponic substrates. Acta Geologica Slovaca, 14, 2, 131–141.

The use of the zeolite from Nižný Hrabovec for zeoponic substrates

Peter Uhlík, Martina Vajdová & Alhadi Shiwa

Comenius University Bratislava, Faculty of Natural Sciences, Dept. of Mineralogy, Petrology and Economic Geology, Mlynská dolina, Ilkovičova 6, 842 15 Bratislava, Slovakia; peter.uhlik@uniba.sk

Abstract

Zeoponic substrates are artificial soils having zeolites as a major component. Other components frequently added to the zeoponics are apatite-rich phosphate rocks. The possibility of using zeolite from Nižný Hrabovec for zeoponic substrates was investigated in this work. The KOH solution used to prepare K-saturated zeolite has dissolved the weakly crystalline silica phases and thus helped to increase the amount of clinoptilolite. Mixtures of NH₄^- and K-zeolites were mixed with deionized water to determine their K⁺ and NH₄⁺ release and exchange capacity. The highest amount of NH₄⁺ was released when the fraction of K-zeolite was 50 and 80 %. Since a phosphate-rich rock is unavailable locally, we have chosen alginite from Pinciná (South Slovakia) as an alternative component for the zeoponic substrates. Mixtures of NH₄^- and K-zeolite (1:1) in two fractions (< 0.1 mm and < 4 mm) were mixed with apatite and alginate in various ratios preparing zeoponic substrates. The ability of the prepared zeoponic substrates to release ions was tested in open and closed water systems depending on the time. The gradual ion release was observed for both zeolite-alginite and zeolite-apatite substrates. This is in contrast with the behaviour of a commercial (Klinofert) zeolite fertilizer and alginite from Pula. These substrates were releasing ions rapidly, and the final concentration of ions was significantly higher than that for the other substrates. The relative phosphate concentration increased with the increasing zeolite : apatite ratio, with a concomitant decrease in the released Ca²⁺. This trend confirms that zeolites preferentially uptake Ca²⁺ from the solution driving apatite dissolution. The pure alginate from Pinciná released a higher P concentration than the pure apatite. The highest concentration of K+ and NH₄⁺ was released from the zeolite-alginite 5:1 substrate in the water system. The concentration sum of analysed elements was increased with time and with coarser zeolite fraction in zeoponic substrates. The zeolite-alginite or zeolite-apatite mixtures were mixed with quartz sand, and horticulture grass was sown into these artificial soils. The grass production was better with the alginite-based zeoponics. On the other hand, alginite has a low N content, and therefore the plant production on the pure alginite is lower than on the substrates with the alginite-zeolite mixture.

Key words: Nižný Hrabovec zeolite, alginite, apatite, NH₄^- and K-clinoptilolite, zeoponic

Manuskript doručený: 2022-02-09

Manuskript revidovaný: 2022-12-05