TY - JOUR

T1 - Physicochemical transformation of expanded vermiculite after long-term use in hydroponics

AU - Kremenetskaya, Irina

AU - Ivanova, Liubov

AU - Chislov, Mikhail

AU - Zvereva, Irina

AU - Vasilieva, Tatiana

AU - Marchevskaya, Valentina

AU - Semushin, Vasilii

AU - Slukovskaya, Marina

N1 - Funding Information: This study was supported by the Russian Science Foundation (№ 19-77-00077 ) and Russian Academy of Sciences (№ 0186-2019-0011 ). Thermal analysis was conducted in the Center for Thermal Analysis and Calorimetry of St. Petersburg State University . Authors are gratitude to Dr. Marina Strelkova, Dr. Taras Panikorovskii, and MSc. Andrey Novikov for their support on different stages of article preparation. Publisher Copyright: © 2020 Elsevier B.V. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2020/11/15

Y1 - 2020/11/15

N2 - Physicochemical properties of expanded vermiculite-phlogopite products from Kovdor (Murmansk region, Russia) used for 15 years as a hydroponics substratum were studied. The four investigated samples were as follows: natural vermiculite, initial expanded (roasted at 700 °C) vermiculite, spent expanded vermiculite and spent vermiculite roasted again at the same temperature. Data on the bulk density, field capacity, hygroscopicity, and expansion coefficients showed that the degradation of the substratum was accompanied by mechanical destruction, reduction of water absorption by half, and transformation of mineral phases. The structural transformation of expanded vermiculite was studied using X-ray diffraction (XRD), thermogravimetric analysis (TG), and differential scanning calorimetry (DSC), coupled with a mass spectrometric analysis of the released gases. Under conditions with a sufficient supply of plants with potassium of nutrient solution, a change in the mineral composition occurred: a decrease in the content of vermiculite and an increase in phlogopite. The formation of organomineral complexes on the surface of the vermiculite was detected. There was no noticeable change in the chemical composition of the expanded vermiculite during its use in hydroponics. In essence, the levels of potentially toxic elements (Mn, V, Ni, Cr, Co, Cu, Zn) met environmental regulations, and the levels of major elements (Mg, Ca, K, Fe, Mn) corresponded to those found in natural vermiculite. The chemical composition and structure of spent vermiculite allows its use as an ameliorant to improve soil, water, and air regimens.

AB - Physicochemical properties of expanded vermiculite-phlogopite products from Kovdor (Murmansk region, Russia) used for 15 years as a hydroponics substratum were studied. The four investigated samples were as follows: natural vermiculite, initial expanded (roasted at 700 °C) vermiculite, spent expanded vermiculite and spent vermiculite roasted again at the same temperature. Data on the bulk density, field capacity, hygroscopicity, and expansion coefficients showed that the degradation of the substratum was accompanied by mechanical destruction, reduction of water absorption by half, and transformation of mineral phases. The structural transformation of expanded vermiculite was studied using X-ray diffraction (XRD), thermogravimetric analysis (TG), and differential scanning calorimetry (DSC), coupled with a mass spectrometric analysis of the released gases. Under conditions with a sufficient supply of plants with potassium of nutrient solution, a change in the mineral composition occurred: a decrease in the content of vermiculite and an increase in phlogopite. The formation of organomineral complexes on the surface of the vermiculite was detected. There was no noticeable change in the chemical composition of the expanded vermiculite during its use in hydroponics. In essence, the levels of potentially toxic elements (Mn, V, Ni, Cr, Co, Cu, Zn) met environmental regulations, and the levels of major elements (Mg, Ca, K, Fe, Mn) corresponded to those found in natural vermiculite. The chemical composition and structure of spent vermiculite allows its use as an ameliorant to improve soil, water, and air regimens.

KW - Organo-mineral complexes

KW - Phase analysis

KW - Physicochemical properties

KW - Soil amelioration

KW - Vermiculite-phlogopite

UR - http://www.scopus.com/inward/record.url?scp=85091258182&partnerID=8YFLogxK

U2 - 10.1016/j.clay.2020.105839

DO - 10.1016/j.clay.2020.105839

M3 - Article

AN - SCOPUS:85091258182

VL - 198

JO - Applied Clay Science

JF - Applied Clay Science

SN - 0169-1317

M1 - 105839

ER -