Effect of Water Immersion on Raw and Expanded Ugandan Vermiculite

Celia Marcos

doi:10.3390/min12010023

Abstract

Effect of water immersion at different times (from 1/2 h to 24 h) on raw and expanded vermiculite from Uganda was investigated. The expansion was carried out by electrical heating at different temperatures and by irradiation with microwaves. After, the expansibility (k) and the water absorption content (WA) were obtained and the samples were characterized. The elemental and mineral composition was determined by X-ray fluorescence and X-ray diffraction, respectively; the thermal behavior by thermal gravimetric analyses; and the textural parameters by BET. The expansibility of Ugandan vermiculite is relatively lower than the other commercial vermiculites due basically to its lower K2O content (0.36%) and higher water content (about 20%). The water absorption capacity of samples significantly increased with the increase in heating temperature. The maximum WA content, about 130 mg/g, was obtained at 900 °C for 24 h. The loss of water during the expansion process in the Ugandan vermiculite caused loss of structural order and crystallinity. Moreover, in the samples expanded and subsequently immersed in water, the structural order and crystallinity increased with increasing WA values. Specific surface area and porosity hardly vary with temperature and are practically independent of vermiculite purity. Expanded commercial vermiculites could be a suitable hygroscopic material, given its efficient water absorption. Microwave expanded commercial vermiculites, in this case, would not be recommended.

Highlights

The materials used as pavement in large cities are generally characterized by their low thermal conductivity and high absorption of solar energy due to their dark color
The other effective way is to improve energy efficiency, which can be realized through the use of thermal insulating materials with high performance [2]
Raw and treated samples were subjected to characterization of the composition using X-ray fluorescence, expansibility, identification of the mineral composition by X-ray diffraction, thermal behavior using thermal gravimetric and analyses textural parameters with BET

Summary

Introduction

The materials used as pavement in large cities are generally characterized by their low thermal conductivity and high absorption of solar energy due to their dark color. The expansion occurs only at right angl age planes, and the sheets spread apart into an accordion like 2sotfr1u3 cture c between them and, increasing the spaces available for water ads the exfoliated vermiculite becomes a powerful desiccant. This structure is rfeoternVtiiteosrnmbpicrruoeplaiteterhtiisaeasbpoiplfircoteypmr,ieadntertiaftoiiornuiamsgmperao,tveairnniagdlsthc[e1a1wt,1iao2te]n.r Tadbheseoscreopmmtioapntecoraisapliastciciootynn, swtaiatbuteitrle/ittfhyeer.tmiliozestr importaInnt coormdpeornteontsuosfeplvaentrimngiccounlcirteetea[1s3r–o15o].f and floor insulation in a house, it knoTwhe imtsaiwn cahtaerracrteertiestnictioofnvecrampicaucliittey, .wSeoll kfanor,wsnobmy eallr,eissethaericrhexhfoalisatbioeneanndcarried ebhxeptawavneiseoinorntohcfeavpsaielcircitmaytewicshuheelniettiest ii[s1nh6–eina2t1ea]d.

Experiments

Characterizations

Findings

Conclusions