The Physico-Chemical and Mineralogical Characterization of Mg-Rich Synthetic Gypsum Produced in a Rare Earth Refining Plant

Abstract

The physical, chemical and mineralogical characterization of the constituents of magnesium-rich synthetic gypsum produced in a rare earth-refining plant located in Gebeng, Pahang, Malaysia was conducted through elemental chemical analysis, scanning electron microscopy with Energy Dispersive X-ray (EDX)-analyzer, thermal analysis, X-ray fluorescence and X-ray diffraction. The crystalline nature of the by-product was studied using FTIR spectroscopy. Elemental analysis confirmed the presence of Ca and Mg, which are essential macronutrients required by plants and this Ca alongside the high pH (9.17) of MRSG may confer on the material a high acid neutralization capacity. From the result, it was observed that the studied by-product is a heterogeneous crystalline material comprising of gypsum (CaSO4.2H2O) and other major components such as calcium (magnesium) compounds (hydroxide, oxide, silicates, and carbonate) and sulfur. These aggregates may contribute to give an acid neutralization capacity to MRSG. The XRD study of MRSG indicated a high content of gypsum (45.4%), shown by the d-spacing of 7.609 Å (2-theta 11.63) in the diffractogram. The infrared absorption spectra of MRSG indicate close similarities to mined gypsum. The results of the characterization indicated that MRSG has valuable properties that can promote its use in amending soil fertility constraints on nutrient-deficient tropical acid soils.

Mg-Rich Synthetic Gypsum or Basalt as an Alternative Source of Ameliorant to Manage Soil Acidity for Plantation Tree Crops

“…Thus, lime application was recommended to alleviate soil acidity problem so that the growth and production of rubber could be sustained. This notion is consistent with the result of a study conducted in Thailand by Damrongrak et al (2015).…”

“…A study by Ayanda et al (2021) confirmed that the MRSG had pH higher than 7. Besides, it contained high amounts of Mg, Ca and S with some micronutrients, but no heavy metals of concern were detected.…”

“…Mg-rich synthetic gypsum, an industrial by-product, is found to have beneficial properties that makes it a potential alternative. MRSG with pH greater than 7 contains high amounts of Mg, Ca and S, with some calcium carbonate (Ayanda et al, 2021). Its application on an Ultisol cropped to oil palm in Bera, Malaysia, sustains the growth, giving comparable result to that of kieserite or GML (Ayanda et al, 2020).…”

“…The topsoil (0-15 cm) pH in the rubber plantations was strongly acidic (4.0-4.4). Based on a study conducted in Thailand (Damrongrak et al, 2015), liming soils of this nature with dolomite enhanced rubber growth.…”

Modified natural kaolin clay as an active, selective, and stable catalyst for methanol dehydration to dimethyl ether

“…The change in the position and the intensities of the latter two bands in the modified kaolin may have a role in the catalytic dehydration of methanol to DME. Meanwhile, two doublet bands also appeared at 610 and 594 cm −1 , which may be due to the bending modes of SO 4 −2 50 , 51 . The asymmetric and symmetric stretching modes of O=S=O also detected at 1120–1230 cm −1 and 1010–1080 cm −1 , respectively, and these bands are overlapped with that of the Si–O–Si band 52 .…”