Publikationsserver der RWTH Aachen University
Untersuchungen zur Eignung von natürlich alterierten sowie mit Oxalsäure aktivierten Bentoniten als Bleicherde für Pflanzenöle
Abstract
dc:descriptionBleaching earths have been utilised for the refining of vegetable oils for more than 100 years. They are manufactured during the reaction between bentonite and acid. This acid activated bentonite is both a catalytic and adsorptive reagent. The major disadvantage of the production, is the output of large quantities of waste acid. The aim of this study was to investigate the possibility of producing an environmentally friendly bleaching clay. Two ideas were formulated: The application of oxalic acid as a suitable agent for acid activation. With the ecological advantage that the acid can be decomposed of biologically and/or chemically. The possibility of managing natural acid clays from the island of Milos, which were generated by natural acid alteration systems. Acid activation of a bentonite can be monitored by N2-ad/desorption, IR-spectroscopy, titration, chemical analysis and CEC-determination: The octahedral layering of smectites is dissolved during acid attack. The remaining tetrahedral layer forms an x-ray amorphous, in a sodium-carbonate-solution soluble and porous phases which provides most of the activity. The natural acid alteration of the milosbentonites is comparable to a technical reaction. The activated clay represents a thermodynamically unstable material because of its trend towards recrystallisation of the silicious phase (finally: CT-Opalum). This mineral forms throughout geological periods from the remaining tetrahedral layer. Within 1,5 years it was not possible to crystallize CT-Opalum from a bleaching clay. However, the effect of time could be monitored by IR-spectroscopy, pore size distribution and the solubility of SiO2. Mineralogical-chemical characteristics of the rather different natural acid milosbentonites were classified by an „alteration-recrystallization-model“ with respect to mineralogical-genetic aspects as well as applicability. Using bleaching tests a high decolourisation ability with respect to soybean oil of some samples was detected. These materials are applicable for particular oils. However, they cannot fully compete against technical bleaching clays.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2001
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Kaufhold, Stephan
- Contributors dc:contributor
-
- Meyer, Franz Michael
Subjects
dc:subject × 8Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- ger