Filtern
Erscheinungsjahr
- 2014 (2) (entfernen)
Dokumenttyp
Sprache
- Englisch (2)
Schlagworte
- Filtration Residues (1)
- Re-Use of Industrial Waste (1)
- Reaction Kinetics (1)
- Silica Residue (1)
- Superalkaline Conditions (1)
- Zeolites (1)
Zeolite synthesis was studied using two silica rich filtration residues (FR 1 and FR 2) as Si-source
and sodium aluminate in a direct synthesis at 60°C at strong alkaline conditions (8 M - 16 M NaOH).
In addition to these one-pot syntheses, a two-step process was investigated. Here, an alkaline digestion
of FR at 60°C was followed by gel precipitation with sodium aluminate and gel crystallization
under usual conditions of 80°C - 90°C. The results show that the substitution of chemical
reagent sodium silicate by a waste material like FR as Si-source is possible but requires fine tuning
of the reaction conditions as zeolite crystallization is a process under kinetic control. The
solubility behaviour and impurities of the inserted filtration residues strongly influenced the
course of reaction. Thus zeolites like hydrosodalite or intermediate zeolite between cancrinite
and sodalite, or zeolite NaA or Z-21 in cocrystallization with hydrosodalite could be observed in
the one pot syntheses already in a short time interval between 1 - 4 h depending on the alkalinity.
The two step process yield to zeolites NaA and NaX in very good quality. The reaction process of FR
in both reaction methods was characterized by chemical analyses, X-ray powder diffraction,
Fourier transform infrared spectroscopy as well as scanning electron microscopy. Surface area
and water content of selected products were further characterized by the BET-method and by
thermogravimetry. Summing up the results, we can show that zeolite formation from filtration residues
is possible by several reaction procedures as model cases for a re-use of industrial waste
materials. Beside the importance for environmental protection, the reactions are of interest for
zeolite chemistry as the re-use of FR is possible under economically conditions of low energy consumption
at 60°C and short reaction periods.
Citrus pectins, necessary for the food industry and many other applications, are produced by large companies and distributed worldwide. On their way to the customers, the pectins may be stored under unfavourable environmental conditions for longer periods. This can alter their properties and affect their quality in the final application. It can be assumed that (1) pectins from different suppliers, produced from varying raw materials and under different processing conditions, have also varying material properties and water binding behaviour, and (2) the storage of pectins at 60 °C and 80 % humidity might alter these properties and the increase of hydrophilic groups might increase also their water binding ability. The aim of the present study was to investigate the water binding properties of different commercial pectins prior to and after storage by differential scanning calorimetry (DSC) at different water contents.