Study of the physical and chemical characteristics of a range of chemically treated, lignite based carbons

It is already known that activated carbons may be developed by chemically treating the adsorbent precursor to produce a carbon which displays improved adsorption characteristics and possibly preferential adsorption of one particular molecule over another. For the purposes of this study, a selection of carbons produced by the chemical treatment of N.I. lignite were studied. A range of transition metal compounds were used for the study as oxo-complexes of these metals have previously been associated with micropore widening in activated charcoal cloth. The adsorption of different concentrations of aqueous solutions of phenol, basic red dye and copper ions onto each carbon was examined. The adsorption equilibrium isotherms obtained for the carbons were plotted to obtain the Freundlich and Langmuir constants for each system. The adsorption capacity of each carbon was found to depend on its method of activation. In order to make a connection between the adsorptive behaviour of each carbon and its method of treatment, the physical and chemical morphology of the carbon was studied. Gas sorption on the Fisons instruments Sorptomatic 1900 and mercury porosimetry on the Fisons instruments Porosimeter 2000 were the methods used to study the micro-, meso- and macropore volumes, surface areas and pore radius distributions of the carbon samples. Infra-red spectroscopy showed that only minor changes occurred in the surface functional groups between the untreated lignite and the carbons and also between carbons themselves. Finally data obtained for these carbons was compared with the results of a previous study of untreated Northern Ireland lignite and lignite chars.