Abstract:
Textile industries use dyes and pigments to color their products and thus produce
wastewater containing organics with a strong color. However most of the synthetic
dyes used in textile industry usually composed of aromatic structure, which makes
them carcinogenic and mutagenic and non-biodegradable when discharged into
waste streams. The removal of such colored agents from aqueous effluents is of
significant environmental, technical and commercial importance. Clay has been
accepted as one of the appropriate low cost adsorbents for removal of dyes from
wastewater. Among the clay types montmorillonite has received considerable
recognition because of its high adsorption capacity due to their lamellar structure
which provides higher specific surface area and possibility to adsorb ions and other
polar organic molecules on particle external site and in interlayer positions. In this
study the adsorption of basic dye: Bromothymol blue (BTB) from aqueous solution
by Sri Lankan montmorillonite was investigated. Montmorillonite clay used in this
investigation was obtained from Murunkan clay deposit in Sri Lanka.
Montmorillonite clay was examined for its performance as an adsorbent for the BTB
removal. The effect of key operational parameters, such as contact time, initial dye
concentration, adsorbent dosage, stirring rate and temperature were experimentally
studied. Adsorption of BTB onto montmorillonite samples was studied by batch
adsorption technique at 30±1 ºC using UV-Visible spectrophotometric method. For
the BTB initial concentration of 70 ppm with the use of only 20 g/L of
montmorillonite clay, the dye removal efficiency was found to be 63%. The
equilibrium data was analyzed using Langmuir and Freundlich adsorption isotherms.
Langmuir isotherm provided a better fit to the data. Characterization of clay before
and after the adsorption was carried out by using X-ray diffraction (XRD), Fourier
transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM)
methods. XRD, FTIR and SEM data revealed that the dye did not penetrate in to the
interlayer space of clay fully, but rather adsorbed on external surface by forming
hydrogen bonding with the dye molecules creating a void free film on the clay
surface. Experimental results confirmed that the Sri Lankan montmorillonite clay is
an efficient adsorbent for basic dye removal. Therefore, Sri Lankan montmorillonite
can be used as a promising low cost alternative adsorbent for removing basic dyes
from dye wastewater.
