Investigation of the adsorption of some dyestuffs onto sepiolite

Sepiolite mineral and organo-sepiolites (nonylammonium sepiolite, NS anddodecylammonium sepiolite, DS) were used as adsorbents for the removal of Methylene Blue(MB), Alizarin Yellow (AY), Remazol Yellow (RY) and Remazol Red (RR) dyes that wereconsumed largely in textile industry for dying purposes, from aqueous solution. For thispurpose, organo-sepiolites were prepared by modifying sepiolite with nonyl- anddodecylammonium chlorides. Specific surface area values of the samples were determined asa result of nitrogen gas adsorption-desorption at 77 K with B.E.T method. X-ray powderdiffraction (XRD) analysis of the mineral samples were carried out and thermogravimetricanalysis of the mineral samples were investigated. Organic matter contents were determinedin an elemental analysis instrument and the percentage of H, C and N were also obtained.Adsorption experiments were carried out at 25 degree according to the batch equilibriumtechnique. After adsorption, equilibrium dye concentration were determined UV-VisSpectrophotometrically by measuring absorbance values for MB, AY, RY and RR and usingcalibration curves. Adsorption isotherms were plotted from adsorption data for the removal ofdyes. The results were also fitted to Langmuir and Freundlich equation. The effects of pHand temperature onto the adsorption of dyes from aqueous solution were also investigated.Isotherms were generally L-types. Data were obeyed Langmuir and Freundlich equations.MB adsorption were increased with the increase in pH, while adsorption were decreased forAY, RY and RR. MB adsorption were also increased with temperature. The results showedthat sepiolite and organo-sepiolites can be used for the removal of dyes from aqueoussolution.Keywords: Dyestuff, adsorption, sepiolite, modified sepiolite, pH