Use of Iraqi Attapulgite (ATP) and Surfactant-modified Iraqi attapulgite for Adsorption of Crystal Violet from Aqueous Solutions

Abstract

Iraqi attapulgite (ATP) mineral clay was modified using anionic surfactant (Sodium dodecyl sulfate (ATP-SDS)) to improve its adsorption capacity for crystal violet (CV⁺) dye. Different techniques were used to characterize the ATP and ATP-SDS such as FTIR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The adsorption properties of crystal violet (CV⁺) from aqueous solutions by ATP and ATP-SDS were further evaluated. Many parameters like adsorbent dosage, contact time, pH and temperatures were investigated and discussed. The adsorption kinetics were described using pseudo-first-order and pseudo-second-order models. The CV⁺ dye uptake process obeyed the pseudo-second-order kinetic. The experimental data were examined using Langmuir, Freundlich and Temkin isotherms models. The results showed better fit to Freundlich and Temkin models than Langmuir model. Thermodynamic values (∆G^o, ∆H^o and ∆S^o) showed that adsorptions of CV⁺ onto ATP and ATP-SDS were endothermic, spontaneous and randomness increasing for both sorbents. The results indicate that this natural and modified Iraqi attapulgite could be employed as low-cost alternative for removal of cationic dye CV⁺ from wastewater.    

Keywords: Adsorption, attapulgite, Sodium dodecyl sulfate, crystal violet, Thermodynamic parameters.