Adsorption of Chromium (VI) from Industrial Wastewater with Solphonated Lignite

The thermodynamics characteristics of Cr (VI) adsorption, the effects of pH, concentration and contact time and the adsorption isotherm line at different temperature from aqueous solution with solphonated lignite under static conditions were studied. The results showed that the Langmuir isotherm equation well described experiment data in dilute solution because fitting correlation coefficients were higher than 0.99 at the different temperature. Cr (VI) ion was adsorbed by solphonated lignite in the form of HCrO^4- ion owing to porous structure of solphonated lignite and the adsorption activation center of oxygen-containing function group existed in solphonated lignite surface. The desorbing of water molecules and H⁺ ion formation made the thermodynamics function ΔS₀ increase. The adsorption of Cr (VI) onto solphonated lignite is spontaneous, endothermic and chemical reaction and it is feasible for Cr (VI) adsorption removal from dilute aqueous solution with solphonated lignite.