Preparation of carbon adsorbents from lignosulfonate by phosphoric acid activation for the adsorption of metal ions

Activated carbons were prepared from sodium lignosulfonate by phosphoric acid activation at carbonization temperatures of 400-1000 degrees C. The resulting materials were characterized with regard to their surface area, pore volume, pore size distribution, distribution of surface groups and ability to adsorb copper ions. Activated carbons were characterized by nitrogen adsorption, scanning electron microscopy, Fourier transform infrared spectroscopy and thermal gravimetric analyses. The results indicate that with increasing carbonization temperature, the surface area decreased from 770 m(2)/g at 400 degrees C to 180 m(2)/g at 700 degrees C and increased at higher temperatures to 1370 m(2)/g at 1000 degrees C. The phosphorus content peaked at 11% for carbon obtained by carbonization at 800 degrees C. Potentiometric titration revealed the acidic character of all the phosphoric acid-activated carbons, which were found to have total concentrations of surface groups of up to 3.3 mmol/g. The carbons showed a high adsorption capacity for copper ions even at pH values as low as 2. (C) 2014 Elsevier Ltd. All rights reserved.