Adsorption and removal of acid red 3R from aqueous solution using flocculent humic acid isolated from lignite

Humic acid (HA) was isolated from lignite. Flocculent HA was made and used to adsorb and remove dye acid red 3R from aqueous solution. The adsorption experiments were carried out in a batch process to observe the effect of various parameters such as contact time, dose of flocculent HA, ionic strength (NaCl) as well as adsorption kinetics and isotherm. Results showed that adsorption of acid red 3R on flocculent HA could reach equilibrium at less than 180 min. The adsorption kinetics obeyed the pseudo-second order model (R2=0.994). The adsorption was described with Freundlich equation on the basis of value of regression coefficient (R2=0.984). The removal rate of the dye increased with the increase of the dose of flocculent HA, while it decreased with the addition of NaCl in the aqueous solution. These suggested that the adsorption mechanism was the electrostatic attraction, to form hydrogen bonds, and van der waals' force between molecules of HA and acid red 3R. Conclusion was made that flocculent HA isolated from lignite could be used as an adsorbent to remove the dye from aqueous solution. (C) 2013 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license