The adsorption mechanism of sodium lignosulfonate on Al2O3 particle in the aqueous solution

The adsorption properties of sodium lignosulfonate (SL) on Al2O3 particles under different pH values have been investigated. Results show that at low pHs, SL adsorbs on the Al2O3 particles in the form of aggregate as dosage of SL increases; at high pHs, the adsorption is approximately monolayer coverage. With pH values ranging from 3 to 11, the adsorption results are found to be not significantly affected by the addition of urea, ruling out the hydrogen bond as the controlling factor. The paper demonstrates that the main driving force of adsorption is considered as the synergistic effect of electrostatic and hydrophobic interactions when pH < pH(IEP) (IEP: isoelectric point); whereas, hydrophobic interaction and cation-pi interaction are the dominant forces in the adsorption process when pH > pH(IEP) with additives of Na2SO4 and NaCl.