Physicochemical properties of sodium lignosulfonates (NaLS) modified by laccase.

The ability of commercial laccase for improvement of the physicochemical properties of sodium lignosulfonate (NaLS) without any mediator has been investigated. Surface tension, adsorption characteristics, rheological behaviors and fluidity of cement pastes were in focus. Gel permeation chromatography (GPC) shows an initial decrease and then an extensive increase of molecular weight (MW) of NaLS after incubation with laccase. Parallel to MW decrement, the content of phenolic groups is increasing, while an MW increment has the opposite effect. The UV-Vis spectra and the zeta potential of NaLS do not indicate further modification of the substitution pattern on the aromatic ring. The surface tension of NaLS and the adsorbed amount of NaLS on MgO particles is elevated after laccase treatment. The electrostatic attraction between MgO particles and NaLS is the main driving force during this adsorption process. The dispersion efficiency of laccase modified NaLS on the MgO slurry and cement paste is improved. [ABSTRACT FROM AUTHOR]