Lignin Powder Research Articles

A new process for toxic metal uptake by a kraft lignin

AbstractA new approach toward removing toxic metals from industrial process water has been investigated using kraft lignin, a by‐product of paper production. A detailed study on a kraft pine lignin powder (Indulin AT from MeadWestvaco), which has acid functions that can act as ion‐exchange sites, has shown that uptake of divalent toxic metals is accompanied by a release of protons or existing metals from the lignin. Equilibrium constants for displacement of protons decreased with pH, and equilibrium constants for metal–metal exchange showed that binding strengths follow the order (highest to lowest): Pb, Cu, Zn, Cd, Ca, Sr. A demonstrated stoichiometry of one mole Ca displaced for one mole of metal (Sr or Cd) sorbed is fully consistent with a chemical reaction of ion exchange and difficult to explain by frequently used adsorption models (Langmuir adsorption isotherm and biotic ligand model). Since the powder after metal uptake is hard to separate from purified water on a large scale, a novel formulation has been investigated for toxic metal removal.© 2003 Society of Chemical Industry

Lignin-filled polyolefins

Dry lignin powder was used as a filler in low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP) up to 30% w/w. The tensile strength reduced for all polymers. Impact properties were almost unaffected for PP but reduced for the other two polymers, Use of five parts of ethylene acrylic acid copolymer (EAA) and 0.5 parts of titanate coupling agent improved mechanical properties considerably. The melt viscosity increased steadily with increasing amounts of lignin. Electrical properties showed improved electrical resistance. The color of the resulting compound could be evaluated only up to a 10% lignin level, beyond which the compounds became very dark. At lower concentrations, samples of HDPE showed a more reddish tinge, while at higher concentrations, all samples showed a green–blue tinge. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1321–1326, 1999

Weathering of wood and protection by chromium studied by XPS

AbstractIn order to understand better the protection mechanism of aqueous CrO3, the surface of untreated and treated wood, before and after weathering, was studied by XPS. For comparison, the reaction of CrO3 with filter paper, used as a model compound for cellulose, and with lignin powder was studied as well.Owing to differences in the O/C ratio and the shape of the C 1s signal, cellulose and lignin can be distinguished from each other with the aid of XPS. The low O/C ratio and the high C1 (CC, CH) contribution found for the surface of wood show that the upper layer is enriched with ligin and extractives. Weathering of wood starts with the degradation of lignin, and the appearance of cellulose on the surface increases the O/C ratio and shifts the maximum of the C 1s signal to the C2 (COC, COH) position.Aqueous CrO3 oxidizes lignin powder and possibly also cellulose. The effect on wood, as observed with XPS, is small. The protection, however, is very clear; the increase of the O/C ratio of CrO3‐treated wood during weathering is much slower than the increase for untreated wood. After weathering, the C 1s signal still resembles the C 1s signal of lignin, so the CrO3 protects the lignin from degradation.

Energy storage composite with an organic PCM

This research work is primarily aimed at exploring possibilities of storing an organic phase change material (PCM) in a new kind of composite. Phase change materials have previously been successfully impregnated in gypsum wallboard. During the present research, certain aggregate and filler materials were selected after detailed laboratory study as possible constituents of the proposed composite. Absorption of PCM and retention there-of in materials like expanded shale, volcanic rock, activated charcoal, gypsum and vermiculite was determined. Composite specimens were prepared using coarse aggregates, gypsum, cement, sawdust and vermiculite and sand with water. Several mix compositions with different proportions of these materials were prepared. These gypsum/cement concrete specimens were cured, dried and impregnated with PCM. The absorption capacities of PCM in the specimens were determined and compressive strength tests, differential scanning calorimetry analysis, infrared spectroscopy and thermal conductivity tests performed.The composite, depending on the mix composition, is capable of storing up to 30 wt% of PCM. In order to ensure complete encapsulation of PCM, the composite specimens were coated with a film of polyester resin. This, however, resulted in lowering of the heat transfer capability of the composite. Thermal conductivity tests showed great improvement on introduction of aluminum or lignin powders in the resin. The composite can be produced in the form of floor, wall or ceiling tiles capable of storing energy up to 766 kJ/m2.

Elastic modulus of lignin as related to moisture content

The Young's and shear moduli of two lignins have been measured at several moisture contents. Cylindrical test specimens moulded from periodate and Klason lignin powders were conditioned to the required moisture contents and tested in tension and torsion. The Young's modulus of periodate lignin increased linearly from 3.1x109 to 6.7x109 Pa, and the shear modulus from 1.2x109 to 2.1x109 Pa as the moisture content of the lignin decreased from 12 to 3.6%. Klason lignin showed similar behaviour but its moduli were always much lower. This was probably a consequence of the more drastic alteration undergone by the Klason lignin during its isolation from the wood cell wall.