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A new process for toxic metal uptake by a kraft lignin
Author(s) -
Crist DeLanson R,
Crist Ray H,
Martin J Robert
Publication year - 2003
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.735
Subject(s) - chemistry , adsorption , metal , lignin , inorganic chemistry , divalent , ion exchange , metal ions in aqueous solution , kraft process , equilibrium constant , kraft paper , stoichiometry , dissolution , ion , organic chemistry , chemical engineering , engineering
A 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