Substrate for soil improvement having a water-storing property, method for producing same, and use thereof
In a method for producing a substrate for soil improvement with water-storing property on the basis of lignin, lignin is provided and oxidized alternatively in an aqueous alkaline or a pH-neutral aqueous suspension, wherein the pH-neutral aqueous suspension after oxidation of the lignin is converted into an alkaline medium. The lignin is cross-linked in an aqueous alkaline medium by multi-functional compounds. Subsequently, the lignin is neutralized, dried, and comminuted. The produced lignin is used as a substrate for improvement of soil properties in that the substrate is used as a water storage that, compared to water storages of non-modified technical lignins, exhibits a significantly higher water adsorption capacity or swelling capacity.
1. A method for producing a substrate for soil improvement with water-storing property on the basis of lignin, characterized by the steps:
providing lignin,
oxidation of lignin alternatively in an aqueous alkaline or a pH-neutral aqueous suspension, wherein the pH-neutral aqueous suspension after oxidation of the lignin is converted into an alkaline medium, wherein the oxidation is carried out with:
hydrogen peroxide, or
a Fenton system, the Fenton system comprised of the combination of hydrogen peroxide and an Fe(II) salt, or
a mixture of hydrogen peroxide and a Mn(II) salt,
crosslinking of the lignin in an aqueous alkaline medium by use of multi-functional compounds,
neutralizing, drying, and comminuting the lignin.
2. The method according to claim 1 , characterized in that technical lignin such as alkaline lignin, organosolv lignin or hydrolysis lignin is provided.
3. The method according to claim 1 , characterized in that for crosslinking of the lignin bi-functional epoxides are used.
4. The method according to claim 1 , wherein in the step of comminuting the lignin is comminuted to a grain size of 100 μm to 5 mm.
5. The method according to claim 3 , wherein the bi-functional epoxide is poly (ethylene glycol) diglycidyl ether.