Methods and systems for solvent purification

1. A method comprising:

(a) contacting lime with an extract carrying a contaminant load comprising an S1 solvent, to form a lime treated extract and solids;

(b) reducing said contaminant load by removing at least a portion of said solids from said lime treated extract and solids;

(c) carbonating said removed solids or said lime with CO 2 gas to form a slurry comprising calcium carbonate; and

(d) contacting said slurry comprising calcium carbonate with additional lime.

2. The method of claim 1 , wherein said contaminant load is reduced by more than 20% (wt/wt).

3. The method of claim 1 , wherein the method further comprises prior to step (a) contacting an extractant comprising said S1 solvent with an acid hydrolyzate of a lignocellulosic substrate to produce an acid-carrying extract; and de-acidifying said acid-carrying extract to produce said extract carrying a contaminant load.

4. A method comprising:

(a) cyclically contacting a first portion of an extractant comprising Si solvent with an acid hydrolyzate of a lignocellulosic substrate to produce an acid-reduced hydrolyzate and an extract comprising acid and S1 solvent carrying a contaminant load;

(b) de-acidifying said extract to form a de-acidified extract with S1 solvent carrying the contaminant load; and

(c) cyclically routing a second portion of said extractant comprising S1 solvent carrying a contaminant load to a decontamination module which applies a contaminant reduction process to said second portion to produce an extractant with a reduced contaminant load.

5. The method of claim 4 , wherein said contaminant reduction process comprises treatment of said second portion of said extractant with lime.