fallen below a desired point the carbon adsorbent contact materials are preferably regenerated as by contact with a heated vapor stream such as nitrogen or air at a temperature of at least 200 u00b0 c or by wash with a solvent such as methanol acetone or water it is advantageous to employ a plurality of parallel contact zones such that while one zone is being regenerated the feed is passed through a zone containing fresh or regenerated contact material so that optimum impurities removal can be achieved following the purification method a purified propylene glycol monoalkyl ether product having a decreased carbonyl impurities content is recovered preferably the purified propylene glycol monoalkyl ether product has a uv absorbance at 245 nm of 0 5 or less the following examples merely illustrate the invention those skilled in the art will recognize many variations that are within the spirit of the invention and scope of the claims a stainless steel tube 1 inch i d u00d7 2 ft is packed with various activated carbon adsorbents from calgon corporation cal 12 u00d7 40 cpg lf 12 u00d7 40 sgl 8 u00d7 30 filtrasorb 600 apc 12 u00d7 40 and bpl 6 u00d7 16 the tube is placed in an electric furnace and the temperature is controlled to 28 u00b0 c the feed of propylene glycol monoalkyl ether containing 73 ppm carbonyl impurities and uv absorbance 1 25 is passed upflow through the bed at a lhsv from 0 7 1 h u2212 1 and.