Treating polluted soil to remove metal cpds. - by percolation with recirculated aq. reagent soln., esp. EDTA, then washing with water

摘要

Method for removing metals from metal cpds., present in any form in porous surface soil material, comprises (i) filling the material into a container having a permeable base, surface area at least 10 sq. m and 0.5-5m tall, the material being mixed, no later than during the filling step, to produce a homogeneous permeable mass; (2) spraying the material with an aq. soln. of a reagent (A) which reacts with the metal cpd., so that is percolates through, using 40l/hr of soln. per 0.25 sq.m. of material surface; (3) recycling the eluate, via a reflux container, with removal of the contaminating cpd. and with replacement of any (A) lost in the process; (4) repeating the cycle until the metal ion content of the material has been reduced to an acceptable level, then washing out residue (A) with water at pH 3-11. The material may be lightly compacted (pref. by vibration) and opt. mixed with sand or other additives. (A) is esp. a 2-40 wt. % soln. of EDTA with pH about 6.