Cr(VI) concentration from batch contact/tank leaching and column percolation test using fly ash with additives.
Batch contact, tank leaching and column percolation tests were conducted to investigate the Cr(VI) concentration in the solution/leachate from two fly ashes (fly ash A and B) with additives. The additives used were cement, low alkalinity additive and Ariake clay. There are several factors influencing Cr(VI) concentration in solution/leachate, namely (1) properties of solid/liquid mixture (chemical composition, pH value, etc.), (2) cementation effect, (3) amount of water in contact with the solid mass (solid/liquid ratio in case of batch contact test), and (4) adsorption characteristics of the solid particles to Cr ions. The test results indicate that fly ash A has less cementation component (CaO of 1.92%) and the amount of water in contact with the fly ash played an important role. As a result, Cr(VI) concentration from the column percolation test was much higher than that of the batch contact test. Adding Ariake clay had more effect on reducing Cr(VI) concentration for fly ash A than B because the pH value of the solution from fly ash A was lower, which provided a favorable condition for Cr(VI) ions to be reduced to Cr(III) and possibly to be adsorbed by clay particles. Fly ash B has more cementation component (7.15%) and for column percolation test, curing the sample for 1 week reduced Cr(VI) concentration significantly. The test results indicate that in engineering practice, a method which closely simulates the field condition should be selected to assess possible environmental effects and corresponding countermeasure methods.
Chai
Jin-Chun
JC
Department of Civil Engineering, Saga University, Saga, Japan. chai@cc.saga-u.ac.jp
Onitsuk
Katsutada
K
Hayashi
Shigenori
S
D000327:Adsorption; D000538:Aluminum Silicates; D017610:Calcium Compounds; D002244:Carbon / Q000737:chemistry*; D002857:Chromium / Q000032:analysis*; D000077215:Clay; D060729:Coal Ash; D007220:Industrial Waste / Q000517:prevention & control*; D010087:Oxides; D052638:Particulate Matter / Q000737:chemistry*; D012106:Research; D012996:Solutions; D014874:Water Pollutants, Chemical / Q000032:analysis
D000538:Aluminum Silicates; D017610:Calcium Compounds; D060729:Coal Ash; D007220:Industrial Waste; D010087:Oxides; D052638:Particulate Matter; D012996:Solutions; D014874:Water Pollutants, Chemical; D002857:Chromium; D002244:Carbon; C016538:lime; D000077215:Clay