Table 3 *Leaching potential = Cr released from the sludge without S/S treatment. ** These studies collect the sludge after the Cr precipitation process. ***No quantification on the amount of water used nor on the exact amount of chromium in the sludge. ****The value is presented with more significant figures to allow a better comparison
S/S approaches | Pretreatment of Cr-bearing wastewater | Cr in solution* (leaching potential) | Additional water | Cr in the product (mg kg−1) | Leaching (mg L− 1) | Mass increase | % of Cr retained |
|---|---|---|---|---|---|---|---|
Ladle furnace slag + organoclay [13] | Yes** | 42 mg kg− 1 | Yes, no indication of the amount | *** | 1.2 | 1:3.3 | *** |
Portland cement [14] | Yes** | 385 mg kg− 1 | 40 wt% | 5080 | 194.7 | 1:1.55 | 96.2% |
Portland cement [15] | Yes (filtration) | 7.50 mg L− 1 | no | 0.68 | 0 | 1:11 | 100% |
Metakaolin (this work) | No | 4100 mg L−1 | no | 400.55 | 0.024 | 1:10 | 99.994%**** |