Stabilization/Solidification of Nitrobenzene Contaminated Soil based on Hydrophobilized CaO

From aliphatic compounds contaminated soil to active building material: An emerging opportunity for soil remediation and waste utilisation

Soil contaminated with the production wastewater of 4,4'-diaminostilbene-2,2'-disulfonic acid is extremely hazardous and difficult to bioremediate. In this study, a cost-effective method was developed to reduce the risk of contaminated soil and produce building materials through a combination of ultrasonic processing and solidification/stabilisation. Ultrasonic processing conditions of 5 min at 40 kHz were found to significantly improve the compressive strength of bricks. The results of scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis demonstrated that the enhanced strength was due to the ultrasonic processing controlling the shape and scale of the crystals and microstructure of the cement paste. Furthermore, the effect of the activating agent, CaO, on the leaching toxicity of the bricks was closely related to the curing temperature. Under natural dry conditions (10-25 °C), the leaching toxicity decreased along with the reduction of CaO. However, under high artificial temperature conditions (40 °C), increasing the CaO was beneficial for decreasing the leaching toxicity. The addition of 2.91% CaO was suitable for improving brick performance under both natural dry (10-25 °C) and artificial temperature curing conditions (40 °C). The results of GC-MS revealed that 64.8% and 66.7% of organic species and organic volume, respectively, were reduced in the leachate of the bricks, which was produced by CaO activation and ultrasonic treatments. It was demonstrated that the optimal combined process for cost-effectively transforming hazardous soil to active building materials is feasible.

Effects of an Integrated Carbide Slag-Mushroom Dreg-Calcium Superphosphate Amendment on the Stabilization Process of Pb, Cu, Zn and Cd in Contaminated Soils

In the present study, the integrated use of organic and inorganic amendments (CS–MD–CSP) including carbide slag (CS), calcium superphosphate (CSP) and mushroom dreg (MD) are employed for the stabilization of heavy metals in contaminated soils. A response surface methodology combined with immobilization efficiency was employed to evaluate and optimize the proportion of the integration amendments on the stabilization process. The results predicted by a Box–Behnken design indicated that the maximum immobilization efficiencies of soil Pb, Cu, Zn and Cd could be achieve up to 99.88, 96.11, 99.78 and 87.88%, respectively, when the dosage of CS, CSP and MD were set as 4, 1 and 6%, respectively. European Community Bureau of Reference (BCR) speciation analysis indicated that the acid-soluble proportion of Pb, Cu, Zn and Cd in the soils decreased by 72.68, 37.03, 9.36 and 12.94%, respectively. Thus, this CS–MD–CSP integration amendment could potentially be used for the remediation of Pb, Cu, Zn and Cd in contaminated soils.