Leaching Test Protocols to Evaluate Contaminant Response of Nano-Calcium Silicate–Treated Tropical Soils

• Published in: Journal of hazardous, toxic and radioactive waste toxic and radioactive waste, 2023-04, Vol.27 (2)
• Main Authors: Moghal, Arif Ali Baig, Sanaulla, P. F., Mohammed, Syed Abu Sayeed, Rasheed, Romana Mariyam
• Format: Article
• Language: English
• Subjects: Abandoned waste sites; Agglomeration; Calcium; Calcium silicates; Contaminants; Environmental monitoring; Hazardous materials; Heavy metals; Immobilization; Interstices; Iron and steel plants; Landfills; Leaching; Lead; Metals; Mixtures; Municipal wastes; Nickel; Pollution levels; Pollution monitoring; Pollution transport; Sediment pollution; Soil contamination; Soil pollution; Soils; Steel industry; Technical Papers; Test procedures; Toxicity; Tropical environments; Tropical soils
• ISSN: 2153-5493; 2153-5515
• DOI: 10.1061/JHTRBP.HZENG-1200

Abstract The current study deals with the interaction of toxic metals with soils by conducting a series of leaching tests on four kaolinitic soils procured from locations with varying pollution levels, such as a pristine location, vicinity of steel mill works, battery works unit, and an abandoned municipal waste dump site. The procured soils were spiked with 3,000 mg/kg of toxic metals, lead (Pb), and nickel (Ni) to understand the contaminant transport. An innovative amendment, such as synthesized nano-calcium silicate (NCS), was also mixed with the soils for toxic metal immobilization. Leaching tests. such as the toxicity characteristic leaching procedure (TCLP), extended TCLP, and caged TCLP, were conducted on soil samples. These tests were successful in predicting the interactive behavior of the composite mix containing soil, NCS, and toxic metals, comprehensively. The vulnerability of soils based on TCLP can be expressed in the order of Soil C > Soil D > Soil B > Soil A. These results were concurrent with extended TCLP, wherein the response of these composites at various pH levels was presented. Caged TCLP quantified the leaching rate for different mixtures, and it was found that the leaching rate for virgin soils reduced from 1.3 to 0.075 cm/yr after the NCS amendment. The addition of NCS resulted in the agglomeration and aggregation of soil particles. This increased the density and reduced the void spaces of the soil–nano mix, thereby encapsulating the toxic metals permanently within its interstices. The highest attenuation was observed for Pb2+ compared with Ni2+ for all the mixtures considered. Thus, leaching tests can be considered a prospective short-term technique for monitoring polluted soil media compared with tedious and time-dependent column studies.