Impact of real and simulated municipal solid waste leachates on the hydraulic and swelling behaviour of bentonites for landfill application.

For the efficient functioning of a landfill, compacted bentonite is an acclaimed liner element due to its excellent adsorption capability, minimal hydraulic conductivity, and superior specific surface area (SSA). However, the leachate generation within the landfill worsens the liner material's quality, causing migration of the leachates, contaminating groundwater, and causing pollution of surrounding environment. With this perspective, a comparative assessment of the influence of real and simulated municipal solid waste (MSW) leachate on two different bentonites has been carried out in the present investigation. The two bentonites, differing precisely by their cation exchange capacity (CEC), liquid limit (LL), and swelling capability, were examined for variation in their LL, free swell (FS), and hydraulic behaviour concerning their interaction with both leachates. Results depicted that in both the leachates, LL and FS, swelling potential (SP) and pressure declined, whereas hydraulic conductivity (HC) rose. Furthermore, the bentonite quality greatly influenced the LL, FS, SP, swelling pressure, and hydraulic behaviour. Bentonite having higher CEC, SSA, and swelling ability experienced a higher variability in the LL (55.5 and 65.2% decrease), free swelling (76.9 and 83.1% decrease), SP, swelling pressure (53.3 and 56.4% decrease), and HC (13.1 and 49.4 times increase) values when permeated with simulated and real MSW leachates, respectively. The study also showed that the real MSW leachate interaction causes a higher variation in bentonite behaviour than its simulated counterpart. The study's findings would prove beneficial to design engineers for selecting bentonite types for landfill liners.

Effect of calcined clay on the improvement of compaction, swell and microstructural characteristics of expansive soil.

Expansive soil is problematic soil because its alternate swell shrink behaviour depends on the presence of water. Soil stabilization technique was widely adopted to alter the characteristics of the expansive soil which is suitable for construction. Among the various soil stabilization techniques, chemical stabilization was found to be more suitable method of sustainable stabilizing the soil due to its effective and timely reaction with the chemical compound. Calcined form of clay material is used as an admixture to study the effects on the improvement of soil properties. Calcined Clay (CC) is added into the virgin soil with different percentages of 2%,4%,6%,8% and 10% under varying 1,3,7,14,28 and 60 days of curing by conducting experiments such as standard proctor test, Free Swell test to analyse the compaction characteristics and swelling behaviour of the soil. In addition to that the X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) on virgin and treated soil were studied by varying 2% incremental of CC up to 10% at 28 days of curing. From the test results it shows the variation in the compaction characteristics by rising in Maximum Dry Density (MDD) and reduction in Optimum Moisture Content (OMC) that merges at 8% as an optimum to develop the soil behaviour and from the free swell test, it was found that the Free Swell Index (FSI) of the soil decrease from 210 to 80 at 10% calcined clay added soil and the Mineralogical studies also show the variation in the compounds. Thus, this naturally available calcined clay was used to improve the soil Compaction and swell characteristics that influences the reduction in deformation and increase in shear strength of soil which helped to minimize the environmental problem as well as one of the effective admixtures to improve the expansive soil characteristics.

The swelling performance of raw and modified bentonite of geosynthetic clay liner as the leachate barrier exposed to the synthetic E-waste leachate.

Heavy metals are prevalent in electrical and electronic waste. The sealing of this type of waste disposal site is critical due to the existence of toxic materials. In this regard, Geosynthetic Clay Liners (GCLs) are widely used as one of the most common engineered barriers at disposal sites. Recently, attention has been drawn to modifying the bentonite of GCL with polymers to improve barrier performance against leachate. The aim of this study was to evaluate the swelling performance of the raw and modified GCL with a hydrophilic anionic polymer called CarboxyMethyl Cellulose (CMC) with weight percentages of 8, 10, and 12 of dried bentonite against synthetic heavy metals' leachate, containing copper and zinc, simultaneously and separately, based on ASTM D5890. It was found that adding this polymer could improve the swelling rate of the GCLs. The optimum CMC rate for modified GCLs exposed to the cationic solutions, including copper and zinc, was estimated at 10%. It could also be noted that the swell index of both natural and modified bentonites against solutions, including two cations of copper and zinc, simultaneously, was more sensitive to the changes in zinc ion concentration versus copper metal concentration.