The Positive Effects of Nanoclay on the Hydraulic Conductivity of Compacted Kahrizak Clay Permeated With Landfill Leachate

This study evaluates the effect of nanoclay on permeability, swelling, compressive strength, and cation exchange capacity of a compacted Kahrizak landfill clay liner. The results show that 4% nanoclay significantly reduces permeability (3 x 10(-9) to 7.74 x 10(-11) cm/s in neutral, 3.66 x 10(-9) to 7.9 x 10(-10) cm/s in acidic, and 3.25 x 10(-9) to 5.24 x 10(-10) cm/s in alkaline condition), and increases compressive strength (by 36.28%) and the percentage of swelling (from 16.67 to 41.82, 23.33 to 45.45, and 15 to 38.18 at pH 7, 4.8, and 9, respectively) compare to raw clay samples. Moreover, the results of cation exchange capacity tests show that adding 4% nanoclay to the Kahrizak clay, permeated with landfill leachate, helps the sample maintain its mono-valent ions between layers and remains dispersed. The results of SEM and XRD analyses show that by adding nanoclay, nanoclay clusters are formed in the sample; as a result, the interlayer spacing decreases which makes it remain dispersed. XRF analyses also demonstrate that by adding nanoclay to the mixture, the permeability and therefore, the amount of heavy metals which can penetrate into it decreases. The results justify the construction of clay barriers with nanoclay in order to prevent leachate penetration, and consequently reduce the operation costs.