Abstract
This study was aimed to determine the interaction of cement kiln dust - aqueous solution contaminated with Cadmium ions was studied through set of batch tests with operational conditions of contact time ≤120 min, sorbent dosage from 0.05 to 1 g/100 mL and agitation speed ranged from 50 to 300 rpm for initial concentration of 50 mg/L with initial pH of 3 to simulate the acetogenic phase in the sanitary landfill. The best values of these conditions are 1 hr, 0.7 g/100 mL and 250 rpm respectively, To obtain maximum removal efficiencies of 97.6%. Freundlich and Langmuir models have a high ability in the representation of the sorption data with determination coefficient (R2) greater than 0.97 and the sorption capacity reached to 84.1 mg/g. This certifies that the physical sorption and chemisorption can occur together to remove Cadmium ions from the aqueous solutions. Tests elucidated that the average coefficient of the hydraulic conductivity is equal to 9.7×10-13 m/s and this is suitable for LPB. Finally, COMSOL Multiphysics 3.5a package was able to simulate the distribution of cadmium ions concentrations within two-dimensional physical model packed with sand aquifer and CKD LPB. A good matching between model predictions and experimental results are recognized at selected points up and down gradient of LPB.
Highlights
Water present beneath the ground surface is known as “groundwater” which can be infiltrated from the surface by migration through the soil matrix of geologic formations
The LBPs technology can be used to contain contaminants in an aquifer and prevent the further spreading of contaminants in groundwater. Applying this technique in the restriction of groundwater contaminated with heavy metals has been proved to be successful and most efficient in the redirection or capturing of contamination plume The heavy metals can be captured by the reactive material used within the low permeable barrier technology by the following mechanisms; chemical precipitation, sorption, ion exchange, abiotic reduction and biotic reduction
Cement kiln dust (CKD) is alkaline powder solid waste resulted from the cement industry as byproduct; about 41 kg of this waste can be accompanied with production of 1-ton of cement [23]; so, huge amounts of this waste will form a burden on the environment [4]
Summary
Water present beneath the ground surface is known as “groundwater” which can be infiltrated from the surface by migration through the soil matrix of geologic formations. This study was aimed to consider a good application for the principles of sustainability because it investigates the possibility of using cement kiln dust solid waste as LPB as alternative to natural clay for preventing a further spreading of Cadmium ions in the groundwater. The performance of this material was evaluated by sets of batch and continuous tests as well as COMSOL Multiphysics 3.5a (2008) used to simulate the spreading of the Cadmium ions. The removal efficiency (R) for all contaminants was determined by:
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