Enhancement Of Landfill Daily Cover In Minimizing The Migration Of Heavy Metals Using Mixture Of Laterite, Peat Soils And Rice Husk
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Date
2019-01-01
Authors
Mohamad, Nabilah
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
An engineered landfill is a facility designed for the safe disposal of solid
wastes. The daily soil cover of a landfill is considered as the most critical
components to prevent and minimize leachate generation that finally will infiltrate
into the groundwater. Migration of contaminants has the potential to increase
groundwater pollution. Heavy metals in water are one of the most significant
environmental problems in Malaysia. Therefore, this study examines the
effectiveness of admixture of laterite soil (LS), peat soil (PS) and rice husk (RH) as
daily soil cover in minimizing the migration of heavy metals in landfill. Five types of
metals namely cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni) and zinc (Zn)
were utilized as metal contaminants. Some laboratory tests were employed in
studying the compaction behavior, permeability, unconfined compression strength,
cation exchange capacity (CEC), scanning electron microscopy (SEM) and surface
functional groups. The adsorption capacity of laterite soil-peat soil-rice husk
mixtures towards metal ions was also being studied. The adsorption capacity study
was performed by batch experiments as a function of process parameters (initial
concentration and contact time) was observed. Furthermore, the batch experimental
data were fitted to Langmuir and Freundlich isotherms to determine the best-fit
model. Next, optimization study of the laterite soil-peat soil-rice husk mixture was
conducted by using Central Composite Design then followed by column studies. The
CEC value of laterite soil-peat soil-rice husk mixtures was indicated in the range of
8.7 to 17.9 meq/100g which was higher than LS alone. Results from the batch study
had shown that laterite soil-peat soil-rice husk mixture was found effective in
removing over 90% of Cd, 99% of Cu and Cr, 85% of Ni and 83% of Zn.
Meanwhile, the removal efficiency of heavy metals from the solution in the LS was
less than 61%. According to the equilibrium study, the removals of Cr, Cu, Ni and
Zn were controlled by monolayer adsorption onto homogeneous surface of mixtures
except for Cd. The optimization study of laterite soil-peat soil-rice husk mixture
revealed that 5.76 ppm initial concentration and 15 minutes of contact time were
required for optimum heavy metals removal. Based on the characterization, removal
efficiency and adsorption results, 50LS:40PS:10RH mixture was found to be the
most suitable combination and had a good potential to be used as landfill daily soil
cover. From the column test analysis, it was indicated that the relative mobility of the
heavy metals was in the sequence of Ni>Zn>Cu>Cd>Cr for 50LS:40PS:10RH.