Abstract:
Industrialization and technological advancements have led to the generation of
numerous pollutants such as heavy metals into the aquatic ecosystem. These toxic
compounds are extremely dangerous to human health and the environment due to
their non-biodegradability, severe toxicity, ability to accumulate and contaminate
ground and surface waters. Subsequently, pursuance of sustainable materials and
technologies for better attainment of environmental sustainability is critical. This
study reports the synthesis of geopolymers GP-1, GP-2 and GP-3 from different
clays. Geopolymers were hydrothermally synthesized using clay and rice husks
waste as an alumina and silica source respectively. The geopolymers were
characterized using Fourier transform-infra red, energy dispersive spectrometry,
X-ray diffraction and scanning electron microscope. Batch and gravitational
column experiments using Pb (II) and Cd (II) ions were carried out. Increased
metal ion uptake was recorded with raised Si/Al ratio of the adsorbents. The mean
percentage uptake of 90.23 ± 0.4 and 89.63 ± 0.18 of Pb (II) and Cd (II) were
achieved at pH of 4.0 and 5.0 respectively using GP-3. Langmuir, Freundlich and
modified Langmuir Freundlich isotherms were used in equilibrium studies. Data
for adsorption of Pb (II) and Cd (II) fitted best in the modified Langmuir
Freundlich model. The highest adsorption capacities of Pb (II) and Cd (II) were
209.9 and 136.2 mg/g respectively, attained using GP-3. Based on the results
obtained, geopolymers produced from common clay and rice husk waste
displayed promising potentials in the removal of heavy metal ions from the
aqueous phase. Considering the availability of raw materials for
geopolymerization and the high metal ions uptake capacities of geopolymers,
they can also be used as adsorbents for removal of heavy metals in industrial
wastewater.