Remediation of turbid water containing lead and cadmium ionsusing zeotype materials derived from rice husks and water hyacinth ashes
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Date
2015-11
Authors
Ngugi, Hellen Wambui
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Water scarcity problem is of great concern globally especially in developing countries
including Kenya which has per capita available water of 650 m3 per year as opposed to
the recommended 1700 m due to rapid growth in population, industrialization and
pollution a situation likely to worsen if drastic deliberate measures are not taken.
Common water pollutants include pesticides, sewage, heavy metals and suspended
particles. Lead and cadmium are among the most prevalent heavy metal contaminants
due to their extensive uses in batteries, paints, fertilizers and pesticides. These heavy
metals are absorbed by the body mainly through intake of food and water and at high
levels bioaccumulate causing health problems which range from less severe cases of
stomach upsets to more severe cases of damage of brain and the nervous system.
Although several water treatment materials are available in the market they are expensive
and inaccessible to many. There is need for continued search for alternative adsorbents
that are locally available and accessible to the poor majority. The current study was
geared towards synthesis of zeotype material, an adsorbent, and determination of its
effectiveness in removal of heavy metal ions and turbidity from contaminated water. Four
zeolitic blends were synthesized using the ashes from rice husk waste as the source of
silica and fast growing water hyacinth ash as the base. The different zeotype materials
were obtained by varying the ratio of water hyacinth ash while keeping that of rice husk
ash constant. Batch sorption studies were done at various conditions of contact time, pH ,
temperature, shaking speed, adsorbent dose and concentration of the metal ion in solution
and the data obtained was fitted in the Freundlich and Langmuir adsorption models to
obtain adsorption capacities. Data for adsorption of both lead and cadmium ions on the
zeotype materials fitted best onto Freundlich isotherm based on adsorption capacity
values (Kf) and correlation coefficient (R2). Zeotype material Z2had the highest
adsorption capacities of 4.05 and 14.01 mg/g and also removed the highest percentages of
99.89% and 99.97% for lead and cadmium ions respectively at the various conditions. Z4
indicated the lowest ability to remove lead and cadmium ions with percentages of as low
as 50.00% and 57.15% respectively. However, this zeotype material demonstrated the
highest ability in the removal of turbidity (46.94%) at a dosage of 0.4 g. This study
demonstrates that zeotype materials can be synthesized from water hyacinth and rice husk
ashes and that they can be used to effectively adsorb lead (II) and cadmium ions and
coagulate turbidity from contaminated water.
Description
A thesis submitted in partial fulfillment of the requirements for the award of Degree of Master of Science (Analytical Chemistry) in the School of Pure and Applied Sciences of Kenyatta University