Ian Wark Research Institute
ARC Special Research Centre
ARC Special Research Centre
Research Area: Minerals engineering, materials engineering,
environmental engineering, chemical/biochemical engineering, physical
chemistry
Supervisors:
Prof Jonas Addai-Mensah
Description: In recent years, potable water has become a vital
natural resource whose quality and increasing scarcity are paramount for
the survival flora and fauna globally. Several human activities such as
mining, construction and agriculture around surface water bodies
contribute markedly to extensive particulate matter erosion, fugitive
dust dissemination, exposure to and deposition into those water bodies.
In the case of mining activities, impoundment dam failures, surface
run-offs and careless disposal practices of mineral waste tailings of
fine particles result dramatic increase total suspended solids of
streams and rivers. In addition to the undesirable, high water
turbidity, particulate matter entrainment in rivers and streams can
sometimes create salinity and even toxicity problems due to the
perennial presence of soluble soil or mineral particles, some of which
may comprise heavy metal compounds. For instance, the suspended
particulate matter may have significant adverse effect on aquatic life,
thereby leading to possible extinction, excessive algal growth, high
organic matter content and formation of foul odour-causing substances.
As the human activities take place throughout the year, the resulting
surface water pollution is a continual problem for communities whose
existence and/or livelihood directly depend upon these water bodies.
Conventional water treatment reagents include chemical aids, such as
synthetic low molecular weight, charged polymers (poly-electrolytes) or
lime, ferric sulphate, activated silica, alum and other inorganic
aluminium poly-cation salts as coagulants. The efficacy of these
coagulants increases sharply with increasing ionic charge in accordance
with the Schulze-Hardy rules. In addition to coagulants, synthetic high
molecular weight polymers flocculants of polyacrylamide chemistry are
conventionally used in water and dilute mineral waste suspensions
treatment1-7. Previously, starch, polysaccharide and guar gum based
polymers from natural resources, such as corn potatoes and legume seeds,
have been as flocculant used in industrial dewatering processes7.
Without original structure modification, however, most of the natural
polymers have been generally found to be less effective than the
synthetic polyacrylamide based flocculants, on equivalent dosage basis7.
Both the synthetic and natural dewatering aids induce aggregation of
suspended colloidal to fine particles dispersed in water through a
dominant particle bridging mechanism(s). Consequently, particles
settling rate are dramatically amplified to produce optically-clear
supernatant and compact sediment. Whilst the application of such
synthetic additives has experience dramatic growth and significant
commercial success in recent years, their over use and failure to
degrade rapidly in aqueous media may lead to undesirable water
pollution. Alternatively, the use of novel, natural flocculants which
are bio-degradable, reasonably cheap and readily available is attractive
if their flocculation performances and efficacies can be demonstrated to
be good enough for a range of particulate matter found aqueous
suspensions. Recently there has been marked interest in the development
of bio-flocculant from moringa olifera plant seeds. Some anecdotal
evidence gathered indicates that the seed extracts have beneficial
flocculating and coagulating properties for water clarification. With
current, extremely high demand for corn and potato as food for human
consumption, their use in the manufacture of natural starch-based
polymeric products is becoming less attractive. Hence, the possible
development a bio-flocculant from natural sources such as moringa
olifera plant seeds is considered an attractive and sustainable means
for cleaning up water bodies. For sustainability, the moringa olifera
plant may be cultivated in large plantations for this purpose.
Research Aims, Objectives and Approach
The main aim of this project is to undertake the development moringa
olifera seed extract and other natural extracts into cost effective
coagulant and/or flocculant for clarification polluted surface waters
(rivers and streams). Relevant literature on the plant moringa olifera
seeds and extracts will be undertaken and suitable polymeric materials
extracted. Characterization (polymer functionality, charge and mol. wt)
will be undertaken. Orthokinetic flocculation ability and dewatering
performance flocculating of the polymeric extracts will be undertaken
with simulated suspensions containing particulate matter of inorganic,
organic and biological origin and of positive, negative and neutral
charge (zeta potential) over a range of pH values and field studies will
be undertaken with the possibility of establishing flocculation nets in
specific sections of identified water bodies.
References
1. Fleer, G.J. and Scheutjens, J.M.H.M., 1993. Coagulation and
Flocculation, Theory and Applications, Marcel Dekker Pub. Co. New York.
USA.
2. Duan, J, Gregory, J. 2002. Coagulation oh Hydrolysing Metals Ions,
Advances in Colloid and Interface Science, 100-102 475-502.
3. Addai-Mensah, J., Prestidge, C.A., 2005. Chapter 4: Structure
Formation in Dispersed Systems. Coagulation and Flocculation, (Eds.
Hansjoachim Stechemesser, and Bohulav Dobias), Surfactant Series Vol.
126, 2nd Ed. CRC Press/Taylor and Francis Publishers (ISBN
1-57444-445-7) London, New York. pp 137-216.
4. Addai-Mensah, J., Yeap, K.Y and McFarlane, A.J., 2007. The
Influential Role of Pulp Chemistry, Flocculant Structure Type and Shear
Rate on Dewaterability of Kaolinite and Smectite Clay Dispersions Under
Couette Taylor Flow Conditions, Powder Tech. 179 79-83.
5. Addai-Mensah, J., Bal, H. M., Yeap, K. Y., 2008. Polyelectrolyte
Enhanced Flocculation, Particle Interactions and Dewaterability of Fine
Gibbsite Dispersions, Asia-Pacific Journal Chemical Engineering, 3(1)
4-12.
6. Addai-Mensah, J., 2007. Enhanced Flocculation and Dewatering of Clay
Mineral Dispersions. Powder Technology, 179 73-78. McFarlane, A.,
Bremmell, K., Addai-Mensah, J., 2005.Optimising the Dewatering Behaviour
of Clay Tailings Through Interfacial Chemistry, Orthokinetic
Flocculation and Controlled Shear. Powder Technology 60(1) 27-34.
7. Audsley, A. Flocculation of Suspensions of Solids with Organic
Polymers - A Literature Survey, Mineral Processing Information Note No.
5. Warren Spring Laboratory. Ministry of Technology, Herts, UK. 1965.
Funding: Potential applicants must be highly qualified to win an appropriate scholarships (e.g. Endeavour, IPRS, UPS and UNISAPA) to cover living allowance and tuition (where necessary).
