Diatomite consists predominantly of
microscopic siliceous spines of diatomeae algae, although other
silica-secreting organisms can sometimes be found. It resembles
chalk or clay, but mainly contains silica and between 3-10%
water. It is friable, porous and floats on water when dry,
while its absorption rate means it can carry between 25-45%
Its key properties are its
porosity, fineness of pores, absorptive power, leightweight and
low-heat conductivity. The mineral is used as a filter and
absorber, and has applications in heat and sound insulation,
abrasives, building materials, ceramics and chemicals.
Diatomite deposits are present in
the southern provinces of Vietnam at Phu Yen (South-Central)
and Kon Tum, Lam Dong and Binh Thuan (Highland region), of
which the Hoa Loc deposit in Phu Yen is the largest reserve
with the highest ore quality.
Preliminary prospecting took place
at the Hoa Loc deposit in 1991, with later research work into
ore processing and the use of diatomite as a filter aid for
discarded oil (lubricant) treatment producing important
Total reserves of diatomite in
Vietnam are estimated to reach around 130m tonnes, making it
one of the worlds largest diatomite resources.
Total global diatomite production
in 2012 was estimated at 2.1m tonnes by the USGS, remaining
constant with the 2011 level and up from a slight fall of
around 10,000 tonnes, to 1.83m tonnes, in 2010. Consistently,
the main producers have been the US and China, producing over
half of total output. Denmark and Japan both continue to be
Countries with an output below
100,000 tonnes include: the CIS, France, Spain, Argentina,
Turkey, Iceland and Italy.
The filtration market continues to
rely heavily on diatomite, with the mineral accounting for 65%
of the market in 2010. Diatomite is also used in absorbents and
fillers and prices range from $275/tonne for filter-grade
diatomite to $400/tonne for speciality products.
There is a certain threat to
diatomite in the filtration industry from a number of
substitutes, including expanded perlite and synthetic fibres,
but diatomites unique properties help it to retain much
of the market.
Distribution and potential of Vietnamese diatomite
Connected with young volcanic
formations, diatomite, as well as bentonite, deposits only
occur in south Vietnam, predominately in the South-Central and
Diatomite deposits in Phu Yen
province are distributed in four areas: Hoa Loc, Tuy Duong,
Trung Luong and Tra Rang, with total combined reserves of 90m
tonnes. The diatomite clays have lacustrine sedimentary genesis
in the volcanically-active Neogene period. Diatomite products
are used in fields such as drilling fluid, filter-aids for
quenched water and as an absorbent material as an environmental
treatment for cultivating water products.
Diatomite deposits occur in several
locations in the Highland region.
In Kon Tum province, diatomite is
found in Neogene sediments, mainly of fine-grained sandstone
intercalated with siltstone and well preserved plant-bearing
argillite. There are three deposits, Vinh Quang, Phuong Quy and
Ia Le, of which Vinh Quang is largest.
The Vinh Quang (Kon Tum town)
diatomite-bearing deposits have a thickness of between 3-120
metres, consisting of two narrow bands 2-3km long and 0.2-0.7km
wide. The upper bed is two metres thick, comparatively
clean-bedded and white to white-grey coloured. It is friable,
light and smooth. The lower bed is four metres thick,
thin-bedded, greenish-grey to yellowish-grey coloured and mixed
with quantities of clay. A bed of clay is present between the
Mineral composition of the ore is
predominately of clean silica, formed by diatomeae spines.
The chemical composition is
principally silicon dioxide (SiO2 50.7-60.2%),
aluminium oxide (Al2O3 14.03-23.52%), and
iron oxide (Fe2O3 9.02-10.62%). It also
contains smaller concentrations of elements including calcium
oxide (CaO 0.55-0.67%), magnesium oxide (MgO 0.04-0.95%),
potassium oxide (K2O 0.85-0.95%), sodium oxide
(Na2O 0.1-0.57%), and sulphur trioxide
(SO3 0.44-0.87%) and titanium dioxide
The potential resource of Vinh
Quang is estimated at 26.19m tonnes.
In Lam Dong province, diatomite is
found in the Bao Loc and Di Linh districts. The Dai Lao
diatomite deposit in Bao Loc is a large deposit of 12.92m
The chemical composition is
principally SiO2 (38.34-67.42%),
Al2O3 (15.79-28.19%) and
Fe2O3 (2.39-15.31%). It also contains
smaller concentrations of elements including CaO (0.0-0.67%),
MgO (0.01-1.22 %) and TiO2 (0.77-1.24%).
The mineral composition is made up
mainly of diatomite (86%), but also contains sericite (20%) and
quartz (10%). The deposits have plasticity of 25.75-58.35% and
lime attraction of 62.1-98.4mg CaO/100mg soil.
In Lam Son (Bao Loc), there is also
a prospective occurrence, with a diatomite bed 2-11.6 metres in
thickness, with ore of lime attraction 58.10-100.80mg CaO/100mg
The Da Le diatomite deposit (Di
Linh district) occurs in Neogene lacustrine sediments, covered
by basalt eruptive rocks of the Pliocene-Pleistocene age. Above
and below the diatomite, there are intercalated layers of shale
and bentonite clay. The diatomite-bearing stage is 0.2-1.5km
wide, around 6km long and stretches from the Da Le bridge to
The diatomite clay is
yellowish-white coloured, light-porous, easily broken and bears
silica algae spines in its composition.
The chemical composition is
principally SiO2 (58-62.56%),
Al2O3 (13.19-20.12%) and
Fe2O3 (2.95-6%). It also contains smaller
concentrations of elements including CaO (0.2%), MgO (0.31%),
MnO (0.01%), SO3 (0.18%), P2O5
(0.06%), K2O (1.25%) and TiO2
The deposit also has a lime
attraction of 218.7-753.3mg CaO/g soil at 700oC.
In Binh Thuan province, the Da Kai
diatomite occurrence at the Sung Nhon commune, Duc Linh
district, is covered by a siltstone layer of grey, ash-grey,
greenish colour, confused by a small amount of brown coal from
the Neogene era.
The thickness of diatomite layer is
between 7-10 metres, while the covering layer is of 12-18
metres thickness. Diatomeae algae remains are very high, up to
90%, with clay minerals at 5-6% and quartz at 3-4%.
The chemical composition is
principally SiO2 (56.16%),
Al2O3 (19.86%) and
Fe2O3 (3.84%). It also contains smaller
concentrations of elements including CaO (1.08%), MgO (0.05%),
SO3 (0.2%) and TiO2 (1.09%).
The deposit has not yet been
evaluated on the reserve scale.
On the whole, the diatomite in
South-Central and Highland regions is of a fair quality, and
can be used in applications including heat insulations, light
aggregate, hydraulic cement, in filters, absorbents, additives
in rubber, soap and insecticides and a variety of other
It can also be used in polishing
technology, and is particularly applicable against acidic and
As well as this, when heated to
650-750oC, Highland diatomite-bearing sediment is a
potential source of pozzolan for use in the cement
Hoa Loc diatomite
The Hoa Loc diatomite deposit
located in An Xuan commune, Tuy An district, Phu Yen province
in South-Central Vietnam, consists of three ore bodies of
industrial value. Each body is 5.5km long, with thickness
ranging from 4.3-33.4 metres.
The average density of the crude
ores is 1,078 kg/m3, wind dry 0.906g/cm3
and drying at 105oC as 0.730g/cm3.
If calculated after volume mass of
wind dry (0.906 g/cm3), the reserve of Hoa Loc
diatomite deposit is 61,385,377 multiplied by 0.906
kg/m3, giving 55,616, 975 tonnes.
The SiO2 content in the
first body is 64.16%, with Fe2O3 at
4.39%. The SiO2 reduces gradually to the southwest
of the body, while the Fe2O3
In the second body, the average
SiO2 content is 62.67%, with an
Fe2O3 content of 4.72%. SiO2
content is stable along the direction line.
In the third body, the average
content SiO2 is 64.87% and is generally stable along
the direction line and follows a deep trend. The
Fe2O3 content is 4.89%.
Figures provided by Phu Yen Service
of Industry show that the crude ore taken at the diatomite
resource is composed of principally SiO2 (67.96%),
Al2O3 (12.12%) and
Fe2O3 (2.97%). It also contains smaller
concentrations of elements including CaO (0.17%), MgO (0.39%),
SO3 (0.15%), K2O (0.21%), Na2O
(0.17%) and TiO2 (1.17%), according to research by
Tran Van Lung 1997.
Hoa Loc provides the
highest-quality diatomite when compared with other resources as
shown in Table 2.
Technological research of filter-aid powder
The Scientific Institute of
Materials has carried out research into filter-aid powder
processing of the Hoa Loc diatomite through a combination of
mechanic floatation and chemical treatment. This consists of
Step 1: Crude ores
are struck to 10mm grain size, ground and rubbed, passed
through a 0.25mm sieve to a hydraulic cyclone where
the diatomite is separated from
grits and clays (Fig 1).
SiO2 content of
concentrate after the separating processing reached 75.74%, an
increase of 6.44% compared with crude ore (67.3%), but still
with a high iron content of 3.47%.
Step 2: The
diatomite concentration is blended with an
H2SO4 / HCl (1/1) solution. The acid
spend here is 8% wt, the ratio of solid and liquid is 2.5 and
the reaction maintaining temperature is 150oC. The
reaction maintaining time is 150 minutes, followed by washing
for careful sorting and heating at 900oC (Fig
The combination of mechanic
floatation and chemical treatment has produced diatomite with
SiO2 content of 90.02%, Al2O3
1.6% and Fe2O3 0.35%, equivalent to
imported filter-aids from Japan (Radiolite 500 and Radiolite
800) and the US (Hyflo RV) for use in the foodstuff
These results have been used as the
basis of a pre-feasibility report named: Plant construction of
filter-aids powder production from diatomite ores at the An Phu
zone, Phu Yen province.
Testing of discarded lubricant
treatment by diatomite powder
The cleaning process of used
lubricants reduces or rejects impurities such as dregs, resin,
sulphur compounds, aromatic compounds, acids and other matters.
The regeneration of used lubricants has, therefore, clear
financial benefits, while helping to preserve the
The Phu Yen diatomite powder has
been used with four samples of grain sizes:
Sample A1 of grain size
> 100 microns (µ)
Sample A2 of grain size
from 88 - 100µ
Sample A3 of grain size
from 71 - 88µ
Sample A4 of grain size
The process involves mixing 500g
diatomite powder with 500g discarded lubricant; stirring with
speed of 1,500 rounds/minute for 30 minutes at
75-80oC; cooling and settling for between 20-24
hours; decanting the deposit; and concentrifuging the oil
portion and rejecting the hovering grains.
Measurement results of the
chemico-physical specifications of samples before and after
treatment are shown in Table 3.
After treatment of discarded
lubricant by diatomite powder with four different grain sizes,
the dynamic viscosity of oil samples has reduced from 2.3 to
2.4 centistrokes (cSt).
The index of all alkaline reduces
significantly, first with A2 and A3
samples of grain size 88 - 100µ and 71 - 88µ
respectively, reducing to 50% compared with the index of all
alkaline in the discarded lubricant sample. An explanation of
this is that large-mass resin or asphane molecules are attacked
and adsorbed by diatomite.
Diatomite samples of different
grain sizes all adsorb water strongly, so after treatment of
the discarded oil, water content is equal to zero.
Content of undissolved dregs
reduces significantly from 66.7% to 83.4%, in which the samples
of grain size 88-100µ and 71-88µ are the most
effective, reducing from 83.4% to 80.6%.
Conclusions and proposals
The potential of the diatomite in
Vietnam is considerable. Of the deposits found in the
South-Central and Highland regions, Hoa Loc in Phu Yen province
is the largest and yields the highest-quality ore. This means
it may be the most suitable for investment and exploitation on
an industrial scale.
The success of studies into
processing technology of filter-aid powder from Hoa Loc
diatomite by combining mechanic floatation and chemical
treatment has opened the prospect of this raw material source
being of significant use in various industrial sectors, while
also being important contributor to environmental
Foreign investment should be
encouraged to aid the effective exploitation and processing of
these abundant natural resources in Vietnam.
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Geology and Natural resource, volume I, p. 265-269. National
Center of Science and Technology, Ha Noi.
Nguyen Cuong, 1991. Evaluate -
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Vietnam Department of Geology and Minerals, Ha Noi.
Nguyen Duc Quy et al. 2008:
Sustainable development of diatomite mineral industry of
Vietnam. The 19th National Conference on mining
Science and Technology, Proceedings, p. 295-301. Vietnam Mining
Science and Technology Association, Ha Noi.
Nguyen Thi Thanh Huyen, Nguyen Van
Hanh, Tran Van Lung, 2006. Technological study of filter-aid
preparation from the Hoa Loc, Phu Yen diatomite ore. Journal of
mining Industry, No 2 - 2006, p. 12-15.
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diatomite ores. Selected scientific works, Tome 24. University
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