FIELD OF THE INVENTION
The invention generally relates to a process of removing arsenic and associated
impurities from the underground water by application of naturally occurring
Nanoparticles as a metal absorbent. More particularly, the present invention
proposes an innovative process in which goethite based composite generated
from rejects of beneficiated iron ore slime are used which having high
adsorption capacities for metal such as arsenic, lead, mercury.
BACKGROUND OF THE INVENTION
Natural geochemical weathering of subsurface soil has now reached an
unacceptable level of dissolved arsenic in groundwater in many regions of the
Asiatic subcontinent1-4 Rainfall in this geographical area is quite high but the
surface water is not fit for drinking. Due to poor sanitation system prevailing in
the region, practices with the potential for an outbreak of waterborne diseases
remain in the surface water. To mitigate this problem, thousands of well-head
units attached to manual hand pumps were sunk during the last four decades
to provide safe potable water to millions of villages in the region. As the

presence of unacceptably high levels of arsenic does not prima-facie alter the
taste, color, or odor of water, it is not possible to easily defect in a
geographical area, even if the arsenic concentration in groundwater exceeds
well over 100 μg/L An estimated 100 million people in the Asia-pacific region
are currently affected.
Arsenic in the groundwater was first detected in the year 1993, based on
several reports indicating that a large number of people are suffering from
arsenical skin diseases. Further investigations revealed that water supply in
large areas of the country is affected and millions of people are at serious risk
of arsenic poisoning. Technology for arsenic removal from water already exists
(Kartinen and Martin, 1995). However, the socio-economic conditions do not
permit implementation of this type of technology on the grounds of high cost.
A further problem in the groundwater in parts of the world is the presence of
iron. While iron-content is not a health hazard as such, however, the iron
maintaining better taste and restricting is usually removed from the drinking
water staining problems. It is well known that iron hydroxide adsorbs arsenic
(Ferguson and Gavis, 1972) and other heavy metals.

It is known that the iron-ore mines generate a large quantity of slime through
beneficiation of the iron ore obtained from the mines. Slimes are defined as -
25μm particles. As the slime contains an inseparable part during operations of
beneficiation processes which contain significant amount of gangue as
compared to RUN of Mine ore.
During the beneficiation process of the slime, the rejects are obtained as an
overflow of the hydro-cyclone used in the process. Overflow from the hydro
cyclone when collected exhibit an appreciable amount of iron and other oxides
with particle size of nano scale. These hydroxide-base composite nanoparticles
are considered to be a potential source for heavy metal removal by adsorption.
Nanoparticles and other Nanomaterials are reported to possess many
advantages, especially in the area of environmental science. Nanomaterials
exhibit novel physical and chemical properties that are not observed in bulk
sized particles. Surface, magnetic, and optical properties in bulk-sized particles
appear to change due to decreasing size, different structures, and new
methods of Nanomaterials synthesis.

Nanoparticle properties show marked departures from their bulk analog
materials, including large differences in chemical reactivity, molecular and
electronic structure, and mechanical behavior. The greatest changes are
observed in the smallest sizes, e.g. 10 nanometers and less, where surface
effects dominate bonding shape, and energy considerations. The precise
chemistry at nanoparticles interfaces have a profound effect on structure,
phase, transformations, strain, and reactivity. Certain phases exist only as
nanoparticles, requiring transformations in chemistry, stoichiometry, and
structure with evolution to larger sizes. In general, mineral nanoparticles have
hardly been studied in the art.
OBJECT OF THE INVENTION
It is therefore an object of the invention to propose a process for removal of
heavy metals like arsenic, lead and mercury from water body by utilizing the
rejects of beneficiated slime of iron ore as potential sources of goethite based
composite mineral nanoparticles.

SUMMARY OF THE INVENTION
According to the invention, contaminant sequestration is accomplished mainly
by surface complication, but aggregation of particles may encapsulate
adsorbed surface species into the multigrain interior interfaces, with significant
consequences for contaminant dispersal or remediation processes. Particularly
for particle sizes in the order of 70 - 100 nm. The sorption capacity and
surface molecular structure differ in important ways from bulk material. The
invention reviews the factors affecting geochemical reactivity of these
nanophases, focusing on the ways they may remove toxins from the
environment, and include recent results of studies on nanogoethite growth,
aggregation and sorption processes.
According to the invention, the naturally occurring iron hydroxide based
composite nanoparticles are adapted as a means for removal of arsenic as well
as other heavy metals, based on an innovative technique of adsorption-co
precipitation and settlement.

According to the invention, the potential of removing arsenic along with lead
and mercury from water by co precipitation with naturally occurring iron
hydroxide along with alumina and silica is implemented. The invention
determines the sensitivity of removal of arsenic in response to manual mixing
and prolonged settlement. It is found that about 90% of said heavy metals
removal could be achieved after 24 h settlement. It has also been observed
that when the iron levels are sufficiently high (say 1.2 mg/l), a simple shaking
of a container and allowing the iron-arsenic complex to settle out for 3 days,
reduces the concentration of the arsenic from 0.10 mg/l to 0.05 mg/l.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS AND
TABLES
Table -1 shows data relating to arsenic impurities in underground water
including the removal and residue data.
Table - 2 Artificial effluent prepared by different concentrations of the As,
Pb and Hg.
Figure - 1 Graphically represents arsenic removal with different setting time
in artificially prepared groundwater.

DETAILED DESCRIPTION OF THE INVENTION
Double distilled water was used for preparation of a specimen. The chemicals
employed for the process are GR grade and used without any purification. The
PPM Solutions of arsenic As (lll)/lead/mercury prepared from pure metal oxide
respectively in 0.5 M/l HCI.
The process has been performed with a constant ionic strength of 0.01 M/l
NaNO3and 0.1 g/l NaHCO3 to provide necessary alkalinity, pH being maintained
by adding 0.1 M NaOH. All glassware are cleaned by soaking chromic acid and
rinsed thoroughly with distilled water. Repeated blank tests (without Fe)
confirmed that no arsenic was lost through adsorption onto the glassware.
Arsenic was measured by Inductively Coupled Plasma Atomic Emission
Spectrometry (ICP-AES) method.
Mixing is a necessary stage in order to ensure aeration and to induce
flocculation as well as assuring dispersion of the chemicals. At the village level,
shaking is a straightforward means of achieving the mixing. The result was
compared with a mechanical mixing separately taken-up for reference purpose.

Similarly filtration was introduced for reference purpose, but the prime focus
has been to exploit sedimentation as a means of achieving solid-liquid
separation following the initial As-Fe, AS-Pb & As- Hg interaction. Mechanical
mixing was applied to 1 litre sample water (0.01M/I NaNO3 and 0.1 g/l
NaHCO3) containing 0.2 mg/l As(lll), Hg & Pb at pH 7.5. Sample containing in a
2-litre capacity conical glass flask was mixed in an orbital shaker (KL2) at a
rapid rate (410 rpm) for 5 min, at a slow rate (100 rpm) for 25 min and
allowed to settle. In the series based on manual mixing, samples were shaken
vigorously for periods in the range of 15 s to 5 min and then allowed to settle.
After 2 h settlement, two sets of supernatant were collected at a depth of 20
mm from the top surface from each type of samples (both mechanical and
manually mixed samples). One set of sample was analysed for residual As(lll),
Pb & Hg concentration with filtration through 0.45 mm filter papers and
another set was analysed for the same conditions but without filtration. Table 1

presents the one set of results. Same experiments are performed by column
absorption through different bed size, and the treated water was analysed and
shown in Table 2.
It is absorbed that the removal efficiency is insensitive to the mixing regime,
whereas for the unfiltered samples, removal depends on mixing type and time.
In the latter case, the duration of mixing probably enhances flocculation,
because the larger removal rates are associated with larger particle sizes. It is
seen that 5 min manual mixing is almost as effective as the mechanical mixing.
To investigate the effects of settlement on As(lll)/Pb/ Hg removal, several tests
were carried out following the same procedure in a manual mixing method, the
samples being allowed to settle for 24 h. Supernatant was collected at
specified time intervals, 2, 4, 6 and 24 h. unfiltered samples at varying mixing
times. In contrast, at longer settling time (24 h) the removal is less sensitive
to the initial stage of mixing. Similarly in bed absorption it is observed that the
retention time is greatly influenced by heavy metal removal.

References
1. Bagla, P.; Kaiser, J. India's spreading health crisis draws global arsenic
experts Science 1996, 274,174-175.
2. Ravenscroft, P.; Burgess, W.G.; Ahmed, K.M.; Burren, M.; Perrin, J.;
Arsenic in groundwater of the Bengal Basin, Bangladesh: Distribution,
field relations, and hydrogeological setting Earth Environ, Sci. 2005, 13
(5-6), 727-751.
3. Lepkowski, W. Arsenic crisis in Bangladesh, C&EN News 1998, 27-29.
4. Chatterjee, A.; Das, D.; Mandal, B.K.; Chowdhuri, T.R.; Samanta, G.;
Chakraborti, D. Arsenic in Groundwater in Six Districts of West Bengal,
India: The Biggest Arsenic Calamity in the World. Part 1 - Arsenic
Species in Drinking Water and Urine of the Affected People. Analyst
1995, 120.

5. Ahmed, M.F., All, M.A. and Hossain, M.D. 1998 Groundwater treatment
for arsenic-iron removal. International conference on arsenic pollution of
ground water in Bangladesh: causes, effect and remedies, Dhaka,
Bangladesh.
6. APHA, AWWA, and WEF. 1995 19th edition Standard methods for the
examination of water and wastewater, Washington, DC. BGC and
MottMacdonald Ltd. UK. 1999 Phase I, Groundwater studies of arsenic
contamination in Bangladesh. Executive summary, Main report for Govt,
of Bangladesh, Ministry of local Govt. Rural Development Co-operatives,
Dept. of Public Health Engineering (DPHE) and Dept. for International
Development DFID-UK).
7. Cheng, C.R., Liang., S., Wang. H-C and Beuhler, M.D. 1994 Enhanced
coagulation for arsenic removal. J. American Water Works Association.
86 (9), 78-90. Department for international Development (UK), British
Geological Survey (UK), Govt, of Peoples Republic of Bangladesh,
Ministry of Local Govt, and Cooperatives, Dept. of Public Health
Engineering Groundwater studies of arsenic contamination in
Bangladesh. Final report Summery, June 7, 2000.

8. Driehaus, W. Jekel, M.R. and Hilderbrandt, U. 1998 Granular ferric
hydroxoidea new adsorbent for the removal of arsenic from natural
water. J. Water Supply Research and Technology-AQUA. 47 (1), 30-35.
9. Edwards, M. 1994 Chemistry of arsenic removal during coagulation and
Fe-Mn oxidation. American Water Works Association. 86 (9), 64-78.
EGIS (ENVIRONMENT AND GIS SUPPORT RROJECT FOR WATER
SECTOR PLANNING). 1997 Spatial Information System for Arsenic
Mitigation Programs. Draft Report, Ministry of Water resources,
Government of Bangladesh.
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WE CLAIM:
1. A process for removing arsenic from underground water in which said
arsenic remains as an admixture, comprising contacting the underground water
under absorption conditions, with goethite based composite nanoparticles from
rejects of beneficiated iron slime, wherein said contacting takes place in a
liberating state at a pH range 7.8, and wherein said goethite based rejects
slime has at least 30% iron content with >70 % particles are less than 100nm.
2. The process as claimed in claim 1 wherein said goethite based
composite nanoparticles is a naturally occurring iron hydroxide mixed with
gibbsite and quartzite.
3. The process as claimed in claim 1, wherein the heavy metals like As, Pb
& Hg are recovered from water/industrial effluent and wherein the heavy
materials comprises As, Hg & Pb, being recovered under absorption conditions
with goethite based composite naturally occurring nano-particles.

4. The process as claimed in claim 3, wherein said contacting take place in
the absorption and metal oxidation state.
5. The process as claimed in claim 4, wherein said heavy metals are in the
form of As (IV), Pb(ll) & Hg (II).
6. The process as claimed in claim 4, wherein said reject slime is selected
from the group consisting of iron hydroxide, hematite, gibbsite & quartz and
water.
7. The process as claimed in claim 4, wherein said nano-particles comprises
goethite, hematite and gibbsite obtained from rejects or hydro-cyclone over
flow of beneficiated iron ore slime.
8. The process as claimed in claim 4, wherein said arsenic/lead/Hg is
passed through intermetallic compounds.

9. A process for removing arsenic from underground water substantially as
herein described and as illustrated in the accompanying drawings.

A process for removing arsenic from underground water in which said arsenic
remains as an admixture, comprising contacting the underground water under
absorption conditions, with goethite based composite nanoparticles from
rejects of beneficiated iron slime, wherein said contacting takes place in a
liberating state at a pH range 7.8, and wherein said goethite based rejects
slime has at least 30% iron content with >70% particles and less than 100nm.
FIG. 1