Overall CEL795 Term Paper Summary Slides - PowerPoint PPT Presentation

Title: Overall CEL795 Term Paper Summary Slides


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Overall CEL795 Term Paper Summary Slides November
15th 2012
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Removal of pesticides from water using Nano
Filtration and Reverse Osmosis
Group members
Karishma Bhatnagar 2012CEV2274 (Group Leader)
Megha Kanoje 2012CEV2283 Shailvee 2012CEV2
273 SreelakshmiBabu 2012CEV2267 MeenakshiKayesth
2011CET3585
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Introduction
The main objective of this study is to
investigate the removal of pesticides by NF and
RO membranes and to study the effect of Membrane
characteristics, Pesticide properties, Feed water
and Membrane fouling.

• The presentation includes
• Basic information about Nano Filtration and
  Reverse Osmosis.
• Factors affecting the performance of NF/RO
  system.
• Benefits of using NF/RO system over other
  conventional methods

Nano Filtration
Nano filtration is a process in which membranes
with Nano size pores are used to separate
solutes or salts based on size/and or charge. It
can effectively remove multivalent ions,
pesticides, pathogens, hardness and nitrates.
Reverse Osmosis
RO membranes are effectively non-porous and thus
are very effective in removal of particles with
low molar mass species.
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Summary of factors to be considered while
designing a NF/RO system
NF/RO System
Membrane Properties Feed water
composition Pesticide Properties
MWCO
Water pH
Molecular weight
Membrane Porosity
Solute Concentration
Molecular Size
Membrane material
Ionic Strength
Chemical property

Organic matter
Polarity
Study on three different membranes NF90, NF270
and NTR7250 for removal of Atrazine
Parameters Effects on all three membrane
Feed Concentration Negligible effect
Pressure Retention increased with increased pressure
pH Best retention at 7 reduces at 4 and 10
Humic Acid Rejection increased
Humic Acid Flux decreased
TiO2 Rejection increased
TiO2 Flux decreased
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Effect of membrane material
Property Comments
Membrane molecular weight cut-off Most effective membranes are in range of 200 to 400 Da
Membrane porosity Micro-porous membranes are most effective
Membrane material Synthetic organic polymers are more efficient than ceramic and metallic membranes. Composite Polyamide (PA) are more effective than Cellulose Acetate (CA) Poly Vinyl Alcohol membranes are more effective than SulfonatedPolyehtesulfone Poly Vinyl Alcohol membranes.
Effect of the feed water composition
Property Comments
WATER pH Higher pH values - reduced removal rates. Reason-ion adsorption on membrane surface.
SOLUTE CONCENTRATION No significant effect on removal.
IONIC ENVIRONMENT High ionic concentrations - Better removal. Reason - reduction in electrostatic forces inside membrane.
PRESENCE OF ORGANIC MATTER(OM) Presence of natural OM - Increased removal. Reason - Binding between pesticides and humic substances.
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Effect of pesticide properties
Property Property Comments
Physical Properties of Pesticides Molecular size Higher the molecular size, higher will be the rejection
Physical Properties of Pesticides Molecular Length works in positive direction for removal of organic compound
Physical Properties of Pesticides Molecular Width Better indicators for removal of alcohols and carbohydrates
Physical Properties of Pesticides Mean molecular Size Better indicators for removal of alcohols and carbohydrates
Pesticides chemical properties Sorption Capacity Higher the sorpotion capacity, higher will be the rejection
Pesticides chemical properties Hydrogen Bonding Hydrogen bonding between hydrogen component of pesticide and hydrogen component of membranes works in positive direction for removal of pesticides
Pesticides chemical properties Hydrophobic interactions hydrophobic interactions are mostly responsible for pesticides adsorption on membrane
Pesticide polarity Dipole moment Solute rejection decreases
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• Benefits of reverse osmosis
• RO does not add any other chemical to water.
• Eco-friendly, do not produce or use any harmful
  chemicals during the process.
• Can remove contaminants such as arsenic,
  nitrates, sodium, copper and lead,
• some organic chemicals, and the municipal
  additive fluoride.
• It requires a minimal amount of power.
• Works well in home filtration systems because
  they are typically small in size.
• Removes unpleasant smell, unwanted taste, unusual
  colours and also benefits
• plumbing because of no corrosion issues.
• Benefits of nano-filtration
• Nano Filtration is chemical-free, as it needs no
  salt or chemicals during operation.
• Reduces nitrates, sulphates and heavy metals,
  colour and turbidity of water.
• In brackish water, it helps to reduce salt
  content and dissolved matter content (TDS).
• Nanoflitration softens hard water when specific
  softening membranes are used.
• The pH of water after nano-filtration is normally
  non-aggressive.
• Nano-filters are close in size to Reverse Osmosis
  filters, but cost much less to run.
• Also special properties of nano-sized particles
  can be exploited. We can design new
• nano-filters that catch particles smaller than
  they would catch based on size alone.

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TANNERY WASTEWATER TREATMENT THROUGH DIFFERENT
TECHNOLOGIES UNDER THE INFLUENCE OF
TOXICOLOGICAL EXPOSURE TO THE ENVIRONMENT

• Submitted by
•  
• Nidhi Gera 2011CEV3063
• Varsha Singh 2011CEV3064 
• Swati Sharma 2011CEV3065 
• Vikas Agrawal 2009TT10835

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introduction
A significant number of operations within a
tannery are wet operations consuming large
amounts of water, chemicals and energy and
leading to large amounts of polluted water. The
uncontrolled release of tannery effluents to
natural water bodies increases health risks for
human beings and environmental pollution.
Effluents from raw hide processing tanneries
produce wet blue, finished leather, contain
compounds of trivalent chromium (Cr3) ,sulphides
(S2-) and colour. Organic and other ingredients
are responsible for high BOD (Biological Oxygen
Demand), COD (Chemical Oxygen Demand)and TSS
values and represent an immense pollution load,
causing technical problems, sophisticated
technologies and high costs in concern with
effluent treatment. Through this term paper we
will demonstrate that by means of a combination
of biological and physico-chemical treatment
technologies, complex tannery wastewater can be
effectively and efficiently treated with high
reduction rates.
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methodology
Sr. No. Different Treatment Process Treatment Technologies
1 Primary treatment ( involves Metal grating, shortening the retention time). Primary settling tank is used for removing almost half of suspended solids.
2 Secondary treatment Aerobic Treatment Anaerobic Treatment activated sludge trickling filter - for biological Treatment oxidation ponds Chlorination - applied for disinfection UASB- for Anaerobic treatment of wastewater converts the organic pollutants into a small amount of sludge and large amount of biogas as methane and carbon dioxide
3 Tertiary treatment (involves a series of additional steps to further reduce organics, turbidity, N, P, metals, colour and pathogens) - Coagulation Filtration Activated carbon adsorption of organics Physiochemical Process Disinfection
4 Sludge Treatment Thickening Digestion Dewatering Incineration Final Disposal
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Results Different Technologies for effective
removal of pollutants
Sr No. Technologies Efficiency/ Effectiveness (on the basis of data available through experiments)
1 Electro coagulation and Electro-Fenton methods EF Process is much efficient than the EC process in terms of COD and sulfide removal.
2 Catalytic oxidation Aeration is required in Catalytic Oxidation of almost 7 n half with 98 removal efficiency of sulfide to maintain the optimum concentrations of the catalysts. With no catalyst used in the process, the sulfide removal was found to be 80 effective with an 8-hour aeration period.
3 Chemical oxidation using manganese oxide (IV) The amount of sulphides and the pH of solution have an influence on oxidation process duration it is longer when the sulphide amount and pH in WW is higher.
4 Wet Oxidation The pre-treatment is favoured by the fact in wet oxidation that it contains high amounts of NaCI 0.25-4.6.which reduces the phenolic compound/ ammonium Nitrogen/ oxidation of sulfides.
5 Galvanostatic electrolysis Higher current densities resulted in a faster COD removal due to a greater electro generation of active chlorine.
6 Batch Settling Effective in removal of Suspended solids and Total solids and helps in removal of MLSS.
7 Constructed wetland system This study is carried out with Pilot units which is vegetated with plants like Canna indica, Typha latifolia for surface water/ ground water in which it was shown that horizontal subsurface flow can be a viable alternative for reducing the organic matter content from tannery wastewater.
8 Removal of Chromium from Tannery Effluents. By Adsorption/Biological/ Chemical techniques -Cr3 around 98-99 get precipitated as cr (0H)3. Cr (VI) can be removed by biological treatment. Cr(VI) concentration decreases until reach nil after 96hr in all isolates except (S46).- - In Adsorption, chromium removal is controlled by degree of stirring. As rate of stirring increased the removal.
9 Electrodialysis Dimensional stability of membrane (MTS ,MCS) is used which increases as the polymer affinity for water decreases.The membranes had higher resistance due to the residual organic matter present in the effluent, which might have caused the membranes fouling, hindering the transport, and consequently increasing electric resistance thus helping in removal of color.
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summary

• The extent of pollution created by tanneries
  required different biological/chemical /Physical
  treatment and disposal of effluent wastewater for
  effective removal of unwanted toxicological
  exposure to plants and living beings.
• Biological treatment methods is a better choice
  for removal of organic and certain inorganic
  content yet the process efficiency is questioned.
• It is generally accepted that anaerobic treatment
  is less energy intensive and superior in most
  respect for the tannery wastewater treatment than
  the aerobic treatment.
• The application of combined process of physical
  or chemical with biological process to treat
  tannery wastewater would give satisfactory
  results compared to individual treatment
  processes.

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• INTRODUCTION
• Nanotechnology manipulates matter at the
  nanoscale (1100 nm) producing nanoproducts and
  nanomaterials -physicochemical properties
• The Woodrow Wilson Database lists- 1015 consumer
  products in market incorporating NPs -259
  containing silver nanoparticles (AgNPs)- largest
  and fastest growing class of NMs in product
  applications
• Sources of Silver Nanoparticles present in
  sludge  
• Silver is used as an antimicrobial agent in
  ointments and creams.
• Manufacturers add silver nanoparticles to
  hundreds of consumer products, including food
  storage containers, computer keyboards,
  cosmetics, pillows, cell phones, and medical
  appliances.
• Manufacturers of clothing articles exploit its
  antimicrobial property to produce novel items
  like No stink socks.

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• Effect of Silver nanoparticles (AgNPs)
• Silver is water soluble, unwanted AgNPs are
  formed in the sludge produce by sewage treatment
  plants.
• These antimicrobial nanoparticles could adversely
  impact desirable microorganisms that decompose
  waste in sewage treatment plants. For instance,
  they affect many nitrifying bacteria responsible
  for biological oxidation of ammonia with oxygen
  into nitrite followed by the oxidation of these
  nitrite into nitrates.
• Nanosized silver sulphide applied to agricultural
  land could oxidize in soils and release toxic
  silver ions that kill beneficial soil
  microorganisms.
• Occurrence of bio magnification of silver
  nanoparticles along the food chain.
• High exposures to silver compounds can cause
  Argyria, an irreversible condition in which the
  deposition of Ag in the body tissue results in
  the skin turning bluish in colour.

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• OBJECTIVE
• To find the different types of microorganisms
  which biosynthesize Silver nanoparticles under
  controlled laboratory conditions.
• To analyse different factors affecting Silver
  nanoparticle synthesis.
• To quantify field study and lab studies done on
  Silver nanoparticles in the past 5 years.
• METHODOLOGY
• The term paper was prepared by referring to
  journals available on published scientific
  research sites like ScienceDirect.
• Research papers were thoroughly studied -detailed
  analysis was done on our understanding.

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  DATA INTERPRETATION
Microorganisms which biosynthesize Silver
nanoparticles under controlled laboratory
conditions
Sl.No. Name of micro organisms which reduce silver nano particles Amount of AgNO3 added Incubation Conditions Incubation Conditions pH Absorbtion (nm) Size of NPs synthesised (nm) Reference
Sl.No. Name of micro organisms which reduce silver nano particles Amount of AgNO3 added Temp (C) Time (Hr) pH Absorbtion (nm) Size of NPs synthesised (nm) Reference
1 Shewanella oneidensis 1mM 30 48   410 93.5 1
2 Fusarium oxysporum 1mM   72   413 5 to 50 4
3 Escherichia coli 1mM 27 24   390 to 410 35 to 45 6
4 Bacillus subtilis 1mM 40 120 8.5 410 5 to 50 7 23
5 Penicillium fellutanum 1mM 5 24 6 430 5 to 25 8
6 Pseudomonas aeruginosa 0 to 30 mg/l 37 24 5 - 9 425 43  23
7 Micrococcus luteus 0 to 30 mg/l 37 24 5 - 9 425 43  23
8 Bacillus barbaricus 0 to 30 mg/l 37 24 5 - 9 425 43 23 
9 Klebsiella pneumoniae. 0 to 30 mg/l 37 24 5 - 9 425 43 23 
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• Various factors affecting the biosorption and
  toxicity of silver nanoparticles
• pH
• salt concentration
• Maximum adsorption and toxicity of AgNPs on
  bacterial species was
• observed at pH 5, and NaCl concentration of lt0.5
  M but, very less
• adsorption was observed at pH 9 and NaCl
  concentration gt0.5 M,
• resulting in less toxicity.
• It was also seen that Zeta potential plays an
  important role in
• adsorption of nanoparticles by microorganisms.
• In our research on the types of study done on
  silver
• nanoparticles it was found that the laboratory
  work on
• concentration of nanoparticles have been widely
  done in the
• past 5 years but the field study on environmental
  concerns
• over harmful effects of AgNPs in the wastewaters
  has paced in last
• three years.

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CEL 795TERM PAPERM.Tech ENVIRONMENTIst Sem
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• TOPIC
• REMOVAL OF ARSENIC FROM WATER USING ADSORPTION
  AND OXIDATION TECHNIQUES

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Group Members

• SWAGAT DAS 2012CEV2275
• GOVIND NARAIN 2012CEV2280
• DHEERAJ CHAUDHARY 2012CEV2284
• ARNAV KUMAR GUHA 2012CEV2268
• NANDAN 2011CEZ8473
• FATEMEH ZAHER 2012CE19042

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Methodology studied

• REMOVAL OF ARSENIC BY SOLAR OXIDATION AND
  ADSORPTION-
• The removal of arsenic by solar oxidation in
  individual units (SORAS) is currently being
  explored as a possible economic and simple
  technology to treat groundwater in Bangladesh and
  India.
• Light plays the role of accelerating the
  oxidation of As(III) to As(V), and also affects
  the nature of the solid and, hence, its sorptive
  properties.
• The efficiency of As removal depends on-
• the mechanism of formation of the solid iron
  (hydr)oxide,
• the rate of As(III) oxidation, and
• the possibility to include As(V) in the growing
  solid.
• Given enough Fe and alkalinity, As may be
  removed by the simple dark flocculation.
• 2) REMOVAL OF ARSENIC BY OFF-LINE COUPLED
  ELECTROCAT
• OXIDATION AND LIQUID PHASE POLYALYTIC MER
  BASED RETENTION (EO-LPR)-
• Electrochemistry and membrane ultrafiltration
  methods (electro-oxidation and liquid phase
  polymer based retention technique, LPR,
  respectively) were off-line coupled to remove
  As(III) inorganic species from aqueous solutions
  to achieve an efficient extraction of arsenic
  species by associating a polymer-assisted liquid
  phase retention procedure, based on the As(V)
  adsorption properties of cationic water-soluble
  polymers ,with an electrocatalytic oxidation
  process of As(III) into its more easily removable
  analogue As(V)
• Treatment by the liquid phase polymer based
  retention technique of aqueous arsenic solutions
  previously submitted to an electrocatalytic
  oxidation to convert arsenic(III) to arsenic (V)
  species quantitatively removes hazardous arsenic
  from these aqueous solutions.

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• REMOVAL OF ARSENIC BY SAND-ADSORPTION AND
  ULTRA-FILTRATION-
• in situ precipitated ferric and manganese binary
  oxides (FMBO) adsorption, sand filtration, and
  ultra-filtration (UF) for arsenic removal
• FMBO shows higher capability of removing arsenic
  than hydrous ferric precipitate (HFO) and hydrous
  manganese oxide (HMO)
• This is ascribed to the combined effects of
  oxidizing As(III) and adsorbing As(V) for FMBO.
  The continuous experiments indicate that this
  process is effective for arsenic removal.
• The rate of arsenic adsorbing onto FMBO is fast,
  and most arsenic is removed by the sand filter.
  UF increases the arsenic removal to a certain
  extent.
• 4) REMOVAL OF ARSENIC FROM DRINKING WATER USING
• ADSORPTION BY MODIFIED NATURAL ZEOLITE-
• The structure of modified and unmodified
  clinoptilolite samples from the GördesManisa
  deposit was studied. The elemental composition
  and specific surface areas of zeolitic samples
  were also determined.
• Iron concentrations in the solution to modify
  clinoptilolite play important role in the
  arsenate adsorption. However arsenate adsorption
  kinetics was slightly affected by them.
• At lower initial arsenate concentration, arsenate
  exhibited greater removal rates and best removed
  when the Fe1-GC was used for adsorbent. Thus,
  iron modified zeolite can be used as an efficient
  and economic adsorbent for arsenate removal.
•  

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• 5)REMOVAL OF ARSENIC FROM WATER USING PINE LEAVES
• use of Chir pine leaves (Pinus roxburghii) to
  remove As(V) ions from aqueous solutions.
• Maximum adsorption has taken place at pH 4.0
  while equilibrium was achieved in 35 min.
• Langmuir, Freundlich, Temkin, Elovich,
  DubininRadushkevich and FloryHuggins isotherm
  models were used to explain the phenomenon.
• Maximum adsorption capacity of P. roxburghii was
  3.27 mg/g that was compared with the capacities
  of some previous adsorbents used for arsenic
  removal.
• Adsorption mechanism was explored by Pseudo
  first- and second-order kinetic models, and it
  was found that the process followed second order
  kinetics. The study concluded that the Chir pine
  leaves can be a good adsorbent for removing As(V)
  from water owing to the fine adsorption capacity.
• 6)ARSENIC ADSORPTION PERFORMANCE OF HYDROUS
  OXIDE NANOPARTICLES
• exceptional arsenic removal performance on both
  As(III) and As(V)species.
• At near neutral pH environment, the maximum
  adsorption capacity of HCO nanoparticles is over
  170 mg/g on As(III), and 107 mg/g on As(V). Under
  very low equilibrium arsenic concentrations,
• the amount of arsenic adsorbed by HCO
  nanoparticles is over 13 mg/g (Ce at 10 g/L) and
  over 40 mg/g (Ce at 50 g/L).
• Over awide pH range from 3 to 11, HCO
  nanoparticles demonstrated an unique capability
  to readily remove As(III), which was not observed
  previously and is beneficial to their
  applications for water bodies with various
  conditions.
• HCO nanoparticles demonstrated fast arsenic
  removal rate and high adsorption capability
  without the need of pre-oxidation and/or pH
  adjustment, which is very attractive for their
  real application.
•  

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BIOREMEDIATION FOR THE REMOVAL OF URANIUM FROM
GROUND WATER

• Submiteed to Dr. Arun Kumar
• Neha Mehta-2012 cev2271
• Neeraj Golhani-2012cev2281
• Samarpreet Singh- 2012cev 2270
• Swati Srivastava- 2012cev3043

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Introduction

• bioremediation is the use of living organisms,
  primarily microorganisms, to degrade the
  environmental contaminants into less toxic forms.
  Bioremediation techniques prove to be
• more ecofriendly,
• low cost and easy technique as it uses naturally
  occurring bacteria and fungi or plants to degrade
  or detoxify substances hazardous to human health
  and/or the environment.
• The bioremediation techniques prove to be much
  better in comparison to conventional remediation
  methods especially at low concentrations i.e.
  high efficiency in detoxifying very dilute
  effluent and also generate less sludge at the end
  of the treatment (minimum ratio of disposable
  chemical and/or biological sludge volume).
• OBJECTIVE
• Reduction of uranium present in ground water into
  less harmful by-products by using bio-remediation
  techniques.
• If possible complete removal of uranium from
  affected water by using microbes.
• Converting soluble uranium compounds to insoluble
  forms to treat water containing uranium.
•  PATHWAYS OF URANIUM TO WATER-
• Uranium can enter ground water because of its
  presence in earths crust.
• Due to radioactive wastes from nuclear industry.
• Due to institutional use of radioisotopes(medicine
  , industry, agriculture, research reactors and
  test facilities)

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Methods used

• Bioremediation of uranium through reduction of
  the metal-
• Microbial reduction of soluble U (VI) to
  insoluble U (IV) plays an important role in the
  geochemical cycle of uranium and also serves as a
  mechanism for the bioremediation of
  uranium-contaminated waters. Enzymatic U (VI)
  reduction converts dissolved U (VI) to an
  extracellular precipitate of the U (IV) mineral
  uraninite (UO). Thus this has provided a possible
  mechanism for the removal of contaminating
  uranium from groundwaters.
• Bioremediation through rhizofiltration-
• Rhizofiltration is a type
  of phytoremediation, which refers to the method
  of using cultivated plant roots to remediate
  contaminated water through absorption,
  concentration, and precipitation of pollutants.
  In this, suitable plants with stable root systems
  are supplied with contaminated water to acclimate
  the plants. These plants are then transferred to
  the contaminated site to collect the
  contaminants, and once the roots are saturated,
  they are harvested.
• Biomineralization-
• The term biomineralization refers to the
  process of production of minerals by biological
  organisms. The complex mineral produced not only
  includes metallic or mineral part but also
  organic part of organism.

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• Bioaccumulation refers to the accumulation of
  substances, such as pesticides, or other organic
  chemicals in an organism. Bioaccumulation occurs
  when an organism absorbs a toxic substance at a
  rate greater than that at which the substance is
  lost.
• Bioremediation of uranium through biosorption-
• Biosorption is a physiochemical process that
  occurs naturally in certain biomass which allows
  it to passively concentrate and bind contaminants
  onto its cellular structure. The chemical
  tolerance
• of microbes to radionuclides/heavy metals
  rather than radiation tolerance is therefore
  preferable for remediation of metal
  contamination.

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Results

• Reduction of uranium from U (VI) to less toxic,
  insoluble U (VI) has been the method of choice
  for many scientists. Since this reaction is
  performed by bacteria, the results are obtained
  generally at a fast rate and with more
  efficiency. Handling bacteria both at lab scale
  and in fields is easier as their growth rate is
  high and short if optimum conditions are
  provided. Bacteria and few algae are able to use
  a number of metals as electron acceptors e.g.
  Uranium. Many a times the change in the redox
  state alters the toxicity or solubility of the
  metals.
• Bioaccumulation processes are under study, for
  removal of uranium, and researches show that
  bioaccumulation processes are used In acidic
  medium only.
• application of biosorption by the brown alga in
  purification of wastewater for the removal of
  uranium ions from industrial wastewaters can be
  suitable for large-scale exploitation. More
  studies are needed to optimize the system from
  the regeneration point of view and economic
  variance
• Adsorption of uranium ions was quite sensitive to
  pH of the medium and the maximum biosorption was
  obtained at acidic pH between 4.5 and 5.5.
  Temperature has not a favourable effect on
  biosorption capacity of fungal biomass in the
  range of 535 ?C.

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• Rhizofiltration allows in-situ treatment,
  minimizing disturbance to the environment.
  Various plant species have been found to
  effectively remove toxic metals such as cadmium,
  zinc, uranium etc.
• Bioremediation can provide final treatment to
  the contaminated water by reducing uranium levels
  upto 20 µg/L which is even lower than the US EPA
  guideline.
• Limitations-
• cases include where the metal removal by means of
  algae was not feasible in practice even though it
  showed satisfactory results under lab study.
• Sometimes the living organism is able to intake
  or tolerates uranium upto a certain concentration
  only. Beyond which uranium proves toxic to the
  organism as well.
• If substantial portion of the U(VI) is strongly
  associated with the sediments then it cannot be
  reduced microbially..
• In all the methods , efficiency of processes is
  highly dependent on pH of the system, and
  efficiency may drasticlly reduce in basic or
  alkaline mediums. Considering the abundance and
  diversity of microorganisms in the natural
  domain, it is of immense importance to identify
  and characterize microbial strains with high
  metal accumulation capacity and specificity,
  Understanding and exploring potential of
  microbemetal interaction.

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A potential of Biosorption derived for removal of
Arsenic from contaminated water
31
INTRODUCTION

• The experiment was conducted for banana peel due
  to its natural, renewable, abundance and thus
  cost effective biomass.
• Maximum efficiency found to be 82 at pH 7,
  contact time 90 minute, dosage 8g, temperature 35
  degree and 10 mg/L ion concentration of arsenic.

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Effect of pH

• removal of As increased with pH of solution and
  reached optimum value of 86 at pH 7.
• If pH value is lowered below 7, electrostatic
  repulsion between metal ions and H increased and
  removal of As was seen.
• If pH is above then 7, electrostatic repulsion
  decreases and metal adsorption process enhances
  and it is found to be maximum at a range of 6-8
  i.e. at neutral condition.

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Effect of temperature

• removal increases with the increase in
  temperature but upto 35 degree and then decreases
  due to breaking down of bond on the surface of
  biomass at higher temperature.

34
Effect of dosage

• Maximum removal is observed at 8 g/L.
• It is observed that increase in biosorbent dose
  results in increase in the number of active
  sites, which lead to increase in the percentage
  removal of As ion.
• However no significant increase in the percentage
  removal was observed with the increase in
  biosorbent concentration beyond 8g/L.

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Effect of contact time

• At initial stage of removal there is rapid
  removal of As ion and later on removal becomes
  slow and reaches optimum stage at 90 minutes.
  Further time wont significantly effect removal
  due to the accumulation arsenic species.