PHOSPHATE REMOVAL FROM AQUEOUS SOLUTION USING FLY ASH,BLAST FURNACE SLAG AND ELECTRO

COAGULATION

IntroductionIntroduction

Present in low concentration.Present in low concentration.

Essential for the growth of Micro organisms.Essential for the growth of Micro organisms.

Excess amount causes Eutrophication.Excess amount causes Eutrophication.

Harmful to aquatic life.Harmful to aquatic life.

Depletion of dissolved oxygen.Depletion of dissolved oxygen.

Conventional methodsConventional methods

Chemical treatment methodChemical treatment method

i.i. Reaction between aluminium and phosphateReaction between aluminium and phosphate

ii.ii. Reaction between calcium and phosphateReaction between calcium and phosphate

iii.iii. Reaction between iron and phosphateReaction between iron and phosphate

Biological treatment methodBiological treatment method

Case StudiesCase Studies

1)1) Lu S.G, et. al (2008)Lu S.G, et. al (2008)

2)2) Ensar Oguz (2004)Ensar Oguz (2004)

3)3) Nihal Bekthas et. al (2003)Nihal Bekthas et. al (2003)

Removal of phosphateRemoval of phosphate from Aqueous from Aqueous

solution using fly ashsolution using fly ash (source: Lu S.G, et .al 2008)(source: Lu S.G, et .al 2008)

Materials and methodMaterials and method

• High ,medium and low Calcium content.High ,medium and low Calcium content.

• Coded as FA1,FA2,FA3.Coded as FA1,FA2,FA3.

• The pH is determined using pH meter.The pH is determined using pH meter.

• Particle size distribution is calculated by using Particle size distribution is calculated by using

sieving and laser beam technique.sieving and laser beam technique.

Chemical composition of fly ashChemical composition of fly ash(Source Lu. S,G. et. al ,2008)(Source Lu. S,G. et. al ,2008)

ParameterParameter FA 1FA 1 FA 2FA 2 FA 3FA 3pHpH 10.910.9 10.910.9 12.112.1

SiOSiO22(%)(%) 49.5149.51 47.2347.23 43.0643.06

Electric conductivityElectric conductivity 1.141.14 1.061.06 5.645.64

AlAl22OO33(%)(%) 31.1231.12 34.2334.23 2828

FeFe22OO33(%)(%) 5.365.36 6.326.32 8.638.63

Ca O(%)Ca O(%) 5.445.44 5.545.54 10.8210.82

Density(gm/cmDensity(gm/cm33)) 1.931.93 2.202.20 2.292.29

Scanning electron microscopy of FA1Scanning electron microscopy of FA1(Source Lu. S,G .et. al ,2008)(Source Lu. S,G .et. al ,2008)

Scanning electron microscopy of FA2Scanning electron microscopy of FA2 (Source Lu. S,G. et. al ,2008)(Source Lu. S,G. et. al ,2008)

Scanning electron microscopy of FA3 Scanning electron microscopy of FA3 (Source Lu. S,G. et. al ,2008)(Source Lu. S,G. et. al ,2008)

Batch adsorption experimentBatch adsorption experiment 0.5gm of fly ashes and acid treated fly ashes were 0.5gm of fly ashes and acid treated fly ashes were

weighed and equilibrated in 50ml centrifuge tubes weighed and equilibrated in 50ml centrifuge tubes containing 25ml of 100mg/l phosphate solution at room containing 25ml of 100mg/l phosphate solution at room temperature. temperature.

The tubes were stopped and continuously shaken at a The tubes were stopped and continuously shaken at a spinning speed of 120 cycles /min .spinning speed of 120 cycles /min .

The shaking was interrupted momentarily at The shaking was interrupted momentarily at predetermined time interval for the tube to be removed.predetermined time interval for the tube to be removed.

The suspension was filtered to determine the The suspension was filtered to determine the concentration of phosphate concentration of phosphate

Results and DiscussionResults and Discussion

Mechanism of Phosphate removalMechanism of Phosphate removal

Adsorption and Precipitation.

High pH and calcium concentration are required.

Major form of precipitation is hydroxy apetite.

Variation of pH with phosphate added Variation of pH with phosphate added (Source Lu. S,G. et. al ,2008)(Source Lu. S,G. et. al ,2008)

Variation of Calcium concentration with Variation of Calcium concentration with phosphate addedphosphate added (Source Lu. S,G et. al ,2008)(Source Lu. S,G et. al ,2008)

Phosphorus adsorption kineticsPhosphorus adsorption kinetics

• Freundlich model, q = k CFreundlich model, q = k C1/n1/n (5) (5)

• Langmuir model, C/q = C /Q m+1/ bQm (6)

Where C= Phosphate concentration in equilibrium (mg/l)

Q= Amount of phosphate adsorbed/unit of sorbent

Qm = Langmuir sorption maximum

k, n = constants related to adsorption capacity

b = constants related to binding strength of phosphate

Characteristic parameters and determination Characteristic parameters and determination of coefficients of the experimental data of coefficients of the experimental data according to according to Freundlich and Freundlich and Langmuir equations

AdsorbentAdsorbent Freundlich equationFreundlich equation 1/n k R1/n k R22

Langmuir equationLangmuir equationQQm m b Rb R22

FA1FA1 0.483 6.17 0.9740.483 6.17 0.974 90.09 0.040 0.77590.09 0.040 0.775

FA2FA2 0.450 8.96 0.9670.450 8.96 0.967 90.91 0.078 0.87790.91 0.078 0.877

FA3FA3 0.584 13.47 0.9620.584 13.47 0.962 107.53 0.207 0.941107.53 0.207 0.941

Variation of pH with time for FA1Variation of pH with time for FA1 (Source Lu. S,G. et. al ,2008)(Source Lu. S,G. et. al ,2008)

Variation of pH with time for FA2 Variation of pH with time for FA2 (Source Lu. S,G .et. al ,2008)(Source Lu. S,G .et. al ,2008)

Variation of pH with time for FA3Variation of pH with time for FA3 (Source Lu. S,G. et. al ,2008)(Source Lu. S,G. et. al ,2008)

Variation of Percentage of Removal Variation of Percentage of Removal with Timewith Time (Source Lu. S,G et. al ,2008)(Source Lu. S,G et. al ,2008)

Removal of Phosphate From Aqueous Removal of Phosphate From Aqueous Solution Using Blast Furnace SlagSolution Using Blast Furnace Slag

(Source Ensar Oguz ,2004)(Source Ensar Oguz ,2004)

Materials and MethodsMaterials and Methods

Iskenderun blast furnace slag is used.Iskenderun blast furnace slag is used.

Adsorption studies are carried at phosphate Adsorption studies are carried at phosphate concentrations of 180 ppm.concentrations of 180 ppm.

Minimum equilibrium time of removal is 20 min.Minimum equilibrium time of removal is 20 min.

(contd…)(contd…)

Experiments were carried out at different temperature Experiments were carried out at different temperature and pressure.and pressure.

Phosphate is measured using calorimetric method.Phosphate is measured using calorimetric method.

Precipitated as phosphates of aluminium, calcium Precipitated as phosphates of aluminium, calcium and iron.and iron.

Chemical composition of Iskenderun blast Chemical composition of Iskenderun blast

furnace slagfurnace slag (Source Ensar Oguz ,2004)(Source Ensar Oguz ,2004)

ParameterParameter Component (%) Component (%)

SiOSiO22 39.5639.56

FeFe22OO33 0.330.33

AlAl22OO33 10.8210.82

CaOCaO 37.6837.68

MgOMgO 6.796.79

SOSO33 0.330.33

ChlorideChloride 0.1250.125

undeterminedundetermined 3.993.99

Results and DiscussionResults and Discussion

Variation of phosphate concentration and Variation of phosphate concentration and phosphate dose per kg blast furnace slagphosphate dose per kg blast furnace slag

(Source Ensar Oguz ,2004)(Source Ensar Oguz ,2004)

Relation between Phosphate concentration Relation between Phosphate concentration and Phosphate dose absorbed per kg blast and Phosphate dose absorbed per kg blast

furnace slagfurnace slag

(Source Ensar Oguz ,2004)(Source Ensar Oguz ,2004)

Effect of agitation rate on adsorption Effect of agitation rate on adsorption

(Source Ensar Oguz ,2004)(Source Ensar Oguz ,2004)

Effect of temperature on adsorptionEffect of temperature on adsorption

(Source Ensar Oguz ,2004)(Source Ensar Oguz ,2004)

Effect of pH on adsorptionEffect of pH on adsorption

(Source Ensar Oguz ,2004)(Source Ensar Oguz ,2004)

Nature of SlagNature of Slag

Before and after X-Ray Diffraction Before and after X-Ray Diffraction

Before and after Scanning Electron MicroscopyBefore and after Scanning Electron Microscopy

Scanning electron microscopy of blast Scanning electron microscopy of blast furnace slag before adsorptionfurnace slag before adsorption

(Source Ensar Oguz ,2004)(Source Ensar Oguz ,2004)

Scanning electron microscopy of blast Scanning electron microscopy of blast furnace slag after adsorptionfurnace slag after adsorption

(Source Ensar Oguz ,2004)(Source Ensar Oguz ,2004)

Removal of Phosphate from AqueousRemoval of Phosphate from AqueousSolution using Electro CoagulationSolution using Electro Coagulation (Source Nihal Bekthas et. al ,2003)(Source Nihal Bekthas et. al ,2003)

Materials and MethodsMaterials and Methods

Phosphate removal using electrochemical reactorPhosphate removal using electrochemical reactor

No other chemicals are used.No other chemicals are used.

Precipitated as phosphates of aluminium.Precipitated as phosphates of aluminium.

Electrochemical Reactor Electrochemical Reactor (Source Nihal Bekthas et. al ,2003)(Source Nihal Bekthas et. al ,2003)

Results and DiscussionResults and Discussion

Variation of Phosphate removal with Variation of Phosphate removal with

initial pHinitial pH (Source Nihal Bekthas et. al ,2003)(Source Nihal Bekthas et. al ,2003)

Variation of Phosphate removal with time Variation of Phosphate removal with time and initial concentrationand initial concentration (Source Nihal Bekthas et. al ,2003)(Source Nihal Bekthas et. al ,2003)

Variation of charge loading with time and Variation of charge loading with time and

initial concentrationinitial concentration (Source Nihal Bekthas et. al ,2003)(Source Nihal Bekthas et. al ,2003)

Variation of percentage of phosphate removal Variation of percentage of phosphate removal with current density and initial concentrationwith current density and initial concentration

(Source Nihal Bekthas et. al ,2003)(Source Nihal Bekthas et. al ,2003)

ComparisonComparison

ParametersParameters Phosphate removalPhosphate removalusing fly ashusing fly ash

Phosphate removalPhosphate removalusing blast furnaceusing blast furnaceslagslag

Phosphate removalPhosphate removalusing electrousing electrocoagulationcoagulation

pHpH High (9.4-11.6)High (9.4-11.6) Low(3-4.5)Low(3-4.5) Medium(6-6.9)Medium(6-6.9)

Adsorption isothermAdsorption isotherm Freundlich isothermFreundlich isotherm Freundlich isothermFreundlich isotherm Not mentionedNot mentioned

Time for maximumTime for maximumremovalremoval

Within 5minutes Within 5minutes (95.6%)(95.6%)

Within 60 minutes Within 60 minutes (99%)(99%)

Depends uponDepends uponconcentration andconcentration andcurrent densitycurrent density

Grain size of adsorbentGrain size of adsorbent Small (>150microSmall (>150micrometer)meter)

LargeLarge (0.020.03mm)(0.020.03mm)

Not mentionedNot mentioned

Form of precipitateForm of precipitate Phosphates ofPhosphates ofcalcium calcium

Phosphates ofPhosphates ofaluminium, calciumaluminium, calciumand ironand iron

Phosphates ofPhosphates ofaluminiumaluminium

Removal efficiencyRemoval efficiency 95.6%95.6% (within 5 minutes)(within 5 minutes)

99%99%(within60 minutes)(within60 minutes)

Depends upon time,Depends upon time,concentration andconcentration andcurrent density)current density)

TempTemp Not mentionedNot mentioned DifferentDifferenttemperature(25-65)temperature(25-65)

21-22 degree 21-22 degree celciouscelcious

ConclusionConclusion

Using fly ash maximum removal efficiency obtained within 5 Using fly ash maximum removal efficiency obtained within 5 minutes. Removal of phosphate occurs mainly by the minutes. Removal of phosphate occurs mainly by the formation of calcium phosphate. formation of calcium phosphate.

Removal efficiency depends upon the calcium ion Removal efficiency depends upon the calcium ion concentration in the fly ash. Availability of fly ash makes this concentration in the fly ash. Availability of fly ash makes this method more economic. method more economic.

Availability and low cost are the main advantages by using Availability and low cost are the main advantages by using blast furnace slag. In the method of blast furnace, slag removal blast furnace slag. In the method of blast furnace, slag removal efficiency increases with temperature, time and concentrationefficiency increases with temperature, time and concentration

(contd….)(contd….)

Maximum efficiency occurs within 60 minute, it is a main Maximum efficiency occurs within 60 minute, it is a main drawback compared to other methods drawback compared to other methods

In electro coagulation removal is carried out by using electro In electro coagulation removal is carried out by using electro chemical reactor. Phosphate is removed as precipitates of chemical reactor. Phosphate is removed as precipitates of aluminum aluminum

As the three methods of phosphate removal have some As the three methods of phosphate removal have some limitations, fly ash could be a promising solution to the limitations, fly ash could be a promising solution to the removal of phosphate in the wastewater treatment and removal of phosphate in the wastewater treatment and pollution control.pollution control.