treatment of landfill leachate using nanoparticals
TRANSCRIPT
TREATMENT OF LANDFILL LEACHATE USING
NANOPARTICALS
PROJECT REFERENCE NO.: 41S_BE_1927
COLLEGE : B.L.D.E.A‟s VACHANA PITAMAHA Dr. P. G. HALAKATTI
COLLEGE OF ENGINEERING AND TECHNOLOGY, VIJAYAPURA
BRANCH : DEPARTMENT OF CIVIL ENGINEERING
GUIDE : Mr. NAVEEN DESAI
STUDENTS : Ms. POOJA MATH
Ms. MADHUMALA.J.BAGALI
Mr. DEEPAK C KUSUR
Mr. RAJ GUTTEDAR
ABSTRACT
A trend of significant increase in the municipal solid waste generation has been recorded
worldwide. This hasbeen found due to over population growth rate, industrialization,
urbanization and economic growth.Most of the countries have adopted sanitary landfilling
as the best method for disposal of their MSW. One of the major pollution problems
caused by the sanitary landfill is landfill leachate, which is generated as consequences of
infiltration of water into landfills and squeezing of the waste due to self-weight. Landfill
leachate contains a wide variety of recalcitrant compounds such as organic matter, heavy
metals and inorganic salts, which makes it quite difficult to treat using conventional ways
of treatment due to its high chemical stability and/or low biodegradability.In recent years,
a great deal of attention has been focused on to the application of nanosized metal oxides
to treat heavy metals, organic and inorganic matter by nanosized titanium oxides, ferric
oxides, manganese oxides, aluminium oxides and magnesium oxides as adsorbents and
photocatalysts. The utilization of TiO2 nanomaterial as an adsorbent and photocatalytic
has received much attention due to its chemical stability, non-toxic and photostable.
In the present study, the photocatalytic degradation of synthetic leachate was investigated
in natural sunlight by using TiO2 as Nanomaterial. The parabolic trough collector is used
as solar photoreactor, which can efficiently bring solar photons and chemical reagents
into contact with the photocatalyst. The characterization of TiO2is conducted by X-Ray
Diffraction (XRD) and Scanning Electron Microscope (SEM).The influences of various
parameters such as photocatalytic dosage and contact time are studied on leachate
removal efficiency. The result indicates thatXRD and SEM confirm that the selected
photocatalyst TiO2 is an anatase with spherical in shape. The crystallite size is
approximately 19nm and specific surface area of 120.32 m2/gm. The recipe used for the
preparation of synthetic leachate have a similar composition of real landfill leachate. The
influencing parameters dosage and contact time are able to remove the maximum
percentage of organic and inorganic compounds from synthetic leachate.The average
removal efficiency of lead is 97.82% in alkaline pH 9 with contact time 80 minutes and
dosage of 0.3g/l
1. INTRUDUCTION
1.1 Solid Waste
Solid waste is the unwanted or useless solid materials generated from human activities in
residential, industrial or commercial areas. It may be categorised in three ways. Based on,
origin(domestic, industrial, commercial, construction or institutional), contents (organic
material, glass, metal, plastic paper etc) and hazard potential (toxic, non-toxin,
flammable, radioactive, infectious etc).
Municipal solid waste (MSW) consists of household waste, construction and demolition
debris, sanitation residue, and waste from streets, generated mainly from residential and
commercial complexes. In metro cities in India, an individual produces an average of 0.8
kg/ waste/ person daily. The total municipal solid waste (MSW) generated in urban India
has been estimated at 68.8 million tons per year (TPY). The average collection efficiency
of MSW ranges from 22% to 60%.MSW typically contains 51% organic waste, 17%
recyclables, 11% hazardous and 21% inert waste.
The remaining 40% of MSW lies littered in the city/town and finds its way to nearby
drains and water bodies, causing choking as well as pollution of surface water. The
collected MSW will be disposed by various methods such as sanitary land filling,
incineration, open burning, composting, and dumping into the sea. One of the most
commonly used MSW disposal method all over the world is sanitary landfill.
1.2 Sanitary Landfill
Sanitary landfills are a method of waste disposal where the waste is buried either
underground or in large piles. This method of waste disposal is controlled and monitored
very closely. The sanitary landfillare classified into three types, Mechanized sanitary
landfill, Semi-mechanised sanitary landfill and manual sanitary landfill.
For sanitary landfills, the process starts by digging a large hole in the ground that is then
lined with thick plastic (normally 2-4 feet thick) and a layer of impervious clay. The
bottom of the landfill is also lined with a network of plumbing that functions as a
collection system for any liquids. There will be two types of wastes are generated from
the sanitary landfill those are of methane gas and leachat.Leachate is the term used to
describe liquids that leach or leak from the landfill.
Fig 1 Sanitary Landfill
1.3 Landfill Leachate
Leachate may be defined as liquid that has percolated through solid waste and has
extracted dissolved or suspended materials from it. In most landfills, the liquid portion of
the leachate is composed of the liquid produced from the decomposition of wastes and
liquid that as entered the landfill from external sources such as surface drainage, rainfall,
ground water and water from underground springs. The black liquid contains organic and
inorganic chemicals, heavy metals as well as pathogens; it can pollute the ground water
and represents the health risk. Its composition varies a lot, both from time to time and
from site to site so that it is difficult to treat the liquid in the right way.
1.3.1 Leachate generation Leachates from landfill are generated by a number of factors, such as:
Infiltration of ground water;
Infiltration of leachate into the ground (a potential pollution of the ground water
may occur);
Rainfall (precipitation);
Water from the deposited waste, mainly due to the static pressure;
Evaporation from the site.
1.3.2 Leachate Treatment Methods
Leachate is highly complex and polluted waste water that is produced by the introduction
of percolation water through the body of landfill treatment. Leachate treatment is
essential as it could threaten the surrounding ecosystem when discharge as it is and when
it mixes with groundwater. There are different methods of leachate treatment such as
coagulation-Flocculation, chemical precipitation, flotation, activated carbon adsorption,
ion exchange chemical oxidation and advanced oxidation process and nanomaterial.
Table 1 General Characteristics of young leachate
Properties Young leachate
Ph 4.5-9.0
Conductivity, mS/m 1200-2500
COD, mg/l 600-60000
Sulphate, mg/l 10-420
Chloride, mg/l 100-5000
Calcium, mg/l 10-2500
Alkalinity, mg/l 50-1150
Sodium, mg/l 50-4000
Nitrate, mg/l 1-150
Iron, mg/l 20-2100
Copper, µg/l 4-1400
Chromium, µg/l 1-300
Cadmium, µg/l 0.5-140
Lead, µg/l 8-1020
Zinc, µg/l 30-4000
Nickel, µg/l 2-200
Source -N. MlKACet al. War. Sci. Tech. Vol. 37. No.8, pp. 37-44, 1998.
Heavy metals appear in the leachate due to batteries,consumers electronics, ceramics,
light bulbs, house dust and paint chips,. Concentration of heavy metals in a leachate is
generally higher at earlier stages because of higher metal solubility as a result of low pH
caused by production of organic acids. It is now recognised that most trace elements are
readily fixed and accumulate in soils, and providing threat to human health and
environment.
1.4 Nanoparticles
Nanoparticles are those which have structured components with at least one dimension
less than 100nm. In nanotechnology a nanoparticle is defined as a small object that
behaves as a whole unit with respect to its transport and properties. Particles are further
classified according to its diameter. Two principal factors cause the properties of
nanoparticles to differ significantly from other materials: Increased relative surface area
and quantum effects. These factors can change or enhance properties such as reactivity,
strength and electrical characteristics. As a particle decreases in size, a greater proportion
of atoms are found at the surface compared to those inside. Thus nanoparticles have a
much greater surface area per unit mass compared with large particles. Due to this unique
properties nanoparticles are used as adsorbent and photocatalyst in treatment of water
wastewater.
1.5 Photocatalysis
Photocatalysis is the acceleration of a photoreaction in the presence of a catalyst.A
photocatalyst is defined as a substance which is activated by adsorbing a photon and is
capable of accelerating a reaction without being consumed. There are two types of
photocatalysis they are homogeneousphotocatalysis and heterogeneousphotocatalysis.
In homogeneous photocatalysis, the reactants and photocatalysts exits in the same phase.
The most commonly used homogeneous photocatalysts include ozone and photo-Fenton
systems. The efficiency of Fenton type processes is influenced by several operating
parameters like concentration of hydrogen peroxide, pH and intensity of UV. The main
advantage of this process is the ability of using sunlight with light sensitivity up to
450nm, thus avoiding the high costs of UV lamps and electrical energy. These reactions
have been proven more efficient than the other photocatalysis but the disadvantages of the
processes are the low pH valueswhich are required, since iron precipitates at higher pH
values and the fact that iron has to be removed after treatment.
Heterogeneous photocatalysis has the catalyst in different phase from the reactants. The
most commonly used heterogeneous photocatalysts are transition metal oxide and
semiconductors. Semiconducting oxide photocatalyst have been increasingly focused in
recent years due to their potential applications in solar energy conversion and
environmental purification. Semiconductor heterogeneous photocatalysis has enormous
potential to treat organic contaminants in water and air, this process is known as advanced
oxidation process (AOP) and is suitable for the oxidation of wide range of organic
compounds. Among AOPs, heterogeneous photocatalysis have been proven to be of
interest due to its efficiency in degrading recalcitrant organic compounds.
The several semiconductors Tio2, ZnO, Fe2O3, CdS and ZnS can act as photocatalysts but
TiO2 has been most commonly used due to its ability to break down organic pollutants
and even achieve complete mineralization. Photocatalytic and hydrophilic properties of
TiO2 makes it close to an ideal catalyst due to its high reactivity, less toxic, chemical
stability and lower costs.
Fig 2 Mechanism of photocatalysis
1.6 Photocatalytic Process
Photocatalytic treatments by advanced oxidation processes utilizing the combination of
strong oxidants such as O2, H2O2, irradiation light, and catalysts to produce hydroxyl
radicals have been considered as a promising technique for landfill leachate treatment.
The photocatalytic treatment has revealed a great potential as a low cost, nontoxic,
chemically stable, high photo activity, environmental friendly, and sustainable treatment
to fulfill the zero waste scheme in landfill waste treatments. The photocatalytic processes
can either break down or rearrange molecular structures of different bio-recalcitrant
compounds or convert them to more readily biodegradable intermediates, improving the
efficiency and reducing the cost of further biological steps.
1.7 Photoreactors
Photochemical reactions may be carried in the most of the photoreactors types used for
the thermal or thermal catalytic process. Generally, photoreactors are used for the study
of photochemical reactions are parabolic collectors and compound parabolic collecting
reactors. The parabolic trough collector is used as solar photoreactor, which can
efficiently bring solar photons and chemical reagents into contact with the photocatalyst.
Photocatalytic experiments were carried out in compound parabolic collector specifically
developed for photo-Fenton application.
1.8 Objectivesof the Study
The main aim of this work is to study the performance and suitability of semiconductor
TiO2 nanomaterials in treatment of heavy metals and organic compounds in the landfill
leachate. In this context objectives are as listed below.
1. Characterization study of TiO2nanomaterial, such as particle size, specific surface
area, and surface morphology.
2. Preparation of synthetic leachate in mark with young landfill leachate.
3. To study the influencing parameters on photocatalytic such as dosage and contact
time
4. To determine the photocatalytic activity of titanium dioxide in removal of heavy
metal lead.
5. To determine photocatalytic activity of titanium dioxide in removal of other
parameters of leachate such as COD, nitrate, sulphates.
2. LITERATURE REVIEW
1. J. S. Sudarsanet. al. (2015) carried out work on “Role of Titanium Oxide on Heavy
Metal Reduction in Electroplating Waste Water Treatment”. The objective of this study is
to compare the efficiency of the wetland technique conventionally and with nanoparticles.
Nanoparticles in constructed wetlands give good result due to its high surface area and
this can be used large scale water purification, from the analysis of samples in the
lab.Study shown that lower concentrations (between 30-100 ppm) Titanium dioxide has
the highest percentage removal. At 30-ppm concentration, all the TiO2 and Fe3O4
nanoparticles were able to remove Cr with 100% efficiency. Values of nZVI and
Magnetite reduced with increase in concentration. At 100 ppm concentration, nZVI
caused 42.25% removal and Fe3O4 caused 90% removal while, TiO2 caused almost 95%
removal. In case of magnetite nanoparticles, it is possible to reuse particles for 5-7 times.
It is a good adsorbent but it has a less life because it is made up of Iron. On the other hand
TiO2 needed UV source for irradiation but it shows very high efficiency in the treatment
of heavy metals and there is no harm from the product during treatment. Since it does not
contain Fe, it has no risk of oxidation. So, from all the three particles, TiO2 is found to be
most efficient in the removal of heavy metals from the effluents, as it has an efficiency of
over 96% removal of Cr and Pb impurities from the polluted water.
2. Kavitakabra et.al. (2008) studied about“Solar Photocatalytic Removal of Metal Ions
from Industrial Wastewater”.The objective is to describe the photocatalytic reaction and
deposition of force metal ions i.e, Cr, Ni, Zn and Cu present in the waste water from
chrome plating industry using solar energy irradiated TiO2. The solar photocatalytic
process is effective in removing most of the metal ions in specific condition. This paper
describes the photocatalytic reduction and deposition of four metal ions Cr (VI), Ni (II),
Zn (II), and Cu (II) present in the wastewater from a chrome plating industry using solar
energy irradiated TiO2. A parabolic trough reactor was used to carry out the reaction.
Experiments were carried out to find an optimum dosage of hole scavenger used (citric
acid). The adsorption and reduction of the metal ions at different pH values was also
investigated.. Alkaline pH was found to be more suitable for removal of nickel and zinc.
However, Cr (VI) reduced completely even at catalyst concentrations as low as 0.5 mg/l
at pH 2. Maximum reaction was completed in the first 4 hr of solar exposure.
3. Elisangela M.R. Rocha et al. (2010) carried out their work on “Landfill leachate
treatment by solar driven AOP’s”. Advanced oxidation treatment technologies are
investigated for leachates using natural solar radiation as UV photon sources. The
Photo-Fenton reaction presents a much higher degradation rate, more than 20 times
higher than the heterogeneous photocatalytic. In this study, different heterogeneous
(TiO2/UV, TiO2/H2O2/UV) and homogenous (H2O2/UV, Fe2+
/H2O2/UV) photocatalytic
processes were investigated as an alternative for the treatment of a mature landfill
leachate. The addition of H2O2 to TiO2/UV system increased the reduction of the aromatic
compounds from 15% to 61%, although mineralization was almost the same. The DOC
and aromatic content abatement is similar for the H2O2/UV and TiO2/H2O2/UV processes,
although the H2O2 consumption is three times higher in the H2O2/UV system. The low
efficiency of TiO2/H2O2/UV system is presumably due to the alkaline leachate solution,
for which the H2O2 becomes highly unstable and self-decomposition of H2O2 occurs. The
efficiency of the TiO2/H2O2/UV system increased 10 times after a preliminary pH
correction to 4. The photo-Fenton process is much more efficient than heterogeneous
(TiO2, TiO2/H2O2/UV) or homogeneous (H2O2/UV) photocatalysis, showing an initial
reaction rate more than 20 times higher, and leading to almost complete mineralization of
the wastewater. However, when compared with TiO2/H2O2/UV with acidification, the
photo-Fenton reaction is only two times faster.
4. Xin Zhang et al. (2012) investigated on “Effects of Electron Donors on the TiO2
Photocatalytic Reduction of Heavy Metal Ions under Visible Light”. Photocatalytic
reduction of Cr could be encouraged by methanol, methanal and formic acid Cr could
hardly be reduced by TiO2 without electron donors. The effects on TiO2 photocatalytic
reduction of Cr (VI) under visible light, using methanol, methanal and formic acid as
electron donors were investigated. The results showed that the photocatalytic reduction of
Cr (VI) could be encouraged by methanol, methanal and formic acid. The fastest rate of
Cr (VI) photoreduction was observed in the presence of formic acid followed by methanal
and methanol. Cr (VI) could hardly be reduced by TiO2 without electron donors. The
conversion percent of Cr (VI) was 100% using formic acid as electron donors after 80
min. For the methanal and methanol systems, the conversion percent of Cr (VI) were
93.62% and 22.69% after 6 hr, respectivel
5. Reza Barati et al. (2014) conducted their work on “Photocatalytic removal of
cadmium and lead from simulated wastewater at continuous and batch system”. The
reactors used in this study consists of Ultra Violet (UV) source, reaction cell and mixing
chamber. The increasing TiO2 dose and pH the cadmium and lead removal increases. The
aim of this study was to evaluate the photocatalytic processes for cadmium (Cd2+
) and
lead (Pb2+
) removal at continuous and batch system. This study was performed at
laboratory scale. The reactors used in this study consisted of three parts: Ultraviolet (UV)
source, reaction cell, and mixing chamber. The experiments were carried out in a batch
and continuous reactor for synthetic wastewater. The concentration of Cd2+
and Pb2+
was
constant (25 mg/l) in all experiments and effect of titanium dioxide (TiO2) dosage, pH,
and air dispersion was investigated on the removal efficiency. The results showed that
with increasing TiO2 dosage and pH, the cadmium and lead removal increase. The
maximum removal of cadmium and lead was obtained in TiO2 dosage of 0.9 g/l and pH
11 that were equal to 99.8 and 99.2% respectively. Furthermore, when air dispersion
increased, the removal efficiency increased; while in the air dispersion 2cm3/l the removal
efficiency was maximum. According to these results the TiO2 has been considered as
photocatalyst is the separable and recyclable, so UV/TiO2 process is an environment
friendly process for toxic metal removal.
3. MATERIALS AND METHODOLOGY
3.1 Characterization of TiO2 Nanomaterial
The Scanning Electron Microscope (SEM) and X-Ray powder diffraction (XRD) is used
to study particle size, specific surface area and morphology of TiO2 Nanomaterials. Tests
are carried out at Shivaji University Kolhapur. The titanium dioxide (TiO2) used was
supplied from Sisco Research Laboratories Pvt. Ltd.
3.2 Construction of Parabolic collector (Trough)
After conducting more research on solar energy and solar collection, the decision was
made to attempt to build a parabolic trough solar concentrator. In parabolic concentrator
all the incoming rays from a light source are reflected back to the focal point of the
parabola.Parabola is built by eccentricity method. The photoreactor used was a
transparent borosilicate glass tube with 3 cm internal diameter, 20.4 cm length, mounted
on a parabolic collector of aperture length 38 cm and aperture width 18.2 cm (Fig. 3.1).
The parabolic collector is coated with Aluminium foil to bring about 100% reflection of
sunlight during photocatalysis. The photoreactor used for the study will be prepared with
borosilicate glass tube with 38mm internal diameter, 1.8m length, mounted on a parabolic
trough reflector of aperture length 172cm and aperture width 57.75cm.
Fig 3: Construction of parabolic concentrator(diagram)
3.3 Preparation of Solutions
3.3.1 Preparation of Synthetic Leachate:-
The synthetic landfill leachate was prepared in line with the real landfill leachate .The
synthetic landfill leachate was prepared by dissolving the corresponding analytical grades
of chemicals in distilled water as per table 3.1.
Table 2 constituents of synthetic landfill leachate
Constituents Per litre
Acetic acid (99%) 7ml
K2HPO4 30mg
KHCO30 312mg
K2CO3 324mg
NaNO3 50mg
NaHCO3 3012mg
CaCL2.2H2O 2882mg
MgCL2.6H2O 3114mg
MgSO4 156mg
NH4HCO3 2439mg
CO(NH2)2 695mg
3CdSO4.8H2O 80mg
NiSO4.6H2O 80mg
NaOH solution (4mol/l) 125ml, titrate to a pH of 5.8-6.1
To make the presence of heavy metal into the leachate solution, along with this
constituents lead of 20ml were added, mixed it well.
3.4COD, Nitrate and Sulphate test procedures
3.4.1 Chemical Oxygen Demand Test Procedure
COD is a measure of total quantity of oxygen required for oxidation of nearly all oxygen
compounds in waste water, by the action of strong oxidising agent.
Reagents used:
Standard potassiumdichromate (0.25 N), COD reagent, Standard ferrous ammonium
sulphate (0.1 N), Mercuric sulphate, Ferroin indicator.
Procedure for chemical oxygen demand test
1. Place 0.4 gm HgSO4 in a reflux flask.
2. Add 20 ml sample or an aliquot of sample diluted to 20ml. Mix well.
3. Add glass beads followed by 10ml standard potassium dichromate.
4. Add 30ml COD reagent (while adding the reagent cool the flask). Mix well. If the
colour turns green either take fresh sample or with a lesser aliquot.
5. Connect the flask to condenser and reflux for 2 hours.
6. Cool the flask to room temperature.
7. Add 4-5 drops of Ferroin indicator. Bluish green colour is observed.
8. Titrate this solution against 0.1 N Standard Ferrous Ammonium Sulphate till colour
changes to wine red.
9. Note down the burette reading.
Calculation
COD in mg/l = (A−B)× Normality of titrant ×Equivalent weight of oxygen ×1000
ml of sample titrated
Where, A= ml of titrant used for blank
B= ml of titrant used for sample
3.4.2 Nitrate Test procedure
This method is suitable for screening samples that have low organic matter contents. The
NO3 calibration curve follows Beer‟s law up to 11 mg/l. Measurements of UV absorption
at 220nm enables rapid determination of NO3.
Reagents used:
Stock nitrate solution, Standard nitrate solution.
Procedure for nitrate test
1. Pipette 10, 20, 30, 40 ml (2, 4, 6, 8mg/l) of standard nitrate solution in 50ml Nessler‟s
tubes/volumetric flask.
2. Switch on the instrument which is located of the left hand rear side of the instrument.
3. The display will show „Elico‟ *SL 210*.
4. Press ENTER, the display will show D2 lamp testing alignment in progress.
5. Press ENTER, the display will show base line scan. Then press YES.
6. Press ENTER, the display will show MENU.
7. Then the different modes are displayed. Select the required mode. Example,
quantitative from the main MENU.
8. Press the „1‟ and select „Standard‟ option.
9. Keep the prepared samples and distilled water in reference point.
10. Press ENTER and feed the wave length value.
11. Press ENTER number of standards.
12. Press ENTER and select the concentration units Ex. Ppm.
13. Press ENTER and cuter values standard 1 concentration value. Similarly enter values
for all standards.
14. Press ENTER and select mode of absorbance input Ex. Measure.
15. Press ENTER and enter number of samples.
16. Keep cuvette filled with reference and other cuvettes filled with standards in the
cuvette holder drum.
17. Display will show auto zero option say always „NO‟.
18. The spectrophotometer will start reading the reference and all the standards.
19. Then the display will ask for samples. Remove the standards and place the samples in
the cuvettes and press „ENTER‟.
20. Now the instrument will start reading the samples.
21. Now the display will show different option like 1.View, 2. Print, 3. Modes.
22. Press view to see readings.
23. The data option like standards and samples are displayed.
24. Press „ESCAPE‟ to come back to main menu.
25. Switch of the Instrument.
. 3.4.3 Sulphate Test procedure
Sulphate is widely distributed in nature and may be present in natural waters in
concentrations ranging from a few to several thousand milligrams per litre. Mine drainage
wastes may contribute large amounts of SO4 through pyrite oxidation. Sodium and
magnesium sulphate exert a cathartic action.
Reagents used:
Conditioning reagent, Barium chloride, Standard sulphate solution (1000mg/l)
Procedure for sulphate test
1. Prepare standards containing 20, 40, 60, 80, 100, & 120 mg/l of sulphate.
2. Take distilled water in the test tube. Add 5ml conditioning reagent. Add few grains of
barium chloride. Mix well and adjust set 0 controls to get 0 displayed on the read out.
3. Replace the distilled water filled test tube with reference standards of the highest
known concentration (120 mg/l). Add 5 ml conditioning reagent. Add few grains of
barium chloride. Mix well and adjust set 1000 control to get 1000 displayed on the
read out.
4. Repeat step 3 for all the standards and find the respective turbidity values.
5. Plot a standard graph with concentration (mg/l) on X-axis and turbidity(NTU) on Y-
axis.
6. Take suitable volume of sample in volumetric flask and dilute to 100ml.
7. Add 5ml conditioning reagent accurately mix well.
8. Keep the flask constantly stirred with the help of stirrer. Add BaCl2 crystals while
stirring.
9. Measure the turbidity developed after every 30 seconds on nephelometer.
10. Find the sulphate concentration of the sample with the help of standard graph.
11. Samples having higher turbidity require dilution. Then the turbidity can be calculated
as follows
Nephelometric Turbidity Unit (NTU) = 𝐴×(𝐵+𝐶)
𝐶
Where, A= NTU found in diluted sample
B=volume of dilution water, ml and
C=sample volume taken for dilution, ml.
3.4.4 Conductivity Test procedure
Conductivity is a numerical expression of the ability of an aqueous solution to carry an
electric current. This ability depends on the presence of ions, their total concentration,
mobility, valence and relative concentrations and on the temperature of measurement.
Reagents used:
Standard conditioning solution
Procedure for conductivity test
1. Switch on the instrument by pressing on/off key.
2. The full LCD lights up for a few second to display all segments as a self-diagnostic
test of the LCD. Then display the conductivity measurement.
3. Rinse the electrode thoroughly with deionised water
4. Note that mode is (COND).
5. Immerse the electrode into the selected standard solution (1413 micro mhos/cm) and
press CAL. Now the primary display shows the measured reading while the secondary
display indicates the temperature of calibrating solution.
6. Use MI/∆ or MR/∇ key to scroll to the correct standard solution value on the meter.
7. Press ENTER to confirm the calibration value. The programme will resume to its
measurement mode.
8. Immerse the electrode in the given sample and note down the conductivity value.
3.5 Experimental work
The experiments were carried out in a batch sequence under natural sunlight at Vijayapur,
(16.83°N 75.71°E) Karnataka state, India. The parabolic trough (Fig3.1) is used with an
angle of 450to receive the maximum sunrays. The 100ml glass tube is used for
experimental work. At the end of each experiment, filter paper is used for separation of
TiO2 particles. The lead and zinc analysis was done by using Atomic Absorption
Spectroscopy (Varian 240). The COD, Nitrate, Sulphate, Conductivity and pH analysis
done as per the above procedure.
4 RESULTS AND DISCUSSION
4.1 Analysis of TiO2 Photocatalytic characteristics
4.1.1 Particle size of Titanium dioxide adsorbent
The XRD pattern of TiO2 Photocatalytic is shown in table 3. The results shows six peaks
at 25.29, 37.92, 48.09, 53.86, 55.12, and 62.7. The 2θ peaks at 25.29˚ and 48.09˚ confirm
its anatase structure according to JCPDS Card.
Table 3 XRD pattern of TiO2 Photocatalytic
Average crystallite size is calculated by considering the 2θ peak values. The simplest and
most widely used method for estimating the average crystallite size is from the full width
half maximum (FWHM) of diffraction peak using Debye-Scherer formula
D= 0.9𝜆
𝛽𝑐𝑜𝑠𝜃
Where, λ is wave length of X-Ray (0.1540 nm), β is FWHM, θ is diffraction angle, and D
is crystallite size. The average crystallite size obtained by the above equation is 19 nm.
The intensity of XRD peaks of the sample reflects that the smaller the crystal size the
broader the peak confirming small size crystallite
4.1.2 Specific Surface Area (SSA) by X-ray diffraction
SSA is a material property. It has a particular importance in case of adsorption,
heterogeneous catalysis and reactions on surfaces. SSA is the Surface Area (SA) per
mass. The specific surface area and surface to volume ratio increase dramatically as the
size of materials decrease. The SSA can be calculated using following equations and both
the equations yield the same result. The observed results are in Table 4.
𝑆𝑆𝐴 =𝑆𝐴𝑃𝑎𝑟𝑡
𝑉𝑃𝑎𝑟𝑡 ×𝜌
S=6000
𝐷𝑃×𝜌
Where SSA and Sare the specific surface area, VPart is particle volume and SApart is
surface area, Dp is the size (Spherical Shaped) and ρ is the density of thematerial.
Table 4 Specific Surface Area of TiO2 Nanoparticles
Particle size (nm) Surface area
(nm2)
Volume (nm3) Density (g.cm
-3) SSA (m
2.g
-1)
19 1134.262 3597.82 2.62 120.32
The results show 120.32 m2/gmSSA which is responsible for the enhanced photocatalytic
degradation of lead.
4.1.3 Scanning Electron Microscope (SEM)
The surface morphology is studied by Scanning Electron Microscopy (SEM) in the
physical Instrumentation Facility Centre (PIFC), Department of Physics, Shivaji
University, Kolhapur, Maharashtra. The SEM images of TiO2 at different magnifications
are shown in Fig 4, which confirms that the TiO2 used for the study is spherical in shape.
Fig.4 SEM images of TiO2
nanoparticles with different
magnification
4.2Analysis of synthetic leachate
4.2.1 Initial characteristics of synthetic
leachate
Initial characteristics of synthetic leachate are
determined with the standard procedures. The
initial characterisation study is carried out to
compare the synthetic leachate with the real
landfill leachate characteristics. Table 4.3
shows the comparison table. The results
obtained on synthetic leachate are almost
resembling with the real landfill leachate.
Parameters Prepared synthetic
leachate Real leachate
pH 9.07 4.5-9.0
Conductivity 13860µmhos/cm 12000-25000 µmhos/cm
Chemical oxygen
demand
12800 mg/l 600-60000 mg/l
Nitrate 117.83 mg/l 1-150mg/l
Sulphate 280mg/l 10-420 mg/l
Table 5 comparison of synthetic leachate and real leachate characteristics
The heavy metal Pb2+
concentration considered in synthetic leachatewas higher level
compare to the real landfill leachate. This higher level concentrations help in the proper
analysis ofthe degradation of the heavy metal by TiO2.
4.2.2Degradation study of COD, conductivity,sulphate and nitrate by TiO2
Photocatalytic
Table 6 shows the organic and inorganic compounds reduction by TiO2photocatalyst.
These studies have been carried out with different dosages of TiO2 and time variation.
Table 6 Experimental results for organic and Inorganic compounds
Sl.No Dosage
(gm\lit)
Irradiation
(minutes)
COD
(mg\lit)
Conductivity
(μmohs/cm)
Sulphate
(mg\lit)
Nitrate
(mg\lit)
Pb2+
%
removal
1 0.2 20 10000 11288 268 100.48 95.28
2 0.2 40 9200 10085 243 93.76 96.38
3 0.2 60 8400 1255 230 82.45 98.28
4 0.2 80 8000 1223 200 74.32 98.92
5 0.2 100 7200 1215 189 60.09 97.28
6 0.3 20 6400 1190 171 55.39 96.68
7 0.3 40 6000 1162 156 50.01 97.15
8 0.3 60 5600 1134 140 44.21 97.92
9 0.3 80 4800 1096 128 39.69 98.55
10 0.3 100 4400 1058 110 33.33 96.23
Lead 19.28 mg/l 0.008-1.020mg/l
100009200
8400 80007200
6400 6000 56004800 4400
0
2000
4000
6000
8000
10000
12000
20 40 60 80 100
CO
D r
emo
val i
n m
g/l
Irradiation time in minutes
Series1
Series2
268
243230
200189
171156
140128
110
0
50
100
150
200
250
300
20 40 60 80 100
Sulp
hat
e re
mo
val i
n m
g/l
Irradiation time in minutes
Series1
Series2
COD Removal by photocatalysis process: -The Graph 5 shows the reduction of COD in
the synthetic leachate with 0.2g/l and 0.3g/l. As the catalysis dosage plays an important
role in photocatalytic activity as the density of particle in the area of illumination
increased. This was attributed to the increased availability of catalyst sites for the
adsorption of the reactant molecules, better generation of reactive free radicals and their
interaction.
Fig 5
COD removal with 0.2g/l and 0.3g/l dosage
Nitrate and Sulphate Removal by photocatalysis process: - The Graphs 4.3 & 4.4
shows the reduction of sulphate and Nitrate in the synthetic leachate for 0.2g/l and 0.3g/l
for TiO2 dosage at different time intervals in minutes. As expected, solar photocatalytic
reaction rates increase with increasing solar irradiance. In heterogeneous photocatalysis,
reaction rate profiles areproportional to the number of incoming photons on the solid
photocatalyst. Performance is almost linear when solar irradiance is low.
Fig 6
Sulphate removal with 0.2g/l and 0.3g/l dosage
100.4893.76
82.4574.32
60.0955.39
50.0144.21
39.6933.33
0
20
40
60
80
100
120
20 40 60 80 100
Nit
rate
rem
ova
l in
mg/
l
Irradiation time in minutes
Series1
Series2
20 40 60 80 100
Series1 95.28 96.38 98.28 98.92 97.28
Series2 96.68 97.15 97.92 98.55 96.23
92
93
94
95
96
97
98
99
100
%re
mo
val o
f le
ad
Irradiation time in minutes
Fig 7
Nitrate removal with 0.2g/l and 0.3g/l dosage
4.2.3Degradation of lead (Pb2+
)
Heavy metals are one of the major concerns in the sanitary landfill leachate. Heavy
metals enter in the landfill by electroplating waste, painting waste, used batteries etc.
Heavy metal lead (Pb2+
) can cause a harmful effects such as anemia, abdominal pain,
irritability, as well as it disturbs the functioning of the brain resulting in memory loss and
headache. Therefore lead is considered for the study and results are shown in below graph
4.6
The results of lead show that as the time interval increases the removal efficiency of lead
increases. The longer irradiation time accelerates mixing and dispersion of adsorbent into
the solution and providing more vacant sites for metal ions. Furthermore, theincrease of
irradiation time leads to precipitation of the adsorbed lead back into the solution.It was
seen that at the lower adsorbent dosage, the increasing pH caused a higher adsorption
capacity, due to deprotonation of the more adsorption sites
Fig 8 Lead removal with 0.2g/l and 0.3g/l dosag
5 CONCLUSIONS
In the present study, TiO2Photocatalytic nanomaterial is used for the removal of organic
and inorganic compounds from synthetic leachate. Based on the present study following
conclusions were drawn.
1. The TiO2 characteristics study, such as XRD and SEM results confirms that the
selected photocatalyst TiO2 is an anatase with spherical in shape. The crystallite
size is approximately 19nm and specific surface area of 120.32 m2/gm
2. The recipe used for the preparation of synthetic leachate have a similar
composition of real landfill leachate.
3. To major two influencing parameters dosage and contact time, selected for the
photocatalytic study has the ability to remove the maximum percentage of organic
and inorganic compounds from synthetic leachate.
4. The removal efficiency of lead is maximum in alkaline pH 9 with contact time 80
minutes and dosage of 0.3g/l
5. The removal efficiency of COD, nitrate and sulphates were studied. COD removal
efficiency found lesser due to the high pH value (alkaline) in synthetic leachate.
The nitrate and sulphate removal efficiency were comparatively good by the
TiO2photocatalyst