Evt 621 Research Methodology Slide

Removal of Zinc (II) Ion from Synthetic Wastewater Solution

by using Activated Carbon Prepared from Corn Cob

By:

Mohd Aminurrasyid bin Mohd Amin(2005679824)

B. Sc. (Hons.) Environmental Technology

Under supervision of:

Mr. Mohd Nizam bin Yusof

Introduction

Removal of Zinc (II) Ion from Synthetic Wastewater Solution by

using Activated Carbon Prepared from Corn Cob

Introduction:Industrial Wastewater

Disposal of industrial wastewater is one of the major environmental issues the pollutants inside are usually so toxic wastewater has to be treated before it can be reused or

disposed in water bodies Industrial processes generate wastewater containing

heavy metal contaminants Most of heavy metals are hard to be degraded into non-toxic

forms Their concentrations must be reduced to acceptable levels

before being discharged into the environment Otherwise, it could pose threats to public health and/or affect

the aesthetic quality of potable water Metals of most immediate concern are chromium, zinc, iron,

mercury and lead (WHO, 1984)

Introduction:Heavy Metals

Heavy metals in wastewater come from industries and municipal sewage

One of the main causes of water and soil pollution

The presence of heavy metals in wastewater strongly reduces microbial activity, thus adversely affecting biological wastewater treatment processes

Heavy metal contamination that does get into the environment could cause permanent negative ecological effects (Micera et al., 1988)

Introduction:Zinc

Zinc is the 23rd most abundant element in the Earth's crust (Wikipedia, 2007b)

Most zinc ore found naturally in the environment is found as the salt, zinc sulfide

Zinc salts are widely used in industry Zinc sulfide and zinc oxide are used to make white paints,

ceramics, and several other products Zinc oxide is also used in producing rubber Zinc acetate, zinc chloride, and zinc sulfate, are used in

preserving wood and manufacturing and dyeing fabrics (Irwin, R.J., 1997)

Introduction:Zinc (cont’)

Natural zinc level in surface water < 0.01 mg/l Natural zinc level in groundwater < 0.05 mg/l

May be varied due to natural processes and human activities which cause the release of zinc to water bodies

Waste streams from zinc and other metal manufacturing and zinc chemical industries, domestic waste water, and run-off from soil can discharge zinc into waterways

The level of dissolved zinc in water may increase as the acidity of water increases (Irwin, R.J., 1997)

Problem Statement

Discharge of zinc into natural streams and rivers from the industries cause severe environmental problems

Elevated zinc concentration in water is particularly toxic to many species of algae, crustaceans, and salmonids, and have especially strong impacts on macroinvertebrates such as molluscs, crustaceans, odonates, and ephemeropterans (Irwin, R.J., 1997)

Problem Statement (cont’)

In mammals, excess zinc can cause copper deficiencies, affect iron metabolism, and interact with the chemical dynamics of lead and drugs (Irwin, 1997)

In human, excessive absorption of zinc in can suppress Cu2+ and Fe2+ absorption (Wikipedia, 2007), nausea, vomiting, fever, headache, tiredness, and abdominal pain (Irwin, 1997)

The free zinc ion in solution is highly toxic to plants, invertebrates, and even vertebrate fish (Wikipedia, 2007)

Problem Statement (cont’)

According to EQA 1974, Environmental Quality (Sewage & Industrial Effluents) Regulations 1979, [Regulations 8 (1), 8 (2), 8 (3)], 3rd Schedule: Parameter limits of effluent of Standard A and B (Appendix A), Zinc concentration for both Standard A and Standard B effluent should not exceed 2.0 mg/l.

Significance of Study To find other type of activated carbon as an

alternative for the removal of Zinc from industrial wastewater

Current methods for removal of zinc from wastewater: Precipitation Coagulation/Flocculation Sedimentation Filtration Membrane process Electrochemical process Ion exchange Biological process Chemical reaction

(Rachakornkij et al., 2003)

Significance of Study (cont’) Most common methods to remove or reduce the zinc and

other heavy metals concentrations in the environment are found to be somewhat impractical and costly

Adsorption by activated carbon: Has excellent adsorption capability Very efficient in removing heavy metals from waste streams Widely used High cost – unsuitable for developing countries Demand for low-cost activated carbon

(Rachakornkij et al., 2003) Activated carbon produced from agricultural waste

Low-cost May reduce solid waste disposal problem May minimize the cost of activated carbon production

Objectives of Study

1. To examine the ability of activated carbon prepared from corn cob in the removal of Zn (II) ion in aqueous solution

2. To determine: optimum contact time between adsorbent and

solution optimum adsorbent dosage effect of interfering anions (SO4

2- and Cl2-)

for the removal of Zn (II) ion by using activated carbon prepared from corn cob

Literature Review



Literature Review: Utilization of Corn Cobs as Activated Carbon

Many studies reported on the utilization of agricultural waste as activated carbon, especially corn cob

Most of the research on utilization of corn cob as activated carbon is focused on the process of carbonization and activation by impregnation with chemical activator such as zinc chloride (Tsai et al., 1998), potassium carbonate (Tsai et al., 2001), and potassium hydroxide (Cao et al., 2006; Tsai et al., 2001) with different approaches

Even though corn cob is considered as a potential low-cost adsorbent, only a few studies have been done on the application of this corn cob activated carbon in removing heavy metals including zinc

Literature Review:Tsai et al. (1998)

Preparation of activated carbon by chemical activation with ZnCl2 Powdered corn cobs (1.44 mm) was impregnated with ZnCl2

Impregnation ratio: 20-200 wt% T: 85°C Done in a boiler-reflux condenser for 2 h

Activation T: 400-800°C Heating rate: 10°C/min N2 flow rate: 300 cm3/min at STP

Post-activation: Boiled with 3 N HCl for 30 min Washed several times with warmed distilled water

to remove chlorine ions and other residues Dried at 105°C overnight

Literature Review:Tsai et al. (1998) (cont’)

Findings: Percentage of micropore decrease at higher

impregnation ratios Optimal condition for producing high surface area

carbons with ZnCl2 activation Activation temperature of 500°C Impregnation ratio of 175 wt% Soaking time of 0.5 h

Literature Review:Tsai et al. (2001)

Potassium salts (KOH and K2CO3) was used in stead of ZnCl2 as activator

since it has the least impact on the environment than other activators such as ZnCl2 and H3PO4

Powdered corn cobs (1.0 – 2.0 mm) was impregnated with potassium solution (KOH or K2CO3) of known concentration, at 80°C in a boiler-reflux condenser for 2 h

Activated with pyrolysis temperature ramp rate of 10°C/min in a N2 flow (200 cm3/min at STP), then switched to CO2 flow (200 cm3/min at STP) after reaching 800°C

Post-activation: Washed with 3 N hot HCl solution Vacuum filtered Washed several times with 80°C distilled water

to remove chlorine ions and other residues Dried at 120°C overnight

Literature Review:Tsai et al. (2001) (cont’)

Findings: Large surface areas > 1600 m2/g of were obtained KOH and K2CO3 were effective activating agents for

chemical activation The optimal condition

Ramping rate of 10°C/min Subsequent gasification (physical activation) at a soaking

period of 800°C

Literature Review:Cao et al. (2006)

Process effects on activated carbon with large specific surface area from corn cob Powdered corn cobs (250 µm) was carbonized

Done in a column-typed stainless steel tube of 200 ml for 4 h T-ramp rate: 30°C/min T: 450°C Protective gas: N2 (flow rate: 90ml/min)

Treated with 3 different activator (KOH solid, KOH solution and KOH-soap mixture) for 30 min

Activated for 1.2 h at 850°C after drying Neutralized with distilled water Filtered and dried at 120°C

Literature Review:Cao et al. (2006) (cont’)

Findings: The SSA of activated carbon from corn cobs reached

2700 m2/g with narrow pore size distribution (78% micro-pores) under optimal conditions

Addition of soap as surfactant shortens the soaking time

SSAs of activated carbon obtained from carbonized material with activator was found to be relatively higher than the one from raw material with activator Indicate that a great deal of activator could not get into the

inner of raw material and could not react with the carbon effectively

Literature Review:Abia and Igwe (Jun 2005)

Kinetics of sorption and intraparticulate diffusivities of Zn, Cd and Pb using maize (corn) cob Activated carbon was prepared in a simpler chemical

activation method process Powdered maize cobs (850 – 1000 µm) was soaked with

dilute HNO3 solution (2% v/v) overnight Rinsed with deionized water Air dried

Effect of contact time was studied, and the intraparticulate diffusivity and the fractional attainment of equilibrium were calculated

Literature Review:Abia and Igwe (Jun 2005)

Findings: Amount of the metal ions adsorbed increasing with time Highest sorption rates:

Zn2+: 71% Cd2+: 32% Pb2+: 30%

Zn2+ reached equilibrium first, followed by Pb2+ and Cd2+

The sorption of these ions on maize cob is particle diffusion controlled Coefficients for particle diffusion: Zn2+: 0.070 min-1 Pb2+: 0.053 min-1

Cd2+: 0.081 min-1

Materials and Methods



Materials and Methods

Materials Sample:

Corn cobs obtained from local market in Shah Alam, Selangor

Chemicals: Zinc stock solution (1000 ppm) Zinc sulphate (ZnSO4) Zinc chloride (ZnCl2) Distilled water Deionized water Potassium hydroxide (KOH)

Materials and Methods (cont’)

Materials (cont’) Equipment:

Grinder Sieve 300 µm & 250 µm (mesh No. 50 & 60) Oven Muffle furnace Dessicator Shaker Atomic Absorption Spectrophotometer (AAS)

Materials and Methods (con’t)

Method Preparation of Activated Carbon

Involve 2 steps: Pulverization (Pre-treatment) Carbonization & Activation

Derived from Abia and Igwe (2005), Igwe et al.(2005), Tsai et al. (1997 & 2001) and Cao et al. (2006).

Adsorption Studies Effect of contact time Effect of adsorbent dosage Effect of interfering anions (SO4

2- and Cl2-)

Pulverization of Sample

Carbonization & Activation of Sample

Effect of Adsorbent

Dosage

Effect of Contact Time

Effect of Interfering

Anions

Adsorption Studies

Preparation of Activated Carbon

Corn cobs(separated from its pitch/chaff)

Rinsed with distilled water

Air dried

Cut into small pieces

Grinded into powder

Sieved (300 µm)

Sieved (250 µm)

Heated (105°C, 12 h) in oven

Cooled / stored in dessicator

- To get a uniform particle size- The powdered corn cob retained on the 250 µm mesh is used

- Obtained from local market

- To remove impurities

- To remove moisture content

- To ease grinding process

- Reduce the particle size

- To make sure the sample is really dry

- Keep pre-treated sample dry until use

Preparation of Activated Carbon

Step 1: Pulverization (Pre-treatment)Step 1: Pulverization (Pre-treatment)

100 g powdered corn cobs

Heated to 450°C(T-ramp rate 30°C/min, 4 h)

Cooled to room temperature

Treated with KOH solution for 30 min

Air dried

Activated in furnace (850°C, 1.2 hr)

Washed with warm distilled water until neutralization

Filtered

Dried at 120°C

Cooled / Stored in dessicatoruntil use

- From pre-treated sample

- Carbonize the raw material

- Cool down the sample

- Open up the pores

- Dry the sample prior to activation

- Activate the sample

- Neutralize the sample

- Separate / recover the sample

- Remove moisture content

- Keep sample dry until use

Step 2: Carbonization & ActivationStep 2: Carbonization & Activation

Adsorption Studies

Based on 3 parameters: Effect of contact time Effect of adsorbent dosage Effect of interfering anions (SO4

2- and Cl2-)

Determination of: Optimum contact time Optimum adsorbent dosage Effect of interfering anions

Put in 250 ml conical

flask (Flask 1A)

Take 100 ml

Add 2 g adsorbent

Add 2 g adsorbent

Add 2 g adsorbent

Add 2 g adsorbent

Add 2 g adsorbent

Add 2 g adsorbent

Add 2 g adsorbent

Leave for 10 min

Filter

Determine final conc.

Leave for 20 min

Leave for 30 min

Leave for 45 min

Leave for 60 min

Leave for 90 min

Leave for 120 min

Filter


Filter


Filter


Filter


Filter


Filter


Plot Graph

Take 100 ml

Take 100 ml

Take 100 ml

Take 100 ml

Take 100 ml

Take 100 ml


flask (Flask 1B)


flask (Flask 1E)


flask (Flask 1C)


flask (Flask 1D)


flask (Flask 1F)


flask (Flask 1G)

Zinc Synthetic Wastewater Solution (1000 ppm)Determine initial concentration

Determine equilibrium contact time

Experiment #1: Different contact time at constant adsorbent dosageExperiment #1: Different contact time at constant adsorbent dosage

Put in 250 ml conical flask (Flask 2A)

Take 100 ml

Add 2 g adsorbent

Add 8 g adsorbent

Add 4 g adsorbent

Add 6 g adsorbent

Add 10 g adsorbent

Filter


Leave for adsorption process, according to the equilibrium contact time obtained from experiment #1

Filter


Filter


Filter


Filter


Plot Graph

Take 100 ml Take 100 ml Take 100 ml Take 100 ml

Put in 250 ml conical flask (Flask 2D)

Put in 250 ml conical flask (Flask 2B)

Put in 250 ml conical flask (Flask 2C)

Put in 250 ml conical flask (Flask 2E)

Zinc Synthetic Wastewater Solution (1000 ppm)Determine initial concentration

Determine optimum adsorbent dosage

Experiment #2: Different adsorbent dosage at constant contact time Experiment #2: Different adsorbent dosage at constant contact time

Leave for adsorption process, according to the equilibrium contact time obtained from

experiment #1

Filter


Filter


Determine percent removal of Zinc (II) ion

Put in 250 ml conical flask (Flask 3B)

Put in 250 ml conical flask (Flask 3A)

Zinc Sulfate Solution(1000 ppm)

Determine initial concentration

Experiment #3: Effect of interfering anion (Experiment #3: Effect of interfering anion (SOSO442-2- and Cl and Cl2-2- ))

Zinc Chloride Solution(1000 ppm)

Determine initial concentration

Add adsorbent according to the optimum adsorbent dosage obtained from experiment #2

Compare result with result in experiment #2

Interpretation of Results

Experiment 1: Effect of Contact Time

Percentage of zinc removal (%) = (C1 – C2) × 100

C1

where, C1 is the initial concentration (mg/l) C2 is the final concentration (mg/l)

Graph of percentage of zinc removal versus time is plotted

The optimum contact time was obtained when there is almost no more adsorption occurred

Interpretation of Results (cont’)

Experiment 1: Effect of Contact Time (cont’)

Amount of zinc adsorbed = (C1 – C2) × V where,

C1 is the initial concentration (mg/l)

C2 is the final concentration (mg/l)

V is the volume of synthetic wastewater (l)

The maximum uptake capacity of the adsorbent, expressed in mg of heavy metal adsorbed per g of adsorbent, is calculated based on adsorption at optimum contact time


Experiment 1: Effect of Contact Time (cont’)

The maximum zinc uptake capacity of the activated carbon (mg/g) is calculated by using the following formula:

Zinc uptake capacity of A.C. = (A × V) / D where,

A is the amount of zinc adsorbed V is the volume of synthetic wastewater (l) D is the adsorbent dosage (g)

Interpretation of Results (cont’) Experiment 2: Effect of Adsorbent Dosage

Percentage of zinc removal (%) = (C1 – C2) × 100C1

where, C1 is the initial concentration (mg/l) C2 is the final concentration (mg/l)

Graph of percentage of zinc removal versus adsorbent dosage is plotted

The optimum adsorbent dosage was obtained when there is almost no more adsorption occurred


Experiment 3: Effect of Interfering anion

Percentage of zinc removal (%) = (C1 – C2) × 100

C1

where, C1 is the initial concentration (mg/l)

C2 is the final concentration (mg/l)

Percentage removal of both ZnSO4 and ZnCl2 are

compared with the result obtained in experiment 2.

References



ReferencesAbia, A.A. & J.C. Igwe (2005). “Sorption kinetics and intraparticulate diffusivities of

Cd, Pb and Zn ions on maize cob”. African Journal of Biotechnology, Vol. 4 (6): 509-512, June 2005.

Cao, Q, Ke-Chang Xie, Yong-Kang Lv & Wei-Ren Bao (2005). “Process Effects on Activated Carbon with Large Specific Surface Area from Corn Cob”. Bioresource Technology, 97 (2006): 110-115.

Igwe, J.C., Ogunewe, D.N. & Abia, A.A. (2005). “Competitive adsorption of Zn (II), Cd (II) and Pb (II) ions from aqueous and non-aqueous solution by maize cob and husk”. African Journal of Biotechnology, Vol. 4 (6): 509-512, October 2005.

Irwin, R.J. (1997). Environmental Contaminants Encyclopedia: Zinc Entry. Water Resources Divisions, Water Operations Branch, National Park Service, Colorado. July 1, 1997, pp. 88.

Micera, G. & A. Dessi (1988). “Chromium Adsorption by Plant Roots and Formation of Long-Lived Cr (V) Species: An Ecological Hazard?” Journal of Inorganic and Biochemistry, 34 (1988): 157-166.

ReferencesRachakornkij, M., S. Ruangchuay & P. Satidwattanaporn (2003). “Utilization of

Bagasse and Bagasse Fly Ash as Adsorbent for Removal of Lead from Aqueous Solution”. National Research Center for Environmental and Hazardous Waste Management (NRC-EHWM) Chulalongkorn University, Bangkok, Thailand. Proceedings of INREF-AGITS Conference 2003, Chiang Mai University, Chiang Mai, Thailand, October 10-12, 2003.

Tsai, W.T., C.Y. Chang & S.L. Lee (1998). “A Low Cost Adsorbent from Agricultural Waste Corn Cob by Zinc Chloride Activation”. Bioresource Technology, 64 (1998): 211-217.

Tsai, W.T., C.Y. Chang, S.Y. Wang, C.F. Chang, S.F. Chien & H.F. Sun (2001). “Preparation of Activated Carbons from Corn Cob Catalyzed by Potassium Salts and Subsequent Gasification with CO2”. Bioresource Technology, 78 (2001): 203-208.

World Health Organization (1984). Geneva, Guidelines for drinking Water Quality.

Wikipedia (2007b). “Zinc”. Wikipedia, the free encyclopedia. Wikimedia Foundation, Inc. Retrieved March 7, 2007 from http://en.wikipedia.org/wiki/Zinc

Plan of Studies



Questions & Answers

Thank You

Evt 621 Research Methodology Slide

Technology

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