International Journal of Environment, Ecology, Family and Urban Studies (IJEEFUS) ISSN 2250-0065 Vol. 3, Issue 1, Mar 2013, 127-132 © TJPRC Pvt. Ltd.
ANALYSIS OF HEAVY METALS BY USING ATOMIC ABSORPTION SPECTRO-SCOPY FROM THE SAMPLES TAKEN AROUND VISAKHAPATNAM P. SRIKANTH, S. A. SOMASEKHAR, G.K.KANTHI & K. RAGHU BABU Department of Engineering Chemistry, Andhra University College of Engineering, Visakhapatnam, Andhra Pradesh, India
ABSTRACT The experimental analysis of Heavy metals in industrial effluents. Industrial effluents discharged into the environment pose a serious threat gricultural products and living organisms. In view of this, levels of some heavy metals, Pb, Cd, Cu, Zn, Hg were determined in water samples collected from (Steel Plant) an industrial area and Thatipudi Reservoir around Visakhapatnam. The levels of Heavy Metals were determined by Atomic Absorption Spectroscopy. The results obtained show that the mean values of all Heavy Metals( with exception of Hg) in water samples collected from the above two places were analyzed where effluent water from Steel Plant recorded more than the standard values
KEYWORDS: Trace Metals, Waste Water, Water Pollution, Industrial Effluents and Industrial Areas, Ecosystem INTRODUCTION Analysis of Heavy metals (Pb, Cd, Cu, Zn, Hg ) in industrial effluent using Atomic Absorption spectroscopy. A Heavy metal is a member of a loosely-defined subset of elements that exhibit metallic properties. It mainly includes the transition metals, some metalloids, lathanides and actinides. Many different definitions have been proposed some based on density, some on atomic number or atomic weight and some on chemical properties or toxicity. The term has been called “misinterpretation” in an IUPAC technical report due to the contradictory definitions and its lack of a “coherent scientific basis”. There is an alternative term toxic metal, for which no consensus of exact definition exists either. As discussed below, depending on the context, heavy metal can include elements lighter than carbon and can exclude some of the heaviest metals. Heavy metals occur naturally in the ecosystem with large variations in concentration.In modern times, anthropogenic sources of heavy metals, i.e. pollution, have been introduced to the ecosystem. Waste derived fuels are especially prone to contain heavy metals, so heavy metals are a concern in consideration of waste as fuel.Heavy metals contamination has been recognized as a major environmental concern due to their pervasiveness and persistence. These heavy metals are not biodegradable; hence there is a need to develop such remediation technique, which should be efficient, economical and rapidly deployable in a wide range of physical settings. For the characterization of heavy metals, like As, Cd, Cu, Fe, Mn, Ni, Pb and Zn were analyzed.
HEAVY METAL EMISSION Heavy metals can be emitted into the environment by both natural and anthropogenic causes. The major cause of emission are the anthropogenic sources specifically mining operations. In some cases, even long after mining activities have ceased, the emitted metals continue to persist in the environment. Peplow (1999) reported that hard rock mines operate from 5-15 yrs until the minerals are depleted, but metal contamination that occurs as a consequence of hard rock mining persist for hundreds of years after the cessation of mining operations. Apart from mining operations, Hg is introduced into the environment through cosmetic products as well as manufacturing processes like making of NaoH. Heavy metals are emitted both in elemental and compound (organic and inorganic) forms. Anthropogenic sources emission are the various
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industrial point sources including former and present mining sites, foundries and smelters, combustion by-products and traffics. Cd is released as a by-product of (Zn and occasionally Pb) refining; Pb is emitted during its mining and smelting activities, from automobile exhausts (by combustion of petroleum fuels treated with tetraethyl lead antiknock) and from old Pb paints; Hg is emitted by the degassing of the earth’s crust. Generally, metals are emitted during their mining and processing activities. Environmental pollution by heavy metals is very prominent in areas of mining and old mine sites and pollution reduces with increasing distance away from mining site ( Peplow,1999). These metals are leached out and in sloppy areas, are carried by acid water downstream or run-off to the sea. Through mining activities, water bodies are most emphatically polluted. The potential for contamination is increased when mining processes metal-bearing ores rather than natural exposure of ore bodies through erosion and when mined ores are dumped on the earth surfaces in manual dressing processes. Through rivers and streams, the metals are transported as either dissolved species in water or as an integral part of suspended sediments, (dissolve species in water have the greatest potential of causing the most deleterious effects). They may then be stored in river bed sedimentor seep into the underground water thereby contaminating water from underground sources, particularly wells; and the extent of contamination will depend on the nearness of the well to the mining site.[5]
HEAVY METAL POLLUTION Motivations for controlling heavy metal concentrations in gas streams are diverse. Some of them are dangerous to health or to the environment ( e.g. Hg, Cd, Pb, Cr) , some may cause corrosion (e.g. Zn, Pb ), some are harmful in other ways( e.g. As may pollute catalysts). Within the European community the 13 elements of highest concern are As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Tn, Th, the emissions of which are regulated in waste incinerators’. Some of these elements are actually necessary for humans in minute amounts (Co, Cu, Cr, Mn, Ni) while others are carcinogenic or toxic, affecting, among other, the central nervous system( Mn, Hg, Pb, As). Study Area Visakhapatnam (Longitude83°13`07.53``E,Latitude17°41`18.16``N) is a port city located on the south east coast of india. the climate is tropical savanna climate with little change in temperature throughout the year. May is the hottest month with an average maximum temperature about 36 °C (97 °F), and January is the coolest month with an average maximum temperature near 29 °C (84 °F).With the city's location on the Bay of Bengal, the humidity is high throughout the year. Total annual rainfall is about 945 millimetres (37.2 in), most of which falls during the southwest monsoon. October is the wettest month, with about 204 millimetres (8.0 in) of rainfall. Visakhapatnam is undergoing urbanization and industrialization. The waste water generated from diverse industries is subjected to primary and secondary treatment at the individual industry itself.[6,7,8]
MATERIALS AND METHODS Waste water samples were collected from 2 different sites thet is steel plant & thatipudi reservoir of Visakhapatnam city. Samples were collected in good quality screw capped high density pre sterilized polypropylene bottles, each of 1lt capacity, labeled properly and analyzed in laboratory for trace metals by Atomic Absorption Spectrometer(AAS). For assessment of the water quality, monitoring was done during Nov,2011 to Feb, 2012. High pure (Anal R grade) chemicals and double distilled water were used for preparing solutions for analysis. Preservation and analysis of water samples were based on Standard Methods proposed by American Public Health Association (APHA). The selected heavy metals (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) were analyzed. The detection of traced metals in the environment are accomplished by various methods but here the AAS technique was used, which is relatively simple, versatile, accurate and free from interfe-
Analysis of Heavy Metals by Using Atomic Absorption Spectro-Scopy from the Samples Taken Around Visakhapatnam
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rences. Heavy metals readily form complexes with organic constituents; therefore, it is necessary to destroy them by digestion with strong acids. Digestion destroys the organic matter, removes interfering ions and brings metallic compounds in suspension to solution.[1]
DIGESTION WITH NITRIC ACID The suitable volume of the water samples in evaporating dishes were taken and acidified to methyl orange with conc. HNO3. Further, 5ml conc. Nitric acid was added and evaporated to 10ml. Then it was transferred to a 125ml conical flask. 5ml of conc. Nitric acid and 10ml of perchloricacid (70%) were added. Then heated gently, till white dense fumes of HClO4 appear. The digested samples were cooled at room temperature, filtered through whatmann no41 or sintered glass crucible and finally the volume was made opto 100ml with distilled water. Then this solution was boiled to expel oxides of nitrogen and chlorine. This solution contained 0.8N in HClO4 . The solution was used for the use of determination of heavy metals. Procedure •
Apparatus set-up : Inlet of reaction cell was connected with auxillary purging gas controlled by flow water . In case of need of a dry imf cell between the reaction cell and atomizer, only anhydrous CaCl2 was used . Before using the hydride generation, operating parameters were optimized. Dilute aqueous solution of As was aspirated directly into the flame to facilitate atomizer alignment. Quartz atomizer for max. absorbance was aligned. A blank was aspirated until memory effects were removed. Recommended wavelength is 193.7nm for As determination.
•
Instrument caliberation standard : 0,1,2,5,10,15and 20 ml standard solutions of As( III) were transferred to 100ml volumetric flask and made-up to the volume with water containing the same conc.of 50% v/v acid (40% HCl and 10% H2SO4) used for sample preservation (commonly 2-5ml) con. HNO3/L ). This yielded blank and standard solutions of 0,1,2,5,10,15 and 20 mg As/L.
•
Preparation of samples and standards for total As : 50mL sample or standard was added to a 200mL Berzelius beaker and then added 1ml , 2.5N H2SO4 and 5ml K2S2O8 . Then the solution was gently boiled on pre heated hot plate until a final volume of 10Ml was reached. After Digestion, it is diluted to 5oml for subsequent as measurement.[1]
Analysis Analysis of Heavy metals( Pb, Cu, Cd, Zn and Hg) has been done by using Atomic absorption spectroscopy.[1,3,4] Digestion of Water Sample The EPA vigorous digestion method described by Gregg (1989) was adopted.100mL of each of representative water samples were transferred into pyrex beakers containing 10ml of conc.HNO3. The samples were boiled slowly and then evaporated on a hot plate to the lowest possible volume( about 20 ml). The beakers were allowed to cool and another 5ml of conc.Nitric acid was added. Heating was continued with addition of conc. Nitric acid as necessary until digestion was complete. The samples were evaporated again to dryness (but not baked) and the beakers were cooled, followed by addition of 5ml of HCl solution( 1:1 v/v). The solutions were warmed and 5ml of 5M NaOH was added, then filtered. The filterates were transferred to 100ml volumetric flasks and diluted to the mark with distilled water. This solutions were then used for the elemental analysis.
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SAMPLE PREPARATION LEAD SOLUTIONS Lead, Stock Solution Corresponding to 1000mg/l of Pb Weigh to the nearest + 0.0002gm, apx 1.0000gm Pb metal (minimum purity 99.5%) and dilute in a covered 250ml glass beaker with 10ml HNO3 . Then add 100ml of water. Boil to expel nitrous fumes, cool, transfer to 1000ml volumetric flask and fill to the mark with water. Lead, Standard Solution Corresponding to 10mg/ l of Pb Pippette 10.00ml of Pb stock solution into a 1000ml volumetric flask. Add 20ml of nitric acid, fill the mark with water and mix well. Lead, Standard Solution Corresponding to 0.4mg/ l of Pb Pippette 20.00ml of Pb standard solution into a 500ml volumetric flask. Add 10ml of nitric acid, fill the mark with water and mix well. Prepare this solution on the day of use.
CADMIUM SOLUTIONS Cadmiu, Stock Solution Corresponding to 1000mg/l of Cd Weigh to the nearest + 0.0002gm, apx 1.0000gm Cd metal (minimum purity 99.5%) and dilute in a covered 250ml glass beaker with 40ml HNO3 . Then add 100ml of water. Boil to expel nitrous fumes, cool, transfer to 1000ml volumetric flask and fill to the mark with water. Cadmium, Standard Solution Corresponding to 10mg/l of Cd Pippette 10.00ml of Cd stock solution into a 1000ml volumetric flask. Add 20ml of nitric acid, fill to the mark with water and mix well. Cadmium, Standard Solution Corresponding to 0.4mg/l of Cd Pippette 20.00ml of Cd standard solution into a 500ml volumetric flask. Add 10ml of nitric acid, fill to the mark with water and mix well. Prepare this solution on the day of use. Cadmium, Standard Solution Corresponding to 0.02mg/l of Cd Pippette 5.00ml of Cd standard solution into a 100ml volumetric flask. Add 2ml of nitric acid, fill to the mark with water and mix well. Prepare this solution on the day of use.
COPPER SOLUTIONS Copper, Stock Solution Corresponding to 1000mg/l of Cu Weigh, to the nearest + 0.0002gm, apx 1.0000gm Cu metal (minimum purity 99.5%) and dilute it in a covered 250ml glass beaker with 10ml HNO3 . Then add 100ml of water. Boil to expel nitrous fumes, cool, transfer to 1000ml a volumetric flask and fill to the mark with water. Copper, Standard Solution Corresponding to 10mg/l of Cu Pippette 10.00ml of Cu stock solution into a 1000ml volumetric flask. Add 20ml of nitric acid, fill to the mark with water and mix well. Copper, Standard Solution Corresponding to 0.4mg/l of Cu Pippette 20.00ml of Cu standard solution into a 500ml volumetric flask. Add 10ml of nitric acid, fill to the mark
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with water and mix well. Prepare this solution on the day of use.
ZINC SOLUTIONS Zinc, Stock Solution Corresponding to 1000mg/l of Zn Weigh to the nearest + 0.0002gm, apx 1.0000gm Zn metal (minimum purity 99.5%) and dilute in a covered 250ml glass beaker with 40ml HNO3 . Then add 100ml of water. Boil to expel nitrous fumes, cool, transfer to 1000ml volumetric flask and fill to the mark with water. Zinc, Standard Solution Corresponding to 10mg/l of Zn Pippette 10.00ml of Zn stock solution into a 1000ml volumetric flask. Add 20ml of nitric acid, fill to the mark with water and mix well. Zn, Standard Solution Corresponding to 0.4mg/l of Zn Pippette 20.00ml of Zn standard solution into a 500ml volumetric flask. Add 10ml of nitric acid, fill to the mark with water and mix well. Prepare this solution on the day of use. Zinc, Standard Solution Corresponding to 0.02mg/l of Zn Pippette 5.00ml of Zn standard solution into a 500ml volumetric flask. Add 10ml of nitric acid, fill to the mark with water and mix well. Prepare this solution on the day of use.
DATA COLLECTION The Standard Values Collected Through Personal Interview Name of the Heavy Metal Pb Cd Cu Zn
Concentration (Mg/Lit) 0.039 0.028 0.044 0.048
The given Heavy metals are analyzed by using Atomic Absorption Spectroscopy and the obtained values are caliberated against the standard values SAMPLE 1: (Steel Plant) Name of the Heavy Metal Pb Cd Cu Zn
Concentration (Mg/Lit) 0.054 0.059 0.067 0.063
SAMPLE 2: (Thatipudi Reservoir) Name of the Heavy Metal Pb Cd Cu Zn
Concentration (Mg/Lit) 0.028 0.025 0.040 0.036
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CONCLUSIONS Analysis of Heavy metals in industrial effluent is carried out by caliberating graph between conc of analyte and absorbance using AAS. The results show that the water from the industrial effluents in the area studied had larger content of heavy metals( Pb, Cd, Cu, Zn )exception of Hg are capable of polluting the environment. Although high level of heavy metals under study, yet there are some factors effecting their absorption by the soil and ofcourse their availability to the plants. These findings imply that the consumption of the polluted water by animals or human beings could be hazardous to their health. The soil contaminated by these effluents will produce unhealthy food as heavy metals can enter the food chain and thus be consumed by human beings.
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Delbruck, A.Schimassek, H.Bartsch , K. Bucher , Th.(1959). Biochem.Z.
3.
Atomic Absorption Spectroscopy by James W. Robinson
4.
“Spectrochemical Analysis by Atomic Absorption and Emission” by L.H.J.Lajunen, Royal Society of Chemistry, 1992
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Dr. Thomas G. Chasteen; Dept of Chemistry, Sam Houston State University Huntsville,Texas
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Template:Http://www.citymayors.com/statistics/urban growth1.httml
7.
“Visakhapatnam”. India Meteorological Department, May 2011. Retrieved 2010-03-26.
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National Oceanic and Atmospheric Administration. Retrieved December 24, 2012
