16-10-2012, 02:08 PM
Performance Evaluation of Waste Activated Carbon on Atrazine Removal from Contaminated Water
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INTRODUCTION
Atrazine (2 chloro-4 ethylamino-6-isopropylamino-1, 3, 5 triazine) is one of the
most widely used herbicides. Removal of pesticides from contaminated water by
activated carbon adsorption is considered as one of the best available technologies
(BAT). However, pesticides removal from wastewater containing dissolved
organic carbon (DOC) by adsorption seems to suffer due to nonselective nature
of the activated carbon, which adsorbs both pesticides as well as DOC.
MATERIALS AND METHODS
All the chemicals used in the present investigation were of analytical
reagent grade (purity > 98%). Rallis India Limited, Mumbai, India, had supplied
atrazine of technical grade (purity = 98%). WatersTM Sep-Pak R Cartridge
(Sep-Pak C18 cartridge with pore size 0.45 μm) used for the extraction
of atrazine was procured from Waters (Milford, MA, USA).
Adsorbent
The adsorbent selected in the present study was a waste charcoal. Eureka
Forbs Limited, India, markets water purifier with the brand name of Aqua
Guard in India. Nowadays, suchwater purifiers are commonly used in hospitals,
commercial and educational institutes, and households to enhance the quality
of tap water. Such a water purifier contains 200–300 g of activated carbon
impregnated with 0.2% silver depending upon the size and capacity of the unit.
The uniform grain size of activated carbon is around 3 mm. The useful life of
activated carbon varies from 6 months to 1 year, and it is then replaced by
fresh activated carbon. Wasted activated carbon from 5–6 water purifiers was
collected. This was used as the raw adsorbent in the present study. Usually this
exhausted activated carbon is thrown away as a solid waste.
Analytical Methods
Atrazine Determination
Regular measurement of atrazine was carried out in a UV-visible spectrophotometer
(model UV-160A, Shimadzu, Japan). Atrazine was extracted
from wastewater by liquid-liquid separation process using dichloromethane as
extractant. The detail of extraction procedure is described elsewhere.[7] Extracted
atrazine in dichloromethane was measured in UV-visible spectrophotometer
keeping dichloromethane as blank. The spectra were taken at a range of
220–250 nm keeping dichloromethane as reference. Maximum absorbance was
observed at 228.8 nm. Detectable limit of atrazine by this method is 0.1 mg/L.