Biosorption Of Malathion Pesticide Using Spirogyra Sp.
Abstract
The biosorption of Malathion from aqueous solution by green algal biomass was investigated. The green algae used were of the species Spirogyra and was collected from Neugal river near Sujanpur, Himachal Pradesh. Batch biosorption experiments were performed to examine the effect of contact time, pH, biomass concentration and initial Malathion concentration. The concentration of residual Malathion concentration after biosorption was determined using UV-Vis Spectrophotometer at a wavelength of 309 nm. The maximum adsorption was found to be at pH 7 after a contact time of 5 hours with initial Malathion concentration of 100 mg/L and biomass of weight 75 mg. The equilibrium biosorption data were analyzed using Langmuir and Freundlich isotherm. Freundlich isotherm was found to be more favorable than Langmuir isotherm.
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Introduction
The use of pesticide is essential for the modern agricultural practice. Pesticides not only kill unwanted pests and insects, they also increase the productivity o f agriculture. In India, agricultural production increased by 100% while the cropping land increased by only 20% [1]. Pesticide residues that get released into the environment tend to stay in the environment for a very long time, and get accumulated throughout the food chain, making it hazardous to the environment. The U.S. Geological Survey conducted a study from which they reported that more than 90% of the water and fish samples that they collected from major rivers or water streams were contaminated with pesticides. The rivers and streams which were contaminated by pesticides were influenced by agriculture and urban land use [2]. Currently, India ranks 10th in the world pesticide consumption list [3] and the Indian agrochemical market is expected to reach U.S $ 6.3 billion by 2020 [4].
Pesticides are classified into many classes, out of which, organophosphates and organochlorines are deemed the most important ones. Malathion is an organophosphorus pesticide which is most commonly used in agriculture all over the world. It is used for killing insects on agricultural crops and stored products. It is also widely used for killing mosquitos in urb an and residential areas. It is also used for the control of flies, household insects and head and body lice. In 2006, it was reported that approximately 15 million pounds of Malathion were used worldwide annually [5]. The Environmental Protection Agency has identified Malathion as a toxicity class III pesticide and a general use pesticide (GUP). Malathion interferes with the normal function of the nervous system and thus indirectly affects the function of other organs. The effect of exposure to Malathion on human health may include, but not limited to, difficulty in breathing, vomiting, diarrhoea, headaches, dizziness and loss of consciousness and death [6]
Several methods have been proposed for the removal/treatment of Malathion from raw water and wastewater such as electrocoagulation, advanced oxidation and coagulation/flocculation [7, 8, 9]. The limitations to these methods are that they are quiet expensive and the chemicals used for these methods require constant observation and it is preferable that they be handled by a skilled person. Adsorption with activated carbon is an easy and cost effective method for the removal of pesticides and has been extensively studied for the removal of Malathion [10- 11]. In recent years, studies about the removal of Malathion by biological materials have increased due to their easy availability, low cost and efficiency. Biosorption by activated sludge, isolated bacillus sp., Rhizopus oryzae, nanocellulose, algal biomass of Chlorella vulgaris, chesnut shells and the fungal biomass of Phanerochaete chrysosporium has been studied with positive results [12, 13, 14, 15, 16, 17, 18].
Either live or dead biomass can be used in biosorption process. Live biomass has been used for the removal of heavy metals in the past [19- 20]. The use of dead biomass is more desirable than the live ones as dead biomass do not require nutrients to sustain them and can be stored to be used later. While using live biomass, sorption as well as biodegradation may also occur and it is very difficult to distinguish which one of them has more contribution.
The present study investigates Malathion removal from aqueous solution by biosorption using green algal biomass of species Spirogyra, which is abundant in fresh water lakes and rivers. Laboratory batch experiments were carried out using a shaker-incubator at a constant temperature to determine the optimum contact time, pH, weight of biomass and initial Malathion concentration for maximum removal. Langmuir and Freundlich isotherms were used for determining the sorption capacity of Spirogyra sp.
Conclusion
Malathion removal from aqueous solution by biosorption using Spirogyra sp. was studied. The residual Malathion concentration was determined using UV -Vis spectrophotometer. It was found that 76.34% of Malathion was removed from initial Malathion concentration of 100mg/L when the initial pH was kept at 7, using biomass concentration of 75mg and a contact time of 5 hours. Biosorption isotherm study showed that Freundlich isotherm was found to fit the experimental data more than Langmuir isotherm with R2 value at 0.9352 indicating that sorption occurred on heterogeneous surface. Further studies can be done by pre -treating the biomass to see if Malathion removal increases with it.