Tea (Camellia sinensis) Waste for the reduction of Malathion and Phorate in aqueous solutions

A great number of pesticides are being used now to increase the crop productivity in modern agricultural practices. It is calculated that the productivity losses would double if the pesticides were put out of use [1]. Slow degradation of pesticides in the environment and extensive or inappropriate use by farmers can lead to environmental contamination of the water, soil, air, several types of crops and indirectly humans [2]. Pesticides have also been used in non-agricultural sectors such as wood preservation, disinfection or household uses. Inspite of the several advantages, some pesticides can be toxic to humans and animals and their continuous application is causing serious problems of environmental and food contamination [3]. The wastewater discharged from pesticide factories is poisonous. It would kill aquatic organisms and threaten public health if it was discharged without proper disposal [4]. However, the use of pesticides requires great care and control as they can pollute the environment and harm human health [1]. There was a rapid global growth in the routine use of organophosphorous pesticides by the agricultural community during last half a century. Such practices have led to increasing concerns with respect to human, animal and insect health. In the last few decades organochlorine insecticides, (e.g. aldrin, lindane) have been progressively replaced by OP (Organo Phosphorous) pesticides (e.g. parathion, malathion) and insecticides based on derivatives of carbamic acid (e.g. carbaryl, aldicarb), both families showing decreased persistence in the environment but at a cost of higher acute toxicity. Organophosphorous compounds are neurotoxic and structurally similar to the nerve gases soman and sarin and operate by inhibiting the cholinesterase enzymes which are essential in modulating the central nervous system in both animals and insects As acetylcholinesterase (AChE) promotes the hydrolysis of the natural neurotransmitter, acetylcholine (ACh), its inhibition terminates the propagation of nerve impulses [5]. 

Of late, hectic research based on adsorption phenomenon have done to reduce the pesticide contamination in drinking water. Activated carbon is a highly effective adsorbent but lack of cost effectivity prohibits its use in many countries including India. Intense research attention is now focused on cost effective, eco-friendly and easily available adsorbent particularly of biological origin. Different adsorbents such as agricultural byproducts, waste materials and microbial biomass have been utilized for removing different toxicants from wastewater. Malathion and Phorate are organophosphorus pesticides (Fig. 1 and Fig.2) of high selective toxicity are widely used in agriculture throughout the world [6]. 

 Malathion is suited for the control of sucking and chewing insects on fruits and vegetables and is also used to control mosquitoes, flies, household insects, animal parasites (ectoparasites), and head and body lice [7]. Phorate is used to control sucking and chewing insects, leafhoppers, leaf miners, mites, some nematodes, and rootworms. It is also used in pine forests and on root and field crops, including corn, cotton, coffee, some ornamental and herbaceous plants and bulbs [8]. To date adsorptive removal of organophosphorous pesticides from wastewater has not been studied in detail and only a few reports are available in this regard [9-14]. Materials investigated as adsorbents for pesticides includes: Charcoal from agro waste [15], straw [16], date and olive stones, wood chips/corn cob [17], lignocellulosic substrate from agro industry [18], bark [19], baggasse fly ash [20] and coal fly ash [21]. Tea powder is basically a waste after using it for the preparation of Tea. In India yearly production of tea is approximately 857000 tonnes which is 27.4% of total world production. The amount of dry tea produced from 100kg green tea leaves is 22 kg on average and approximately 18 kg tea is packed for the market. The other 4kg of dry tea material is wasted. With such a great production and consumption large quantities of tea wastes (From the Caff, Cafeteria, or tea –processing factory) are usually discarded into the environment without any treatment. Furthermore, additional amount of tea leaves enters the environment by defoliation and pruning annually [22]. Like other biomass residues tea waste represent an unused resource and pose increasing disposal problem. Based on these reasons it is being investigated strategically to evaluate their possible use as an energy source or in other value added application. The cell wall of waste tea consist of cellulose, lignin carbohydrate which have hydroxyl groups in their structures [23]. In the present study removal of Malathion and Phorate from water has been taken up by batch adsorption technique using waste tea powder as the adsorbent material.