# Recent Strategies for Environmental Remediation of Organochlorine Pesticides  
[PERSON]  
1 Material Science Innovation and Modelling (MaSIM) Research Focus Area, Faculty of Natural and Agricultural Sciences, North-West University, Mafikeng Campus, Private Bag X2046, Mmabatho 2735, South Africa; [EMAIL_ADDRESS]  
[PERSON]  
2 Department of Chemistry, School of Physical and chemical Sciences, Faculty of Natural and Agricultural Sciences, North-West University, Mafikeng Campus, Private Bag X2046, Mmabatho 2735, South Africa  
Nanotechnology and Water Sustainability Research Unit, College of Science, Engineering and Technology, University of South Africa, Florida 1709, South Africa; [EMAIL_ADDRESS]  
2 Correspondence: [PERSON]; Tel.: +27-18-389-2545; Fax: +27-18-389-2420  
smail and slugs (molluscides), viruses (virucides), mites (acaricides), insects and mites (ovicides), weed (herbicides), bacteria (bactericides), fungi (fungicides) [3]. The second classification is based on the active components and chemical composition of the pesticides. Pesticides may be synthetic pyrethroid, carbamates, organophosphorus or organochlorine as shown in Figure 1[4].  
One of the most commonly used pesticides are organochlorine pesticides. Organochlorine pesticides are designed to specifically impede some particular living organisms. Just like other pesticides, they are different from other chemical pollutants because they are intentionally released into the environment. They are predictably toxic and disrupt the neural function of the pests, leading to their death [5]. Organochlorine compounds are part of persistence organic pollutants (POPs) and they are characterized by chlorine attachments, possession of functional groups that are polar, and the presence of cyclic structure which may be aromatic. They generally remain in an undegraded form in the environment for a long time. In addition, they can travel over long distance because of their semivolatile property and they are lipophilic (they mount-up in tissues that have fats like nerves) in nature [6]. When humans or animals consume fish that are contaminated with organochlorine pesticides, the active components of the pesticides could be released into the system which have detrimental effect. Due to their nature and properties, organochlorine pesticides are found in every part of the ecology including desert, snow, water bodies, soil and air despite the fact that their usage have been banned by several countries. Examples of organochlorine pesticides are furan (dibenzo-p-furans), dioxin (dibenzo-p-dioxins), polychlorinated biphenyls, chlordane, toxaphene, dichlordiphenyltrichloroethane (DDT) and dieldrin. Others include aldrin, mirex, hexachlorobenzene, heptachlor [7,8]. New organochlorine pesticides such as imidacloprid have recently being reported [9]. The structures of some of the organochlorine pesticides are shown in Figure 2.  
Figure 1: Types of pesticides based on chemical composition.  
Their persistence in the environment could be attributed to the difficulty in hydrolyzing the carbon-chlorine bond of the aromatic compounds. This bond is strong due to the overlap of the p-orbital of chlorine and the pie bond of benzene. It has been reported that the more the number of chlorine attachments to the aromatic ring, the higher the stability of the organochlorine compounds to hydrolysis [11]. Other factors that affect their hydrolysis rate are catalysis by metal ions, ionic strength, presence of sediments, pH and temperature. A very important point to note about these organochlorine pesticides is that they are all toxic in nature and this makes their removal from the environment (water, soil and air) extremely important.  
Figure 2: Structures of some organochlorine pesticides. Reprinted from [10]. Copyright (2017), with permission from Elsevier.