# Recent Strategies for Environmental Remediation of Organochlorine Pesticides
## 3 Methods for Removal of Organochlorine Pesticides from the Environment
Interestingly, this group [58] proposed a probable mechanism that is involved in ultrasonic degradation of pollutants as shown in Equations (1)-(5):  
\[\text{Ultrasound}+\text{H}_{2}\text{O}\rightarrow\text{HO}^{\prime}+\text{H} \tag{1}\]  
\[\text{Ultrasound}+\text{O}_{2}\to 2\text{O} \tag{2}\]  
\[\text{H}_{2}\text{O}+\text{O}\rightarrow\text{2 HO}^{\prime} \tag{3}\]  
\[\text{O}_{2}+\text{H}^{\prime}\rightarrow\text{HO}^{\prime}+\text{O} \tag{4}\]  
\[\text{O}_{2}+\text{H}^{\prime}\rightarrow\text{HO}_{2}. \tag{5}\]  
Catalytic hydrogenation has also been adopted for removing organochlorine pesticides from waste water. This involves the use of hydrogen over noble metal catalyst. The byproduct of the reaction are hydrogen chloride and low molecular weight hydrocarbon [53]. Endrin and some other organochlorine pesticides have been successfully degraded by hydrogenation, followed by deodorization [40]. Furthermore, the research conducted by [PERSON] and [PERSON] [7] removed polychlorinated biphenyl, DDT and dieldrin from margarine by dehydrogenation followed by deodorization. Molten salt oxidation is also reported for the remediation of the environment from organochlorine pesticides. It involves the use of a bed of molten salt in alkaline medium (Na\({}_{2}\)CO\({}_{3}\) in most cases) at a temperature of approximately 1000 \({}^{\circ}\)C. Any ash products, phosphorus, sulfur or chlorine in the pesticides are retained as inorganic salt in the bed [59]. [PERSON] reported the use of this technique for the successful degradation of hexachlorocyclohexane [24]. The study showed that this technique was particularly useful for the removal of chlorine-containing compounds. Similarly, molten metal pyrolysis uses molten metal as both catalyst and solvent for the conversion of toxic organochlorine compounds into more useful substances. This technology was patented by Massachusetts Materials Technologies (MMT) in Walham. The metal that is commonly used is iron heated to a very high temperature. The high temperature breaks down the pesticides into their elements which may now be removed with the assistance of some selected materials and chemicals such as alumina and oxygen [25]. [PERSON] et al. [60] reported molten metal pyrolysis as one of the methods that is effective for removing and degrading polychlororodibenzo-furan and polychlororodibenzo-p-dioxin. Fenton oxidation technique involves the degradation of organic pollutants, including organochlorine pesticides to different compounds. This is achieved through oxidation by hydroxyl radicals derived from the reaction between iron (II) and hydrogen peroxide [61; 62] as presented in Equations (6) and (7) and shown in Figure 4.  
\[\text{Fe}^{2+}+\text{H}_{2}\text{O}_{2}\rightarrow\text{Fe}^{3+}+\text{OH}^{-}+ \text{OH}^{\bullet} \tag{6}\]  
Figure 3.0  
The efficiency of Fenton oxidation largely depend on the pH, concentration of both iron(II) and the hydrogen peroxide [61; 62]. The favorable pH for Fenton oxidation ranges from 3-5. One of the studies that investigated the degradation of pesticides by Fenton oxidation was carried out by [PERSON] et al. [62]. The study reported more than 90% removal efficiency of organochlorine compounds. Four different pesticides, 4-chlorophenoxyoxyacetic acid, 4-chloro-2-methylphenoxyacetic acid, fenitrothon and atrazine have been successfully degraded using this Fenton oxidation technique by [PERSON] et al. [41]. Similarly, iron in the oxidation state of zero has been used for organochlorine remediation. The use of iron for the removal of contaminants is based on its cost-effectiveness, nontoxicity, abundance and ease of its preparation. Different mechanisms have been proposed for this reaction, such as zero-valence iron mechanism, which involves the transfer of electrons from zero-valence iron to the organochlorine pesticide. This leads to the mineralization of the pesticides to less-toxic or nontoxic species [64]. Different mechanism occurs in the presence of oxygen.