بررسي اثر مواد آلي، كي‌ليت كننده‌ها , سورفكتنت‌ها بر واجذب فنانترن و فلزات سنگين از خاك رسي: مخلوط كائولن، مونتموريلونيت و ماسه

effect of organic matter, chelatant and surfactants on desorption of phenanthrene and heavy metals from clayey soil: mixture of kaoline, montmorillonite and sand

درك بهتر اندركنش‌هاي تركيبي مواد آلي خاك (SOM)، سورفكتنت‌ها و كي‌ليت كننده‌ها بر رفتار هيدروكربن‌هاي آروماتيك چندحلقه‌اي (PAHs) و فلزات سنگين در سيستم آبيخاكي، براي پيش بيني دقيق‌تر بازدهي سورفكتنت‌ها و كي‌ليت كننده‌ در افزايش بازدهي پاكسازي خاك از اين تركيبات ضروري به‌نظر مي‌رسد. در اين مقاله اثر ميزان مواد آلي خاك و حضور سورفكتنت‌ها و كي‌ليت كننده‌ها بر واجذب PAHs و فلزات سنگين و همچنين اثر حضور و عدم حضور فلزات سنگين بر واجذب PAHs بررسي شد. در حضور تريتون ايكس100 (Trition X 100) و تويين80 (Tween 80) به عنوان سورفكتنت و EDTA به عنوان كي‌ليت كننده در محلول پايه، واجذب PAHs و فلزات سنگين افزايش قابل ملاحظه‌اي نسبت به حالت محلول پايه تنها (M CaCl201/0) داشته است و اين در حالي است كه تريتون ايكس 100 هم در واجذب PAHs وهم در واجذب فلزات سنگين بهتر از تويين 80 عمل كرده است. همجنين نتايج نشان‌گر اين بودند كه مواد آلي خاك باعث كاهش واجذب PAHs و فلزات سنگين مي‌شود و با افزايش محتواي ماده آلي خاك، واجذب اين تركيبات از خاك كمتر شد. همچنين در اين مطالعه مشاهده شد كه حضور فلزات سنگين در خاك مي‌تواند موجب كاهش واجذب PAHs از خاك شود.

Understanding the combined effect of soil organic matter (SOM), surfactants and chelatant on the partitioning of polycyclic aromatic compounds and in soil/water systems and on their desorption is important to predict the effectiveness of surfactantchelatantenhanced remediation systems. In this paper the effect of soil organic matter’s content and presence of surfactants and a chelatant on desorption of six different polycyclic aromatic hydrocarbons namely acenaphthene , fluorine , phenanthrene , anthracene , fluoranthene , and pyrene was investigated and the results of phenanthrene was reported. It also investigates the effect of coexistence of three differenet heavy metals namely: lead, zinc and nickel on polycyclic aromatic hydrocarbons and their effects on desorption of these compounds. The basic soil was made from a mixture of kaolinite, montmorillonite and sand. Then this basic soil was spiked by two diffrenet level of organic matter through batch experiments to achieve three different soils named S0, S1 and S2 which has 0.33, 1.29 and 2.11 percent organic carbon, respectively. After that, this three different soils was spiked by heavy metals with the same way mentioned before (bathch experiments). As a result, six differenet soils was created under the name of: S0, S0M, S1, S1M, S2, S2M. and finally these six soils were spiked by mentioned polycyclic aromatic hydrocarbons. And finally the whole desorption experiments was done on these mentioned soils. Two surfactants chosen in this paper was triton x 100 and tween 80 and the chelatant was ethylene diamine tetraacitic acid (EDTA). Results showed that, surfactants improved the deorption of both heavy metals and polycyclic aromatic hydrocarbons and it also could be understood that triton x 100 had higher effectiveness than tween 80 in deorption of both heavy metals and polycyclic aromatic hydrocarbons. Furthermore it was found that soil organic matter had preventative effect on desorption of both heavy metals and polycyclic aromatic hydrocarbons. Both soil organic matter and surfactants are amphiphilic substances and because of that it is possible that this result is due to the sorption of surfactants into soil organic matter and consequently caused a reduction in desorption effectiveness of polycyclic aromatic hydrocarbons. and further increase in soil organic matter content caused more reverse effect on surfactants productivity. It was also found that, presence of lead, zinc and nickel could have preventative effect on desorption of polycyclic aromatic hydrocarbons too, and this could be due to some specific interactions like cation л binding between heavy metals and phenanthrene while they coexist in the interface of soil and water. Another reason of heavy metals preventative effect on desorption of polycyclic aromatic hydrocarbons could be due to their indirect effect through which, heavy metals act as an cation bridge between clay particles and organic matter mollecules and by this mean prevent soil organic matter mollecules to be dissolved in water. On the other hand scientists have proved that polycyclic aromatic hydrocarbons have great affinity to partition in to soil organic matter. Therefor by retaining more organic matter in soil through cation bridge mechanism, desorption of phenanthrene was reduced.