Mineralogy Geochemistry and Sorption Efficiency of Palygorskite of Digma and Akashat Formations Western Iraq

الموضوعات

علوم بيئية

الملخص

Palygorskite-rich sediments in Digma (Maastrichtian) and Akashat (Paleocene) Formations, within the Western Desert of Iraq are studied in terms of mineralogy, geochemistry and some technical applications. The technical applications include the separation of palygorskite from raw sample and conduct set of laboratory experiments that would indicate the ability of palygorskite to absorb and adsorb the heavy metals from the liquid phase. For this reason, targeted sampling approach is used to follow-up and to collect the palygorskite-rich sediments from 17 sites, some samples were collected from each site and tested mineralogically to select the appropriate sample; then finally, one representative sample was chosen from each site. X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared (FTIR) techniques have been used together to study the raw samples (palygorskite-rich sediments) and the separated sample (palygorskite). The current study reveals the association of palygorskite with the siliceous rocks represented by poracellanite, Opal-CT (crystobalite and tridymite), a considerable amount of dolomite and kaolinite with little amount of calcite within marly limestone, and apatite in Digma Formation. While in Akashat Formation, palygorskite is associated mostly with montmorillonite, dolomite, marly limestone and little porcellanite represented by opal-CT (crystobalite and tridymite) and quartz. This facies indicates a shallow marine environment of inner platform. The present study suggests two models for the genesis of palygorskite; the first one is the reaction of pore water rich in silicic acid with dolomite to form sepiolite, which eventually transforms into palygorskite by taking alumina from the surroundings, and the second is the transformation of smectite to palygorskite in environment rich in Mg. In terms of geochemistry, the palygorskite-rich sediments and the pure palygorskite that had been separated from the raw sample are analyzed for SiO2, Al2O3, MgO, Fe2O3, TiO2, MnO, Na2O, CaO, K2O, P2O5, LOI. The content of MgO in the palygorskite-rich sediments varies between 0.61 to 9.38%, where some of MgO comes from dolomite. In pure palygorskite, the high content of MgO (10.2%) with suitable LOI (19.1%) indicates a success of laboratory separation process which was enhanced by SEM. The structural formula of the separated palygorskite and the charge distribution in the octahedral layer, tetrahedral layer and interlayer were calculated. In term of technical applications, the pure palygorskite (separated from raw sample) is subjected to a set of laboratory experiments to test the efficiency of palygorskite for sorping the heavy metals (Pb, Cd, Ni, Cr, Co, V, Zn, Cu, Fe and Mn) as well as boron (B) in concentration of 10, 25, 50, 75, 100, 125, 150, 175, 200 and 225 ppm for each element. More than 110 laboratory experiments are conducted as patch process at room temperature. The solid(palygorskite)to liquid ratio (initial solution) is determined to be (1gm/100ml), and the equilibrium reaction time is 1h. TDS and EC decrease with the trend of alkaline pH in the final solutions (after the end of the reaction). The tendency toward the alkaline occurs with the solutions of low concentration rather than the solutions of high concentration due to lack of cations competes the H+ on the negative site of palygorskite. The ability of palygorskite sorption (in percentage) increases when thermally activated, up to 93% at 600°C due to the driving of zeolitic water by heating, the surface area and thus the sorptivity is increased too. Whilst, at 800 ̊C sorption decreases to minimum due to the collapse of palygorskite structure. The palygorskite is expressed as an active receptive of heavy metals, while Ca2+, Mg2+, Al3+ and K+ are desorb ions from the palygorskite into the solution indicating a one-to-one ion exchange mechanism is responsible for the incorporation of cations into the structure of palygorskite. The expulsion of these cations causes a decrease in positive charge on palygorskite which encourages additional cations to adsorb on surface. The efficiency of palygorskite sorption (%) of heavy metals varies depending on the nature of the metals. Laboratory experiments have identified a lot of relationships, from which the palygorskite sorption (%) for initial solutions of concentration 50 ppm can be ordered as follows: B < V < Mn < Ni < Co < Cu < Zn < Cd < Cr < Pb < Fe.

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التعريف والنوع

رقم الوثيقة

05936122-e84a-427f-94bb-dcf0d7213c68

رقم العقد

0

نوع الوسائط

Crawler

نوع المحتوى

الرسائل العلمية

صيغة المصدر

رسائل دكتوراة

نوع الملف

pdf text

أسماء الملفات

05936122-e84a-427f-94bb-dcf0d7213c68_1.pdf

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ألقاب المؤلفين

[{"name_ar":"Saad Muhi Towfik","title_ar":"اعداد","title_en":"Preparation"},{"name_ar":"Salih Muhammed Awadh","title_ar":"اشراف","title_en":"Supervision"}]

اللغة

English

المصدر والدورية

اسم المصدر

Mineralogy Geochemistry and Sorption Efficiency of Palygorskite of Digma and Akashat Formations Western Iraq

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عدد الصفحات

0

إشراف وإعداد

الإشراف

Salih Muhammed Awadh

الإعداد

Saad Muhi Towfik

الاقتباسات الببليوغرافية