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    TREATMENT OF SELENOCYANATE (SeCN—) CONTAMINATED AQUEOUS STREAMS USING Fe-BASED SYSTEMS

    TREATMENT OF SELENOCYANATE (SeCN—) CONTAMINATED AQUEOUS STREAMS USING Fe-BASED SYSTEMS. Masters thesis, King Fahd University of Petroleum and Minerals.

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    Arabic Abstract

    إن وجود مركبات السیلینوسیانات (-SeCN) في میاة الصرف الناتجة من عملیات تكریر البترول وصناعات التعدین تشكل خطرا كبیرا علي حیاة الانسان والحیوان. اخذا ھذا بعین الاعتبار, فإن ھذا البحث یعمد الي معالجة میاة الصرف من ھذه المركبات بستخدام مركبات الحدد المختلفة مثل عملیة Fenton-Photo/Fenton و مركبات الحدید 2LFh و SiO2/(III)Fe. نتایئج البحث اظھرت ان استخدام عملیة Fenton تؤثر تأثیرا كبیرا علي عملیة المعالجة حیث تم معالجھ میاة الصرف بنسة 90% , في حین ان استخدام عملیة Fenton-Photo اظھرت عدم فعالیتھا. من ناحیة اخري, تم حضیر كلا من مركب 2LFh و SiO2/(III)Fe وتم استخدام تقنیات XRD و FTIR لتعین بعض خواص ھذه المواد. اتضح من نتائج ھذه الاختبارت انھما مواد غیر منتظمة ترتیب الذرات amorphous وان ھناك بعض مجموعات OH عند اسطح العینات. في ھذا البحث ایضا تم استخدام مركبات 2LFh و SiO2/(III)Fe لمعالجة میاه الصرف من مركبات -SeCN عن طریق امتزازھا علي اسطح مركبات الحدید المذكوة. وعلي ھذا فإن النتائج اظھرت قابلیة مركبات الحدید السابق ذكرھا لمركبات -SeCN ولكن قابلیتھا ضعیفة جدا, حیث یصل اقصي سعة امتزاز لكلا من 2LFh و SiO2/(III)Fe الي 3 و 65.2 مجم/جم علي التوالي. وتم نمذجة عملیة الامتزاز طبقا لنموزج Langmuir وكذلك kinetics order Second في حالة استخدام 2LFh. ھذا وقد تم ایضا استخدام عملیة Photocatalysis معتمدة اولا علي استخدام TiO2 لكسر الرابطة في مركب -SeCN وتحویلھا الي عنصر السیلینیوم ومن ثم اكسدتھا الي -SeO32 ثم الي -SeO42. جمبا الي جمب تم استخدام مركبات الحدید 2LFh او SiO2/(III)Fe مع TiO2 في عملیة Photocatalysis لمعالجة مصادر السلیلنوم المتكونة في میاة الصرف عن طریق ایضا امتزازھا علي اسطح مركبات الحدید المذكورة. ھذه التقنیة ساعده كثیرا للتخلص من مركبات -SeCN بشكل كبیر.

    English Abstract

    The presence of selenocyanate species in some specific industrial wastewaters pose risk to human and animal health. Considering this, the present work investigated the removal of aqueous phase selenocyanate using different iron-based systems including Fenton/PhotoFenton (PF) process, 2 Line Ferrihydrite (2LFh), and Fe(III)/SiO2 binary oxide system. The results showed that Fenton process was efficient with about 90% selenocyanate removal achieved at 360 min at pH 4. However, the use of photo-Fenton process showed comparatively reduced selenocyanate removal. The surface characterization of 2LFh and Fe(III)/SiO2 solids was also completed with XRD and ATR-FTIR techniques. The XRD findings indicated both 2LFh and Fe(III)/SiO2 to be amorphous, and ATR-FTIR results showed several Fe and O-based surface groups. Furthermore, selenocyanate adsorption onto 2LFh and Fe(III)/SiO2 was also explored. The adsorption capacity of 2LFh and Fe(III)/SiO2 for selenocyanate were about 3 and 2.65 mg/g, respectively. In addition, it was noted that the results of selenocyanate adsorption onto 2LFh better fitted to the Langmuir model isotherm, whereas those for Fe(III)/SiO2 better fitted to the Freundlich model isotherm. The qe/Ce results for respective Fe-adsorbents also supported the above-mentioned results, i.e., a plateau was noted for 2LFh system, whereas the Fe(III)/SiO2 showed an increasing qe/Ce trend. This work was further extended to examine the selenocyanate removal using TiO2-based system photocatalysis followed by the adsorption of released Se-species by 2LFh or Fe(III)/SiO2 system. In this regard, PCD process using TiO2 initiated the selenocyanate complex degradation with selenite and selenate species formed over 360-min reaction time. The results from the mixed TiO2 photocatalysis and 2LFh adsorption showed that the combination of the two systems though efficient, but was affected by process variables including pH. Complete selenium removal was achieved atpH 5, whereas the removal decreased significantly with an increase in pH to 9. This was attributed to lower degradation of selenocyanate at higher pH during photocatalysis. Furthermore, the response surface methodology (RSM)-based models also showed that the RSM approach can be used to predict aqueous phase selenocyanate removal under a varying set of operational conditions. A similar trend was also observed for TiO2 and Fe(III)/SiO2 system. In general, the present work showed the successful removal of selenocyanate species from aqueous phase under the varying set of process conditions using several Fe-based systems.

    Item Type: Thesis (Masters)
    Subjects: Civil Engineering > Water and Environmental Engineering
    Department: College of Design and Built Environment > Civil and Environmental Engineering
    Committee Advisor: Vohra, M. S.
    Committee Members: Al-Suwaiyan, M. S. and Bukhari, Alaadin
    Depositing User: SAMEH ARABY (g201405300)
    Date Deposited: 04 Jun 2017 11:41
    Last Modified: 31 Dec 2020 09:22
    URI: http://eprints.kfupm.edu.sa/id/eprint/140342