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Kinetic and Thermodynamic Study of the Adsorption of some Organic Acids by MnO2
دراسة حركية وثرموداينمكية لامتزاز بعض الحوامض العضوية باستخدام MnO2

Authors: Emad A. S .Al-Hyali --- Khalil I . Al – Niemi --- Safwan A Al-Dubunee
Journal: Tikrit Journal of Pure Science مجلة تكريت للعلوم الصرفة ISSN: 18131662 Year: 2012 Volume: 17 Issue: 2 Pages: 105-111
Publisher: Tikrit University جامعة تكريت

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Abstract

In this research work, the adsorption efficiency of three structurally related acids namely, glycolic, mandelic and benzylic acids by MnO2 from their aqueous solutions is investigated.The study is aimed at developing a better understanding of the adsorption mechanism regarding the molecular level. The experiments were achieved as batch methods.The factors affecting the adsorption efficiency such as; contact time, initial concentration, initial pH of the acid medium and temperature are studied. The results obtained showed that, the increase of initial concentration increases the adsorption efficiency. The initial pH of the medium plays an important role in controlling the attachment of acid molecules on the solid surface of MnO2. The highest adsorption efficiency is observed in the acid medium (natural pH of the acid solutions).This study proved that, the acid is connected to the solid surface of absorbent in its anion form.The thermodynamic functions of adsorption are estimated at different initial concentrations (0.005-0.05 N). The study also included the application of the two kinetic models on the adsorption data namely; the pseudo first order and pseudo second order equations. The investigation is performed at certain concentration and various temperatures. The results denoted that, the studied systems are better fit the second order model.

تضمن هذا البحث دراسة كفاءة امتزاز بعض الأحماض العضوية ( الكلايكوليك و المندليك و البنزيليك) والتي تتفاوت بصيغها التركيبية من محاليلها المائية.وقد هدفت الدراسة التوصل إلى فهم عميق وواضح لميكانيكية امتزاز هذه الأحماض وعلاقتها بالتركيب ألجزيئي لها. وقد أنجزت التجارب العملية باستخدام طريقة الدفعة الواحدة. لقد أشتمل البحث على دراسة العوامل المؤثرة على الامتزاز مثل زمن التماس والتركيز الابتدائي والدالة الحامضية والامتزاز ودرجة الحرارة.أظهرت النتائج إن زيادة التركيز الابتدائي يزيد من كفاءة الامتزاز وان الدالة الحامضية الابتدائية لوسط الامتزاز تلعب دورا أساسي في التحكم بطريقة ارتباط الجزيئات الممتزة بالسطح ألماز . وتبين النتائج إن أعلى كفاءة امتزاز تم ملاحظتها في الوسط ألحامضي (عند الدالة الطبيعية لمحاليل الحوامض) .وقد أثبتت الدراسة إن الأحماض العضوية المدروسة ترتبط مع سطح الـ MnO2 بشكلها ألايوني السالب . وقد حسبت الدوال الثرموداينميكية لنظام الامتزاز بالاعتماد على النتائج المحصل عليها من دراسة تأثير درجة الحرارة عند مدى من التراكيز (0.005-0.05)N.أشتمل البحث أيضا على دراسة حركية امتزاز هذه الأحماض على سطح الـ MnO2 وذلك من خلال تطبيق نموذجي معادلتي المرتبة الأولى الكاذبة والثانية الكاذبة في عدد من درجات الحرارة وعند تركيز ثابت . أظهرت النتائج إن النظام المدروس يتبع نموذج المرتبة الثانية الكاذبة.


Article
Indirect Electrochemical Oxidation of Phenol Using Rotating Cylinder Reactor

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Abstract

Indirect electrochemical oxidation of phenol and its derivatives was investigated by using MnO2 rotating cylinder electrode. Taguchi experimental design method was employed to find the best conditions for the removal efficiency of phenol and its derivatives generated during the process. Two main parameters were investigated, current density (C.D.) and electrolysis time. The removal efficiency was considered as a response for the phenol and other organics removal. An orthogonal array L16, the signal to noise (S/N) ratio, and the analysis of variance were used to test the effect of designated process factors and their levels on the performance of phenol and other organics removal efficiency. The results showed that the current density has the higher influence on performance of organics removal while the electrolysis time has the lower impact on the removal performance. Multiple regressions was utilized to acquire the equation that describes the process and the predicted equation has a correlation coefficient (R2) equal to 98.77%. The best conditions were found to get higher removal efficiency. Removal efficiency higher than 95% can be obtained in the range of C.D. of 96-100 mA/cm2 and electrolysis time of 3.2 to 5 h. The behavior of the chemical oxygen demand (COD) mineralization denotes to a zero order reaction and the rate of reaction controlled by active chlorine reaction not by mass transfer of phenol towards the anode.

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