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Home > Reaction Kinetics and Mass Transfer Studies in Selective Leaching of Low-Grade Calcareous Phosphate Rock

Reaction Kinetics and Mass Transfer Studies in Selective Leaching of Low-Grade Calcareous Phosphate Rock

Thesis Info

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Author

Ashraf, Muhammad

Program

PhD

Institute

Bahauddin Zakariya University

City

Multan

Province

KPK

Country

Pakistan

Thesis Completing Year

2010

Thesis Completion Status

Completed

Subject

Chemistry

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/975

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727068314

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In the present thesis, the dilute solutions of succinic acid have been used to investigate the selective leaching of calcareous material in low-grade phosphate rock. The effective parameters on the dissolution rate are reaction temperature, particle size, acid concentration and liquid-solid ratio. The results indicate that succinic acid can be used to selectively dissolve the calcareous material in low-grade phosphate rock as it improves the P 2 O 5 content of the rock and makes it viable as a feed to an acidulation plant. Using the known size particles of the sample, acid concentration and liquid-solid ratio, the influence of different reaction temperatures has been studied in order to elucidate the leaching kinetics of calcareous material in the rock. The results show that the leaching rate of calcareous material increases with increasing temperature. A kinetic model has been suggested to describe the selective leaching process of calcareous material analyzing the kinetic data. The selective leaching curves have been evaluated in order to check the validity of shrinking core models for liquid-solid systems. The experimental data have been tested by graphical and statistical methods and it is found that the leaching of calcareous material in the rock is controlled by the chemical reaction i.e. 1 - ( 1 - x ) 1 / 3 = 1 . 47 ´ 10 6 e - 64 . 92 / RT t . The apparent activation energy of the dissolution process has been found to be 64.92 kJ mol -1 over the reaction temperature range from 313 to 353 K. Such a value of activation energy indicates that the process is a chemically controlled reaction and agrees with the values obtained in the similar research of fluid- solid reaction systems. The agreement between the experimental conversion and the 17values calculated from the suggested empirical equation has been tested, and which is found to be very good. For a comparison study, lactic acid has also been used to study the selective leaching kinetics of calcareous phosphate rock. The effect of acid concentration, liquid/solid ratio, particle size and temperature has been studied in order to expound the leaching kinetics of calcareous material in the rock. It has been found that the leaching rate of calcareous material increases with increasing the acid concentration, liquid/solid ratio and temperature and decreasing particle size. A semi-empirical model has been suggested to illustrate the selective dissolution of calcareous material analyzing the experimental data. The selective leaching curves have been evaluated to test the validity of kinetic models for liquid-solid systems. The kinetic data are analyzed by graphical and statistical methods and it has been found that the dissolution of calcareous material in the rock is controlled by 1 - ( 1 - a ) 1 / 3 = 19 . 1 C 1 . 753 ( L / S ) 1 . 627 D - 0 . 737 e - 42954 chemical . 62 / RT reaction i.e. t . The analysis of the obtained results reveals that the applicability of the suggested model is good and it can work within a certain range for the choice of adjustable parameter values depending on the degree of selective leaching. The results show that the controlling step of the overall process of the heterogeneous reaction is a chemical change. According to the analyzed results, it is recommended that the parameter values for the optimum selective leaching rate are C = 8% v/v, L/S = 7 cm 3 g -1 , T = 318 K, SS = 350 min -1 and D = 0.1255 mm.
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مولانا عبدالسلام قدوائی

مولانا عبدالسلام قدوائی
افسوس ہے ہمارے فاضل اوردیرینہ دوست مولانا عبدالسلام صاحب قدوائی بھی کم وبیش ستربرس کی عمر میں۲۴/اگست کواپنے گاؤں تہیلنڈی ضلع رائے بریلی(اترپردیش)میں راہی ملک بقاہوگئے۔خاتمہ اچانک ہوا،۲۴/اگست کو آخری روزہ تھا، مرحوم سحری کے وقت پہلے خود اُٹھے، پھر گھر کے لوگوں کو اٹھایا لیکن ابھی سحری کھائی نہیں تھی کہ بیت الخلا جاتے ہوئے گرپڑے، تھوڑی دیر کے بعد حالت غیر ہوگئی اوربے ہوش ہوگئے، نفس کی آمدوشد میں فرق آگیا،اورآخر چند گھنٹوں کے بعد جان جانِ آفریں کوسپرد کردی۔انا ﷲ واناالیہ راجعون۔
مرحوم دارالعلوم ندوۃ العلماکے آخری درجہ میں زیر تعلیم تھے کہ ندوہ میں ایک مشہور اورعظیم الشان اسٹرائیک ہوئی، اس سلسلہ میں احمد جعفری اوردوسرے بہت سے طلباء کے ساتھ مرحوم بھی خارج کردیئے گئے۔ اب وہ جامعۂ ملیہ اسلامیہ میں داخل ہوگئے لیکن کئی برس یہاں مقیم رہنے کے باوجود تکمیل یہاں بھی نہ کرسکے۔بہرحال تھے ذہین اورجو کچھ پڑھا تھا محنت اورشوق سے پڑھا تھا اس لیے استعداد پختہ تھی، اس بناپر چندبرس ندوہ میں مدرس رہے۔لکھنؤ میں ادارۂ تعلیمات اسلام کے نام سے ایک ادارہ قائم کیا۔بمبئی میں اخبار خلافت کے عملۂ ادارت سے بھی وابستہ رہے۔ آخرکار جامعہ ملیہ اسلامیہ میں ناظم شعبۂ دینیات ہوگئے، یہاں سے سبکدوش ہوکرندوۃ العلماء میں معتمد تعلیمات ہوئے، پھر شاہ معین الدین احمد صاحب کاانتقال ہوا توان کی جگہ سید صباح الدین عبدالرحمن صاحب کے ہاں ماہنامۂ ’معارف‘ کے شریک ادارت ہوگئے۔مولانا مرحوم نے اگرچہ کم لکھاہے لیکن جوکچھ لکھاہے بہت خوب لکھاہے۔سادگی کے ساتھ طرفگی اور سنجیدگی ومتانت کے ساتھ شگفتگی اُن کے قلم کی خصوصیت تھی۔طبیعت رسااورنکتہ آفریں پائی تھی، کم گواورکم سخن،مرنج ومرنجان اوربڑے بااخلاق ومتواضع تھے۔ اللھم اغفرلہ وارحمہ
[ستمبر۱۹۷۹ء]

 

أثر القرآن الكريم في الشعر الفلسطيني "محمود درويش" أنموذجاً

يشكل القرآن الكريم منبعا ثريا، يلجأ إليه الشعراء والأدباء في أعمالهم الأدبية المختلفة، لأنّه جزء ثابت في حياتهم، واستنادا على هذا وجد الشعراء ضالتهم في القرآن الكريم للتعبير عن خواطرهم مستلهمين منه معانيه، وقد ارتبط الشعر الفلسطيني خاصة بالقرآن الكريم باعتبار أن قضية احتلال فلسطين قضية دينية أكثر منها سياسية، إذا كيف تأثر الشعراء الفلسطينيين بما جاء من قصص وعبر في القرآن الكريم وكيف ترجموها في شعرهم لإشعال المقاومة والثورة؟ والهدف من هذه الدّراسة توضيح أنّ الشعر الفلسطيني ارتبط بالقرآن الكريم لاعتبار الشعراء الفلسطينيين قضية فلسطين قضية دينية ومن النتائج التي توصلنا إليها تأثر شعراء فلسطين بالقرآن الكريم في عدة جوانب منها استلهام المفردات القرآنية والرموز الدّينية والتّناص والإيقاع والموسيقى، وقد اعتمد الباحثان في الدّراسة على المنهج الوصفي التحليلي

Fabrication and Study of Organic Electronic and Optoelectronic Devices

From the last few decades, organic semiconductors based electronic and optoelectronic devices have been the area of intense research. Organic semiconductors have gained optoelectronic industry due to remarkable importance in electronic and conjugated structure, low cost production, mechanical flexibility, ease of device fabrication and environmental friendly processing. In the research work reported in this dissertation, electronic, optoelectronic and amplified spontaneous emission (ASE) studies are carried out on (i) junction diodes using n-type organic semiconductors, (ii) sensors fabricated using organic semiconductors and organic-inorganic nanocomposites, and (iii) newly synthesized single crystal oligothiophene, respectively. The organic n-type semiconductors N-Butyl-N′-(6-hydroxy-hexyl) perylene- 3,4,9,10- tetracarboxylic-acid-diimide (N-BuHHPDI) and perylene- 3,4,9,10- tetra-carboxylic acid di-anhydride (PTCDA) have been synthesized and employed for their potential applications in organic devices such as Schottky barrier junction (SBJ), heterojunction (HJ) and organic multifunctional sensors. The fabricated rectifying junctions, i.e. Schottky junction and heterojunction, are characterized by conventional current-voltage (I-V) method at ambient atmospheric condition at in dark. Different junction factors i.e. turn-on voltage (V t ), ideality factor/quality factor (n), rectification ratio (RR), barrier height (φ b ), reverse saturation current (I 0 ), series resistance and shunt resistance are determined from the I-V curves. Other two well known characterization techniques, Norde’s technique and Cheungs’ functions, are applied to measure the aforementioned parameters of the diode. The parameters extracted by these different characterization methods are compared and found in good agreement with each other. To understand the temperature dependence of the heterojunction device parameters, the I-V properties of the heterojunction are studied at various temperatures from 300 K to 330 K. This has been observed that with the viiiincrease in temperature the ideality factor, turn-on voltage and series resistance of the junction are significantly decreased. While the reverse saturation current and rectification ratios are increased. The morphological study of the thin films of N-BuHHPDI and PTCDA deposited on quartz glass has been carried out by scanning electron microscope (SEM) and atomic force microscope (AFM). Size of the grain, shape, orientation and average surface roughness of the thermally deposited films has been measured from the microscopy. Energy dispersive spectroscopy (EDX) has been done for these samples to confirm the composition of these newly synthesized organic materials. To measure the optical band gap of these materials, ultra-violet and visible (UV-Vis) spectroscopy has been performed. The N-BuHHPDI is insoluble in water and possesses excellent hydrophobic properties. This hydrophobic property makes these materials more distinctive candidates for humidity sensing applications as compared to other water soluble organic materials. The high sublimation temperature (700 K) is another convincing characteristic of this class of materials for their potential application as a temperature sensor to monitor temperature at elevated levels. At the same time, the broad UV-Vis spectrum and good absorption of light recommend perylenes equally useful for light sensing applications. Thus, taking advantages of these motivating properties, the potential of perylene has been explored for humidity, temperature and light sensing applications due to the possession of such interesting properties all together. To enhance the performance of the organic semiconductor based sensors, one way is to make the sensor at nanoscale and the other is to blend organic semiconductor with some functional nanoparticles/nanofibers. For this reason, an organic azo dye, methyl orange (MO), has been used as an active semiconducting matrix in which the TiO 2 nanoparticles have been disapersed. The fabricated sensor response has been observed at different humidity and ixtemperature values. Fast recovery time and response time of the sensor has been achieved due to the introduction of TiO 2 nanoparticles by taking advantage of large surface-to-volume ratio of the nanoparticles. Concerning photonic characteristics of organic polymers and small molecules, conjugated polymers based optically pumped lasers have been produced both from solution and thin films. However, significant hard work is being carried out on these conjugated molecules to enhance their carriers’ mobility and to minimize the threshold energy required for lasing to develop electrically pumped polymer laser diodes. Such types of materials for lasers may ultimately compete with their inorganic counterparts in many ways such as inexpensive, low-temperature and high throughput fabrication. One special type of these materials is single crystal oligomers which, in the last decade, have got incredible attention due to their interesting properties such as high charge carriers’ mobility, chemically adjustable wavelengths, large photoluminescence quantum efficiency (PLQE), large stimulated emission cross-sections and as a high optical gain media for their prospective uses in solid state lasers and broadband amplifiers. The amplified spontaneous emission (ASE), optical gain and PLQE properties of a newly synthesized single crystal oligothiophene 5, 5’’’’’-diphenyl-2, 2’:5’, 2’’:5’’, 2’’’:5’’’, 2’’’’:5’’’’, 2’’’’’-sexithiophene (P6T) are reported. This oligomer crystal has been grown on glass substrate in a dimension of 5mm x 2mm with 10 μm thickness, by Prof. Shu Hotta, Kyoto Institute of Technology, Japan and its photonic properties have been studied at Cavendish Lab, Cambridge, UK.