Synthetic modifications of metal organic framework adsorbents for environmental remediation

The widespread usage of organic chemicals has led to an unprecedented level of pollution and associated health risk concerns. Although activated carbon (AC) based adsorption is commonly used in wastewater treatment and air purification processes, now, new metal-organic frameworks (MOFs) adsorbents with superior surface areas, chemically tuneable structures, and excellent reusability are available. This thesis evaluates the application of selected MOFs and their modified variants for removing organic pollutants from aqueous and humid air streams, reporting adsorption capacity and kinetics. For the removal of aqueous phase pollutant 2-chlorophenol, the higher surface area of MIL-101 (Cr) even with improved surface amination, gave inferior adsorption capacity compared to the hydrophobic AC, indicating the importance of MOF’s hydrophobicity. A hydrophobic MIL-101 (Cr) was synthesized using a PDMS vapour coating protocol, creating a new material with the same surface area and pore volume as pristine MIL-101 (Cr). For 0.5% toluene P/P0 vapour co-adsorption at 40% RH, this composite showed a 60% higher uptake capacity and a 34% higher aggregate adsorption rate compared to pristine MIL-101 (Cr), and 360% faster kinetics relative to AC. A solution-based treatment for MIL-100 (Fe) was developed using calixarene, producing super hydrophobic surfaces, which at 40% RH and 0.5% toluene P/P0, exhibited a 68% higher aggregate uptake rate, despite having lower pore volumes and surface areas. Finally, MIL-96 (Al) was modified using hydrolysed polyacrylamide polymer, which enlarged the 3.2-µm particles by 225% and transformed their crystal morphology. The polymer also contains amide with NH2 moieties which improved the modified MIL-96 (Al)’s uptake capacity of perfluorooctanoic acid. Overall, this thesis highlights the complexity of co-adsorption when hydrophobic and hydrophilic adsorbates are both present. It also recalls the importance of adsorption kinetics, in contrast with current MOF research emphases, which are on surface area and adsorption capacity. Faster adsorption kinetics may be preferred over a slow-diffusing adsorbate, even if the final uptake capacity is superior, for some industrial applications.Open Acces

Perceived status towards COVID-19 mitigation measures among medical students in Malaysian Borneo

Introduction: Mitigation measures are important in curbing COVID-19 infection. However, people’s adherence to the control measures is depending upon their knowledge, attitudes and practices (KAP) towards the disease. This study aims to determine the KAP on COVID-19 and its associated factors among medical students in Malaysian Borneo during the period of the pandemic. Methods: A cross-sectional online survey of 248 medical students from University Malaysia Sabah was conducted from August to September 2020. The survey instrument was adapted from a previously validated questionnaire on COVID-19. Descriptive statistics and simple logistic regression were conducted. Results: The mean age of respondents was 22.0 (SD 1.4) years. Majority (65.7%, n= 163) were clinical students, female gender (70.6%, n= 175), and Bumiputera ethnic (46.8%, n= 116). 211 (85.1%), 191 (77.0%) and 163 (65.7%) of the respondents have good level of knowledge, positive attitude and good practice respectively. Conclusion: The medical students are updated with the current health issues especially on COVID-19. They are aware of the attributes of the disease and have concerns in taking good care of themselves. Further study needs to be implemented among the groups of non-medical student of the same institution to compare their KAP on COVID-19

Kemerosotan Prestasi Akibat Daripada Tekanan dan Pencemaran Hati : Analogi Cahaya dan Kecacatan Gelap

Faktor semangat merupakan kilauan mata, langkah kaki, pegangan tangan, aliran darah dan tenaga untuk mewujudkan cita – cita pada setiap manusia. Bagi tujuan untuk melaksanakan atau mewujudkan keadaan ini diperlukan keyakinan, keberanian dan kualiti hidup untuk yang ingin memahaminya. Beberapa aspek terjadinya kemerosotan disebabkan pelanggaran prinsip–prinsip dasar kehidupan. Tuntunan cahaya (Nur) Allah S.W.T akan mampu membuka rahsia – rahsia kehidupan dan membuka mata hati. Cahaya ini membolehkan kita menjalani kehidupan yang penuh ketidakpastian dan menemukan suatu keseimbangan batin, hidup secara kreatif “meskipun” ada ketidakpastian, melainkan adanya ketidakpastian yang penuh ilham. Arah cahaya yang salah boleh memberi kesan kecacatan bagi yang memahaminya. Arah dan fokus cahaya yang lurus (light beam collimation) dan sesuai dengan fitrah manusia akan memberikan manfaat bagi yang menerimanya (Ayat Al-Quran Surah An-Nur 35: ) ٱللَّهُ نُورُ ٱلسَّمَـٰوَٲتِ وَٱلۡأَرۡضِ‌ۚ مَثَلُ نُورِهِۦ كَمِشۡكَوٰةٍ۬ فِيہَا مِصۡبَاحٌ‌ۖ ٱلۡمِصۡبَاحُ فِى زُجَاجَةٍ‌ۖ ٱلزُّجَاجَةُ كَأَنَّہَا كَوۡكَبٌ۬ دُرِّىٌّ۬ يُوقَدُ مِن شَجَرَةٍ۬ مُّبَـٰرَڪَةٍ۬ زَيۡتُونَةٍ۬ لَّا شَرۡقِيَّةٍ۬ وَلَا غَرۡبِيَّةٍ۬ يَكَادُ زَيۡتُہَا يُضِىٓءُ وَلَوۡ لَمۡ تَمۡسَسۡهُ نَارٌ۬‌ۚ نُّورٌ عَلَىٰ نُورٍ۬‌ۗ يَہۡدِى ٱللَّهُ لِنُورِهِۦ مَن يَشَآءُ‌ۚ وَيَضۡرِبُ ٱللَّهُ ٱلۡأَمۡثَـٰلَ لِلنَّاسِ‌ۗ وَٱللَّهُ بِكُلِّ شَىۡءٍ عَلِيمٌ۬ Ertinya: Allah (Pemberi) cahaya (kepada) langit dan bumi. perumpamaan cahaya Allah, adalah seperti sebuah lubang yang tak tembus[a], yang di dalamnya ada Pelita besar. Pelita itu di dalam kaca (dan) kaca itu seakan-akan bintang (yang bercahaya) seperti mutiara, yang dinyalakan dengan minyak dari pohon yang berkahnya, (yaitu) pohon zaitun yang tumbuh tidak di sebelah timur (sesuatu) dan tidak pula di sebelah barat(nya)[b], yang minyaknya (saja) hampir-hampir menerangi, walaupun tidak disentuh api. cahaya di atas cahaya (berlapis-lapis), Allah membimbing kepada cahaya-Nya siapa yang dia kehendaki, dan Allah memperbuat perumpamaan-perumpamaan bagi manusia, dan Allah Maha mengetahui segala sesuatu. [a] yang dimaksud lubang yang tidak tembus (misykat) ialah suatu lubang di dinding rumah yang tidak tembus sampai ke sebelahnya, Biasanya digunakan untuk tempat lampu, atau barang-barang lain. [b] Maksudnya: pohon zaitun itu tumbuh di puncak bukit ia dapat sinar matahari baik di waktu matahari terbit maupun di waktu matahari akan terbenam, sehingga pohonnya subur dan buahnya menghasilkan minyak yang bai

Can Metal Organic Frameworks Outperform Adsorptive Removal of Harmful Phenolic Compound 2-Chlorophenol by Activated Carbon?

Abstract: Removal of persistent organic compounds from aqueous solutions is generally achieved using adsorbent like activated carbon (AC) but it suffers from limited adsorption capacity due to low surface area. This paper describes a pioneering work on the adsorption of an organic pollutant, 2-chlorophenol (2-CP) by two MOFs with high surface area and water stability; MIL-101 and its amino-derivative, MIL-101-NH2. Although MOFs have higher surface area than AC, the latter was proven better having the highest equilibrium 2-CP uptake (345 mg.g-1), followed by MIL-101 (121 mg.g-1) and MIL-101-NH2 (84 mg.g-1). Used MIL-101 could be easily regenerated multiple times by washing with ethanol and even showed improved adsorption capacity after each washing cycle. These results can open the doors to meticulous adsorbent selection for treating 2-CP-contaminated wate

Polymer-Assisted Modification of Metal-Organic Framework MIL-96 (Al): Influence on Particle Size, Crystal Morphology and Perfluorooctanoic Acid (PFOA) Removal

AbstractA new synthesis method was developed to prepare an aluminum-based metal organic framework (MIL-96) with a larger particle size and different crystal habits. A low cost and water-soluble polymer, hydrolyzed polyacrylamide (HPAM), was added in varying quantities into the synthesis reaction to achieve >200% particle size enlargement with controlled crystal morphology. The modified adsorbent, MIL-96-RHPAM2, was systematically characterized by SEM, XRD, FTIR, BET and TGA-MS. Using activated carbon (AC) as a reference adsorbent, the effectiveness of MIL-96-RHPAM2 for perfluorooctanoic acid (PFOA) removal from water was examined. The study confirms stable morphology of hydrated MIL-96-RHPAM2 particles as well as a superior PFOA adsorption capacity (340 mg/g) despite its lower surface area, relative to standard MIL-96. MIL-96-RHPAM2 suffers from slow adsorption kinetics as the modification significantly blocks pore access. The strong adsorption of PFOA by MIL-96-RHPAM2 was associated with the formation of electrostatic bonds between the anionic carboxylate of PFOA and the amine functionality present in the HPAM backbone. Thus, the strongly held PFOA molecules in the pores of MIL-96-RHPAM2 were not easily desorbed even after eluted with a high ionic strength solvent (500 mM NaCl). Nevertheless, this simple HPAM addition strategy can still chart promising pathways to impart judicious control over adsorbent particle size and crystal shapes while the introduction of amine functionality onto the surface chemistry is simultaneously useful for enhanced PFOA removal from contaminated aqueous systems.</div

Polydimethyl siloxane/MIL-101 Composites for Enhanced Toluene Adsorption in the Presence of Humidity

ABSTRACT Competition between atmospheric moisture and volatile organic compounds (VOCs) for an adsorbent’s sites can significantly impact its VOC removal efficiency. The development of moisture-tolerant adsorbents is essential to address this issue. A vapor phase deposition process using polydimethylsiloxane (PDMS) has created a hydrophobic form of the highly porous, normally hydrophilic, MOF MIL-101. After optimizing the PDMS vapor deposition time and molecular weights, hydrophobicity index calculations verified the improved hydrophobicity of the coated MOF (MIL-PDMS-Sigma-0.25) over its pristine form. The surface area, pore volume as well as single component vapor adsorption of water and toluene capacities were also preserved, resulting to similar performance to MIL-101. Toluene-water vapor co-adsorption experiments were conducted at 40% RH using two toluene concentrations: 0.5% P/P0 and 10% P/P0, mimicking environmental VOC and industrial concentrations, respectively. At 0.5% P/P0, MIL-PDMS-Sigma-0.25 exhibited 60% higher adsorption capacity and twice the rate of toluene capture relative to pristine MIL-101, as well as a 3-fold higher toluene uptake relative to a commercial activated carbon. Preliminary adsorbent regeneration experiments confirm the stability and performance of MIL-PDMS-Sigma-0.25. Using a simple vapor phase modification, this new MOF-composite material offers superior competitive toluene vapor uptake in humidified real-world conditions at VOC concentrations. </div