Browsing by Author "Mecha, Cleophas"

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Advances in metal–organic frameworks as adsorbents, photocatalysts and membranes: a new frontier in water purification
(Springer Nature Link, 2024-08-06) Kiteto, Moses; Vidija, Beryl; Mecha, Cleophas; Mrosso, Register; Chollom, Martha
Water is an essential and irreplaceable necessity for life on earth, sustaining ecosystems, nourishing agriculture and vital for human survival. However, increasing population and industrialization has exacerbated water scarcity and pollution. The Sustainable Development Goal 6 focuses on clean water and sanitation for all; thus, water purification and conservation are key priorities globally. Rampant pollution of water sources by emerging bio-recalcitrant contaminants, often deviant of conventional treatment methods, necessitates new approaches to water treatment. In this regard, metal organic frameworks (MOFs) are gaining prominence and offer solutions in versatile applications due to their unique structural characteristics and tunable properties. This review provides a comprehensive analysis of MOFs, covering their diverse structures, types, synthesis methods and characterization techniques. We explore the application of MOFs in water purification, as adsorbents, photocatalysts, and in membrane separation. The mechanism of operation of MOFs in each application is critically evaluated. The effect of the water treatment methods on energy consumption has also been investigated. We propose that for MOFs application in water treatment to be competitive and sustainable, there is need to address key issues such as synthesis of highly selective MOFs, recovery and reuse, scalability (pilot and industrial scale), and integration with existing water treatment technologies to create synergy. We provide future perspectives on these aspects. ·
Performance Assessment of Novel Soda Ash Adsorbent Biogas Sweetening: Fixed Bed Studies, Adsorption Kinetics, and Adsorption Isotherms
(MDPI, 2025-03-17) Mrosso, Register; Mecha, Cleophas
The reliance on greenhouse gas-emitting unrenewable energy sources such as coal, natural gas, and oil, increases climate change. Transitioning to renewable energy, such as biogas, is crucial to reducing environmental degradation and global warming. The existence of impurities such as hydrogen sulfide hampers the application of biogas. Utilizing natural resources for biogas purification is essential to improve access to clean energy for low-income communities. This study used soda ash derived from Lake Natron in Tanzania as a sorbent for H2S removal. Effects of sorbent mass, flow rate, and particle size were investigated. Experimental data were analyzed using kinetic models, adsorption isotherms, and breakthrough curves. Soda ash of 280 μm particle size, a flow rate of 0.03 m3/h, and a mass of 75 g demonstrated the best performance, achieving an efficiency of 94% in removal and a sorption capacity of 0.02 g per 100 g in five repeated cycles. Freundlich and Jovanovich’s isotherms match the data with n = 0.4 and Kj = 0.003, respectively. Adsorption kinetics were best described by the intra-particle model (kid = 0.14, c = 0.59 mg/g, and R2 = 0.972). A breakthrough analysis indicated that the Yoon–Nelson model provided the best fit with an R2 of 0.95. Soda ash from Lake Natron demonstrated great potential in biogas desulphurization, thus contributing to the production and access to clean energy.