Post graduate dissertations (Theses) of Chemical Engineering (Ch.E) http://lib.buet.ac.bd;localhosthttp://:8080/xmlui/handle/123456789/1378 2026-11-10T14:53:00Z 2026-11-10T14:53:00Z Zonaed Sakib http://lib.buet.ac.bd;localhosthttp://:8080/xmlui/handle/123456789/7400 2026-11-08T04:38:21Z 2025-07-16T00:00:00Z

Life cycle assessment of end-of-life management of multilayer plastic waste Dr. Kazi Bayzid Kabir; Zonaed Sakib; 0423022125; 668.4192/ZON/2025 In recent times, multilayer plastic packaging has been in high demand, as it provides better preservation and a prolonged shelf life for various packaging commodities. How-ever, its complicated structure poses a challenge to the existing recycling system and often ends up in a landfill or is incinerated. Unlike the current management system of MLP, the selective dissolution process represents a paradigm shift, as it enables the re-cycling of MLP with high material recovery and at a reasonable cost. Besides the bene-fits it offers, it is important to assess the environmental footprint of this process to ensure sustainability. Therefore, this study conducts a comparative life cycle assessment be-tween the selective dissolution process and the existing end-of-life management tech-niques (landfilling, incineration) to evaluate whether itbenefits to the existing practices. This study defines 1000 kg post-consumer plastic waste as a functional unit. It assumes 50% single-layer PE is mixed with 50% two-layer MLP (76% PE & 24% PET). This study assesses environmental impact in nine impact categories (fine particulate matter formation, freshwater ecotoxicity, marine ecotoxicity, global warming, human carcino-genic toxicity, human non-carcinogenic toxicity, terrestrial acidification, fossil resource scarcity and water consumption) using the ReCiPe Midpoint (E) impact assessment method. The outcome of this study finds the landfilling of plastic to be the least favora-ble, and the selective dissolution process to be the most favorable in terms of environ-mental sustainability among the alternatives. For example, the freshwater ecotoxicity impact of landfilling is 58.96 kg 1,4-DCB, while for selective dissolution the impact is -64.62 kg 1,4-DCB. Incineration of plastic waste with energy recovery is environmental-ly friendly in all impact assessment categories, except for the global warming impact. The global warming impact of incineration is 297.22 kg CO2 eq. A hotspot analysis of the selective dissolution process identifies that the steam energy required for the reboiler in the distillation column (78%-98%), pretreatment of multilayer film (9%-12%), and the solvent consumed (3%-6%) are the significant contributors to the total impact. Finally, a sensitivity analysis of the selective dissolution process has been performed, varying four key input parameters-5% lower reboiler duty, 95% solvent recovery, natural gas heating, and a 70:30 PE: PET ratio. This analysis shows that switching to natural gas for heating reduces the effect by around 70%-80% for every impact category.

2025-07-16T00:00:00Z Fahim Ahmed, Md. http://lib.buet.ac.bd;localhosthttp://:8080/xmlui/handle/123456789/7399 2026-11-02T06:53:44Z 2025-07-12T00:00:00Z

Development of a novel biocompatible cleaning approach to improve reusability of the hemodialyzer Ahmed, Dr. Shoeb; Fahim Ahmed, Md.; 0423022134; 660.285/FAH/2025 In Bangladesh, the high cost of hemodialysis limits treatment access for many patients with end-stage kidney disease (ESKD), which affects up to 22% of the population. Although single-use dialyzers are intended for one-time application, they are often reused up to three times in dialysis centers around Bangladesh to reduce expenses. However, these reused dialyzers are typically cleaned using protocols designed for reusable models, without validation of their safety or performance. This practice raises concerns about dialysis efficacy and patient outcomes. This study aimed to develop an effective dedicated regeneration method for single-use dialyzers, with the goal of extending their usability for at least five dialysis sessions. Eighteen cleaning protocols were evaluated by varying chemical compositions and mechanical flow parameters. Dialyzer performance was assessed based on solute clearance, ultrafiltration capacity, membrane integrity, and albumin retention. Two methods successfully regenerated thrice-used dialyzers. One used a two-step backwash with an alkaline solution followed by Hemocess, a medical-grade cleaning solution. The other applied a two-step backwash with diluted hydrogen peroxide followed by 50% diluted Hemocess. Both achieved over 90% clearance for low-molecular-weight solutes (urea, creatinine, uric acid) and over 75% for vitamin B-12, a middle-molecular-weight marker. Ultrafiltration coefficients remained above 70% of the original, and albumin retention exceeded 92%, surpassing even new dialyzers. Mechanical and SEM analyses confirmed structural integrity and acceptable pore morphology after cleaning. Among the two, hydrogen peroxide-based method offered additional advantages by using clinically approved reagents while reducing chemical consumption by 50%. It is therefore recommended as a cost-effective and safe reprocessing method to extend single-use dialyzer life up to five times, significantly lowering treatment costs and medical waste in resource limited regions.

2025-07-12T00:00:00Z Mohaimenol Islam, Md. http://lib.buet.ac.bd;localhosthttp://:8080/xmlui/handle/123456789/7217 2025-12-08T05:04:38Z 2025-02-25T00:00:00Z

Development of a decision-making framework incorporating safety, environment, and economic criteria for sustainable process design Sultana Razia, Dr. Syeda; Mohaimenol Islam, Md.; 0423022140; 660/MOH/2025 Increasing global legal requirements and rising environmental costs require the chemical industries to minimize their ecological footprint and enhance safety while ensuring economic viability and stability. Conventional sustainability approaches often address these factors separately, leading to suboptimal decision-making in the process design. Currently, there is a growing awareness of simultaneous consideration of all sustainability approaches at the early stage of process design. The present study introduced a unified multi-criteria decision-making (MCDM) framework to identify the most sustainable process routes for the chemical manufacturing process by integrating three key indicators, i.e., safety, environment, and techno-economics. The safety indicator was developed based on chemical hazards as well as equipment safety. Change in Green Degree a measure of greenhouse gas emission was used to determine environmental impact and payback period on the investment was used as economic indicator. The applicability of the proposed framework was demonstrated through a case study of ‘Acetone Production’ by analyzing three acetone production processes with distinct reaction routes, namely, the IPA route, the Cumene Oxidation route, and the Propylene Oxidation route. Each process route was simulated using Aspen HYSYS and the relevant sustainability metrics were computed based on collected data. The MCDM framework was then employed, particularly utilizing The Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method to evaluate and rank the process alternatives. Acetone production through propylene oxidation emerges as the most sustainable process alternative, with a relative closeness score (RCS) of 0.92, whereas the cumene oxidation route is marked as the least favorable process alternative (RCS 0.01). The IPA dehydrogenation route has a moderate 0.64 RCS.

2025-02-25T00:00:00Z Debanjon Sarker http://lib.buet.ac.bd;localhosthttp://:8080/xmlui/handle/123456789/7210 2025-12-07T04:00:35Z 2024-11-30T00:00:00Z

Development of a novel photocatalyst for the degradation of antibiotics in aqueous medium Shahinoor Islam, Dr. Md.; Debanjon Sarker; 0422022049F; 660.2844/DEB/2024 Promising active pharmaceuticals like sulfamethoxazole (SFX), ciprofloxacin (CIP), and metronidazole (MNZ) are bio-persistent and toxic to nature. TiO2 based photocatalysis has been widely utilized in the last few decades to degrade persistent pollutants. Coupling TiO2 with transition metals/metal oxides (Ni, α-Fe2O3) may enhance the efficiency of TiO2. Therefore, this study aims to synthesize single (TiO2, NiO, α-Fe2O3), and composite (α-Fe2O3-TiO2, Ni-TiO2, Ni-α-Fe2O3, Ni-TiO2-α-Fe2O3) photocatalyst to evaluate performance in SFX, MNZ, and CIP degradation with optimization, and kinetics study of superior catalyst. The single and composites catalysts were synthesized by sol-gel, and impregnation method respectively. Characterization was done employing FTIR, SEM, EDS, and XRD. FTIR, validates the presence of respective M-O, and M-O-M bonds α-Fe2O3 (550 cm-1), NiO (435 cm-1), TiO2 (400−800 cm-1). SEM, and EDX show significant modification of the surface morphology, and elemental composition in the composite materials. XRD analysis depicted characteristics peak, and distinct crystallite size of the catalysts. pHpzc analysis shows the synthesized catalysts surface charge between 6.55-7.71. Photodegradation efficiencies were evaluated by degrading MNZ, SFX, and CIP under 21 mW/cm2 UV-254 nm irradiation in a batch reactor. NiO, α-Fe2O3, TiO2, Ni-TiO2, α-Fe2O3-TiO2, α-Fe2O3-Ni, and Ni-TiO2-α-Fe2O3 degrade about 51%, 56%, 59%, 61%, 63%, 64%, and 71% SFX respectively. Accordingly, Ni-TiO2-α-Fe2O3 shows superior photodegradation over CIP (64%), and MNZ (63%). From XRD analysis slightly deviated diffraction peak of both α-Fe2O3 (33.31°), and TiO2 (25.32°) with decreased peak intensity was observed in Ni-TiO2-α-Fe2O3. The average crystallite size decreases from 15.03 nm (TiO2), 45.74 nm (α-Fe2O3), 10.54 nm (NiO), to 9.16 nm in Ni-TiO2-α-Fe2O3. This may lead to the formation of heterojunction and defects in crystal lattice causing decrease of band gap (1.78 eV) and improves of photocatalytic property. Optimization of the reactor performance revealed that Ni-TiO2-α-Fe2O3 performs better at pH 3 for MNZ, and SFX and at pH 9 for CIP. The optimum antibiotic concentration, catalyst dosage, and H2O2 concentration were found to be 10 ppm, 0.25 g/L, and 50 ppm respectively. The kinetic study shows that pseudo-1st order reaction kinetics fits with experimental data. The competitive degradation of SFX, MNZ, and CIP mixture has shown comparatively lower degradation efficiency than single antibiotic. This research establishes Ni-TiO2-α-Fe2O3 composite as a promising photocatalyst for the degradation of persistent pollutant.

2024-11-30T00:00:00Z