Browsing by Author "Rahman, Sazedur"

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Agar from Red Algae (Gracilaria tenuistipitata) as a Valuable Biopolymer: Extraction and Characterization
(Research and Development Wing, MIST, 2025-12-30) Afrin Rimpy, Fawzia; Hoque, Md Enamul; Farsheed Mahmud, Quazi; Nowroj, Itmam; Rahman, Sazedur; El-Bialy, Tarek; Ali, M. Azam
Agar, a natural biopolymer extracted from red algae, holds immense potential for revolutionizing healthcare, including biomedical engineering. This study explores the extraction feasibility of agar from red algae (Gracilaria tenuistipitata) abundantly available in the coastal area of Cox’s Bazar, Bangladesh. Five extraction methods were investigated, including a control group and treatments with water and NaOH solutions at concentrations of 2%, 4%, and 6%. The extraction of agar from algae was characterized through Fourier-transform infrared spectroscopy (FTIR), gel strength testing, melting and gelling temperature assessments, pH value measurement, and sulfate content analysis. Statistical analysis, including ANOVA and Tukey's HSD test, was utilized to assess the impact of the pre-treatment process on the yield and characteristics of agar. The test revealed significant variations among the different extraction methods (p < 0.05), highlighting the crucial role that pre-treatment plays in influencing agar yield and its physicochemical properties. While the control group achieved the highest agar yield (16.67 ± 1.44%), the 2% NaOH pre-treatment showed superior physicochemical attributes. Specifically, this treatment resulted in agar with optimal gel strength (3.25 ± 0.67 N/cm²), melting temperature (84.20 ± 0.80°C), gelling temperature (36.13 ± 1.21°C), pH (7.49 ± 0.26), and sulfate content (3.67 ± 0.58 mg/L), all of which are comparable to those of commercial agar. This preliminary study suggests that the red algae (Gracilaria tenuistipitata) found in Bangladesh is a promising source of agar for wider applications, including biomedical engineering. The agar extracted from abundant local sources in this country could unlock its potential for advancing healthcare solutions and sustainable national economic growth.
Optimum material distributions for minimizing stresses in a rotating functionally graded material circular disk
(Department of Mechanical Engineering, 2022-07-25) Rahman, Sazedur; Ali, Dr. Md. Afsar
Functionally graded materials (FGMs) are an advanced type of composite material having varying material distribution from one to another surface, for which these FGMs become nonhomogeneous in the case of both material characteristics and microstructures. The present study considers a thin circular rotating disk of functionally graded material with a concentric circular hole. The disk is subjected to a thermal load and an inertial force due to the rotation of the disk. The analysis is carried out under plane stress condition. Material properties of the FGM disk are assumed to vary along the radial direction only. In this study, an optimization model is developed for evaluating optimum material distributions in a rotating FGM circular disk corresponding to minimum/prescribed stresses. Further, a mathematical model of direct problem is also developed to calculate stresses and displacements induced in the FGM disk corresponding to a prescribed material distribution. Based on two-dimensional thermoelasticity theories, the problem is formulated in terms of a second-order differential equation. Since a close-form solution of the differential equation is not possible, a standard finite element approach is adopted for the solution of the optimization and direct problems. The models developed in the present study are validated by comparing the results with those available in literature. To demonstrate the developed models, numerical results are obtained for an FGM disk consisting of Al and Al_2 O_3. From the numerical results of direct problem, it is found that the stresses are greatly influenced by material distribution. The results of optimization model ensure that an FGM disk can be designed with optimum material distribution realizing the minimum/prescribed stress profile in the disk. It is also revealed that the stress profile, temperature field, angular speed, and radial thickness of the disk all have significant effects on optimum material distribution of the FGM disk.
Study of the Applicability of Chemical Precipitation and Electrocoagulation Method for Chromium Recovery in CETP at Savar Leather Industrial Park
(Department of Mechanical and Production Engineering (MPE),Islamic University of Technology(IUT), Board Bazar, Gazipur, Bangladesh, 2021-03-30) Rahman, Sazedur; Karim, Tasdee Al; Khan, Munabbih Hasan Nadid
When we visited tanneries at Savar Tannery Industrial Estate in order to gain a deeper understanding of the leather tanning industry of Bangladesh, we realized that the lack of environmental compliance certification is holding the industry back from further development. That is why we decided to work on one of the leading concerns, the release of chromium to the environment. We conducted a thorough search for applicable methods, conducted feasibility studies on the selected topics by analyzing the input water conditions and finally calculated the expected method outcome in regard of collected data. We tried to collect up to date information relating to water conditions and cost analysis. We predicted Chemical Precipitation to be at least 99.5% efficient in removing chromium from the wastewater. The efficiency of CP depends on selected coagulant and pH of inlet water. The amount of chromium in outlet water comes within the allowable limit after one treatment. Electrocoagulation on the other hand gives vastly different efficiencies for different electrodes. Whichever electrode we choose; it takes a minimum of two treatments to bring the chromium content within the allowable limit. We found that aluminum and iron both can be used as electrodes in a EC unit at Savar CETP successfully. Our study gives the concerned authority a reference if they choose to add a chromium recovery unit to the existing CETP. It is of great importance that the industry takes necessary steps to ensure environmental compliance and our study might help achieve that. We could not conduct practical experiments due to the pandemic situation. So, we hope others will build on our research and carry out the experiments using the tannery waste water from Savar TIE. Our study 2 indicates that a chromium recovery unit in conjunction to the Savar CETP will be enough eliminate concerns regarding chromium pollution.