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In the context of processing, utilization and disposal of polylactic acid composites, pyrolysis is a promising technique that addresses this complex synergy. In this work, pyrolysis kinetics and thermodynamic parameters of rice husks/clay fiber-reinforced PLA composites were investigated using Kissinger–Akahira–Sunose (KAS) and Ozawa–Flynn–Wall (OFW) at multiple heating rates (16, 25 and 34 °C min−1). PLA composites’ pyrolysis followed a single-step degradation process. The flammability indices, combustion characteristic indices and mean reactivities obtained for the PLA composites are much lower than those for neat PLA (2.00 × 10−5–2.44 × 10−5% min−1 °C−2, 0.87 × 10−8–1.79 × 10−8% min−2 °C−3 and 6.97 × 10−3–8.04 × 10−3% min−1 °C−1, respectively) which signals that rice husks and clay improved flame retardancy of accruing PLA composites. The average activation energy values obtained from the KAS method were found to be in ranges 137.83–143.99 kJ mol−1 and 124.51–133.95 kJ mol−1 for raw and modified rice husks/clay fiber-reinforced PLA composites, respectively. Corresponding activation energies for raw and modified rice husks/clay fiber-reinforced PLA composites from the OFW method were 141.24–146.92 kJ mol−1 and 128.17–137.50 kJ mol−1, respectively. By comparing activation energy and enthalpy, it was found that the composites were favored to format activated complex due to the low energy barrier.

This paper presents the results of thermal comfort and air quality studies in naturally ventilated residential buildings in Kampala City, Uganda. Questionnaire surveys were used for obtaining occupant subjective thermal sensation votes. Indoor and outdoor measurements for air temperature (Ta), Mean Radiant Temperature (MRT), relative humidity, air speed, and air quality were done for seven buildings over fifteen days during the month of June 2019. DesignBuilder software was used to develop the reference building model and to simulate strategies for improvement of thermal comfort. Survey results showed that 67.8% of the respondents were comfortable with the indoor thermal environment. The indoor air temperature range was 22.7°C - 27.9°C which lies within the 80% acceptable limits set by ASHRAE 55. The measured indoor MRT range was 24.24°C - 25.57°C. Measured levels of indoor PM2.5 were double the World Health Organization recommended limits, while the levels of PM10 were thrice the recommended limits of ASHRAE 62.1. The CO2 concentrations were within the limits set by ASHRAE 62.1. The developed model predicted comfortable indoor conditions with a temperature range of 23.6°C - 25.3°C based on the 80% acceptable limits set by ASHRAE 55. The results show that majority of occupants preferred cooler temperatures during the day which is justified by the use of adaptive measures to obtain thermal comfort.

Background: FDA clinically approved silk for biomedical products in 2013 leading to its increased use. The silk comprises regenerated silk fibroin (SF) rich in β-sheet and with no traces of silk sericin. Removal of silk sericin(degumming) helps to convert silk I into silk II ( β-sheet-rich SF). β-sheets provide silk with biocompatibility, biodegradability, and mechanical properties. Degummed SF is stored in different formats; SF-fibre, SF-solvent, SF-aqueous, and SF powder. Although SF-aqueous is commonly used, it poses challenges in LMICs because of its short shelf life posing the need for new batches. Furthermore, LMICs face limited access to silk solvent alternatives. Aim: To develop a low-cost method for producing a β-sheet packed silk fibroin powder for medical application in LMICs Results: Successful SF dissolution occurred using cheaper solvent alternatives and optimising done for appropriate process. 1 wt% SF dissolution in formic acid: LiCl (FL) occurred at 60oC after 45min while with formic acid: CaCl2 (FC) at 60oC after 55min. UV-Vis analysis showed an increase in SF nanoparticles from e = 1.426 to 2.652 after dialysis indicating that solvent removal purified the solution. FTIR showed the presence of b-sheets in the SF powder at amide I, amide II, and twin amide III bands indicating the presence of silk II.

Rice husks obtained from upland and lowland rice varieties were characterized for composition and content of ash. Each of the rice husk varieties was fired at temperatures of 600, 800 and 900 ℃ for a soaking period of 3 h. The resultant rice husk ash was analyzed for oxide composition and crystallinity using X-ray fluorescence and diffraction techniques, respectively. The generated amorphous ash with the highest silica content, together with metakaolin, aggregate, water, and an alkaline activator was employed to formulate geo-polymer mortar prisms according to the standard EN 196–1. Results showed that the content of ash in the varieties ranged from 18.3% to 28.6% dry basis. Out of this, 89 wt%–96 wt% was silica, with amorphous and crystalline forms of silica obtained at 600 ℃ and 900 ℃, respectively, regardless of the rice variety. However, at 800 ℃, the silica in the generated ash exhibited both amorphous and crystalline forms. The amorphous ash generated at 600 ℃ was used in formulation of geopolymer mortars. Compressive and flexural strength of the formulated mortar after 7 days of curing was 1.5 and 1.3 MPa, respectively. These results reveal the firing protocol to form pozzolanic ash, with potential applications in mortar production.

Activated carbon was synthesized from the New Rice for Africa (NERICA) rice husk variety, followed by its evaluation for removal of humic acid from water. Product values of carbon yield, C and total specific surface area, as,BET were employed as the performance criterion. The best physically activated carbon resulted from char activation at 800 °C for 10 min, leading to as,BET and C×as,BET values of 756.8 and 402.7 m2 g−1, respectively. The best chemically activated carbon resulted from 30 wt% H3PO4 activation of rice husk at 400 °C for 30 min, leading to as,BET and C×as,BET values of 2258.4 and 1058.7 m2 g−1, respectively. Despite the higher as,BET value, the maximum adsorption capacity of the best chemically activated carbon (5.3 mg g−1) was found lower than 8.9 and 27.2 mg g−1 exhibited by the chemically activated carbons prepared at 500 and 600 °C, respectively. The best adsorption conditions included carbon dose of 0.5 g, solution pH of 2, and contact time of 60 min. The adsorption capacity of the prepared activated carbons (27.2 mg g−1) was comparable to that of the commercial activated carbon (30.40 mg g−1). The analyses of the adsorption isotherms and kinetics revealed that the experimental data fits well the Langmuir isotherm model, as well as the pseudo-second-order kinetic model. The latter suggests that the adsorption of humic acid onto the activated carbon was controlled by the chemisorption process. Overall, the study revealed that the NERICA rice husk variety has good prospects for preparation of activated carbons for humic acid adsorption.

It is extremely important to save costs and time while enhancing accuracy in experimentation. However, no study has utilized response surface methodology (RSM) to obtain the effects of independent parameters on properties of PLA/clay/rice husk composites. This study focused on optimization of tensile strength of fiber-reinforced polylactic acid (PLA) composites. RSM using Box-Behnken design (BBD) was used to determine optimum blending parameters of the developed composites. Fiber-reinforced PLA composites were prepared using compression molding. Rice husk fiber and clay filler were used to enhance tensile properties of PLA. Five factors, namely, clay filler loading (1 − 5 wt.%), rice husk fiber loading (10 − 30 wt.%), alkali concentration (0 − 4 wt.%), rice husk variety (K85, K98), and alkali type (NaOH, Mg(OH)2) were varied with 68 individual experiments. Tensile tests were carried out according to ASTM D638 standards. ANOVA results revealed that the quadratic models best fit the tensile strength response, with filler loading and fiber loading factors as the most significant model terms. Interaction effects were more predominant than linear and quadratic effects. The developed models used to determine maximum tensile strengths of PLA/clay/rice husk composites were in close agreement with experimental findings (R2 values of 0.9635, 0.9624, 0.9789, and 0.9731 for NaOH-modified K85 rice husks, Mg(OH)2-modified K85 rice husks, NaOH-modified K98 rice husks, and Mg(OH)2-modified K98 rice husks respectively). Individual optimal conditions were used to predict maximum tensile strengths in each set of developed composites. The predicted tensile strengths were 32.09 MPa, 33.69 MPa, 32.47 MPa, and 32.75 MPa for PLA/clay composites loaded with NaOH-modified K85 rice husks, Mg(OH)2-modified K85 rice husks, NaOH-modified K98 rice husks, and Mg(OH)2-modified K98 rice husks, respectively, which were very close to the obtained experimental values of 31.73 MPa, 33.06 MPa, 32.02 MPa, and 31.86 MPa respectively.

Plastic consumption has continued to grow over the years. Meanwhile, conventional petroleum-based plastics are associated with challenges like environmental unsustainability. As a result, bio-based polymer composites have received much attention in past decades. Polymer matrices can not only be easily be reinforced with agricultural fibers to reduce price, but also improve mechanical and thermal properties. The aim of this study was to investigate the effect of magnesium hydroxide modification on properties of K85 and K98 rice husk varieties in Uganda for their use as reinforcement in polymer composites. Raw rice husks underwent pre-treatment in 4% Mg(OH)2 concentration for 1 h at room temperature. Water absorption, thermogravimetric analysis (TGA), energetic density (ED), and fuel value index (FVI) of rice husks were investigated. Raw husks exhibited higher water absorption capabilities (9.1–11.2%) than modified rice husks (5.6–5.89%). TGA confirmed that alkali modification of rice husks provides a higher resistance to thermal degradation than that of raw husks. Mean reactivity to char residues ratio reduced from 4.3 × 10−4 to 3 × 10−4 °C/min upon modification of K85 rice husks while modification of K98 rice husks led to increasing mean reactivity to char residues ratio by 11.4%. ED sharply reduced upon alkali modification of both K85 and K98 rice husks. FVI of rice husks greatly depended on the amount of ash in the rice husks. As such, K85 husks had higher FVI than K98 husks as the former had lower ash compositions (21.2%). The results suggest that alkali-modified rice husks can be successfully used as reinforcement in polymer composites.

This study was intended to determine the physicomechanical properties of porcelain tiles made from raw materials in Uganda, hitherto not used for the same. The raw materials were mixed in proportions of 40–60% clays, 30–40% feldspar and 10–30% sand, the goal was to identify a mixture with properties that meet the ISO 13006 standards after firing. Test tile samples were formulated at a pressure of 40 MPa and fired from 1050 to 1250 °C in steps of 50 °C. A firing rate of 40 °C per minute and a dwell time of 2 h were applied. The microstructures and phase analysis of the fired samples were studied using a scanning electron microscope (SEM) and X-ray diffractometer (XRD), respectively. The XRD analysis revealed mullite and quartz as crystalline phases present in the fired bodies. At 1150 °C, the SEM micrograph depicted few, short and thick mullite fibers. At 1200 °C, the mullite population increased. The nature of the fibers (long, fine and more interlocking) resulted in an increase in flexural strength. A further rise in temperature had no significant change on the nature of the fibers and flexural strength of the samples. The best properties; flexural strength (33 MPa) and water absorption (0.08%) were exhibited at 1200 °C by samples with 30–40% kaolin, 30–40% feldspar, 20% ball clay and 10% sand. The results indicate that these samples are comparable to the ISO 13006 standards for porcelain tiles which are ≥ 35±2 MPa flexural strength and

Thermal behavior and chemical properties of selected raw and NaOH-pretreated rice husk varieties were investigated. NaOH-pretreatment process involved soaking 5 g rice husk samples in 40 mL of 2%w/v NaOH, shaking (400 rpm) and heating (50 °C) for 3 h. NaOH-pretreated samples were water-washed, oven-dried, and milled for use in the determination of their thermal behavior and surface functional groups. Alkaline wash-water was also analyzed for sugar components. Thermal decomposition temperatures, degradation rates, and the subsequent mass losses varied from one rice husk variety to another. These thermal properties increased after NaOH-pretreatment of the rice husk varieties, reducing their char yields (17.1–20.4% db). These changes mainly had to do with the lignin, hemicellulose, and ash removal from the rice husk varieties, as confirmed by their FTIR analysis, as well as by the sugar composition analysis of their alkaline wash-water. Consequently, the FTIR spectra differed between the raw and NaOH-pretreated rice husk varieties.

Response surface methodology was employed to optimize pyrolysis conditions for production of char with maximum yield, fixed carbon content, and with minimum ash content from Uganda’s New Rice for Africa (NERICA) 1 rice husk variety. The aim was to obtain rice husk char with more suitable properties as an activated carbon precursor. Mathematical models were developed to explain the relationships between the experimental responses and the pyrolysis parameters of temperature (400–600 °C), heating rate (10–25 °C min−1), and heating period (60–120 min). The optimized rice husk char was further characterized for elemental and proximate compositions, thermal behavior, specific surface area, as well as surface functional groups. Results from the analysis of variance (ANOVA) revealed that the quadratic model best fits each of the responses. Pyrolysis temperature had the greatest influence on each of the responses, followed by heating period, and lastly heating rate. Optimum pyrolysis conditions were found to be temperature (406 °C), heating rate (10 °C min−1), and heating period (60 min), resulting in char yield, fixed carbon, and ash contents of 35.26, 55.39, and 35.01% dry basis, respectively. Compared to raw rice husk, the resulting rice husk char was found more suited as activated carbon precursor, due to its enriched carbon content (60.35%) and specific surface area (123.9 m2 g−1). Thermogravimetric analysis of the rice husk char revealed that thermal activation temperatures higher than 400 °C may be required to considerably devolatilize the char, forming a more porous activated carbon.

In recent times, the extinction of fossil fuel resources and emission of harmful pollutants have persuaded the researchers to obtain alternative and renewable fuels. Consequently, in the present experimentation, a ternary fuel blend was acquired and analysed in a modified turbocharged gasoline direct injection (GDI) engine as a feasible alternative to neat fossil fuel. Experiments were carried out using a blend of 8% n-butanol and 8% mass fraction of hydrogen with gasoline fuel at city transport speed mode under stoichiometric and air-fuel ratio of 1.0. Butanol and hydrogen were blended with the gasoline due to their satisfying thermodynamic properties and combustion reactivity. The result shows gradual reduction of particles emitted with n-BH16 by 1.06 × 1011 particles/hr as compared to n-BH00 at 1.89 × 1012 particles/hr. For all fuels, the smallest particles measured by Engine Exhaust Particle Sizer (EEPS) were no longer detectable at phase 2 from 548 s to ~789 s due to low concentrations. However, the gaseous emission of the n-BH16 fueled engine varies with 28 g/kW.h decrement in fuel consumption (FC), while increasing hydrocarbon (HC) emission. As a result, ultra-particles decreased in nucleation mode, which in-turn lead to minimum combustion duration and cylinder gas pressure. Adaptation of n-BH16 fuel blend in light-duty GDI engines might serve as a potential to meet the new particulate emission regulations and improve toxic air contaminant.

In this work, results from characterization of handwashing wastewater from selected stations in Kampala City, Uganda, revealed that handwashing wastewater did not meet permissible international standards for wastewater discharge to the environment. The ratio of BOD5 to COD of ˂ 0.5 implied that handwashing wastewater was not amenable to biological treatment processes. Turbidity of ˃ 50 NTU pointed to the need for a roughing filter prior to slow sand filtration. Subsequently, a handwashing wastewater treatment system consisting of selected particle sizes of silica sand, zeolite, and granular activated carbon as filtration and/or adsorption media was developed and assessed for performance towards amelioration of the physicochemical and biological parameters of the handwashing wastewater. Treated water from the developed wastewater treatment system exhibited a turbidity of 5 NTU, true color of 10 Pt-Co, apparent color of 6 Pt-Co, and TSS of 9 mgL-1, translating to removal efficiencies of up to 98.5%, 98.1%, 99.7%, and 96.9%, respectively. The residual total coliforms and E. coli of 1395 and 1180 CFU(100 mL)-1 respectively, were totally eliminated upon disinfection with 0.5 mL NaOCl (3.5% wt/vol) per liter of treated wastewater. The treated water was thus suitable for recycling for handwashing purpose as opposed to letting handwashing wastewater merely go down the drain. This approach provides a resilient response to COVID-19, where communities faced with water scarcity can treat and recycle handwashing wastewater at the point of washing. It thus enables more people to have the opportunity to practice handwashing, abating the high risks of infection, which could otherwise arise.

Incorporation of agricultural wastes as fillers in fiber-reinforced plastics is gaining momentum in plastics engineering research. In this study, fiber-reinforced polypropylene (PP) with rice and coffee husks as filler material were developed. The effect of alkali (sodium hydroxide) pretreatment of the husks on mechanical and thermal properties of developed PP biocomposites was observed. Filler material loading was varied from 0% to 20% for rice husks and 0% to 10% for coffee husks. A twin-screw extruder was used for compounding the PP matrix with rice and coffee husk filler materials. Tensile strengths and percentage elongation results varied from 27.4 to 37.4 MPa and 2.4% to 70.3% (unmodified coffee husks), 31.1 to 37.4 MPa and 5% to 70.3% (unmodified rice husks), 30.7 to 37.4 MPa and 5.3% to 70.3% (modified coffee husks), and 30.7 to 37.4 MPa and 4.8% to 70.3% (modified rice husks). Young’s modulus ranged between 1656 and 2247.8 MPa for biocomposite PP samples with unmodified filler material. Young’s modulus ranged between 1740 and 2160 MPa after alkali treatment of the filler material. Charpy impact strengths ranged from 1.2 to 4 kJ/m2 and 3.1 to 19.6 kJ/m2 for samples containing unmodified and modified filler material, respectively. Thermogravimetric analysis showed that an increase in filler content resulted into delayed weight loss at high degradation temperatures. The results suggest that these developed fiber-reinforced plastics can be used in applications requiring high thermal stability and good mechanical properties.

In this study, 13 rice husk (RH) varieties from 4 agro-ecological zones in Uganda were characterized, NaOH-pretreated, and evaluated for their potential utilization as precursors for production of bio-oil, ash, char, and activated carbon for selected applications. RH varieties were characterized through particle size analysis, bulk density, proximate and ultimate analyses, specific surface area, pore volume, as well as lignocellulosic and inorganic compositions. Selected RH varieties were subsequently pretreated at NaOH concentrations of 1–4%w/v, using pretreatment ratios of 5 g RH: 40 mL NaOH. Properties varied among RH varieties, suiting them as feedstocks for different applications. Upland rice husk varieties are more suited precursors for production of bio-oil, and activated carbon due to their relatively lower ash content, higher specific surface area, as well as higher volatile matter and fixed carbon contents. Upland rice husks could as well be employed in the preparation of electrodes for electrochemical devices, due to their relatively higher specific surface area. A high ash content (21–32% dry basis) of lowland rice husks presents good prospects for their calcination, since larger amounts of rice husk ash could be obtained, and employed in different applications. Lowland rice husk varieties could also be more suited precursors for production of char for soil amendment, due to their relatively higher ash content, which subsequently increases their char yields. However, alkaline pretreatment of rice husks using 2–4%w/v NaOH can reduce the ash content by as much as 74–93%, depending on the rice husk variety, which paves way for utilizing rice husks with a high ash content in different applications. Aside from ash reduction, the enhanced specific surface area (1.2–1.7 m2 g−1), volatile matter (68–79%db) and fixed carbon (19–24%db) contents of NaOH-pretreated rice husks suggests they are more suited feedstocks than when employed in their raw form, for production of bio-oil, as well as activated carbon.

Adsorption by activated carbon has great potential to improve natural organic matter (NOM) removal from water. However, the high production and regeneration costs limit its wide scale application. ...

This study set out to investigate the properties of husks from ten selected rice varieties in Uganda. Rice samples were collected from one geographical region, identically milled, and the husks ground for analysis. Characterization involved physical, proximate, ultimate, thermal, lignin, hemicellulose and cellulose composition analyses. The samples exhibited bulk density of 88.8–124.3 kg m−3, moisture contents 9.2–11.2%wb, volatile matter contents 58.8–66.4%wb, ash contents 15.9–25.6%db, fixed carbon 14.8–17.8%db, carbon contents 30–34.5%db and carbon to nitrogen ratios of 55:1–87:1. The higher heating values (HHV) ranged between 12.8 and 14.5 MJ/kg, lignin 10.6–13.5%db, hemicelluloses 11.4–20%db and cellulose 31–37%db. The low bulk densities and lignin contents necessitate that the husks should be densified in the presence of binders. The C/N ratios are higher than required for either biogas production or composting. The HHV, ash content and non-concentration of rice husk generation offer prospects for converting rice husk fuel into energy using downdraft gasification for systems capable of 30–500 kW. Results demonstrate that a gasifier generator system of 250 kW operating for 8 h a day for 350 days in year requires 5.8 t of husk per day to produce 700 MW h/year. This results in annual electricity production cost saving of US$98,000 when compared to equivalent diesel plant, with payback period of 2.5 years.

The use of agro-waste in geopolymers, to serve as alternative material to Ordinary Portland Cement (OPC) presents a great potential to the sustainability of the construction sector. Accordingly, this study aimed to optimize the production parameters of geopolymer cement using response surface methodology (RSM) with rice husk ask (RHA), metakaolin (MK) and an alkaline activator as reactants. During the experiment, two-factorial design was run using the central composite design (CCD) to generate 13 combinations of cement (reactant) mixtures with standard sand in order to cast mortar prisms whose compressive strength was evaluated according to BS EN standard. Data analysis on the compressive strength was carried out using MATLAB software. Models for compressive strengths with RHA and MK as predictors were generated for samples cured at 7 and 14 days. Result showed that the overall R2 of these models were 0.8951 and 0.63, respectively. The β values for the multiple linear model for the strength at 7 days of curing was

Ten formulations of triaxial porcelain composed from 30-60% clay, 20-45% feldspar and 20-25% sand, were prepared from raw materials sourced from Ugandan deposits. Specimens were made using the plas ...

Kaolin, ball clay, feldspar, and sand were collected from deposits in Uganda, milled and sieved to particle sizes of 45, 45, 53, and 25 μm, respectively. Three porcelain bodies and five glazes were formulated from them. The glazes were applied on porcelain specimens and subsequently evaluated for their effects on properties of porcelain samples. The formulated specimens were investigated using dilatometry, Steger test, FEG-SEM, XRD, 4-point bending, dielectric strength, and fracture toughness tests. A porcelain specimen consisting of 68% SiO2, 19% Al2O3, 4.7% K2O, and a glaze RO:0.57Al2O3:4.86SiO2 exhibited MOR of 105 MPa with Weibull modulus of 5.6 and a dielectric strength of 18 kV/mm upon firing at a heating rate of 6 °C/min to 1250 °C and holding for 2 h. The microstructure of the high-strength specimen exhibited round mullite needles, quartz, and glass. Holding samples for 2 h at peak temperature resulted in a 22% increase in MOR compared to 1 h holding. Glazing further improved strength by 67% for the best sample. Compressive stresses in glaze contributed to the strengthening effect. The dielectric and mechanical strength values obtained qualify the formulated sample for application in electrical insulation.

The resources for vibrant technological research institutions in Uganda do exist in form of recyclable machine components, government funding, skilled manpower, demand for low cost technological solutions to existing problems, a large and youthful population, and Internet information resources. This paper explores a process to conduct research and orient young engineering students to conduct product research and development for machine automation as it addresses the unique challenges of a limited budget, a scanty resource market, and an inefficient supply chain and limited existing automation expertise.

Porcelains are vitrified and fine grained ceramic whitewares, used either glazed or unglazed. Electrical porcelains are widely used as insulators in electrical power transmission systems due to the high stability of their electrical, mechanical and thermal properties in the presence of harsh environments. They are primarily composed of clay, feldspar and a filler material, usually quartz or alumina. These materials are widely available in Uganda, but little research has been carried out on them in relation to technical porcelains let alone their use for the same. Based on the abundance of the requisite materials and the corresponding demand for insulation materials, this paper reviews the current and traditional methods of manufacturing electrical porcelains. The major objective is to review the processes for production of electric porcelains from the basic raw materials including material characterisation methods.