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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.

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.

The search for alternatives to fossil-based commercial activated carbon (AC) continues to reveal new eco-friendly potential precursors, among which is agricultural waste. The key research aspect in all these endeavors is empirical ascertainment of the core properties of the resultant AC to suit a particular purpose. These properties include: yield, surface area, pore volume, and the active surface groups. It is therefore pertinent to have process conditions controlled and tailored towards these properties for the required resultant AC. Pre-leaching cassava peels with NaOH followed by KOH activation and carbonization at holding temperatures (780 °C) above the melting point of K (760 °C) yielded mesoporous activated carbon with the highest surface area ever reported for cassava peel-based AC. The carbonization temperatures were between 480 and 780 °C in an activation–carbonization stepwise process using KOH as the activator at a KOH:peel ratio of 5:2 (mass basis). A 42% maximum yield of AC was realized along with a total pore volume of 0.756 cm3g−1 and BET surface area of 1684 m2g−1. The AC was dominantly microporous for carbonization temperatures below 780 °C, but a remarkable increase in mesopore volume (0.471 cm3g−1) relative to the micropore volume (0.281 cm3g−1) was observed at 780 °C. The Fourier transform infrared (FTIR) spectroscopy for the pre-treated cassava peels showed distortion in the C–H bonding depicting possible elaboration of more lignin from cellulose disruption by NaOH. A carboxylate stretch was also observed owing to the reaction of Na+ ions with the carboxyl group in the raw peels. FTIR showed possible absorption bands for the AC between 1425 and 1712 cm−1 wave numbers. Besides the botanical qualities of the cassava peel genotype used, pre-leaching the peels and also increasing holding activation temperature above the boiling point of potassium enabled the modified process of producing highly porous AC from cassava peel. The scanning electron microscope (SEM) and transmission electron microscope (TEM) imaging showed well-developed hexagonal pores in the resultant AC and intercalated K profile in the carbon matrices, respectively.

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.

Multiple factors are responsible for the properties of developed briquettes. The effect of the agricultural residue type in determining resulting properties of developed briquettes is seldom elucidated. Agricultural residue biochars from groundnut shells, sugarcane bagasse, coffee husks, and rice husks were used in developing carbonized briquettes using the low-cost compression method. In this study, a general factorial multi-level categorical experimental design method was used to investigate the effects and interactions of the carbonized agricultural type, binder type, and binder amount on physical properties and calorific values of developed briquettes. Statistically significant models (p

Domestic energy sources in sub-Saharan Africa are still mainly comprised of firewood and charcoal. One of the main challenges affecting the uptake of carbonized briquettes is their inefficiency in transferring heat. In this study bio-composite briquettes were developed from rice husks, coffee husks and groundnut shells, in varying proportions. The briquettes were developed under low pressure (≤7 MPa) after carbonization and application of starch binder. Thermal properties of the developed bio-composite briquettes were determined by using a bomb calorimeter and thermogravimetric analysis to determine calorific values and physical properties, respectively. Drop strength tests and particle density determinations were performed to study the mechanical strength and integrity of the developed briquettes. The water-boiling test was used to determine time taken to boil 1 L of water. Fourier’s Law of heat conduction was used to investigate heat transfer rates across the briquettes for conditions of binder/binder-less bonding conditions. Calorific values for the developed briquettes ranged between 16.6 MJ/kg and 22 MJ/kg. Results for drop strength for the developed composite briquettes were all above 86%, indicating satisfactory characteristics. Bio-composite briquettes developed using coffee and rice husks bio-chars took less time to boil water compared to all the other bio-composite briquette combinations. Particle densities ranged between 430 kg/m3 and 580 kg/m3. Heat transfer was enhanced when no binder was present and coffee and rice husks were sequentially placed in the briquette composition. This study showed the advantages of producing bio-char bio-composite briquettes over single constituent briquettes. Bio-composite carbonized briquettes produced from rice husks, coffee husks and groundnut shells are a suitable and sustainable alternative to firewood and charcoal use in sub-Saharan Africa.

For a material to be used as energy, understanding its combustion behavior is crucial. Biomass is one such material that is increasingly gaining traction. Biomass may be utilized by direct combustion or transformation into fluid or solid biomass-based fuels. In this work, slow pyrolysis of groundnut shells, bagasse, rice husks and coffee husks was done to produce briquettes with cassava starch binder. Thermogravimetric analysis (TGA) was carried out using an Eltra Thermostep thermogravimetric analyzer. The samples were heated from ambient to 920 deg. Celsius. This analysis provided combustion explanations in terms of the weight loss, burning rates, peak temperatures, char residues and mean reactivity. TGA results showed that binder inclusion reduced the amount of fixed carbon present in the developed briquettes, thus slightly reducing their calorific values. Rice husks briquettes yielded the least weight loss (20.9% and 24.7% for 30g and 50g binder incorporations respectively) compared to others, owing to former’s higher ash contents. Increase in binder contents reduced the amount of char residues, caused by reducing ash contents in the developed briquettes. Peak temperatures and char residues generally increased with increasing binder content. This signifies increasing thermal stabilities of the developed briquettes. Highest char residues were obtained by briquettes developed with rice husks at 30g binder while briquettes developed with bagasse briquettes developed at 50g binder had the least char residues. The highest mean reactivities were obtained in briquettes developed from bagasse and coffee husks while briquettes developed from rice husks had lowest mean reactivities. Briquettes developed in this study showed sufficient combustion properties suitable to provide energy for domestic and industrial applications.

Firewood and charcoal are relatively abundant in sub-Saharan Africa and have low cost of production, hence their continued dominance as an energy source. However, very few studies have documented any information on pyrolysis kinetics and combustion performance characteristics for firewood and charcoal in sub-Saharan Africa. This information is needed to develop environmentally friendly combustion reactors suitable for these firewood species and charcoal as well as guide policy decisions on fuels appropriation for different purposes. Therefore, this study seeks to identify the thermo-chemical conversion characteristics of five local commonly used firewood species, namely Dichrostachys cinerea, Morus lactea, Piliostigma thonningii, Combretum molle, and Albizia grandibracteata and their charcoals produced after slow pyrolysis. Firewood was characterized by a fibrous network, while charcoal showed a dentritic network structure with micropores. The pyrolysis process resulted in a significant increase in lignification in the process of charcoal formation with highest lignin values recorded for Albizia grandibracteata. The lowest rate of lignification was observed for Morus lactea firewood species. Peak temperatures for firewood species and charcoal ranged between 515.4–621.7 °C and 741.6–785.9 °C. Activation energy of Morus lactea was 16.3 kJ/mol, which was the lowest among firewood species. Activation energy of Piliostigma thonningii was the highest among firewood species at 29.5 kJ/mol. For charcoal, activation energy was highest for both Morus lactea and Dichrostachys cinerea (35.9 kJ/mol). Piliostigma thonningii charcoal had the lowest combustion performance results with maximum burning rate at 0.68%/min, flammability index at 0.18 × 10−5%/min °C, and combustion characteristic index at 0.02 × 10−8%/min2°C3.

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.

The main source of fuel for domestic cooking applications in Sub-Saharan Africa is either locally available firewood species or charcoal produced by slow pyrolysis of these species. However, very few studies exist that characterize and quantify physical properties, burning rates, peak temperatures, and calorific values of typical firewood species and resulting charcoal fuels produced by slow pyrolysis. This study evaluated the mechanical and thermal properties of firewood and charcoal from five tree species namely: Dichrostachys cinerea, Morus Lactea, Piliostigma thonningii, Combretum molle, and Albizia grandibracteata. Characterization was done by scanning electron microscopy, thermogravimetric analysis, bomb calorimetry, Fourier transform infrared spectroscopy, bulk density measurements, and durability, water boiling and absorption tests. SEM images showed the development of macropores on charcoal after slow pyrolysis. Peak temperatures during firewood and charcoal combustion ranged between 515.5–621.8 °C and 741.6–785.9 °C, respectively. Maximum flame temperatures ranged between 786.9–870.8 °C for firewood and 634.4–737.3 °C for charcoal. Bulk densities and calorific values of charcoal species were higher than those for firewood species. Drop strengths for firewood were all 100% while for charcoal were between 93.7 and 100%. Water boiling tests indicated that firewood fuel performed better that charcoal fuel for low amounts of water due to higher maximum flame temperatures obtained during combustion of firewood.

Effects of alkaline surface modification and carbonization on biochemical properties of selected rice and coffee husk varieties in Uganda were studied. Alkali pre-treatment was done by washing the ...

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.

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.

Activated Carbon (AC) remains a key material for both industrial and domestic applications. The aim of this work was to characterize the peels of predominant cassava varieties grown in Uganda for production of AC. The selected varieties were; NASE 1, NASE 3, NASE 14, NASE 19, NAROCAS 1, and NAROCAS 2 due to more guaranteed raw material availability and potential for sustainability for AC production. The peels were characterized through proximate and ultimate analysis, bulk density, water-binding capacity, and lignocellulosic composition. Pre-leaching was done using NaOH of 1–4% w/v concentrations on two representative peel varieties. The dry basis (db) values of ash content, volatile matter and fixed carbon percentages of the peel varieties ranged from 1.93 to 4.36%, 77.93–81.93% and 13.78–15.34%, respectively. The ash content values were below 5% and hence may not necessitate pre-leaching to remove any ash forming agents. The dry basis char yield from the peels at 400 ​°C is in the range of 27.76–31.09%, qualifying them for AC production. The lignin, cellulose and hemicellulose compositions are in the ranges 9.0–16.0%, 5.5–15.0%, and 41.0–65.0%, respectively. The varieties with higher cellulosic content may be more suitable for highly porous AC production. Pre-leaching showed no remarkable reduction in the ash content but increased the volatile matte and char yield at low NaOH concentrations. Predominant Ugandan cassava peel varieties have potential for production of AC with alkaline pretreatment required in applications where high char yields are required.

Globally, a high prevalence of multi-drug-resistant (MDR) bacteria, mostly methicillin-resistant Staphylococcus aureus and carbapenem-resistant Enterobacteriaceae, has been reported. Infections caused by such bacteria are expensive and hard to treat due to reduced efficient treatment alternatives. Centered on the current rate of antibiotics production and approvals, it is anticipated that by 2050 up to 10 million people could die annually due to MDR pathogens. To this effect, alternative strategies such as the use of nanotechnology to formulate nanobactericidal agents are being explored. This systematic review addresses the recent approaches, future prospects, and challenges of nanotechnological solutions for controlling transmission and emergence of antibiotic resistance. A comprehensive literature search of PubMed and BioMed Central databases from June 2018 to January 2019 was performed. The search keywords used were “use of nanotechnology to control antibiotic resistance” to extract articles published only in English encompassing all research papers regardless of the year of publication. PubMed and BioMed Central databases literature exploration generated 166 articles of which 49 full-text research articles met the inclusion guidelines. Of the included articles, 44.9%, 30.6%, and 24.5% reported the use of inorganic, hybrid, and organic nanoparticles, respectively, as bactericidal agents or carriers/enhancers of bactericidal agents. Owing to the ever-increasing prevalence of antimicrobial resistance to old and newly synthesized drugs, alternative approaches such as nanotechnology are highly commendable. This is supported by in vitro, ex vivo, and in vivo studies assessed in this review as they reported high bactericide efficacies of organic, inorganic, and hybrid nanoparticles.

The goal of this study was to develop briquettes from coffee and rice husks agricultural wastes as sustainable fuel sources for domestic cooking applications. Clay and cassava starch were used as binders. Physical properties of the coffee husks and rice husks as well as the developed briquettes were determined using Thermogravimetric analysis. Higher heating value (HHV) results were determined using bomb calorimetry. Drop test method was used to determine the mechanical and storage integrity of the developed briquettes. The results showed that the type of binder used in the development of the briquettes significantly affected both their physical properties and calorific values. Average higher heating values for briquettes developed with cassava starch binder ranged from 21.9 to 23.0 MJ/kg for coffee husks and 15.9–16.6 MJ/kg for rice husks. For coffee and rice husk briquettes developed with clay binder, average higher heating values ranged from 13.0 to 19.5 MJ/kg and 9.5–13.8 MJ/kg, respectively. Generally, cassava starch binder imparted higher drop strengths (over 95%) onto the briquettes than clay binder material. The characteristics were influenced by the physical properties of the raw biomass material as well as the high SiO2 ash in the clay binder.

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. ...

In this study groundnut shells and bagasse briquettes from agricultural wastes were developed with cassava and wheat starch binders using low pressure and high pressure techniques. In the low pressure technique, briquettes were produced after carbonization of groundnut shells and bagasse. The resulting bio-char was mixed with 30, 50, 70 and 90 g of cassava and wheat flour starch binder for each 1000 g of groundnut shells and bagasse bio-char. Groundnut shell briquettes were also developed under high pressure (230 MPa) using groundnut shells (1000 g) without a binder, groundnut shells (1000 g) with cassava flour starch binder (250 g) and groundnut shells with wheat flour starch binder (250 g). Thermo-physical properties of the briquettes were determined using thermo-gravimetric analysis. A Bomb calorimeter was used to determine the higher heating values of the briquettes. Thermal characteristics were determined by observing the flame temperature during combustion. The mechanical integrity of the briquettes was determined using the drop test method. The higher heating values for groundnut shell and bagasse briquettes developed using low pressure techniques were between 21 and 23 MJ/kg for both cassava and wheat starch binders. The results were all above the 16 MJ/kg average recorded for non-carbonized groundnut shell briquettes developed under high pressure.

Innovative value addition to agricultural products and their bi-products is being sought towards achieving prosperity in Africa. This review compiles the work conducted by various researchers over the last few decades on the use of cassava peels to produce activated carbon, while conditions for optimal production and salient economic considerations are discussed. In this review, the value chain of cassava peel AC has been elucidated starting from the cassava tuber, the source of the raw material, to the disposal of spent cassava peel activated carbon. It focuses more on the process quality, economic, and environmental aspects at each stage. The paper also presents a techno-economic analysis of a cassava peel based AC manufacturing plant of 1 t/day capacity with a 35% return on investment, net present value of $ 648,331 over 16 years investment, and a pay-back period of approximately 2 years.

An extensive review on the characteristics of diamond-like carbon (DLC), doped DLC and DLC multilayer films deposited on rubber substrates is presented. Typical deposition technologies used for depositing DLC films on rubber substrates are mentioned. Methods used in characterising DLC films deposited on rubber substrates are presented. The review shows that no film property or characteristic has been discussed in more than 14 publications to-date. Therefore, further research is required on characterisation of chemical composition, chemical bonding, surface roughness, hydrophobicity, surface energy, adhesion, flexibility, electrical resistance, hardness and wear. Raman spectroscopy analysis is a powerful non-destructive method for determining the chemical bonding, intensity ratios, peak positions, multi-wave length analysis, residual stress analysis and bonded hydrogen analysis in the films. Different studies have reported different values for these Raman parameters. The surface morphology for DLC ...

The flexibility and frictional behaviour of DLC and Si-DLC films with and without Si–C interlayers were studied in this paper. The films were deposited onto nitrile rubber using a combination of a closed field unbalanced magnetron sputtering ion plating system and plasma enhanced chemical vapour deposition in Ar/C 4 H 10 plasma. Flex tests were used to determine the film flexibility. The frictional and wear characteristics of these films were investigated using a pin-on-disc tribometer for applied loads of 1 N and 5 N under conditions of dry and wet sliding with a stainless steel counterpart. The induced temperature rise during tribo-testing was used to determine the effect of frictional heating on the frictional behaviour of these films. Lateral cracking was observed for DLC film and Si-DLC film with and without Si–C interlayer after flex tests. More de-bonding was observed for Si-DLC film. The films generally showed excellent frictional results for dry sliding under a normal load of 1 N and for wet sliding under normal loads of 1 N and 5 N. The improved film flexibility was related to enhanced adhesion as a result of the Si–C interlayer. Frictional heating was significant for tribo-testing performed under a normal load of 5 N under dry sliding conditions. The induced surface temperature suggests that the influence of frictional heating of the structural transformation taking place within the wear track is minimal compared to the formation of wear debris.

In this study a hybrid diamond-like carbon (DLC) and silicon doped diamond-like carbon (Si-DLC), with and without Si–C interlayers, were deposited onto nitrile rubber substrates. The deposition was done in a closed field unbalanced magnetron sputtering ion plating (CFUBMSIP) rig in Ar/C4H10 plasma. A combination of visible (488 nm) and ultra-violet (UV; 325 nm) Raman analysis was used to determine the G-peak dispersion of the films. Raman analysis was also used to estimate the hydrogen concentration and residual stress in the films. Calculated hydrogen values for all of the films were between 26 and 31%. The residual stress estimates of the films indicated that the inclusion of Si dopant and Si–C interlayers reduced compressive stress in these films. Raman analysis of the wear tracks indicated an increase in the G-peak position which could indicate that graphitization occurred during pin-on-disc experiments.

Thin films of hydrogenated diamond-like carbon (DLC) and silicon (Si) doped diamond-like carbon (Si-DLC) have been deposited on acrylonitrile butadiene rubber (NBR) using a closed field unbalanced magnetron sputtering ion plating system. A sputter cleaning process was integrated into the deposition process so as to reduce the likelihood of re-contamination between the cleaning and deposition stages. The deposited coatings showed excellent adherence with an adhesion rating of 4 A for films with a Si-C interlayer. The composite micro-hardness was highest for DLC films at 15.5 GPa for indentation load of 147.1 mN using a Vickers micro-hardness tester. Tribological tests undertaken under normal load of 5 N using a pin-on-disc tribometer for all of the samples of DLC and Si-DLC films, with and without Si-C interlayer, show a friction increase between 0.25 and 0.4 to between 0.45 and 0.6. This friction increase has been related to the micro-hardness of the films.

The characteristics and tribological performance of DLC and Si-DLC films with and without Si–C interlayers were studied in this paper. The films were deposited on nitrile rubber using a closed field unbalanced magnetron sputtering ion plating system. The film properties and characteristics were determined by scanning electron microscopy (SEM), hydrophobicity studies, Raman spectroscopy and tribological investigations. Tribological performance of these films was investigated using a pin-on-disc tribometer under applied loads of 1 N and 5 N under conditions of dry and wet sliding. The effect of immersing the films in water on tribological performance was also examined. The results show that the morphology of the films had a crack-like network. At a substrate bias of − 30 V, the coatings were characterised by a very dense non-columnar microstructure. The highest value of the ratio of intensities of the D and G peaks (ID/IG) was 1.2 for Si-DLC film with Si–C interlayer. The lowest value of 0.7 was observed for DLC film. The contact angle (CA) of water droplets showed that the films were hydrophobic. These results are interpreted in terms of hybridisation of carbon in these coatings. The tribological investigation showed a dependence on both the tribological condition under investigation and the atomic percentage of Si in the films. At 5 N normal load the lowest wear depth was observed for DLC films.