Eggshells – assisted hydrolysis of banana pulp for biogas production

In this study, pretreatment of banana pulp using eggshells in both calcined and un-calcined forms to examine the extent of hydrolysis was conducted. Reactor CO containing banana pulp and inoculum but with no eggshells added was used as the control, while reactors C1, C2, C3, C4, and C5 containing banana pulp and inoculum were spiked with 1, 3, 5, 7, and 9 g of un-calcined  eggshells and calcined eggshells, for experiment 1 and 2, respectively. Anaerobic digestion was carried out at mesophilic  temperature (35°C) for a period of 20 days. Digester C3 with 5 g of calcined eggshells gave the largest cumulative biogas yield of 2343 mL with 62% CH4, follow. The least biogas yield of 10 mL was obtained in digester C5with 9 g of calcined eggshells additive.Key words: Anaerobic digestion, banana pulp hydrolysis biogas, eggshells

Fish Swim Bladder-Derived Porous Carbon for Defluoridation at Potable Water pH

This research article published by Scientific Research Publishing Inc., 2016The levels of fluoride in various ground water sources in East Africa are above the World Health Organization upper limit of 1.5 mg/L. Research on diverse defluoridation technologies has proven that adsorption stands out as an affordable, efficient, and facile technology. Fish swim bladder-derived porous carbon (FBPC) activated by KOH and surface oxidized by nitric acid was successfully investigated as an adsorbent for defluoridation at portable water pH. The FBPC was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-raydiffraction (XRD) and energy dispersive spectroscopy (EDS). Batch methods were used to study physiochemical parameters viz., initial fluoride concentration, temperature, adsorbate dosage, contact time and pH. Freundlich, Temkin, Langmuir and Dubinin-Radushkevich isotherms were plotted and analyzed to understand the adsorption process. Bangham, Weber Morris, pseudo first and second-order models were used to elucidate the kinetics of adsorption. Optimal conditions for fluoride removal were found to be: pH of 6, FBPC adsorbent dose of 5.0 g/L and contact time of 50 min. Flouride adsorption followed pseudo second-order kinetic model and Langmuir isotherm best describes the adsorption process

Biogas-slurry derived mesoporous carbon for supercapacitor applications

This research article published by Elsevier Ltd., 2017This study reports on the transformation of biogas slurry into mesoporous carbon for supercapacitor electrodes. Pore structures have been modified by altering activation time, temperature and KOH/carbon mass ratio. The mesoporous carbons are successively developed as evidenced by type IV isotherms obtained in nitrogen sorption studies. BET, micropore and mesopore surface area of 515, 350, and 165 m2 g−1, respectively as well as a narrow pore width distribution of 3–4.5 nm are obtained. X-ray photoelectron results have confirmed the presence of functional groups of oxygen and nitrogen in the samples which facilitates the pseudocapacitance. The electrochemical measurements in 6 M KOH using a three electrode cell with Ag/AgCl as reference electrode and platinum as counter electrode has been performed. The materials activated at 700 °C, 3:1 KOH to carbon mass ratio, and for 120 min exhibit high specific capacitance of 289 F g−1 at a scan rate of 5 mV s−1. Shortening activation time to 30 and 60 min reduces specific capacitance to 163 and 182 F g−1, in that order. Additionally, at 3:1 KOH to carbon mass ratio and 60 min activation time, specific capacitances of 170 and 210 F g−1 at 600 and 800 °C, respectively are obtained. Moreover, specific capacitance increases with increasing the KOH to carbon mass ratio from 148 F g−1 for 1:1–163 F g−1 for 3:1 at 700 °C. Electrochemical impedance spectroscopy studies demonstrate that material has high conductivity. In addition; capacity retention of 96% after 20,000 cycles is shown at scan rate of 30 mV s−1. The study shows that high performance electrodes can be designed from biogas slurry derived porous carbon

Vapor-Phase Oxidation of Benzyl Alcohol Using Manganese Oxide Octahedral Molecular Sieves (OMS-2)

Vapor-phase selective oxidation of benzyl alcohol has been accomplished using cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2) catalysts. A conversion of 92% and a selectivity to benzaldehyde of 99% were achieved using OMS-2. The role played by the oxidant in this system was probed by studying the reaction in the absence of oxidant. The natures of framework transformations occurring during the oxidation reaction were fully studied using temperature-programmed techniques, as well as in situ X-ray diffraction under different atmospheres

Manihot glaziovii-Bonded and Bioethanol-Infused Charcoal Dust Briquettes: A New Route of Addressing Sustainability, Ignition, and Food Security Issues in Briquette Production

This research article published by Springer Nature Switzerland AG., 2019Most of the citizens in developing countries use charcoal for domestic cooking and small-scale enterprises because of its high calorific value, less smoke, and easy to transport. However, a lot of charcoal dust is generated from charcoal trading activities. The dust is left as heaps of solid wastes in urban areas and sometimes thrown in water streams, thus being a nuisance to both humans and the environment. This study aimed to develop and characterize charcoal dust briquettes bonded with wild cassava Manihot glaziovii and also use of bioethanol to enhance briquette ignition. The percentages of binder to charcoal dust were varied from 5 to 30%. Proximate analysis, density, ignition time, burning rate, burning time, and calorific value were determined. The density of the produced briquettes ranged from 0.67 ± 0 to 0.83 ± 0.1 g/cm3; percentage of moisture content varied from 3.4 ± 0.2 to 4.2 ± 0.2; ash content varied from 19.6 ± 0.6 to 21.5 ± 0; percentage volatile matter ranged from 19.8 ± 0.3 to 24.3 ± 0.4; and percentage fixed carbon ranged from 51.9 ± 1.1 to 55.3 ± 0.2. The calorific value ranged from 17.7 ± 0.7 to 19.7 ± 0.3 MJ/kg, ignition time 139 to 163 s, and burning rate 0.3 to 0.7 g/min while water boiling time varied from 14 to 19 min and burning time from 85 to 116 min. Ignition test revealed that bioethanol ratio of 15 mL to 56 g of the briquette showed the best briquette ignition characteristics. It was further found that the amount of binder used influenced the combustion properties of the briquettes. This study also showed that charcoal dust could be compacted to briquettes using Manihot glaziovii as a binder. The overall performance of the briquettes showed that 5% binder gave the best results in terms of combustion characteristics

Hydrogen sulfide and ammonia removal from biogas using water hyacinth-derived carbon nanomaterials

This research article was published in African Journal of Environmental Science and Technology, Volume 11, 2017.The presence of hydrogen sulfide (H2S) and ammonia (NH3) in biogas pose serious human health and environmental challenges. In this study, H2S and NH3 were successfully removed from biogas using water hyacinth-derived carbon (WHC) nanomaterials. Carbonization temperature, biogas flow rate, mass of the adsorbent and activating agent (KOH/water hyacinth (WH)) ratio were found to greatly influence the efficiency of the H2S and NH3 removal. The adsorption capacity of both H2S and NH3 was found to increase with the carbonization temperature as carbon materials prepared at 450, 550, and 650°C afforded removal efficiencies of 22, 30, and 51% for H2S and 42, 50, and 74% for NH3, respectively, after contact time of 2 h. Similarly, the KOH/WHC ratio showed huge impact on the adsorptive removal of the two species. WH materials carbonized at 650°C and activated at 700°C using 1:4, 1:2, and 1:1 KOH/WHC ratios showed removal efficiencies of 80, 84, and 93% for H2S and 100, 100, and 100% for NH3, correspondingly after 2 h contact time. The adsorption capacity of NH3 increased with the decrease in flow rate from 83 to 100% at flow rates of 0.11 and 0.024 m3 /h, respectively, while that of H2S increased from 22 to 93% with flow rate 0.11 and 0.024 m3 /h, respectively. The removal of H2S and NH3 increased with adsorbent mass loading. With the 0.05, 0.1, 0.2, and 0.3 g of the adsorbent, the adsorption of H2S after 1.5 h contact time was 63, 93, 93, and 95%, respectively while that of NH3 was 100% for all the adsorbent masses

Experimental Investigation of Thermal Characteristics of Kiwira Coal Waste with Rice Husk Blends for Gasification

Eminent depletion of fossil fuels and environmental pollution are the key forces driving the implementation cofiring of fossil fuels and biomass. Cogasification as a technology is known to have advantages of low cost, high energy recovery, and environmental friendliness. The performance/efficiency of this energy recovery process substantially depends on thermal properties of the fuel. This paper presents experimental study of thermal behavior of Kiwira coal waste/rice husks blends. Compositions of 0, 20, 40, 60, 80, and 100% weight percentage rice husk were studied using thermogravimetric analyzer at the heating rate of 10 K/min to 1273 K. Specifically, degradation rate, conversion rate, and kinetic parameters have been studied. Thermal stability of coal waste was found to be higher than that of rice husks. In addition, thermal stability of coal waste/rice husk blend was found to decrease with an increase of rice husks. In contrast, both the degradation and devolatilization rates increased with the amount of rice husk. On the other hand, the activation energy dramatically reduced from 131 kJ/mol at 0% rice husks to 75 kJ/mol at 100% rice husks. The reduction of activation energy is advantageous as it can be used to design efficient performance and cost effective cogasification process

Measurement of Pozzolanic Activity Index of Scoria, Pumice, and Rice Husk Ash as Potential Supplementary Cementitious Materials for Portland Cement

Research Article published by HindawiThis work investigated the properties of scoria and pumice as supplementary cementitious materials (SCMs) for Portland cement and compared to those of rice husk ash (RHA). X-ray fluorescence, X-ray diffraction, and pozzolanic activity index (PAI) tests confirmed the suitability of these two materials as potential SCMs. Scoria and RHA samples achieved over 75% PAI at 7 days whereas pumice did this after 28 days. Initial and final mean setting times observed for the composite cement blended with these materials were 166 and 285 min, respectively. These setting times are longer than that of ordinary Portland cement but shorter compared to that of common Portland pozzolana cement. The ultimate mean compressive strengths achieved at 28 days of curing were 42.5, 44.8, and 43.0MPa for scoria, pumice, and RHA, respectively, signifying that these materials are good SCMs. Higher fineness yielded higher ultimate mean strength. For instance, a scoria sample with a fineness of 575m2/kg achieved the strength of 52.2MPa after 28 days

Status of Biomass Derived Carbon Materials for Supercapacitor Application

Environmental concerns and energy security uncertainties associated with fossil fuels have driven the world to shift to renewable energy sources. However, most renewable energy sources with exception of hydropower are intermittent in nature and thus need storage systems. Amongst various storage systems, supercapacitors are the promising candidates for energy storage not only in renewable energies but also in hybrid vehicles and portable devices due to their high power density. Supercapacitor electrodes are almost invariably made of carbon derived from biomass. Several reviews had been focused on general carbon materials for supercapacitor electrode. This review is focused on understanding the extent to which different types of biomasses have been used as porous carbon materials for supercapacitor electrodes. It also details hydrothermal microwave assisted, ionothermal, and molten salts carbonization as techniques of synthesizing activated carbon from biomasses as well as their characteristics and their impacts on electrochemical performance

Direct Sonochemical Synthesis of Manganese Octahedral Molecular Sieve (OMS-2) Nanomaterials Using Cosolvent Systems, Their Characterization, and Catalytic Applications

A rapid, direct sonochemical method has successfully been developed to synthesize cryptomelane-type manganese octahedral molecular sieve (OMS-2) materials. Very high surface area of 288 ± 1 m²/g and small particle sizes in the range of 1–7 nm were produced under nonthermal conditions. No further processing such as calcination was needed to obtain the pure cryptomelane phase. A cosolvent system was utilized to reduce the reaction time and to obtain higher surface areas. Reaction time was reduced by 50% using water/acetone mixed phase solvent systems. The cryptomelane phase was obtained with 5% acetone after 2 h of sonication at ambient temperature. Reaction time, temperature, and acetone concentration were identified as the most important parameters in the formation of the pure cryptomelane phase. OMS materials synthesized using the above-mentioned method were characterized by X-ray diffraction (XRD), nitrogen sorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transformation infrared spectroscopy (FTIR). OMS-2 materials synthesized using sonochemical methods (K-OMS-2_SC) possess greater amounts of defects and hence show excellent catalytic performances for oxidation of benzyl alcohol as compared to OMS-2 synthesized using reflux methods (K-OMS-2_REF) and commercial MnO₂