Characterization of crop residues from false banana/Ensete ventricosum/in Ethiopia in view of a full-resource valorization

Research ArticleFalse banana /Ensete ventricosum [Welw.] Cheesman/ is exploited as a food crop in Ethiopia where it represents an important staple food. The plant is harvested and large amounts of biomass residues are originated, mainly from the pseudo stem (i.e., fiber bundles obtained from the leaf sheaths after being scrapped to produce starchy food) and the inflorescence stalk. These materials were studied in relation to their summative chemical composition, composition of lignin, lipophilic and polar extracts. Moreover, their structural characteristics, in view of their valorization, were scrutinized. The analytical studies were performed with the aid of FTIR, GC/MS, Py-GC/MS and SEM. The fiber bundles are aggregates of mainly long and slender fibers with low ash, extractives and lignin contents (3.8%. 4.4% and 10.5% respectively) and high holocellulose and α-cellulose contents (87.5% and 59.6% respectively). The hemicelluloses in the fibers are mostly highly acetylated xylans and the lignin is of the H-type (H:G:S, 1:0.7:0.8). This lignin composition is in line with the FTIR peaks at 1670 cm-1 and 1250 cm-1.The inflorescence stalk has high ash content (12.3% in the main stalk and 24.6% in fines) with a major proportion of potassium, high extractives (25.9%), and low lignin and α-cellulose contents (5.8% and 17.9% respectively). The stalk includes numerous starch granules in the cellular structure with the predominant presence of parenchyma. The potential valorization routes for these materials are clearly different. The fiber bundles could be used as a fiber source for paper pulp production with the possibility of a prior hemicelluloses removal while the inflorescence stalk has nutritional value for food and fodder. Furthermore, it can also be used for sugar fermentation productsinfo:eu-repo/semantics/publishedVersio

Understanding the effects of mineralogy, ore texture and microwave power delivery on microwave treatment of ores.

Thesis (PhD (Process Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Previous work has shown that microwave heating of mineral ores induces fractures around grain boundaries due to the differences in absorption of microwaves and the resulting differential thermal expansion among the various mineral phases in the ore particles. As a consequence, this reduces the energy required in subsequent grinding and enhances liberation of valuable minerals. In this study, first, the influences of different variables on bulk strength reduction of microwave treated ores have been investigated. Nine different binary ore models were constructed by randomly disseminating 10 vol.% microwave absorbing minerals in transparent matrices. Computational simulations of heating, thermal damage and unconfined compressive strength (UCS) tests on the conceptual binary ores have been undertaken by using finite-difference modelling techniques. The influence of thermo-mechanical properties of minerals on strength reduction of microwave treated ores was examined. It was shown that in general the thermal properties of the microwave absorbing mineral and the mechanical properties of the transparent matrix have the most significant effect on the strength reduction. Binary ores containing a microwave absorbing mineral that has a high thermal expansion coefficient in a strong transparent matrix achieved higher reductions in strength. The influence of absorbent phase grain size on strength reduction of ores was also quantified. It was shown that for the same energy inputs and mineral types, the reductions in strength were much higher in coarse-grained ores. It has also been shown that for the same mineralogy and treatment condition, ores with poorly disseminated heated phase achieved much higher strength reduction. The effect of microwave treatment on the mechanical state of an ore sample was also examined. It was demonstrated that unconfined compressive strength is less sensitive to microwave-induced micro-fractures and found to be a poor descriptor of liberation behaviour. A new method of characterizing damage in microwave treated ore using a continuum approach was developed. The method measures the damage around the grain boundary regions during the heating process. Using the method, it was possible to elucidate in detail the influences of power density, mineralogy, ore texture on microwave treatment of ore. It was shown that the amount of grain boundary damage incurred at a specific power density and energy input is dependent both on the ore mineralogy and its texture. The energy inputs that were required for significant (> 10%) grain boundary damage in the ores range from 0.09 to 7.06 kWh/t depending on the power density applied, the ore mineralogy and its texture. It was also shown that for a given mineralogy and ore texture there is a power density level below which no further increase in grain boundary damage is possible by increasing exposure time. The effect of pulse repetition frequency on grain boundary damage was also elucidated using the method. It was found that high pulse repetition frequencies (³ 50 Hz) resulted in an amount of grain boundary damage that was indistinguishable from that caused by continuous wave operation for a fixed energy input. It has also been shown that for a fixed microwave energy input the best result would be obtained by using the lowest possible pulse repetition frequency and highest peak pulse power. The effect of microwave treatment of ores at different treatment conditions on the extent of damage and crack pattern was also investigated in detail using bondedparticle model (BPM). It has been shown that the amount of micro-cracks and also the cracks pattern in an ore sample after microwave treatment significantly depend on its mineralogy, microwave treatment condition (power density) and absorbent phase grain size. It has also been shown that a minimum power density is required to localize damage around the grain boundary in an ore sample. This minimum power density was found to strongly depend on the ore mineralogy and its texture. Initial simulation test work concerning the effect of microwave treatment on liberation of minerals is also presented. It has been shown that microwave irradiation considerably changed the fracture pattern of an ore in simulated single particle crushing. The fracture pattern of the ore treated at high power density (Pd = 0.1 kW /mm3abs for 1 ms) was along the grain boundary and the absorbent mineral was intact. In the ore treated at lower power density for the same energy input (Pd = 1 W/mm3abs for 0.1 s) both intergranular and transgranular fractures were observed. However, in all cases the fracture patterns were preferentially localized around the grain boundary compared to that of the untreated ore.AFRIKAANSE OPSOMMING: Vorige studies het getoon dat mikrogolfverhitting van mineraalertse tot breuke om die ertskorrelgrense aanleiding gee, omdat die verskillende mineraalfases in die ertsdeeltjies die mikrogolwe verskillend absorbeer, en dus ook verskillend uitsit. Korrelgrensbreuke verminder die vereiste energie vir latere slypwerk, en verhoog die vrystelling van waardevolle minerale. Hierdie studie het eerstens die uitwerking van verskillende veranderlikes op die algehele sterktevermindering van mikrogolfbehandelde ertse ondersoek. Hiervoor is nege verskillende binêre ertsmodelle vervaardig deur mikrogolfabsorberende minerale met ʼn volumepersentasie van 10% lukraak in deursigtige matrikse te versprei. Met behulp van eindigeverskilmodelleringstegnieke is berekeningsimulasies van verhitting, warmteskade en onbegrensde druksterkte (“unconfined compressive strength”) op die konseptuele binêre ertse uitgevoer. Die invloed van termomeganiese mineraaleienskappe op die sterktevermindering van mikrogolfbehandelde ertse is eerste onder die loep geneem. Daar is bevind dat die warmte-eienskappe van die mikrogolfabsorberende mineraal, en die meganiese eienskappe van die deursigtige matriks, die beduidendste uitwerking op sterktevermindering het. Binêre ertse wat ʼn mikrogolfabsorberende mineraal bevat met ʼn hoë warmte-uitsettingskoëffisiënt in ʼn sterk deursigtige matriks, het groter sterkteverminderings getoon. Die invloed van korrelgrootte in die absorbeerfase op die sterktevermindering van ertse is volgende versyfer. Die studie het getoon dat, op grond van dieselfde energie-insette en mineraalsoorte, grofkorrelrige ertse groter sterktevermindering ondergaan het. Eweneens is bewys dat, met dieselfde mineralogie en behandelingsomstandighede, ertse met ʼn swak verspreide verhittingsfase ook groter sterktevermindering ervaar. Die uitwerking van mikrogolfbehandeling op die meganiese toestand van ʼn ertsmonster is boonop ondersoek. Die studie het getoon dat onbegrensde druksterkte minder gevoelig vir mikrogolfgeïnduseerde mikrobreuke is, en as ʼn swak aanwyser van vrystellingsgedrag beskou word. ʼn Nuwe metode om skade by mikrogolfbehandelde ertse te tipeer is gevolglik met behulp van ʼn kontinuumbenadering ontwikkel. Dié metode meet die skade rondom die korrelgrens gedurende die verhittingsproses. Deur middel van voormelde metode was dit dus moontlik om die invloed van kragdigtheid, mineralogie en ertstekstuur op die mikrogolfbehandeling van erts deeglik te ondersoek. Daar is bevind dat die mate van korrelgrensskade by ʼn bepaalde kragdigtheid en energie-inset, van sowel die ertsmineralogie as ertstekstuur afhang. Na gelang van die toegepaste kragdigtheid, die ertsmineralogie en ertstekstuur, het die vereiste energie-insette vir beduidende (>10%) korrelgrensskade van 0,09 tot 7,06 kWh/t gewissel. Dit het voorts geblyk dat enige bepaalde mineralogie en ertstekstuur oor ʼn minimum kragdigtheidsvlak beskik, onder welke vlak geen verlenging in blootstellingstyd enige verdere korrelgrensskade kan veroorsaak nie. Die uitwerking van pulsherhaalfrekwensie op korrelgrensskade is ook met behulp van bogenoemde metode verklaar. Die studie het getoon dat, op grond van ʼn vaste energie-inset, hoë pulsherhaalfrekwensies (≥50 Hz) en gelykgolfwerking presies dieselfde hoeveelheid korrelgrensskade tot gevolg het. Volgende is daar met behulp van ʼn gebondedeeltjiemodel (“bonded-particle model”) noukeurig ondersoek ingestel na die uitwerking van verskillende mikrogolfbehandelingsomstandighede op die hoeveelheid skade en die kraakpatroon by ertse. Die studie het getoon dat die hoeveelheid mikrokrake sowel as die kraakpatroon in ʼn mikrogolfbehandelde ertsmonster in ʼn groot mate van die betrokke erts se mineralogie, mikrogolfbehandelingsomstandighede (kragdigtheid) en korrelgrootte in die absorbeerfase afhang. Daar is ook bevind dat ʼn minimum kragdigtheid nodig is om skade tot die gebied om die korrelgrens te beperk, welke minimum kragdigtheid oënskynlik grotendeels deur die ertsmineralogie en -tekstuur bepaal word. Die studie bevat ook die resultate van aanvangsimulasietoetse oor die uitwerking van mikrogolfbehandeling op mineraalvrystelling. Die toetse het getoon dat mikrogolfbestraling ʼn beduidende verandering tot gevolg het in die ertsbreekpatroon met gesimuleerde enkeldeeltjievergruising. Die breekpatroon van die erts wat by hoë kragdigtheid (Pd = 0,1 kW/mm3abs vir 1 ms) behandel is, het ál langs die korrelgrens gestrek, terwyl die absorberende mineraal nog ongeskonde was. In die erts wat by laer kragdigtheid dog dieselfde energie-inset behandel is (Pd = 1 W/mm3abs vir 0,1 s), is sowel tussenkorrel- as oorkorrelbreuke opgemerk. In teenstelling met die onbehandelde erts, was die breekpatrone by die behandelde erts egter in alle gevalle steeds merendeels rondom die korrelgrens geleë

Magnetic hetero-structures as prospective sorbents to aid arsenic elimination from life water streams

Magnetic materials have been extensively used for the extraction of heavy metal ions from contaminated aqueous streams. This inherent characteristic of the magnetic particles has received considerable attention in recent years. The external magnetic field employed in the sorption process overcomes many hindrances established during the application of conventional sorbents for metal ion removal. Recent studies illustrate the severity of arsenic toxicity to be a major environmental health hazard in the contaminated ground water. Available literature has been reviewed to highlight the problem, including its malignancies. Magnetic sorbents with demonstrated high specific surface area and specific affinity for metal ions have been exceedingly beneficial for removing the toxic arsenic ions. In addition to this, these sorbents have demonstrated a promising performance in practical applications also. This review paper aims to summarize the magnetic structures and all recent progress in the research of novel magnetic materials for arsenic removal making it a promising technique in the frame of engineering chemistry is showcased herein and reviewed scrupulously. Keywords: Adsorbents, Magnetic material, Arsenic removal, Sorption, Water treatmen

Process optimization for the recovery of silver from waste X-ray photographic films

404-410A novel, simple, fast, cheap and pollution free method for utilizing waste X-ray film for silver recovery using sodium hydroxide and sodium sulfide by the stripping and precipitation processes, respectively has been reported. The yield of silver by this process is 1.07% w/w at a stripping temperature of 70.88°C, 10.97 min and NaOH concentration of 1.5M. The composition of recovered silver has been determined by XRF and the results are compared with existing literature for the purity of silver. The study warrants the application of NaOH and Na2S to recover silver from used X-ray photographic film

Process optimization for the recovery of silver from waste X-ray photographic films

A novel, simple, fast, cheap and pollution free method for utilizing waste X-ray film for silver recovery using sodium hydroxide and sodium sulfide by the stripping and precipitation processes, respectively has been reported. The yield of silver by this process is 1.07% w/w at a stripping temperature of 70.88°C, 10.97 min and NaOH concentration of 1.5M. The composition of recovered silver has been determined by XRF and the results are compared with existing literature for the purity of silver. The study warrants the application of NaOH and Na2S to recover silver from used X-ray photographic film

Incorporating Environmental Perspective in Integrated Strategic-Tactical Economic Optimization Model of Biomass-to-Biofuel Supply Chain—A Real Case Study in Ethiopia

Several optimization models, which consider economic and environmental perspectives, have been developed recently to support the sustainable biomass-to-biofuel supply chain (BBSC) design. All of the economic-environmental optimization models rely on solving long-term planning problems with a conventional hierarchical approach, where tactical decisions are made based on the optimal strategic decisions from the strategic-level model, despite it arousing non-optimal solutions. Moreover, almost all of them have used non-monetary-based environmental indicators, which result in difficulties with clarity when comparing with economic objectives. Therefore, in this work, an effort is made to develop a more reliable planning strategy that offers optimal strategic and tactical decisions simultaneously and maximizes the economic and environmental benefits. Furthermore, the environmental performance of the BBSC has been assessed in terms of monetary value by adopting an ecocost approach after performing an LCA on the system. The integrated model is applied in the real biofuel sector of Ethiopia to optimize the country’s bioethanol and biodiesel supply chain over a 20-year horizon. Despite the abrupt rise in the model size, with it being a real countrywide case with many variables and large quantities of data, an alternative semi-heuristic method that offers a feasible solution to the multi-objective problem is provided

Alternative Energy Potential and Conversion Efficiency of Biomass into Target Biofuels: A Case Study in Ethiopian Sugar Industry- Wonji-Shoa

International audienceGlobal energy security relies on fossil-based resources that are affiliated with the source of global warming, apart from punches of political and economic instabilities. Biomass is a promising alternative carbonaceous feedstock used for the production of clean energy that could have the potential to substitute for fossil fuels. This study aims to present a conceptual design that considers the criteria to identify the upper theoretical limits of biomass conversion, thus providing the potential approach to the conversion of three biomass (by-products: dry molasses, dry bagasse, and dry filter cake) through gasification, in order to contribute the biomass carbon-capturing by the model assessment of stoichiometric mass conversion and energy efficiency indicators into simple thermodynamic energy vectors, such as alcohols, alkanes, and syngas (a mixture of carbon monoxide and hydrogen). Modeling plays up the importance of stoichiometric efficiency of biomass conversion with the supply of oxygen and hydrogen. This realizes that the multi-product diversification of feedstock into syngas, hydrocarbons, and alcohol through integrated process schemes could have the potential to fill the energy gap and help to manage environmental load. In regard to biomass conversion results, the mass conversion and energy conversion efficiencies of dry bagasse have better conversion potential than molasses and F. cake (% mass conversion = 129 in syngas, 54.4 in alkane, and 43.4 in alcohol; % energy conversion = 94.3 in syngas and 93.3 in alkane and alcohol)

Valorization of Potential Post-Consumer Polyethylene (PE) Plastics Waste and Ethiopian Indigenous Highland Bamboo (EHB) for Wood Plastic Composite (WPC): Experimental Evaluation and Characterization

The best approaches to minimizing resource scarcity, removing valuable waste streams, and re-establishing a circular economic chain of recycled thermoplastics are to cascade them into product life cycles and their valorization combined with sustainable raw materials. As one part of this goal, WPC was formulated from three recycled PE plastic wastes: linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), and underutilized EHB. The chemical composition of EHD, chemical structure, crystallinity, melting and crystallization points, residual metal additives, and polycyclic aromatic hydrocarbons (PAHs) of recycled PE were investigated using standard chromatographic and spectroscopic methods such as HPAEC-UV/VIS, FTIR, DSC, GC/MSD, and XPS. The properties of WPC formulations from different compositions of bamboo particles (BP) as dispersed phase, individual recycled PE plastics, and equal melt blend (EM) as polymer matrix were investigated extensively and measured with a known standard. These comprised tensile strength (TS), modulus of elasticity (TM), flexural strength (FS), modulus of rupture (FM), and unnotched impact strength (UIS). It also included the effect of various alkaline surface treatment ranges on the interface surface interaction. The results show improved mechanical properties for all blending ratios of surface-treated BP, which resulted from better encapsulation in the polymer matrix. Despite its inherent immiscibility, WPC formulation from equal melt blending revealed unusual properties compared to separate phase blends, which is attributed to thermally induced cross-linking. This implies that melt blending of the weakest and cheapest recycled LLDPE with relatively cheap recycled MDPE and HDPE improves the properties of the blend, particularly toughness, while simultaneously retaining some of their properties

Hydrometallurgical removal of uranium and thorium from Ethiopian tantalite ore

This study focused on the leaching of uranium and thorium from a high grade Ethiopian tantalite ore using sulfuric acid. The effects of variables such as acid concentration, temperature and leaching time were studied. In general, the leaching efficiency of uranium increases with increasing temperature from 100 to 300°C whereas the opposite trend was observed for thorium. The amount of uranium leached increased from 69.1% at contact time of 1 hr to 88.6% when the tantalite ore was leached for 3 hrs. On the other hand, for the experiments conditions considered in this study, the leaching behavior of uranium and thorium did not change significantly with varying sulphuric acid concentration from 70 to 90 wt%. Overall, the highest dissolution of uranium and thorium were achieved at 100°C, 70 wt% H2SO4 concentration and 1 hr contact time

Production of magnetite nanoparticles from Ethiopian iron ore using solvent extraction and studying parameters that affect crystallite size

Crystallite size is one of the fundamental factors controlling the magnetic property of magnetic nanoparticles. In this study, magnetite nanoparticles were produced from Ethiopian iron ore and the effect of solvent extraction parameters on the crystallite size were investigated by considering classical nucleation theory. First, the iron ore was crushed and unwanted gangues were discarded, then followed by further grinding to get a black powder. Finally, the magnetite nanoparticles were produced using solvent extraction and co-precipitation method. For the solvent extraction, tri-butyl phosphate (TBP) and tri-octyl phosphine oxide (TOPO) was used as an extractant, while 2-ethyl-hexanol, and heptanol were used as a modifier and diluent, respectively. The synthesized nanoparticles was characterized using XRD, SEM (EDS), TGA, and FTIR. The results show that leaching temperature and modifier concentration have a significant effect on the crystallite size of the nanoparticles. Comparison of the crystallite size using the Scherrer equation reveals the mean crystallite size of the sample extracted using TBP is smaller than the sample extracted using TOPO