Abstract: The effect of quenching on the mechanical properties of medium carbon steels using coconut (CW) water, pap water (PW) and spent engine oil (SPE) which have been largely considered as wastes was investigated. All specimens were normalized at a temperature of 840 in order to remove residual stresses induced during machining operations. Various specimens were heated to ranges of 730-790 and soaked for the range of 30-60 minutes respectively. Brinnel hardness tester was used to obtain the hardness values while Testometric M500-50AT model machine was used for the tensile test of the specimens. The highest hardness value (609.97 BHN) was obtained from the specimen heated to 790 quenched in pap water as compared with 166.4 BHN for the normalized as-received sample. The yield (YS) and ultimate tensile (UTS) strengths of the quenched specimens were better than the normalized as-received sample. SPE-quenched samples yielded the highest YS and UTS combined. The hardness value increased while YS and UTS decreased with soaking time for different temperatures. The highest hardness value for the specimens was obtained from coconut and pap water. Rather than been considered as wastes, coconut water, pap water and spent engine oil can improve the mechanical properties of medium carbon steel when used as quenching media.
Abstract: Powder metallurgy was mainly used to produce automobile parts such as beds self-lubricating bearings, and gear wheels. In order to investigate the effect of porosity on the mechanical and tribological properties of sintered steel, specimens with 10%, 20%, and 30% porosity were produced on samples of parallelepipedic form, with technical of iron powders that has been used in a large industrial area. Sintering was carried out at 1100 ° C for 2 hours in an argon atmosphere. Metallographic studies such as pore formation, saturated area, and the nitrided layer analyses were performed by microscopy and optical microscopy. It was found that the irregular pore formation tendencies increase with an increase in porosity (%). Furthermore, an increase in porosity has proven to decrease the mechanical properties and increase the wear trace area and the friction coefficient of sintered steel.
Abstract: The present work aims at determining the effects of Nickel addition on the phase’s distribution in sintered part. It aims equally at identifying the effect of such addition on the microstructure and the mechanical properties. The addition to mixtures of alloying elements in their primitive form can lead to the formation of a heterogeneous microstructure in the sintered parts produced by the powder metallurgy (PM) process. It has been proved that the addition of nickel to an iron powder mixture forms nickel-rich areas (NRA) in the sintered parts. This is basically related to the low diffusion rate of nickel in iron at conventional sintering temperatures.
Abstract: Applications of agricultural by-product as substitute for non-renewable material in cement production are desirable in stimulating socio-economic development. In this study, Rice Husk Ash (RHA) blended cement was produced by replacing 5%, 7%, 11.25%, 15%, 20.25% and 25% by weight of Ordinary Portland Cement (OPC) clinker with RHA. The cement without RHA serves as the control. The chemical compositions of RHA, OPC-clinker and the blended cements were determined using X-ray fluorescence analyzer. The physical characteristics of RHA blended cements that were considered are fineness, soundness, consistency, initial and final setting times and compressive strength at 2, 7, 28, 56 and 90 curing ages. The results showed that RHA is a suitable material for use as a pozzolan as it satisfied the minimum requirement by having the sum of SiO2, Al2O3 and Fe2O3 of more than 70%. Incorporation of RHA led to an increase in the composition of SiO2 and reduction in that of CaO. An increase in RHA content showed a decrease in compressive strength at early ages and slightly increase at a later age (90 days). The blended cement produced with lower levels of RHA replacement conforms to standard specifications specified in BS EN 197-1:2000, NIS 439:2000 and ASTM C 150-02. The minimum Strength Activated Index (SAI) of 75% at the age of 28 days of curing as specified by ASTM C 618 was satisfied by RHA replacement of up to 15%. It was concluded that blended cement with the maximum of 15% RHA content is suitable for use for structural purposes.
Abstract: The aim of this paper is to assess the possibility of using natural pozzolans (NPs) from Cameroonian volcanic scoria as supplementary cementitious materials (SCMs) in the production of Portland cement mortars. Four natural pozzolans (Black Natural Pozzolan: BNP, Dark-Red Natural Pozzolan: DRNP, Red Natural Pozzolan: RNP and Yellow Natural Pozzolan: YNP) with 3600, 4500, 4700 and 5200 cm2/g Blaine fineness respectively were produced from different colors (Black, Dark red, Red and Yellow) volcanic scoria in a laboratory mill. Natural pozzolans were characterized with regard to particle size distribution, particle shape, electrical conductivity, X-ray fluorescence (XRF) and X-ray diffraction (XRD). The calcium hydroxide consumption by NPs was assessed firstly by electrical conductivity measurements of calcium hydroxide/NPs suspensions with calcium hydroxide excess. Evidence of pozzolanic reactivity of NPs is revealed in hydrated lime pastes, and low reactivity was observed in aqueous suspensions. The effects of 15, 25, and 35 wt.% of NPs as cement substitution on the properties of Portland cement mortars were investigated. Different properties were studied such as setting time, consistency, mechanical strength, pozzolanic activity, absorption by capillarity and resistance to carbonation. The reactivity of NPs was also assessed by means of the mechanical strength development of mortars. The results obtained show that pozzolanic and hydraulic reactions take place in OPC systems. The correlation between mechanical strengths and physical properties of NPs has been established. The study concludes that using DRNP and RNP at 15 wt. % cement replacement can ameliorate globally the performance of mortar. Using all NPs at 35 wt. % has negative effect on the fundamental properties of cementitious mortars.
Abstract: The objective of this work is to study the phosphate adsorption from natural waters by using a granular activated carbon (GAC). Experiments were carried out with synthetic solutions of phosphate prepared using groundwater (mineralized drinking water). Batch tests were carried out in order to study different operating parameters such as the effect of contact time, pH, initial phosphate concentration and adsorbent dosage. In addition, the adsorption kinetic data were simulated using the pseudo first order, the pseudo second-order and the intra-particle diffusion model. The sorption equilibrium was analyzed by Langmuir, Freundlich and Dubinin–Radushkevich isotherms model. Results show that the phosphate adsorption was reversible and the quantity adsorbed reached its maximum value (2.82 mg/g) after 30 min. It was also found that phosphate uptake was affected by variation of pH, initial concentration of phosphate and granular activated carbon dosage. The adsorption improved with increase in pH values, initial concentration and adsorbent dosage. The results of kinetic studies revealed that pseudo-second-order model adequately described the adsorption phosphate on GAC and the intra-particle diffusion involved in the adsorption mechanism. Also, isotherm study showed that Langmuir isotherm best fit the data and the adsorption was a physical type.
Abstract: The quality and accessibility of drinking water are of paramount importance to human health. Drinking water may contain disease causing agents and toxic chemicals, and to control the risks to public health, systematic water quality monitoring and surveillance are required. Thousands of chemicals have been identified in drinking water supplies around the world and are considered potentially hazardous to human health at relatively high concentrations. Heavy metals are the most harmful of the chemical pollutants and are of concern due to their toxicities to humans. Moringa oleifera seed acts as a natural coagulant, adsorbent and antimicrobial agent while commercial activated carbon is known for its excellent heavy metal removal. It is believed that Moringa oleifera seed is an organic natural polymer. This work has been carried out to analyse the removal of some heavy metals (lead, nickel, iron, and zinc) from borehole water using moringa seed powder, activated carbon and a combination of the two adsorbents. The results obtained showed that Moringa oleifera is environmentally friendly and suitable for water treatment containing undesirable heavy metals. It was also discovered that all the adsorbents were able to completely remove the lead metal in the water. Furthermore, within the adsorbent dosage limit investigated, only activated carbon could remove all the zinc present in the water. However, there was an indication that higher dosage of the coagulants would be able to remove higher percentage of the other metals. It was also found that, in some cases, an increase in the dosage of some adsorbents led to decrease in the percentage removal of some metals. This was observed to be an indication that there could be the need to take note of the optimum dosages of the adsorbents that need to be used in treating any water. The good performances displayed by these local adsorbents have shown that they could effectively replace the chemicals that have been found to have links with some health problems in human.
Abstract: Water contamination seems unavoidable as many human activities involve the use of water in one way or the other. Chemical coagulants, especially aluminium based, which are widely used in treatment of wastewater or contaminated water have been associated with some health issues. Research on the use of plant based coagulants in water treatment now draws a lot of attentions, not only because the natural coagulants are presumed safe but also because of their biodegradable nature. In this present study, efforts have been made to evaluate the effectiveness of locally available tamarind seed powder as natural coagulant and Sodom apple (Calotropis procera) as coagulant aid for the treatment of textile wastewater. The tests were carried out using the conventional jar test apparatus at various pH and coagulant dosage with no aid added. Also, three sets of jar test experiments were performed at constant values of coagulant dosage and pH (which were found to be favourable in the first experiments) by varying the dosage of liquid and solid coagulant aid as well as time. The results obtained show that pH slightly affected the pollutants removal efficiency of the unaided coagulation. The neutral pH was found to be favourable with turbidity and colour removal of 22.25% and 30.36% respectively. The optimum mixing time of turbidity removal efficiency was found to be 2 min with rapid mixing of 30 seconds and 1½ min of slow mixing with turbidity and colour removal of 69.48% and 60.53% respectively. The optimum dosage was found to be 4.0 g of coagulant and 1.0 g of coagulant aid for turbidity, total dissolved solid and colour removal efficiency.
Abstract: Moringa oleifera seeds, being good sources of valuable nutrients, contain appreciable amounts of crude fat, crude fibre, carbohydrate, crude protein, moisture and ash. The seeds contribute significantly to the nutrient requirements and health management of man and should be recommended in diets. So, efforts need to be made to make the seeds be well preserved while still retaining the nutrients contained in them. In an attempt to contribute to that, this research work has been carried out to obtain the optimum values of the parameters required to appropriately make the seeds be dried without much loss in the nutrients. The optimization of the drying parameters has been carried out, in this work, using Box–Behnken design technique of response surface methodology. The technique was used to design a set of 13 experiments that were carried out. The input factors considered were contact time, temperature and fan speed while the response (output) chosen was the residual moisture content of the seeds. A model of the system was formulated and optimized. The results obtained revealed that temperature, contact time and fan speed were affecting the drying of the seeds. Also, a very good agreement given by the comparison of the experimental and the simulated residual moisture content of the seeds showed that the developed model could represent the system very well. Furthermore, the results of the optimization revealed that moringa seeds having a residual moisture content of a value as low as approximately 9.28% could be obtained using the optimum values of drying temperature, contact time and fan speed that were estimated, through the use of a statistical program known as Design Expert, to be 49.40 °C, 90.45 min and 2.5 m/sec, respectively.
Abstract: Direct use of vegetable oil as a fuel on compression ignition engine has been described as impossible, because of its high viscosity and density. Transesterification process and other methods have been identified as ways of reducing these two properties. The high cost of virgin vegetable oils and its competition for food have made the biodiesel unable to compete with fossil diesel and also hike its cost. In order to solve these menaces, in this study, waste frying oil was used as a feedstock for production of biodiesel via transesterification using anthill-eggshell promoted Ni-Co mixed oxides (NiCoAE) as heterogeneous catalyst. The composite catalyst was prepared via incipient wetness impregnation (IWI) method and thermally treated at 1000 °C for 4 h. The developed catalyst was characterized using FTIR and SEM techniques. The biodiesel produced under the favourable reaction conditions was blended with petroleum diesel in three different proportions (B20, B50 and B80) and were tested on diesel engine to evaluate their performance and emission characteristics. The blended fuel containing 20% by volume biodiesel (B20) emitted lowest percentage of CO and CO2. The result obtained herein indicates that the mixture of biodiesel and petroleum diesel containing 20% biodiesel (B20) emitted less carbon monoxide (CO) and carbon dioxide (CO2), thus, indicating best dual fuel combination, which can be used in diesel engines without any adjustment or modification in the engines. This result is in agreement with the findings reported in the literature and Energy Policy Act (EPA) of 1992.