Chemical Engineering Publications

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Chemical Engineering Publications

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    The effect of a sulphate-reducing bacteria on the rate of corrosion of steel alloys
    (2019) L. Shakua, L.; G. Danha, G.; Hlabanganac, N.; Bhero, S.
    three analytical techniques we will employ in measuring the rate of corrosion are the electrochemical impedance spectroscopy, cyclic polarization and the mass loss method. The test material used is the 316L stainless steel and the mild steel coupons. The microorganism we are going to use for this investigation is the sulphate-reducing bacteria (SRB). The scope of the study will cover the cultivation of the micro-organism, cell count, electrochemical testing, cyclic polarization testing, analysis of corrosion product, mass loss and the pitting morphology consistent with the microbiologically induced corrosion mechanism. Our results show that the chemical composition of the mild steel and stainless steel test material conformed to SAE1020 and Type 316L stainless steel respectively. We also found that the corrosion rate of mild steel in both biotic and abiotic systems was significantly higher than that of the 316L stainless steel. The biotic system was more corrosive for both the mild steel and the 316L stainless steel. The biotic system showed a substantial corrosion effect in two days while the abiotic system showed the same effect after seven days. The cell count procedure confirmed the presence of sulphate-reducing bacteria throughout the test. Keywords: Type your keywords here, separated by semicolons ; Available online at www.sciencedirect.com ScienceDirect Procedia Manufacturing 00 (2019) 000–000 www.elsevier.com/locate/procedia 2351-9789 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the organizing committee of SMPM 2019. *Corresponding Author Email: danhag@biust.ac.bw 2nd International Conference on Sustainable Materials Processing and Manufacturing (SMPM 2019) The effect of a sulphate-reducing bacteria on the rate of corrosion of steel alloys L. Shakua , G. Danha*b , N. Hlabanganac , S. Bherob a Department of Metallurgy, P.O Box 16, Johannesburg, South Africa b Department of Chemical Engineering, National University of Science & Technology, Box A.C 939 Ascot, Bulawayo, Zimbabwe c Department of Chemical, Materials and Metallurgical Engineering, Faculty of Engineering and Technology, Botswana International University of Science and Technology, Plot 10071 Boseja Ward, Private Bag 16 Palapye, Botswana Abstract In this article, we investigate the effect of micro-organisms on the rate of corrosion of stainless steel and mild steel alloys. The three analytical techniques we will employ in measuring the rate of corrosion are the electrochemical impedance spectroscopy, cyclic polarization and the mass loss method. The test material used is the 316L stainless steel and the mild steel coupons. The microorganism we are going to use for this investigation is the sulphate-reducing bacteria (SRB). The scope of the study will cover the cultivation of the micro-organism, cell count, electrochemical testing, cyclic polarization testing, analysis of corrosion product, mass loss and the pitting morphology consistent with the microbiologically induced corrosion mechanism. Our results show that the chemical composition of the mild steel and stainless steel test material conformed to SAE1020 and Type 316L stainless steel respectively. We also found that the corrosion rate of mild steel in both biotic and abiotic systems was significantly higher than that of the 316L stainless steel. The biotic system was more corrosive for both the mild steel and
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    Optimisation of using a blend of plant based natural and synthetic coagulants for water treatment: ( Moringa Oleifera-Cactus Opuntia-Alum Blend)
    (2020) Gandiwa, B.I.; Moyo, L.B.; Ncube, S.; Mamvura, T.A.; Hlabangana, N.
    The research presents a comparative study on the effectiveness of blending plant based natural coagulants (Cactus Opuntia and Moringa Oleifera extracts) and a synthetic coagulant (aluminium sulphate or alum) in treatment of raw water. The low production rates of natural coagulants has derailed their commercialization this has driven the idea of blending synthetic coagulants which is envisaged to be the more appropriate means of application in this study. To measure the effectiveness of the coagulant, the following parameters were measured; turbidity, pH, conductivity and total alkalinity. The simplex lattice experimental design was applied using Minitab Software to obtain the optimal coagulant blend. The models were validated by statistical analysis which showed that the model was sufficient and no further modeling was required. The optimization results showed that a combination of alum, Moringa Oleifera and Cactus Opuntia in proportions of 13%, 42.6% and 44.4%, respectively with a total coagulant dosage of 45mg/L gave the best overall results with the resultant water having a turbidity, pH, conductivity and total alkalinity of 2.7 NTU, 6.99, 308 µS/cm and 137.7mg/L respectively. These physiochemical parameters are within required limits for potable water as per WHO guidelines. From the results, it was concluded that aluminum sulphate (alum) can be successfully blended with natural plantbased coagulants for raw water treatment.
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    Investigating the feasibility of using agricultural waste as an adsorbent of gold ions in small scale gold processing plants.
    (2019) Tapfuma, A.; Chakawa, D.P.; Moyo, L.B.; Hlabangana, N.;; Danha, G.; Muzenda, E.
    The recovery of precious metals like gold is increasing each day due to its high market prices along with diverse applications. Bio-sorption represents a biotechnological innovation as well as a cost effective and excellent tool for recovery of precious metals from aqueous solutions. This study offers an overview of a recent scenario of bio-sorption studies carried out on the use of some promising bio-sorbents which could serve as an economical means for recovering gold for small scale gold processing plants. Results show that activated carbon (control) has the highest adsorption efficiency since it contains more active site on the carbon molecules. The activated maize corn cob had the highest adsorption efficiency (77.09%) compared to all other agricultural adsorbents. Banana peels showed a significant adsorption efficiency of 56.87%.
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    Optimization of pulp production from groundnut shells using chemical pulping at low temperatures
    (2020) Musekiwa, P.; Moyo, L.B.; Mamvura, T.A.; Danha, G.; Simate, G.S.; Hlabangana, N.
    Paper production through chemical pulping has been identified as one of the ideal avenues of exploring the uses of groundnut shells as they are rich in cellulose. Ideally, the cellulose can be used to synthesize fibres that can be converted into useful paper products. In this study, chemical pulping was the chosen process for liberating the fibres as it is effective in dissolving lignin embedded within the cellulose. In addition, the fibres produced have superior physical properties compared to mechanical pulping. It is imperative that optimal conditions are identified for the chemical treatment process, in order to ensure that energy and chemical consumption are minimized. All these measures are aimed at reducing production costs and make chemical pulping economically viable, as compared to the mechanical pulping process which is less costly. Response surface methodology (RSM) was used in this study to evaluate the effect of three independent variables (cooking time, temperature, and sulphidity) on pulp yield and kappa number. These parameters are critical in the chemical pulping process and the optimal conditions obtained were 180 min, 100 C and 23.6 wt.%, respectively. At the optimal conditions, the pulp yield was 64.39wt% with a kappa number of 19.5. The results showed that all parameters investigated, had a statistically significant effect on the production of pulp. The increased cooking time was efficient in ensuring complete impregnation of the groundnut shells with chemicals for pulping and ensuring that the dissolution of lignin is not selective and does not result in dead spots inherently compromising the quality of the pulp. On the other hand, lower temperatures limited the peeling effect due to hydrolysis of carbohydrates which increased pulp yield due to a higher cellulose retention. Consequently, this contributed towards obtaining pulp that is well cooked, has a low bleach consumption and a higher quality.
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    Beverage Effluent Treatment Technology
    (2016) Tshuma. J.; Maqhuzu, A.; Bhebhe, S.; Mudon, S.; Kaitano, H.; Mashanga, D.; Mpofu, C.; Tshuma, I.; Mkandla, C.K.
    A detailed beverage effluent treatment technology was developed in a period of 4 months, using samples from an operating beverage plant. The total number of samples collected were 1304. The volume of the sample collected hourly was 500ml for 4 hours to give a composite sample. The plant operated continuously for 6 days a week and had two-12 hour shifts a day. The technology consisted of four water treatment methods combined consecutively which were chemical, physical, biological and physical treatment methods. The aim of developing the technology was to reduce the sCOD, TSS and pH parameters to the required environmental specification. The untreated beverage wastewater has high solids content, high organic matter, and low pH which need pretreatment before it is discharged into the municipal sewage treatment works. The developed technology reduced the high solid content, high organic load and adjusted the pH to the required Bulawayo Municipality environmental specifications. The average percentage reduction in sCOD and TSS was 91.1% and 90.6% respectively. The pH was adjusted to 8.05. The obtained results indicated that the developed technology was effective for treating beverage wastewater at ambient temperature to meet the quality of effluent that can be discharged into public water works.