scholarly journals Reduction crystallization of heavy metals from acid treated phosphogypsum effluent utilizing hydrazine as a reducing reagent

2019 ◽  
Vol 96 ◽  
pp. 01002
Author(s):  
Tebogo Mashifan ◽  
Nastassia Sithole
Keyword(s):  
South African ◽  
Nickel Powder ◽  
Negative Impact ◽  
Operating Conditions ◽  
Optimum Operating ◽  
Optimum Ph ◽  
Powder Particles ◽  
Seeding Material ◽  
Iron Manganese ◽  
Base Substrate

Phosphogypsum is a by-product generated from phosphoric acid production processes. Due to the negative impact posed to the environment by the material, a chemical treatment process was developed to reduce the hazardous constituents in the material and render the final product useful for other applications. The treatment of phosphogypsum produced an effluent laden with contaminants such as copper, iron, manganese and thallium. This study was conducted to investigate the use of hydrazine as a reducing agent to remove and reduce Cu, Fe, Mn and TI from effluent, applying a reduction crystallization process. Nickel powder a base substrate was utilised as a seeding material. A feasibility study was carried out to test the efficiency and find the optimum operating conditions for the process. The predominant detected components in the feedstock were 71% Fe, 14% Tl, 5.1% Mn, 4.12% Cu and 2.4% Zn. The results obtained indicate that hydrazine can effectively remove up to 99.8% of metals from the effluent at the optimum pH of 10.5. Growth of the nickel powder particles was evident indicating a reduction and adsorption of contaminants on the surface of the powder. The treated solution was within South African acceptable limits for effluent discharge, which stipulates a concentration of 20 mg/l of copper, iron, manganese and thulium.

scholarly journals Removal of Arsenic Oxyanions from Water by Ferric Chloride—Optimization of Process Conditions and Implications for Improving Coagulation Performance

2021 ◽  
Vol 18 (18) ◽  
pp. 9812
Author(s):  
Muhammad Ali Inam ◽  
Rizwan Khan ◽  
Kang-Hoon Lee ◽  
Young-Min Wie
Keyword(s):  
Drinking Water ◽  
Ferric Chloride ◽  
Iron Hydroxide ◽  
Operating Conditions ◽  
Effect Of Temperature ◽  
Optimum Operating ◽  
Process Conditions ◽  
As Species ◽  
Adsorption Affinity ◽  
Optimum Ph

The chronic ingestion of arsenic (As) contaminated water has raised significant health concerns worldwide. Iron-based coagulants have been widely used to remove As oxyanions from drinking water sources. In addition, the system’s ability to lower As within the maximum acceptable contamination level (MCL) is critical for protecting human health from its detrimental effects. Accordingly, the current study comprehensively investigates the performance of As removal under various influencing factors including pH, contact time, temperature, As (III, V) concentration, ferric chloride (FC) dose, and interfering ions. The optimum pH for As (V) removal with FC was found to be pH 6–7, and it gradually decreased as the pH increased. In contrast, As (III) removal increased with an increase in pH with an optimum pH range of 7–10. The adsorption of As on precipitated iron hydroxide (FHO) was better fitted with pseudo-second order and modified Langmuir–Freundlich models. The antagonistic effect of temperature on As removal with FC was observed, with optimum temperature of 15–25 °C. After critically evaluating the optimum operating conditions, the uptake indices of both As species were developed to select appropriate an FC dose for achieving the MCL level. The results show that the relationship between residual concentration, FC dose, and adsorption affinity of the system was well represented by uptake indices. The higher FC dose was required for suspensions containing greater concentration of As species to achieve MCL level. The As (V) species with a greater adsorption affinity towards FHO require a relatively smaller FC dose than As (III) ions. Moreover, the significant influence of interfering species on As removal was observed in simulated natural water. The author hopes that this study may help researchers and the drinking water industry to develop uptake indices of other targeted pollutants in achieving MCL level during water treatment operations in order to ensure public health safety.

scholarly journals Valorisation of used automotive lubrication oil

2019 ◽  
Author(s):  
◽  
Taegan Van Zyl
Keyword(s):  
South African ◽  
Impurity Content ◽  
Operating Conditions ◽  
Oil Refinery ◽  
Optimum Operating ◽  
Additive Package ◽  
Operating Variables ◽  
Lubrication Oil ◽  
Light Oil ◽  
Industrial Heating

This study has explored the production of Light Oil 10 (LO10) fuel from used automotive lubrication oil, thus providing a method for producing a cheaper alternative to diesel and paraffin for the South African industrial heating fuel market. Used automotive lubrication oil has different physical properties to that of the specified properties for Light Oil 10 fuel and therefore has to undergo processing that aligns the properties of the two. The low availability of Light Oil 10 fuel in the South African industrial heating market is driving companies such as a Durban based oil refinery to develop a continuous process that will produce Light Oil 10 fuels without the supplementation of paraffin. The supplementation has been done to retain customers but this resulted in the company selling Light Oil 10 fuel at a loss. Used automotive lubrication oil was of particular interest for use as the raw material for the new process as it is of low cost and is readily available. The viscosity (a measure of how easily a fluid flows at a particular temperature) of used lubrication oil was too high and needed to be reduced before it could qualify as Light Oil 10. The reduction of the viscosity of a fluid means that the ability of the fluid to flow at a particular temperature has improved. Additionally the additive package and the impurity content of the used automotive oil were too high. The additive package is added to mineral oil to give it the properties that new automotive lubrication oil requires; this package is still present in used automotive lubrication oil and is responsible for the high level of impurity content because it prevents impurities from agglomerating and dropping out of the oil. The new process was therefore required to be able to reduce the viscosity of used automotive lubrication oil and break the additive package. The required process and operating variables were developed / identified through literature review (qualitative) and the optimum operating variables were identified through experimentation (quantitative). A design of experiment was carried out using Design Expert software. This identified the matrix of runs that were required in identifying the optimum temperature, pressure and residence time for the ranges specified. The product from each of the runs was analysed in the Durban based oil refinery Research and Development lab. The results from the lab along with the corresponding run conditions were used to develop a model, and the model used to identify the optimum operating conditions. The research and experimentation took a total of two years to complete. The literature review found an existing refinery process, the drum type visbreaker to be the most suitable process for reducing the viscosity and breaking the additive package of used automotive lubrication oil. The drum type visbreaker holds oil in the drum for a period of time known as the residence time, at temperatures and pressures of 443oC and 15 bar respectively. These three variables are the critical operating variables in the visbreaking process. The high temperature breaks the large molecules into smaller molecules thereby reducing the viscosity via a process known as thermal cracking. This process also breaks down the additive package. The results from the experimental runs revealed that it is possible to produce Light Oil 10 from used automotive lubrication oil using the drum type visbreaker. The model produced through experimentation was found to be reliable and accurate within the range of variables investigated at predicting results for future runs. The model was also successfully used to identify the optimum operating conditions at which Light Oil 10 is produced from used automotive lubrication oil. The conditions were found to be 475oC, 15 bar and 60 minutes, confirmed by three confirmation runs. In conclusion this study has identified through literature and experimentation that thermal cracking via the free radical mechanism is the preferred process for producing Light Oil 10 from used automotive lubrication oil at liquid yields greater than 90%. An appropriate model was generated using the critical operating variables to predict future viscosity results. It was recommended that the Durban based oil refinery design and build a production scale pilot plant that includes all equipment and the feed heating coil (furnace used to heat feed to 475oC) that a full scale plant would have. This is because the run lengths due to coking (build up of hard carbon on the surfaces of heat exchange equipment) and functionality of the process need to be confirmed before the process can be deemed to be economically viable. Once this has been achieved a full scale production facility can be built.

Reading for pleasure : the influence of reading clubs in selected Bahananwa Limpopo primary schools

2020 ◽  
Vol 1 (3) ◽  
pp. 133-155
Author(s):  
Kgomotlokoa Linda Thaba-Nkadimene ◽  
Maletšema Ruth Emsley
Keyword(s):  
South African ◽  
Primary Schools ◽  
Cultural Theory ◽  
Negative Impact ◽  
Positive Influence ◽  
Reading For Pleasure ◽  
Theory Of Reading ◽  
Research Findings ◽  
African Youth ◽  
Reading Clubs

The challenges of reading experienced by learners exerts a negative impact on reading for pleasure, and learners' outcomes. In an attempt to address such reading challenges, Reading Clubs were launched to promote reading for pleasure among South African youth. This study examines the influence of Reading Clubs on learners' attitudes to Reading for Pleasure and the outcomes thereof. The study was informed by the Top-Down Model of Reading and the Cultural Theory of reading for pleasure. Interviews were conducted in five purposively selected schools with five Sparker coaches and five teachers. The research findings reveal a positive influence of Reading Clubs on reading for pleasure and learners' outcomes. This is reflected through improved levels of reading for pleasure. This study ultimately recommends that schools learn from best practices of Reading Clubs, and that government strive to make Reading Clubs a sustainable project.

scholarly journals A New Method to Determine the Impact of Individual Field Quantities on Cycle-to-Cycle Variations in a Spark-Ignited Gas Engine

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4136
Author(s):  
Clemens Gößnitzer ◽  
Shawn Givler
Keyword(s):  
Kinetic Energy ◽  
Flow Field ◽  
Turbulent Kinetic Energy ◽  
Negative Impact ◽  
Operating Conditions ◽  
Engine Operation ◽  
Gas Engine ◽  
Cycle Simulation ◽  
Simulation Results ◽  
The Impact

Cycle-to-cycle variations (CCV) in spark-ignited (SI) engines impose performance limitations and in the extreme limit can lead to very strong, potentially damaging cycles. Thus, CCV force sub-optimal engine operating conditions. A deeper understanding of CCV is key to enabling control strategies, improving engine design and reducing the negative impact of CCV on engine operation. This paper presents a new simulation strategy which allows investigation of the impact of individual physical quantities (e.g., flow field or turbulence quantities) on CCV separately. As a first step, multi-cycle unsteady Reynolds-averaged Navier–Stokes (uRANS) computational fluid dynamics (CFD) simulations of a spark-ignited natural gas engine are performed. For each cycle, simulation results just prior to each spark timing are taken. Next, simulation results from different cycles are combined: one quantity, e.g., the flow field, is extracted from a snapshot of one given cycle, and all other quantities are taken from a snapshot from a different cycle. Such a combination yields a new snapshot. With the combined snapshot, the simulation is continued until the end of combustion. The results obtained with combined snapshots show that the velocity field seems to have the highest impact on CCV. Turbulence intensity, quantified by the turbulent kinetic energy and turbulent kinetic energy dissipation rate, has a similar value for all snapshots. Thus, their impact on CCV is small compared to the flow field. This novel methodology is very flexible and allows investigation of the sources of CCV which have been difficult to investigate in the past.

scholarly journals Enzymatic Transesterification of Waste Frying Oil from Local Restaurants in East Colombia Using a Combined Lipase System

2020 ◽  
Vol 10 (10) ◽  
pp. 3566
Author(s):  
Mary Angélica Ferreira Vela ◽  
Juan C. Acevedo-Páez ◽  
Nestor Urbina-Suárez ◽  
Yeily Adriana Rangel Basto ◽  
Ángel Darío González-Delgado
Keyword(s):  
Reaction Time ◽  
Methyl Esters ◽  
Enzyme Concentration ◽  
Operating Conditions ◽  
Frying Oil ◽  
Biodiesel Production ◽  
Optimum Operating ◽  
Waste Frying Oil ◽  
Production Chain ◽  
Enzymatic Transesterification

The search for innovation and biotechnological strategies in the biodiesel production chain have become a topic of interest for scientific community owing the importance of renewable energy sources. This work aimed to implement an enzymatic transesterification process to obtain biodiesel from waste frying oil (WFO). The transesterification was performed by varying reaction times (8 h, 12 h and 16 h), enzyme concentrations of lipase XX 25 split (14%, 16% and 18%), pH of reaction media (6, 7 and 8) and reaction temperature (35, 38 and 40 °C) with a fixed alcohol–oil molar ratio of 3:1. The optimum operating conditions were selected to quantify the amount of fatty acid methyl esters (FAMEs) generated. The highest biodiesel production was reached with an enzyme concentration of 14%, reaction time of 8 h, pH of 7 and temperature of 38 °C. It was estimated a FAMEs production of 42.86% for the selected experiment; however, best physicochemical characteristics of biodiesel were achieved with an enzyme concentration of 16% and reaction time of 8 h. Results suggested that enzymatic transesterification process was favorable because the amount of methyl esters obtained was similar to the content of fatty acids in the WFO.

Optimum operating conditions for chiral separations in liquid chromatography

The Analyst ◽  
1999 ◽  
Vol 124 (5) ◽  
pp. 713-719 ◽  
Author(s):  
R. P. W. Scott ◽  
Thomas E. Beesley
Keyword(s):  
Liquid Chromatography ◽  
Chiral Separations ◽  
Operating Conditions ◽  
Optimum Operating

Performance Analysis of a Variable Speed-Ratio Metal V-Belt Drive

1988 ◽  
Vol 110 (4) ◽  
pp. 472-481 ◽  
Author(s):  
D. C. Sun
Keyword(s):  
Operating Conditions ◽  
Computational Scheme ◽  
Optimum Operating ◽  
Speed Ratio ◽  
Belt Drive ◽  
Variable Speed ◽  
Change Effect ◽  
Multiple Band ◽  
Ratio Change ◽  
Metal Block

A model of the metal V-belt drive (MBD), considering its detailed multiple-band and metal-block structure, and the ratio-change effect during its operation, is constructed and analyzed. A computational scheme is devised that adapts the analysis to the computation of the MBD’s performance for any specified drive-schedule. General performance characteristics of the MBD and an example illustrating its response to a given drive-schedule are presented. The use of the analysis and the computational scheme in the design of the MBD and in finding the optimum operating conditions is discussed.

Removal of Dyes from Aqueous Solutions by Adsorption on Chrome-Tanned Solid Wastes Generated in the Leather Industry

2003 ◽  
Vol 38 (2) ◽  
pp. 393-411 ◽  
Author(s):  
Soufiane Tahiri ◽  
Ali Messaoudi ◽  
Abderrahman Albizane ◽  
Mohamed Azzi ◽  
Mohamed Bouhria ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Operating Conditions ◽  
Solid Wastes ◽  
Cationic Dyes ◽  
Optimum Operating ◽  
Leather Industry ◽  
Anionic Dyes ◽  
Ph Values ◽  
Acidic Conditions ◽  
Dyes Adsorption

Abstract In this work, the ability of chrome shavings and of crust leather buffing dusts to remove dyes from aqueous solutions has been studied. Buffing dusts proved to be a much better adsorbent than chrome shavings for cationic dyes. The adsorption of anionic dyes is very important on two studied wastes. The pH has an obvious influence on the adsorption of dyes. Adsorption of cationic dyes is less favourable under acidic conditions (pH <3.5) and at high pH values (pH >10.5). The adsorption of anionic dyes on both adsorbents is more favourable under acidic conditions (pH <3). The adsorption on chrome shavings is improved by the use of finer particles. The kinetic adsorption was also studied. Adsorption isotherms, at the optimum operating conditions, were determined. Adsorption follows the Langmuir model. The isotherm parameters have been calculated. The column technique could be applied to treat significant volumes of solutions.

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