Thabo Falayi

The Namibia University of Science and Technology

Purpose The study compares how work-integrated learning (WIL) placement positioning, duration, assessment strategies and environment at three Southern African universities influence engineering students' academic and employability outcomes. Design/methodology/approach The study used a qualitative case study approach that drew on the principles of...

The aim of the study was to determine the use of sugarcane bagasse ash geopolymer (SCBAG) as an adsorbent for organic compounds to reduce the chemical oxygen demand (COD) from vinasse. The effect of solid loading, time and temperature was investigated for the batch adsorption whilst the effect of bed height and flow rate was investigated for the co...

The COVID-19 restrictions resulted in the most significant disruptions to education in this century. Universities responded differently to the restrictions. For example, some universities in Southern Africa closed and had no academic activities for months. These universities had little online teaching and learning, opting for a phased return to fac...

The aim of the study was to investigate the possibility to use acid-treated sugarcane bagasse ash (SCBA) as a coagulant. The effects of type of acid, coagulant dose, time and pH on the coagulation characteristic were investigated. Synthetic turbid water was used for the tests. The coagulants were treated with H2SO4 (SSCBA) and HCl (HSCBA). A 6% m/v...

The need to reduce carbon emissions to mitigate against greenhouse effects of global warming has necessitated research into alternative renewable green technologies. One of these technologies is the production and application of green hydrogen . It is important to note that hydrogen is not a primary source of energy but rather a carrier1. The cheap...

The greenhouse gases released by various anthropogenic activities have necessitated the research into the recycling of industrial waste into green geopolymer concrete or monoliths . The industrial waste, sometimes called the supplementary cementitious material (SCM), includes secondary resources such as fly ash, steel slags, rice husk ash, mine tai...

The lack of access to safe drinking water has been a global crisis for the longest time, which has encouraged researchers to improve existing technologies or create new strategies to address issues associated with water pollution from both inorganic and organic pollutants. Adsorption and photodegradation are among the simple, cost-effective and env...

Microplastics (MPs), which are tiny plastic materials with size below 5 mm, are ubiquitous in both terrestrial and aquatic environments. They are an emerging pollutant posing potential threats to the biosphere. Once they get into the environment, microplastic wastes are difficult to eliminate and hence are continually accumulating in the environmen...

Moringa Oleifera (MO) seed extract was used as an antimicrobial agent and a biosorbent to remove heavy metals from acidic mineral effluents. Biosorption experiments were conducted in a thermostatic shaker using synthetic acidic mineral effluent(SAME) of composition, 20 ppm, 20 ppm, 100 ppm, and 500 ppm for Ni, Cu, Mn, and Fe, respectively. The Quan...

Ferrochrome (FeCr) slag was milled and stabilised with either ascorbic acid or phosphoric acid. The stabilised FeCr was then geopolymerised with 1 M KOH in order to obtain a monolith with at least an unconfined compressive strength of 1 MPa. The leachability of metals of the stabilised geopolymerised monoliths were then compared with the unstabilis...

Ferrodrrome slag (FeCr-GP) and gold mine tailings (GMT-GP) based geopolymers were synthesized and used as adsorbents of heavy metals in aqueous solutions. Batchwise adsorption experiments were used to determine the effect of solid loading (S/L), temperature and time on the adsorption of Cu, Ni and Mn. X-ray diffraction studies showed that GMT-GP wa...

South African acidic gold mine tailings (GMT) were milled and calcined before alkaline activation with KOH. The objective was to increase their unconfined compressive strength (UCS) through thermo mechanical activation so that competent and durable civil engineering materials can be synthesised from waste. The optimum synthesis conditions were 1...

The adsorptive properties of coal fly ash in removing copper and nickel from waste water was investigated using batch and fixed bed column studies. Various process parameters such as solution pH, solid loading, residence time, temperature, bed height and flow rate were tested to determine the effectiveness of fly ash. The study revealed that fly as...

Fly ash (FA) and Basic oxygen furnace (BOF) slag were used to as additives in the geopolymerisation of gold mine tailings (GMT).The aim of the research was to determine the effects of the two additives on the strength formation and mechanism of metal immobilisation by modified GMT geopolymers. GMT, FA and BOF were mixed, respectively, and made into...

Abstract Ferrochrome (FeCr) slag was used as a precursor for the synthesis of a geopolymer. The effect of KOH concentration, liquid solid ratio (L/S), content of potassium metalisicate (KS) or potassium aluminate (KA), curing time on the unconfined compressive strength (UCS) and metal leachability of the synthesised geopolymer was investigated. A 1...

Tetradecytrimethylammonium bromide (TDTMA) was used to modify the surface properties of desilicated fly ash (DFA). The objective was to improve the removal of sulphates from acid mine drainage using the TDTMA modified DFA (TDTMA-DFA). A 20% addition of TDTMA to DFA produced the optimum sulphate adsorbent. A 4% (m/v) solid loading of TDTMA-DFA was c...

Si and Al were leached from gold mine tailings (GMT) in order to determine if the GMT could be used as precursors for the synthesis of geopolymers. Possible synthesis of geopolymers from GMT would help reduce their potential pollution effects through heavy metal immobilisations. The effect of type of alkali (NaOH/KOH), alkali concentration, tempera...

Remediation of residual fly ash from coal fired electric power plants is beneficial to the environment. The chemical, physical, geotechnical and radiological properties of desilicated fly ash (DFA) were investigated. The DFA: lime ratio of 70:30 composite was found to have an average UCS of 8.8 MPa showing 19.5% water absorption after a 24 h soak w...

Si and Al were leached from gold mine tailings (GMT) in order to determine if the GMT could be used as precursors for the synthesis of geopolymers. Possible synthesis of geopolymers from GMT would help reduce their potential pollution effects through heavy metal immobilisations. The effect of type of alkali (NaOH/KOH), alkali concentration, tempera...

Remediation of residual fly ash from coal fired electric power plants is beneficial to the environment. The chemical, physical, geotechnical and radiological properties of desilicated fly ash (DFA) were investigated. The DFA: lime ratio of 70:30 composite was found to have an average UCS of 8.8 MPa showing 19.5% water absorption after a 24 h soak w...

Mesoporous silica (MCM41) adsorbent was prepared from silicate solution produced from silica leaching of calcined pulverised fly ash. MCM41 was used for the removal of heavy metals and neutralisation of acid mine drainage. Silica leaching was optimised using two level full factorial and 13 run central composite rotable uniform design with 5 centre...

Phosphogypsum (PG), a waste material readily available in large quantities, is generated in the wet process of phosphoric acid production. Due to the contaminants in the material and the radioactivity of PG, the use of this material has limitations. South African phosphogypsum (from Phalaborwa) contains high levels of thorium that could be recovere...

In this study, acidic gold mine tailings were alkali activated using potassium hydroxide (KOH). The effect of potassium silicate (KS) and potassium aluminate (KA) on the strength and durability of the synthesised geopolymers was investigated. An optimisation experimental programme of various conditions was used to get the best geopolymers in ter...

The alkaline leaching of Phosphorous (P) from sewage sludge (SS) using either NaOH or KOH was investigated. The effect of type and concentration of alkali, solid liquid loading and leaching temperature were also investigated. The possibility to stabilise the leached SS residue via geopolymerisation was also explored. The results showed that KOH lea...

Acidic gold mine tailings were alkaline activated using KOH. The effect of potassium aluminate (KA) on the strength and durability of the geopolymers was investigated. A 2.8 KA:KOH geopolymer had a UCS of 18.10 MPa after curing for 5 days at 100 °C. There was an increase in UCS with an increase in loading of KA up to a ratio of 2.8. Beyond the KA:K...

Adsorption of Cr, Al and Zn from a powder coating aluminium process wastewater was achieved using Basic oxygen furnace slag (BOFS) as an adsorbent. Batch adsorption studies were used to investigate the effects of solid-loading effect, temperature and contact time on adsorption. Highest metal removal was obtained at a solid-loading of 4% m/v. The ad...

Gold mine tailings (GMT) were characterised and alkaline activated into geopolymers so as to reduce their pollution potential. The GMT was activated because they are aluminosilicate mate-rials and as such they have the potential to be geopolymerised under alkaline conditions. The main parameters tested were the effect of type of alkali (NaOH and KO...

Coal ash from most of Eskom power plants consists of 70–85% fly ash and 15–30% bottom ash. A total of 25 million tons of ash is produced from approximately 109 million tons of coal per annum. Small percentage of the ash were used in cement production and other construction applications and almost 80% of the ash were disposed into ash dams. The need...

This paper presents study of the kinetic mechanism of lime consumption using desilicated fly ash (DFA). Desilicated fly ash (DFA) a residue from leaching of silica from fly ash was stabilised using lime at elevated temperatures. DFA and lime were mixed in different ratios at optimum moisture content and maximum dry density and then cured at 40 ºC,...

Massive reserves of power plant fly ash dumps in South Africa have necessitated the development of different processes for effective remediation to achieve zero waste generation by secondary processes. Silica was leached from fly ash (FA) at the optimum conditions of a leaching time of 6 h, 3 M KOH, 500 rpm agitation speed, 25 liquid to solid ratio...

The prediction of strength of lime ash composites is critical for quality control, material performance monitoring and material serviceability limit state. A study was conducted to investigate the influence of open porosity (an index of micro grain alignment and macro particle parking), sum of hydration products and extent of hydration of desilicat...

This study presents the use of marginal material as a stabiliser for expansive soil and therefore provides opportunity for high volume use of waste material for low cost, low volume road construction. Desilicated fly ash (DFA) was stabilised with lime up to 40 %. The effect of composite moisture content, lime content and curing temperature was stud...

Attapulgite calcined at 973.15K was characterized and utilized as an adsorbent for the removal of heavy metals and neutralization of acid mine drainage (AMD) from a gold mine. Batch adsorption experiments were carried out using a thermostatic shaker. Activated attapulgite showed that it can neutralize AMD as it raised the pH from 2.6 to 7.3 after a...

Fly ash from a South African power station ash dam was used. The fly ash approximated Class F fly ash but had a loss on ignition greater than 6%. The leaching parameters investigated were leaching time, KOH concentration, agitation speed, fly ash particle size, leaching temperature and liquid solid ratio (L/S). It was found that the optimum leachin...

Natural attapulgite was utilized as an adsorbent for the removal of Al, Fe and Mn from a mixed metal effluent. Adsorption experiments were carried out by agitation of a fixed amount of attapulgite with a fixed volume of effluent waste stream in a thermostatic shaker for varying times. Attapulgite showed that it was capable of neutralising the acidi...

Unactivated attapulgite was characterised and utilised as an adsorbent for the removal of heavy metal and neutralisation of acid mine drainage (AMD) from a gold mine. Adsorption experiments were carried out by agitation of a fixed amount of attapulgite with a fixed volume of AMD in a thermostatic shaker for varying times. Attapulgite showed that it...

Fly ash (FA) was used as an adsorbent for SO42- ions in pretreated AMD (i.e., after removal of heavy metals). The adsorption experiments were done using a thermostatic shaker at varying temperatures with a 50%, 33%, and 25% m/v FA solid loading. The 50% solid loading was chosen as the best as it removed 80% of SO42- ions after 24 h. The adsorption...

The potential use of activated bentonite as an adsorbent for heavy metals in acid mine drainage (AMD) was investigated. The activated bentonite was characterized as sodium bentonite. 1% solid loading was not effective in neutralization and metal removal. 5% solid loading could neutralize AMD as pH increased from 2.08 to 7.88 after 3 h accompanied w...

The ability of activated bentonite to adsorb Cu and Ni was investigated. 6 % solid loading was chosen as the optimum solid loading for activated bentonite with 94.85% Cu and 92.05% Ni removal after 3 hours of agitation. The adsorption process followed the Langmuir isotherm and pseudo second order kinetic models. The maximum adsorption capacities we...

Sewage sludge from ERWAT (East Rand Water Care Company) was investigated to determine its potential as a source of P. The raw sewage sludge was found to be a potential source of P. At least 84% P could be leached from the raw sewage sludge after 60 min using either HCl or H2SO4. Selective precipitation of P as magnesium tetraphosphate could be achi...

Fly ash (FA) was used as an adsorbent for SO4 2- ions in pretreated AMD (i.e., after removal of heavy metals). The adsorption experiments were done using a thermostatic shaker at varying temperatures with a 50%, 33%, and 25% m/v FA solid loading. The 50% solid loading was chosen as the best as it removed 80% of SO4 2- ions after 24 h. The adsorptio...