Synthesis and evaluation of basic oxygen furnace slag based geopolymers for removal of metals and sulphates from acidic industrial effluent-column study

Abstract:Basic Oxygen furnace slag (BOFS) based geopolymers with open porosity ranging from 21%–57 % and density between 1255 kg/m3-2432 kg/m3 were synthesized. The synthesized geopolymers potential; to be used as attenuators for metal removal and neutralization of Acid Mine Drainage (AMD); were assessed and evaluated through column test studies conducted over a period of 133 days. The results show that BOFS based geopolymer composites can be used as attenuators as over 99 % metals were removed during the first 50 days. The results also revealed that higher porosity promoted greater neutralizing ability by dissolution of soluble salts from the BOFS based geopolymer; which improves the removal efficiencies of sulphates, metals and neutralization of AMD. Characterization of the composites after contact with AMD revealed that gypsum was the main mineral phase in the geopolymers indicating that precipitation was the major mechanism that enhanced metal and sulphates removal. BOFS based geopolymers can be used to replace armoring neutralizing agents such as limestone. The research contributes to sustainable development by addressing the environmental pollution posed by AMD and utilization of BOFS as a medium for remediation of AMD. The utilization of BOFS for remediation of AMD mitigates and responds to the environmental problems and demands associated with such waste

Fixed bed column studies for decontamination of acidic mineral effluent using porous fly ash-basic oxygen furnace slag based geopolymers

Abstract: This paper presents column studies conducted to evaluate and assess the potential use of Fly Ash (FA). Basic Oxygen Furnace Slag (BOFS) based geopolymers to remove metals, sulphates and acidity from Acid Mine Drainage (AMD). Geopolymers were prepared using NaOH, Fly ash (FA) was used as source of silica additive to supplement BOFS. The blending ratio was fixed to 10% FA and the S/L ratio was kept 20%. The H2O2 was used as a blowing agent to increase the porosity of the FA/BOFS based geopolymer at four different percentages (1.5%, 1%, 0.5% and 0%). The four different geopolymers with distinct porosities were employed in different columns respectively. It was found that over 99% removal efficiency of metals and sulphates was achieved in the first 60 days of column studies. The dissolution of Ca(OH)2 was the main constituent responsible for the removal of acidity in AMD. Characterization revealed that precipitation was the main mechanism for removal of metals. Gypsum was the main byproduct formed with precipitated metals presented by goethite, spertite and manganite

Compressive strength and durability of fly ash stabilized dolomitic waste as a lightweight construction material

Due to the seriousness of environmental pollution and the production of huge energy consuming building and construction materials, the development of new eco-friendly and energy saving building materials to overcome these issues has been gaining increasing attention. South Africa has largest number of dolomite deposits in Southern Africa, if not in the entire Africa. Nonetheless most of the dolomite in South Africa has some impurities of which they are neglected in dumping site (millions of tons). This paper looked at finding alternative use for this dolomitic waste (DW) by stabilizing this waste with another waste called fly ash (FA), introduction of gypsum as an activator will trigger a pozzolanic reaction in presences of water. As a result of this, the product of this reaction will be a useful material in construction and as well solve the difficulties i.e. environmental, social and cost often associated with storing and handling of this waste. This work went as far as providing an alternative for low-cost construction materials that can help deal with South African housing problems. The waste material was analyzed from geomaterial and geochemistry view point, the chemical reaction between these materials: dolomitic waste and fly ash were illustrated. The XRF, SEM and EDS of the reacted product were looked at, the strength gained by the reaction after sample preparation for 28 days were also shown. However various geotechnical laboratory experiments were conducted ranging from proctor compaction test, compressive strength test and a mathematical model was generated to predict the compressive strength and these results were compared to compressive strength values obtained from the laboratory

Development of lightweight construction blocks by alkaline activation of BOF slag

Abstract: Large quantities of basic oxygen furnace (BOFS) are dumped in landfills of which the available land for land-filling of large quantities of waste is reducing all over the world. It is therefore im-portant to develop processes which beneficiates solid waste; BOF slag specifically. The present study attempts to investigate the potential to synthesize BOF slag based light weight construc-tion blocks. The effects of several factors on the UCS of BOF slag based light weight construc-tion blocks (LWCB) was also investigated. The test variables were molarities of sodium hydrox-ide (NaOH) (5 M, 10 M and 15 M); the solid to liquid ratio (20 %, 25 % and 30 %); the sodium silicate (Na2SiO3) to Na! OH ratio (0.5:1, 1:1, 1.5:1, 2:1, 2.5:1 and 3:1); the curing temperature (40°C, 80°C and 100°C). It was found that optimum synthesis conditions were 5M NaOH, 80°C and 1:1 Sodium Silicate: NaOH ratio. The LWCB composite met the minimum requirements for ASTM C34-13, C129-14a and South African standard (SANS227: 2007)

The geotechnical and microstructural properties of desilicated fly ash lime stabilised expansive soil

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Eclampsia in Irrua Specialist Teaching Hospital: A five-year review

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Mechanical properties and structure of Fly ash modified Basic Oxygen Furnace Slag based geopolymer masonry blocks

Abstract: The objective of this research was to investigate the effect of Fly ash as a source of Si and Na on the mechanical performance of the Basic Oxygen Furnace Slag based (BOFS) geopolymer. BOFS has the lowest SiO2, Al2O3, Na2O content compared to other aluminosilicate sources (fly ash, metakaolin, granulated blast furnace slag and mine tailings); which have been used to effectively in geopolymer synthesis. SiO2 and Al2O3, contents of BOFS are respectively 5-7 times and 6-8 times lower than those of fly ash, metakaolin and granulated furnace slag (GBFS). This study evaluated the potential use of fly ash as a source of Si and Al to improve the mechanical performance of a BOFS based geopolymer. The influence of varying amount of Coal Fly Ash (FA) (10–50%) on UCS was studied. The effects of several factors on the UCS of BOFS geopolymer were also investigated. The test variables were molarities of sodium hydroxide (NaOH) (5 M, 10 M and 15 M); the solid to liquid ratio (20 %, 25 % and 30 %); and the curing temperature (20°C, 40°C, 80°C and 100°C). It was established that most favorable conditions for the geopolymer synthesis were FA was 10% of the mixture, 5M NaOH and 80°C curing temperature. Attempts has been made to relate the microstructure of BOFS/FA based composite with properties of geopolymer. Aggregation was identified as the main particulate process as established by the evolution of the particle size distribution (PSD) and its derived moments during the geopolymerisation process. The morphology of the particles appeared flaky and fluffy. The developed composite met the minimum requirement of ASTM C34-13 for a structural clay load bearing non exposed masonry and load bearing exposed side construction masonry

Development of low content phosphogypsum waste composites modified by lime-fly ash-basic oxygen furnace slag

Abstract: The generation and disposal of phosphogypsum (PG) is a worldwide challenge, due to the environmental pollution posed by the material. The contaminants laden in the material are the major limitations for the utilisation of PG. Other materials considered as wastes such as fly ash (FA) and basic oxygen furnace slag (BOF slag) are generated by numerous industrial activities and disposed into environment. This study investigated the use of three wastes materials for the development of a composite applicable for road construction. Two types of PG were investigated, namely citric acid treated PG (TPG), for the removal of the contaminants and raw PG (RPG). Lower content PG containing 20% and 30% were investigated and modified with FA, Lime (L) and BOF slag. The effect of particle size distribution (PSD) on unconfined compressive strength development, durability of the composites and hydration products contributing to strength development were studied. Modification of PG with FA-L-BOF slag significantly improved the unconfined compressive strength of PG. The PG content of 20% for the RPG and TPG yielded the highest strengths of 7.4 MPa and 5.4 MPa, respectively when cure at elevated temperatures. Normal curing of the composites over 7 days and 28 also showed an increase in strength development. Particle size played a significant role in the unconfined compressive strength development. Kieserite, calcium aluminium sulphate and calcite were the predominant hydration products formed during the curing process

Effects of palm kernel cake supplement on fatty acid profile and milk composition of lactating wad goats fed grass silage

The scarcity of quality feed and cost-effective supplements necessitates verifiable concentrate as a supplement for goat milk production. Palm Kernel Cake (PKC), an oil palm by-product rich in protein and energy, gradually replaced Prepared Concentrate (PC) in this study. This replacement's impact on milk composition and fatty acid profile in lactating WAD goats fed grass silage basal diet was assessed. Five supplement concentrates with varying PC: PKC ratios (100:0, 75:25, 50:50, 25:75, 0:100) were fed to 25 lactating WAD goats in a randomized setting of 5 animals per group. The replacement significantly affected (p<0.05) milk fat, protein, specific gravity, ash, and fat-corrected milk. The highest milk fat (2.17%) came from 100% PKC supplementation, while the lowest (0.77%) came from 25% PKC. Total solid fat values were not significantly affected. Fat Corrected Milk results mirrored the milk fat trend. The 100% PKC group had the highest crude protein (8.22%), while 25% and 75%PKC were not different (p<0.05). Fatty acid profile, expressed as total Fatty Acid Methyl Esters (FAMEs) g/kg, showed increased medium and long-chain fatty acids as PC was replaced. In conclusion, 100% PKC supplementation enhanced milk fat, while 50% PC replacement increased long-chain polyunsaturated fatty acids in goat mil