Nigerian Kaolin Research Articles

Characterisation and Performance of Nigerian Kaolin and Metakaolin in Geopolymer Synthesis

This study is aimed at characterising and understanding the mechanical and microstructural behaviour of natural and calcined kaolin clay for geopolymer applications. The clay samples obtained from Kaduna State, Northern area of Nigeria, were calcined within the temperature range of 700 and 900oC and are represented by MK7, MK8 and MK9. The raw kaolin and metakaolin were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and scanning electron microscopy (SEM). To produce geopolymer binders, the precursors were reacted with a 1:1 combination of sodium hydroxide and sodium silicate solution and a precursor to activator ratio of 1.2 was suitable for preparation. The compressive strength of the samples was determined at three testing age of 7, 14 and 28 days. From the results obtained, the kaolin-based geopolymer generally had a long setting time and testing was impossible at the 7-day testing age. The compressive strength of other samples however, increased with increase in the calcination temperature. The values obtained at the maximum testing age of 28 days for all samples fall between 5.1 -14.9 MPa. The scanning electron microscope morphology of the produced binder, show the presence of air trapped in the paste which may have reduced the strength value. Vibrating samples before setting can improve the performance of the geopolymer binders by removing most of the trapped air. Geopolymers produced from this study based on strength obtained, can be used in less critical areas of the construction industry.

Preparation of Industrial α-Alumina Powder from Ijero Ekiti (Nigeria) Kaolin ore by Acid Leaching Process

The global demand for pure industrial kaolin ores for paper, cosmetics, porcelain and metallurgical industries cannot be over emphasized. Thus, the need to continuously develop feasible and low-cost routes of ore processing to meet industrial demands becomes paramount. In this study, alumina powder of defined industrial utilities was prepared from a Nigerian kaolin ore containing admixtures of kaolinite (Al2.00Si2.00O5.00(OH)4.00: 96-900-9235), albite (NaAlSi3.00O8.00: 96-900-9664) and muscovite (KAl2.00(FOH)2.00: 96-900-1057), with traces of some other valuable mineral phases by acid leaching method using hydrochloric acid (HCl) as the lixiviant was examined. At optimal leaching conditions (6 M HCl, 70 °C, 6 h), the crystalline powder formed after precipitating to remove iron and other associated impurities was followed by washing, drying and quantitatively characterized. The pure α-alumina powder produced (Al2O3: 14-366-9038, melting point = 2064 °C, density = 3.99 g/cm3) as characterized could serve as a valuable product in the metallurgical and cosmetics industries.

Development of nano-silver doped zeolite A synthesized from Nigerian Ahoko kaolin for treatment of wastewater of a typical textile company

In this work, nano-silver synthesized with mango leaf extract as a reducing agent was doped onto synthesized zeolite A (SZA), produced from Nigerian kaolin via green synthesis route. The produced adsorbents were characterized using X-ray fluorescence (XRF), X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier-transform infrared spectroscopy (FTIR) and Brunauer–Emmett–Teller (BET) surface analysis, in addition, it is to be used for the treatment of local textile effluent. The physicochemical parameters of the effluent were analyzed using standard methods. The HRTEM micrographs revealed well dispersed AgNPs on SZA and the BET surface area revealed high surface areas of 119.98 m2/g and 436.44 m2/g for SZA and silver-doped zeolite A (SDZA), respectively. The array of removal of the pollutants was BOD > COD > CN->Cl->NO2->TOC for SZA and CN->BOD > COD > NO2->Cl->TOC for SDZA, with the doped adsorbent removing the higher pollutants in all cases. Isothermal models indicated that Jovanovic model (R2>0.999) was most suitable for describing the adsorption process, which conformed to pseudo-second order kinetics with intraparticle diffusion of micropore type. The thermodynamic studies showed spontaneous and endothermic reactions.

Catalytic cracking of polyethylene plastic waste using synthesised zeolite Y from Nigerian kaolin deposit

The increasing rate of accumulation of plastic waste (PW) is quite disturbing to the world, particularly in developing nations due to its non-biodegradable nature and inadequate waste management practices. The need to properly manage this waste and utilize the potential and chemical energy value that can be derived from this waste justifies the encouragement and employment of newer and better recycling methods and technology of these wastes. Therefore, this has led us to explore the catalytic pyrolysis of plastic waste using zeolite Y synthesized from kaolin deposit in Covenant University, Sango Ota, Ogun state of Nigeria. A stainless steel packed bed reactor was used in the cracking of low-density polyethylene (LDPE) plastic wastes into liquid fuel components at a temperature of 300 ℃ using zeolite Y catalyst. The liquid fuel obtained from the catalytic pyrolysis was analyzed using GC–MS. Fifty compounds were identified, which revealed the presence of mostly alkenes and aromatics in the hydrocarbons range of C8–C29. This is made up of 56% of gasoline fractions range of C6–C12, 26% of diesel and kerosene fractions range C13–C18, and 10% of fuel oil range C18–C23, while 8% is residual fuel range greater than C24.

Influence of transition metal ion (mn4+) on mullite formation in a mixture of 50:50 Nigerian kaolin and calcined alumina

In the present investigation, 5 wt% chemical grade MnO2 was added in a mixture of 50:50 Nigerian sources of kaolin and superfine calcined alumina powder and effect of this transition metal ion on their physico-mechanical properties, phase and microstructural evolution were studied during heating in the temperature range of 1,400–1,650°C. The heated samples were found to be highly porous (>30%) in this entire temperature range. The doping of 5 wt% MnO2 in this mixture did not improved the densification, but resulted into higher flexural strength (26 MPa) at 1,400°C compared to 7 MPa in the undoped sample. At 1,650°C, the reverse trend was observed, the flexural strength of undoped sample was found to be higher (38 MPa) than doped sample (27 MPa). The XRD study revealed the formation of mullite as major and corundum as minor phases in both the samples. The microstructural study shown the presence of needle shaped mullite crystals and corundum grains. The presence of inter-granular and intra-granular pores in MnO2 doped samples might have reduced the strength at 1,650°C. The aspect ratio of mullite needle at 1,650°C was found to be higher in doped sample. The theoretical and experimental value of >4 for MnO2 ion has been validated.

Treatment of a Nigerian Kaolin ore for Improved Industrial Application

A study was carried out on leaching of Nigerian kaolin ore by Oxalic acid (C 2 H 2 O 4 .2H 2 O). The raw kaolin ore from Share, North central Nigeria was characterised by EDXRF (X-ray fluorescence) and major constituents were SiO 2 , Al 2 O 3 , and minor amounts of K 2 O, Na 2 O, CaO, TiO 2 , along with colour-imparting Fe 2 O 3 and MnO that need to be remove to upgrade the kaolin suitability for industrial usages. The effects of parameters such as C 2 H 2 O 4 concentration, temperature, and particle size were investigated. Under the standard leaching conditions of −75+63 μm particle size, 75 °C and 0.15 mol/L C 2 H 2 O 4, about 78.5% of kaolin ore was reacted within 120 minutes. Comparison of the EDX analysis of the raw and leached kaolin showed removal efficiency of 97.1% for the iron at optimal leaching conditions. Energy of activation of 17.65 kJ/mol was obtained in the study supports the proposed diffusion control mechanism for the dissolution process.

Screening Nigerian Kaolin for Use as Potential Sources of Geopolymer Materials

The search for alternative low cost and environment friendly binder has led to the screening of Nigerian kaolinite clay for the production of geopolymer binders. Three batches of geopolymer binders were synthesised using five Nigerian kaolinite clays, locally synthesised sodium silicate and NaOH. The clays were Ikere Ekiti (Ekiti State) kaolin, Ikare (Ondo State) kaolin, fired clay (Ozubulu, Imo state), Enugu (Enugu state) kaolin, and laterite (Lagos State).The first batch was activated with sodium silicate and water in ratio one to one. The second batch was activated with sodium silicate and water in ratio one to half and the last batch was activated with sodium silicate and sodium hydroxide in ratio one to one. Six mixes for each sample were prepared for the first and second batches of geopolymer binder. They were cured at room temperature for seven days, 75oC, 150oC and 500oC. The last batch of the geopolymer binder was cured at 150oC. The result of the research confirmed that compressive strength of kaolinite clay based geopolymer binder increased with increase in curing time from 7 days room temperature to 500oC. All geopolymers activated with both sodium silicate and sodium hydroxide demonstrated sharp increase in their compressive strength values when compare with geopolymer activated with sodium silicate and water. Comparing the geopolymers activated with both sodium silicate and NaOH in ratio one to one with ASTM Specification Standard, Ikare sample satisfied ASTM Specification Standard C62 and C90. Similarly, Ikere Ekiti geopolymer satisfied ASTM Specification Standard C62, C90, C216, and C902. Water absorption test performed showed that all the samples have good water absorption capacity at different conditions when compared with ASTM Specification Standard for water absorption, except Enugu kaolin and Ozubulu clay which did not satisfied the ASTM requirements at room temperature and at 75oC. Nigerian kaolinite clays have potentials to be used as geopolymer binders which may be applied in construction.

ChemInform Abstract: The Direct Synthesis of Pure Zeolite‐A Using “Virgin” Kaolin.

AbstractNigerian kaolin is converted into pure zeolite‐A by calcination of the kaolin at 650 °C for ten minutes, followed by mixing the obtained metakaolin with a zeolite seed, NaOH, and H2O (autoclave, 100 °C, 3 h).

EFFECT OF TEMPERATURE ON THE SYNTHESIS OF ZEOLITE X FROM AHOKO NIGERIAN KAOLIN USING NOVEL METAKAOLINIZATION TECHNIQUE

Zeolite X was synthesized successfully from kaolin using a novel metakaolinization technique. The first step involves refining the raw kaolin sample, followed by metakaolinization. This was done after determining the metakaolinization temperature of Ahoko Nigerian kaolin (ANK) as 600°C using in situ X-ray diffraction (XRD) and simultaneous thermal analysis (STA). A new method for the production of metakaolin was investigated in this work. Metakaolin was obtained after 50 min of exposure at 600°C. The metakaolin produced was used to synthesize zeolite X using the hydrothermal method. Highly crystalline zeolite X was not obtained until the crystallization temperature of 80°C was attained, with aging time and crystallization time fixed at 24 h and 6 h respectively. Zeolite formation increases with increase in crystallization temperature as evident from the increase in the intensity of diffraction peaks. An increase in temperature beyond 100°C leads to a remarkable decrease in the reflectivity of zeolite X, with formation of a completely new zeolitic phase recognized as sodalite, which was formed at 200°C. Finally, the ion exchange behavior of the synthesized zeolite X obtained at 100°C was investigated. The removal of metal ions from synthetic solutions at an initial concentration of 200 ppm was studied using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The cation exchange capacity (CEC) was calculated as 2.31 meq g−1. Removal efficiency was determined at varying contact times with an optimum removal time of 30 min for all the metal ions, except Ni+, with an optimum time of 4 h. It was observed that the as-synthesized zeolite X had a strong ion exchange affinity with the metal ions studied.

The direct synthesis of pure zeolite-A using ‘virgin’ Kaolin

Here we demonstrate the conversion of a Nigerian Kaolin, straight from the source without any form of pre-treatment, directly into pure zeolite-A. The method involves a rapid and low temperature meta-kaolinization step followed by chemical conversion directly into pure zeolite-A. The synthesis step acts as the purification step removing the 80% quartz impurity simultaneously with zeolite growth. The whole process is designed to be both economical and straightforward to facilitate commercialisation.

Effect of Aging on the Synthesis of Kaolin-Based Zeolite Y from Ahoko Nigeria Using a Novel Metakaolinization Technique

Zeolite Y was systematically synthesized from Ahoko Nigerian kaolin in a conventional hydrothermal system using novel metakaolinization technique. The effect of aging on the formation of zeolite phase was investigated during the course of the synthesis. A rapidly processed metakaolin at a temperature of 600°C and exposure time of 50 minutes, which is capable of reducing the energy and cost of producing it was used to study the synthesis of zeolite Y. It was found that aging conditions play a prominent role in the preparation of zeolite Y from Ahoko metakaolin. Aging played a significant role by increasing the crystallinity of the final product even though zeolite Y was obtain without aging. The outcome of zeolite Y synthesized from Ahoko kaolin in 9 hours at 100°C was different from most reports on the synthesis of zeolite Y from kaolin where longing time (72 hours) of crystallization are reported.