silica sand extraction from ash

milltec silica extraction | agi

milltec silica extraction | agi

AGI MILLTEC, as a market leader, strives for continuous improvement to serve customers better and to provide good value for their money. Disposal of rice husk is one of the major challenges faced by millers all over India. India produces around 25 million tons of rice husk every year. Rice husk when burnt in the boiler as fuel, generates ash known as rice husk ash (RHA). While RHA is environmental waste, it contains 60% to 80% amorphous silica, which is useful in various industries.

As an expansion and diversification strategy, AGI MILLTEC has introduced a high-efficiency precipitated silica extraction technology from rice husk ash. The equipment for the extraction plants are designed locally, at AGI MILLTEC. AGI MILLTEC batch processing plants operate at 2 tons per day silica extraction capacity. Along with silica, there are other by-products like carbon and sodium carbonate from RHA that are useful in various industries. This product is currently in its pilot phase.

green technology extraction and characterisation of silica nanoparticles from palm kernel shell ash via solgel - sciencedirect

green technology extraction and characterisation of silica nanoparticles from palm kernel shell ash via solgel - sciencedirect

Silica nanoparticles have numerous applications including drug delivery, lightweight aggregates, and energy storage. It has been manufactured from different agricultural bioresources with limited research on palm kernel shell ash (PKSA). This study produced silica nanoparticles from palm kernel shell ash. Modified solgel extraction technique was used to produce the silica nanoparticles from PKSA. The extracted silica nanoparticles were characterized using X-ray diffraction (XRD), Scanning electron microscope (SEM) with Energy dispersive X-ray (EDX), Fourier transform infrared (FT-IR) techniques, BrunauerEmmettTeller (BET) method and Thermogravimetric analysis (TG). The microstructural analysis reveals that the unit size of the extracted silica nanoparticles is between 5098nm, with a very high specific surface area (438m2g1). EDX confirmed the presence of SiO2 in the sample. FT-IR analysis shows the existence of silanol and siloxane groups. This success means, decrease in environmental contamination caused by indiscriminate disposal of palm kernel shell (PKS) and silica nanoparticles for advanced material applications.

preparation of sodium silicate solutions and silica nanoparticles from south african coal fly ash | springerlink

preparation of sodium silicate solutions and silica nanoparticles from south african coal fly ash | springerlink

The production of amorphous mesoporous silica nanoparticles can be achieved using sodium silicate (Na2SiO3) solutions prepared from South African coal fly ash waste. The first part of this study compared two processes for the preparation of Na2SiO3 solutions. The first process, hereafter called sequential acid-alkaline leaching (SAAL), is a two-stage process, which involves (i) a H2SO4 leaching step for the preferential extraction of reactive aluminium over silicon, followed by (ii) the preferential extraction of silicon over aluminium from the resulting residues using NaOH. The second process is a direct alkaline leaching (DAL) process, which consists of a single-stage elemental extraction from ash using NaOH, i.e. without the preceding acid leaching step used in SAAL. The two processes generated Na2SiO3 solutions with identical pH (11.8), similar silicon (10.210.3g/L), iron (ca. 200mg/L) and potassium (ca. 800mg/L) content, and low calcium concentrations (29mg/L). However, the inclusion of the acid leaching step in the SAAL process yielded a Na2SiO3 solution with significantly lower aluminium content (166mg/L vs. 1158mg/L). The Na2SiO3 solutions obtained from the SAAL and DAL processes were then used as silica precursors to synthesise silica nanoparticles via a solgel method using polyethylene glycol (PEG) as surfactant and sulphuric acid as catalyst. All samples of synthesised silica nanoparticles were characterised by a high level of purity (up to 99.3 wt% SiO2). The insight gained is now being used to improve existing processes for the production of high-grade ultra-pure silica nanoparticles (i.e.99.9 wt% SiO2) for catalyst support applications.

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The project was financially supported by UNISA, University of Pretoria, Council for Geoscience, and the National Research Foundation of South Africa (NRF; Grant No.93641). Any opinion, finding and conclusion or recommendation expressed in this material is that of the authors and the NRF does not accept any liability in this regard. The authors thank Ms Wiebke Grote for XRD, Ms Jeanette Dykstra for XRF, University of Pretoria Laboratory for Microscopy and Microanalysis for assistance with FESEM, and Ash Resources (Pty) Ltd for providing the fly ash sample.

Aphane, M.E., Doucet, F.J., Kruger, R.A. et al. Preparation of Sodium Silicate Solutions and Silica Nanoparticles from South African Coal Fly Ash. Waste Biomass Valor 11, 44034417 (2020).

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