Alkaline Activated Material for pH Control in Biotechnologies

Ruģele, Kristīne; Būmanis, Ģirts; Bajāre, Diāna; Lakevičs, Vitālijs; Rubulis, Jānis

doi:10.4028/www.scientific.net/kem.604.223

Cited by 10 publications

(9 citation statements)

References 7 publications

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“…Apart from the chemical composition, the fine control of the pore structure is also required in order to control alkali diffusion and pH buffering effect (Ruģele et al, 2014). The transfer of OH À ions to the surrounding aqueous media will only occur in case of direct surficial contact (Bumanis et al, 2015b), so highly porous geopolymers will promote a more intense alkalis leaching.…”

Section: Introductionmentioning

confidence: 99%

Red mud-based geopolymers with tailored alkali diffusion properties and pH buffering ability

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et al. 2017

Journal of Cleaner Production

115

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This study develop novel porous red mud (RM) based geopolymers and evaluates their potential to ensure prolonged pH control. Several properties of the novel geopolymers were examined including buffering ability, alkalis leaching behaviour, mineralogical composition, microstructure and physical properties. Two experimental plans were defined to evaluate the influence of porosity and RM content on those properties. The pH values of the eluted water and geopolymers OH À ions leaching have been determined over time showing that total OH À ions and the leaching rate can be tailored by controlling the geopolymers porous structure and the availability of free alkaline species. The lower pH gradient over 28th d (1.64 pH units) was achieved by combining a 0.025 wt% pore forming agent (aluminium powder) with 45 wt% MK replacement by red mud. A high and prolonged buffer capacity was accomplished, proving that red mud-based geopolymers have potential to be applied as pH buffering material.

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Section: Introductionmentioning

confidence: 99%

Red mud-based geopolymers with tailored alkali diffusion properties and pH buffering ability

Ascensão

Seabra

Aguiar

et al. 2017

Journal of Cleaner Production

115

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“…Low-calcium alkali-activated binders (AABs) or geopolymers are well-known zeolite-like materials, which have been studied as pH buffers and adsorbents for heavy metals [1][2][3][4]. It is proven that different types of zeolites in certain amounts (such as zeolite Na-A, hydrosodalite, zeolite X, faujasite, and analcime) can be formed as secondary alkali-activation products in the structure of an AAB [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Alkali-Activated Metakaolin as a Zeolite-Like Binder for the Production of Adsorbents

et al. 2019

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This work reports and describes a novel alkali-activated metakaolin as a potential binder material for the granulation of zeolites, which are widely used as CO2 adsorbents. The alkali-activated binders are zeolite-like materials, resulting in good material compatibility with zeolite-based adsorbents. A major problem during the granulation of zeolites is that their adsorption capacities decrease by about 15–20%, because typical binder materials (for example bentonite or kaolin clay) are inactive towards CO2 adsorption. A possible pathway to solve this problem is to introduce a novel binder that is also able to sorb CO2. In such a case, a binder plays a dual role, acting both as a binding material and as a sorbent. However, it is important that, alongside the adsorptive properties, a novel binder material must fulfil mechanical and morphological requirements. Thus, in this work, physical and mechanical properties of this novel binder for zeolite granulation for CO2 adsorption are studied. Alkali-activated metakaolin was found to be efficient and competitive as a binder material, when mechanical and physical properties were concerned. The compressive strengths of most of the obtained binders reported in this work are above the compressive strength threshold of 10 MPa. The future work on this novel binder will be conducted, which includes granulation-related details and the CO2 adsorptive properties of the novel binder material. Metakaolin was used as a precursor for alkali-activated binders. Binders were synthesized using varying molarity of a NaOH solution and at varying curing conditions. The final products were characterized using density measurements, compressive strength tests, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) analysis, and scanning electron microscopy (SEM).

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“…If Na + based activation solution is used for binder creation then Na + salts will be available for leaching. The activator type and concentration is one of the key factors affecting material properties and alkali diffusion rate [4], [5]. Time factor should be taken into account for material leaching properties due to the carbonization with the atmospheric CO2 because variable salts have different solubility rate in water.…”

Section: Introduction *mentioning

confidence: 99%

The Effect of Alkaline Material Particle Size on Adjustment Ability of Buffer Capacity

Būmanis

2015

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The pH control in biotechnological processes like anaerobic digestion is one of the key factors to ensure high efficiency in the biogas production process. The decrease of pH level in the digestion process occurs due to the rapid acid formation during metabolic processes of bacteria, which leads to the inhibition of the methane producing bacteria; therefore further digestion process is limited. The efficiency of anaerobic digestion reactor decreases dramatically if the pH level falls under pH 6.6. This problem is common for single-stage continuous digesters with a high organic solid content; therefore the active pH controlling method is commonly used. By creating inorganic alkaline material, the passive pH controlling system could be created. Soluble alkalis are enclosed in the matrix of material during the activation process thus providing slow leaching of free alkalis from the material structure in water medium and ensuring pH increase. In this research a porous alkaline composite material was developed as a pH controlling agent for the biogas production. Two mixture compositions with a different Si/Al and Si/Na ratio were created and tested. The effect of particle size of the material was investigated in order to provide different leaching rates for the described material. Granular material with particle fractions 1 -2 mm, 2 -4 mm and 4 -8 mm and a cubical specimen with dimensions 20 × 20 × 20 mm were tested. The pH level of water medium increased up to pH 11.6 during the first day and final pH value decreased to 7.8 after 20-day leaching. Alkali leaching can be increased by 19 -32 % with changing the mixture composition by adding glass powder to the alkaline material. The particle size factor had negligible effect on leaching rate of alkaline material due to the high porosity of material. Research results show that this composite material has a potential to be applied in pH control for biotechnological purposes.

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Alkaline Activated Material for pH Control in Biotechnologies

Cited by 10 publications

References 7 publications

Red mud-based geopolymers with tailored alkali diffusion properties and pH buffering ability

Red mud-based geopolymers with tailored alkali diffusion properties and pH buffering ability

Alkali-Activated Metakaolin as a Zeolite-Like Binder for the Production of Adsorbents

The Effect of Alkaline Material Particle Size on Adjustment Ability of Buffer Capacity

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