Alkaline Activation
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2021 ◽  
Vol 8 ◽  
Author(s):  
Kuisheng Liu ◽  
Zhenguo Liu ◽  
Jianwei Sun

Blast furnace ferronickel slag (BFNS), currently an underutilized metallurgical residue, was investigated for use as a precursor for alkaline activation. Water glass solutions with various moduli (0.5, 1.0, 1.5 and 2.0) were used at the same water glass concentration of 10% to investigate the influence of the modulus on hydration and mechanical properties. The results show that the modulus has a certain impact on the hydration and mechanical strength development of alkali-activated BFNS. Increasing the modulus of water glass does not change the type of hydration product and the activity of the Mg-containing phases, but it decreases the amount of C2AS, the Ca/Si and Al/Si ratios of the (N,C)-A(M)-S-H gel. In addition, a high silicate modulus deteriorates the pore structure, which has an adverse effect on the development of compressive strength and splitting tensile strength.


Author(s):  
Yuliia Tamarkina ◽  
Volodymyr Kucherenko ◽  
Iryna Frolova

The purpose of work is to evaluate the 4-chlorophenol (CP) adsorption capacity of brown coal activated carbons (ACs) prepared at different temperature of KOH activation. ACs were obtained in three stages: 1) impregnation of coal with a KOH solution, 2) heating (4 deg/min) in argon to a given temperature t (400-800°C) and exposure for 1 h, 3) cooling, washing from KOH, drying. The samples are designated as AC(t). Based on the N2 adsorption-desorption isotherms, the ACs total pore volume (Vt, cm3/g) and specific surface area (S, m2/g) were determined. The ACs adsorption capacity were measured at 25°С, CP concentration ≤700 mg/L, АC dosage – 1 g/L. The alkaline activation temperature was found to be a key factor in forming porosity of ACs and ability to adsorb CP. The CP maximum capacity (ACP(m), mg/g) increases 6.6 times up to 307 mg/g for AC(800) having S=1142 m2/g. The specific adsorption capacity (ACP(S) = ACP(m)/S, mg/m2) sharply decreases in a sample range from AC(400) to AC(550) and weakly depends on temperature at 550-800°C. The kinetics of CP adsorption is best described by a pseudo-second order model. The rate determining stage is the interaction of CP molecules with AC surface. The CP adsorption isotherms are best described by the Langmuir model. The dependence of the ACP(m) from S can be approximated by three linear equations that probably correspond to the three regions of forming surface adsorbtion centers (AdCs). The first (S≤370 m2/g) is characterized by a small adsorption capacity increment (kS=0.103 mg/m2), but a significant (16.4 times) decrease in the specific capacity ACP(S). In the second region (S=370-770 m2/g, t=550-750°C), capacity increment is 10 times more (kS=0.985 mg/m2) and in the third region (S≥770 m2/g, t≥750°C) the increase in CP capacity is the smallest (kS=0.067 mg/m2). The thermoinitiated formation of AdCs is assumed to be not proportional to the increase in surface area, and their chemical structure and reactivity is determined by the alkaline activation temperature.


2021 ◽  
Vol 11 (13) ◽  
pp. 6056
Author(s):  
Egle Rosson ◽  
Acacio Rincón Rincón Romero ◽  
Denis Badocco ◽  
Federico Zorzi ◽  
Paolo Sgarbossa ◽  
...  

Spent fluorescent lamps (SFL) are classified as hazardous materials in the European Waste Catalogue, which includes residues from various hi-tech devices. The most common end-of-life treatment of SFL consists in the recovery of rare earth elements from the phosphor powders, with associated problems in the management of the glass residues, which are usually landfilled. This study involves the manufacturing of porous ceramics from both the coarse glass-rich fraction and the phosphor-enriched fraction of spent fluorescent lamps. These porous materials, realizing the immobilization of Rare Earth Elements (REEs) within a glass matrix, are suggested for application in buildings as thermal and acoustic insulators. The proposed process is characterized by: (i) alkaline activation (2.5 M or 1 M NaOH aqueous solution); (ii) pre-curing at 75 °C; (iii) the addition of a surfactant (Triton X-100) for foaming at high-speed stirring; (iv) curing at 45 °C; (v) viscous flow sintering at 700 °C. All the final porous ceramics present a limited metal leaching and, in particular, the coarse glass fraction activated with 2.5 M NaOH solution leads to materials comparable to commercial glass foams in terms of mechanical properties.


2021 ◽  
pp. 167-179
Author(s):  
Juan Carlos Calderón-Peñafiel

La problemática ambiental ha impulsado la investigación de materiales alternativos que ayuden a aminorar el impacto derivado de la construcción. En este contexto, la “tierra” y los materiales a base de arcilla sin cocer se han presentado como una alternativa interesante a materiales convencionales que incorporan gran cantidad de energía. Pese a que existe una creencia generalizada de que la “tierra” y los materiales a base de arcilla cruda están bien entendidos, mediante el estudio del estado del arte en lo referente a los antecedentes  históricos, los limitantes, la innovación del material, sus características y composición, se expone la complejidad que conlleva su estudio y correcta aplicación. Se puede decir que “tierra” es un nombre genérico que se da al material compuesto por diferentes tipos de silicatos. Estos minerales tienen características y propiedades específicas de acuerdo a su estructura y composición química molecular. Entre los silicatos, las arcillas contienen nanopartículas responsables de conglomerar el resto de constituyentes gracias a sus características y, por tanto, son consideradas componentes fundamentales para la exploración e innovación del material. En la actualidad la combinación de modernas técnicas de análisis permite una mayor comprensión de la composición y estructura de la “tierra” y la arcilla. Estos avances han provocado el desarrollo de tecnologías que permiten optimizar los materiales de arcilla tomando en cuenta las características microscópicas mediante procesos microbiológicos; nanotecnología, geopolimerización, activación alcalina, etc.Palabras clave: Construcción con tierra, tierra, arcilla, innovación, composición. AbstractThe environmental problem has prompted research into alternative materials that help reduce the impact from construction. In this context, soil and raw clay-based materials have emerged as an interesting alternative to conventional materials that incorporate a large amount of energy. Although there is a widespread belief that soil and raw clay-based materials are well understood, through the study of the state of the art in relation to the historical background, the limitations, the innovation of the material, its characteristics andcomposition, the complexity involved in its study and correct application is exposed. It can be said that soil is a generic name given to the material composed of different types of silicates. These minerals have specific characteristics and properties according to their structure and molecular chemical composition. Among the silicates, clays contain nanoparticles responsible for conglomerating the rest of the constituents thanks to their characteristics and, therefore, they are considered fundamental components for the exploration andinnovation of the material. Nowadays, the combination of modern analysis techniques allows a better understanding of the composition and structure of soil and clay. These advances have led to the development of technologies that allow the optimization of clay materials taking into account the microscopic characteristics through microbiological processes; nanotechnology, geopolymerization, alkaline activation, etc.Keywords: Construction with soil, soil, clay, innovation, composition.


Author(s):  
Trong-Phuoc Huynh ◽  
Trong-Binh Pham ◽  
Tri-Khang Lam ◽  
Tien-Dat Tran ◽  
Van-Thien Nguyen
Keyword(s):  
Fly Ash ◽  

The purpose of this work was to evaluate the influence of alkaline activation temperature (t) on the pore structure of activated carbons produced from brown coal (ACs) and their adsorption capacity towards the sorption of phenol from aqueous solutions. The ACs were prepared by heating (t=400–8500C, 1 hr) of brown coal impregnated with KOH; the prepared samples were designated as AC(t). Based on the nitrogen adsorption-desorption isotherms (77 K), the total volume and surface (S) of all pores and separately micro- and subnanopores were determined. Maximum phenol adsorption capacities of ACs (Am) were registered at the temperature of 250С. The activation temperature was stated to be the most significant factor influencing the ACs capacity to adsorb phenol. The growth of temperature from 4000С to 8500С in the case of AC(800) results in an exponential increase in the value of Аm from 27 mg g–1 to 240 mg g–1 (a maximal value) according to the following equation: Аm=6.038exp(0.0045t) (R2=0.952). The kinetics of phenol adsorption obeys the second order model (R20.982). The AC(800) adsorption isotherm is described by the Freundlich equation (R2=0.988) within the equilibrium concentrations Ce=0.001–2.5 mg cm–3 with the heterogeneity factor nF=3.23 indicating physical adsorption. The same model for Ce0.001 mg cm–3 (R2=0.951) gives nF=0.52, which suggests chemical adsorption. The specific adsorptive capacity АS=Аm/S sharply decreases from 2.11 mg m–2 to 0.21 mg m–2 with increasing the temperature from 4000С to 5500С and remains constant (0.200.01 mg m–2) for ACs prepared at higher temperatures. The invariability of AS indicates the temperature independence of adsorption centers concentrations of ACs prepared within 550–8500С.


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