NaOH Dosage Research Articles

Alkali-fusion as an effective method for activating low-reactivity silicate wastes: A comparative study

Silicate wastes are used as supplementary cementitious materials (SCM) in Portland cement production, and as precursors to produce alkali-activated materials such as geopolymers to lower the environmental impact of construction. The high crystallinity of some of these wastes lowers their reactivity and hence the production of cementing hydrates. This paper includes a comparative analysis of the efficiency of alkali-fusion to activate three distinct types of silicate waste sourced from diverse sectors. The paper underscores the robustness of this method and its applicability in a wide composition range. It provides a solid foundation for the application of alkali-fusion across a wide spectrum of industrial waste types. Fly ash (FA), crop bottom ash (CBA) and aluminium processing sludge (APS); were fused with NaOH at 600 °C. XRD and FTIR analyses revealed that alkali-fusion disrupts highly cross-linked Si-O-Si structures transforming them into more reactive phases (sodium aluminosilicate and sodium silicates). Alkali-fusion is efficient even at low NaOH dosage(15 %). 15 % NaOH-fusion increased the mechanical activity index of FA, CBA and APS by 108.19 %, 494.61 % and 27.96 % respectively. The mineral composition of the wastes changed at 50 % alkali content: quartz was largely digested, and sodium silicate emerged as the dominant phase. After alkali-fusion, dense and compact matrices with rich hydrates were found evidencing the enhancement of the pozzolanic reaction. Alkali-fusion at relatively low temperature (600 °C) is successful in activating low-reactivity silicate waste, transforming the waste into valuable SCMs.

Exploring carbon dioxide sequestration in desalination reject brine via NaOH reaction: A kinetics study

Seawater desalination is one of the most sustainable means of water supply in arid and semi-arid regions. Despite its undeniable potential to meet the global water demands, there are several environmental impacts associated with its operation, including the generation of reject brine and the emission of considerable amounts of CO2. Recently, the mineralization of carbon dioxide using desalination reject brine has emerged as a potential solution for simultaneous brine management and CO2 sequestration. In this study, the reaction kinetics of desalination reject brine with CO2 in the presence of NaOH are evaluated. The effect of various operating parameters, such as the temperature, CO2 concentration, NaOH dosage, brine salinity, CO2 flowrates and inert particles volume percent were investigated by varying them within the range of 15–55 °C, 3–20 %, 6–16 g/L, 5–72 g/L, 1–5 L/min and 0–20 %, respectively. The experimental data showed that the overall rate of CO2 conversion is equal to the sum of the rates observed for Ca2+ and Mg2+ carbonation reactions and increases proportionally with the increase in CO2 concentration. The addition of NaOH improved the Ca2+ carbonation reaction rate but had no effect on Mg2+ carbonation reactions within the investigated reaction conditions. Interestingly, increasing brine salinity had a negative effect on the reaction rate, while the change in temperature and inert particles had minimal effect on the overall reaction rate. Analysis of the solid products showed that Hydromagnesite and Calcite were the two major products obtained. Finally, experimental data were used to develop a rate model representing the CO2-Brine-NaOH system. The developed model will assist in successfully predicting the performance of the process and pave the way for efficient brine management and CO2 sequestration.

Preparation of solid alkali activator for geopolymer synthesis using vanadium-bearing shale tailing

The vanadium-bearing shale tailing (VST) with large reserves pollutes the environment and urgently needs to be utilized as a resource. Due to its main component being silica, VST has great potential as a raw material for geopolymer. Therefore, this study uses VST to prepare the solid alkali activator (SAA) by thermochemical methods. Analysis show that the temperature and NaOH dosage of thermochemical reaction significantly affect the alkaline activation effect of SAA. Temperature affects the silicate content and the amount of NaOH affects the soluble silicate content in SAA. When the reaction temperature is high (such as above 900 ℃) and the amount of sodium hydroxide is low (such as the mass ratio of sodium hydroxide to VST is 0.6), quartz almost transforms into silicates, but the silicates have a stable cyclic chemical structure and are difficult to dissolve during the geopolymerization reaction. When the reaction temperature is low (such as less than 700 ℃) and the amount of sodium hydroxide is high (such as the mass ratio of sodium hydroxide to VST is 0.9), quartz in VST is difficult to fully convert into silicates, there are unreacted quartz and sodium hydroxide in SAA, and SAA has poor alkaline activation performance. The optimal synthesis process conditions for SAA are as follows: synthesis temperature is 900 °C and the mass ratio of sodium hydroxide to VST is 0.95. The main silicate components of SAA are Na2SiO3 and Na15.6Ca3.8Si12O36. During the synthesis of one-part geopolymer (OPG), Na2SiO3 dissolution generates a strong alkaline reaction environment and provides active silicon-oxygen tetrahedron monomers or oligomers, Na15.6Ca3.8Si12O36 is bonded with geopolymer gel structure by stable cyclic silicate structure, which makes OPG have a compact integrated structure. When the mass ratio of SAA to MK is 1:1.3, the 7-day compressive strength of the prepared OPG is about 49 MPa, SAA has the potential as a substitute for commercial sodium silicate to prepare geopolymers.

Research on improving the flexural performance of alkali-activated geopolymer cemented coal gangue through layered addition of fibers

The brittle characteristics of geopolymers during failure seriously hinder their practical engineering applications. To improve the toughness of low-energy alkali-activated geopolymer cementing coal gangue (AGCCG), the flexural performance of alkali-activated geopolymer cementing coal gangue (AGCCG) was enhanced by layering polypropylene fibers. Based on DIC digital speckle technology, the four-point flexure test of AGCCG was carried out, and the strength formation mechanism of the material was analyzed in depth by combining SEM-EDS and XRD. 3D visualization and analysis of the inside of the specimen with the help of CT scanning technology. The internal crack evolution law of the sample was illustrated by PFC numerical simulation. The results showed that the crack formation threshold, peak flexural strength and residual flexural strength of the specimens reached a local maximum at 3 % NaOH doping. With the increase of NaOH dosage, the cementitious product becomes more and more dense and homogeneous, and the area of void defects in the hydration product within the field of view becomes smaller and smaller. The peak bending strength of specimen B4-#4 is 79.43 % of that of specimen B5-#1–4, in which the cost of specimen B5-#1–4 is four times of that of specimen B4-#4, and the way of fiber assignment in specimen B4-#4 is more reasonable when considered together. The layered addition of fibers has a directional strengthening effect on the mechanical properties of geopolymer, and the overall addition of fibers can improve the overall strength and toughness of geopolymer. The numerical simulation results basically coincide with the macroscopic test results, and are consistent with the progressive damage law of the specimens obtained from the numerical scattering test. The results of the study can provide a theoretical basis for improving the bearing capacity of geopolymer and optimizing its structural performance. As well as reducing the impact of solid waste on the environment and improving the efficiency of resource use.

Escherichia coli persisters in biofilm can perform horizontal gene transfer by transformation

Persisters represent a subset of cells that exhibit transient tolerance to antimicrobials. These persisters can withstand sudden exposure to antimicrobials, even as the majority of normal cells perish. In this study, we have demonstrated the capacity of ampicillin-tolerant and alkali-tolerant persisters to execute horizontal gene transfer via in situ transformation within biofilms. Air–solid biofilms, comprising two Escherichia coli populations each with a distinct plasmid, were formed on agar media. They were treated with lethal doses of ampicillin or NaOH for 24 h, followed by a 1-min glass-ball roll. This process led to a high frequency of horizontal plasmid transfer (10−7–10−6 per cell) from dead cells to surviving persisters within the biofilms. Plasmid transfer was DNase-sensitive and also occurred by adding purified plasmid DNA to plasmid-free biofilms, demonstrating a transformation mechanism. This marks the first evidence of persisters’ novel ability for horizontal gene transfer, via transformation.

Mechanical and Microstructural Analysis of Treated Tuff with Metakaolin Geopolymer Cement for Road Base layers Applications

Traditional road bases materials such as natural gravel and crushed stone are environmentally damaging, and there is a growing need for sustainable and eco-friendly alternatives. One such alternative is using geopolymer cement and tuff as aggregate materials. Geopolymer cement is an innovative and environmentally-friendly alternative to traditional Portland cement, and using locally-sourced tuff as an aggregate material can further reduce the environmental impact of road construction. This article discusses the importance of sustainable road construction practices, particularly in the use of eco-friendly materials for road base layers. It focuses on the treatment of tuff with alkali-activated metakaolin as the geopolymer precursor activated with a mixture of sodium hydroxide and sodium silicate. The effectiveness of treating tuff with metakaolin geopolymer cement is evaluated using several parameters, including dry density, California Bearing Ratio (CBR), shear strength, and microstructure analysis. These evaluations are performed with different NaOH dosages (8, 10, and 12 moles) to determine the optimal molarity for enhancing the material's performance.

Compressive Strength and Microstructure of Carbide Slag and Alkali-Activated Blast Furnace Slag Pastes in China

The alkali-activated blast furnace slag is attracting significant attention in replacing Portland cement due to several characteristics similar to cement hydration. However, there are a few practical problems with commercial alkali activators, such as the fast setting time, relatively high costs, and significant CO2 emissions during preparation. Thus, discovering industrial residues possessing inherent alkalinity are urgent. This study proposes the use of carbide slag at levels of 0%, 5%, 10%, 15%, 20%, and 30% and alkali at levels of 1%, 2%, 3%, 4%, 5%, 6%, 8%, and 10% activated blast furnace slag. The compressive strength and microstructure of carbide slag and alkali-activated blast furnace slag (CAB) pastes were examined using X-ray diffraction analysis (XRD), Differential Scanning Calorimetry/Thermogravimetric Analysis (DSC/TG), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The results revealed that the addition of carbide slag produced more hydrotalcite-like phase as well as decreased the content of ettringite (AFt) and the calcium–silicate–hydrate (C-S-H) gel, which decreased the compressive strength of the CAB pastes. At the age of 28 days, when the dosage was 5%, 10%, 15%, 20%, and 30%, the compressive strength of CAB mixes decreased by 2.1%, 7.1%, 9.2%, 9.8%, and 28.1%, respectively. The addition of NaOH promoted the formation of AFt, and there was an optimum level of NaOH corresponding to the high compressive strength of paste. At the age of 3 days and 7 days, the compressive strength reached its maximum at the dosage of 6% NaOH, which was 24.8 MPa and 36.3 MPa, respectively. However, at the ages of 14 days and 28 days, the compressive strength increased as the dosage of NaOH increased to 5%, which was 43.3 MPa and 44.5 MPa, respectively. The water curing could both enhance the early and later strength, the compressive strength of 23.3 MPa was gained at 3 days, and this increased by 16.3%, 24.0% and 36.9% at 7 days, 14 days and 28 days, respectively. Therefore, water curing was suitable for the strength development of CAB pastes.

Optimizing nutritional value and biological profile of non-conventional forages for animal feeding by utilizing sodium hydroxide

Increasing quality and decreasing quantity represent global trends in the forage processing for animal feed. Consequently, various techniques are applied to achieve these objectives. This study aims to evaluate the internal quality and biological attributes of leaves in animal reproduction by applying sodium hydroxide (NaOH) concentrations (control, 2, 4, 6, and 8%) and utilizing leaves from four non-conventional plants, namely Hedychium gardnerianum (HG), Pittosporum undulatum (PU), Arundo donax (AD), and Acacia melanoxylon (AM), while also examining their interactions simultaneously. NaOH doses did not affect the organic matter digestibility. A 2% NaOH concentration positively affected both acid detergent fibre and neutral detergent fibre. Notably, 6% NaOH significantly impacted dry matter, while ash content and dry matter digestibility peaked under treatment with 8% NaOH. The Arundo donax variety recorded the best values in ash and organic matter digestibility, while the leaves of Acacia melanoxylon significantly (P ≤ 0.05) influenced dry matter, acid detergent fibre, acid detergent lignin, and crude protein. The co-application of 2% NaOH with plant varieties demonstrated the most significant effectiveness on the observed characteristics, followed by 4% NaOH showing a subsequent impact. The findings of this study propose that utilizing NaOH concentrations with these plants represents a promising approach for including these forages in animal feeds.

A study on the performance of a recyclable adsorbent La@Fe for phosphate adsorption in wastewater

Phosphorus(P) is the key element of the growth of phytoplankton, and is also significant cause of water eutrophication. In this work, the magnetic Fe3O4 (FE) microspheres were employed as the core material, the La compound was coated on the surface of the FE microspheres and the adsorbent obtained was denoted as La@Fe. The effects of preparation conditions including the dosage of NaOH, the preparation time, the ratio of FE and LaCl3 (LC), and the stirring time were discussed. The optimized La@Fe has a good adsorption capacity (130–160 mg·g−1) and strong magnetic recovery capacity (43.4 emu/g). In the low concentration (1 mg·L−1), the optimized La@Fe still had an excellent performance. It can keep a good adsorption in a wide pH range (3−8). Except Na2CO3, common anions (NaHCO3, NaCl, NaNO3, Na2SO4, KF, KNO2) in the wastewater could not affect the adsorption capacity of La@Fe. After 7 regeneration, the adsorption capacity of La@Fe reduced by 25% indicating the excellent regeneration property of La@Fe. The La@Fe was analyzed by SEM, TEM, XRD, XPS, BET, and LPS, and the obtained results showed that the particles of La@Fe were spherical, the particle sizes were between 0.1 and 100μm. The main components at the surface of La@Fe was La-(OH), which adsorbed phosphate to form La-PO4. The specific surface area of La@Fe was small and the mesopores were main pore structure. In addition, the adsorption kinetics analysis indicated that the Elovich model worked well on modeling La@Fe adsorbing phosphate, so the adsorption was chemical adsorption with heterogeneous adsorbing surfaces. Adsorption isotherms experiments revealed that the increasing adsorption temperature would enhance the adsorption capacity of La@Fe. It could be obtained from the thermodynamic experiments that the adsorption process was endothermic and chemical adsorption. Therefore, La@Fe is an excellent phosphate adsorbent and has a good application prospect in the field of phosphorus recovery and adsorbent reuse.

Optimization of biogas production from thermal-alkali pre-treated sludge using response surface methodology and random forest regressor model

BackgroundUnderstanding the intricate relationships between input variables and methane potential is crucial for optimizing anaerobic digestion process after thermal-alkali pre-treatment. This study aimed to optimize low-temperature thermal alkali pre-treatment, focusing on dosage based on the total solids (TS) content of raw sludge. A comparative analysis was conducted to optimize input parameters related to biogas generation potential as the primary response. MethodsBiomethane potential data were collected following the pre-treatment of sludge within the temperature range of 40–70 °C, using various doses of NaOH, KOH, Mg(OH)2, and Ca(OH)2 ranging from 40 mg alkali/g TS to 120 mg alkali/g TS. The optimization of biogas and methane production was conducted through Response Surface Methodology (RSM) and the Random Forest Regressor (RFR) model considering dosage and temperature as input variables. Additionally, sensitivity analysis was performed using the permutation feature importance function to gain insights into the influence of alkali types on biogas and methane production. FindingsThe results obtained from the RFR model showcased a notably high accuracy in predicting optimal solutions. NaOH addition was the most effective pre-treatment with an optimal dose of 65 mg/g TS and at a temperature of 56 °C. NaOH pre-treatment increased methane yield to 414.40 mL/g VS, compared to 117.08 mL/g VS for the untreated sludge. The sensitivity analysis results indicated that the temperature had a more significant effect on biogas potential than the alkali dosage.

High efficiency of energy recovery from formaldehyde wastewater over CoS2@MoS2 heterostructure: Enhanced electronic transfer and mechanism

Recently, the simultaneous recovery of hydrogen energy via purification of formaldehyde (FA) wastewater has been recognized as a promising and environmentally beneficial method. In this study, a novel bis-transition metal disulfide heterojunction material CoS2@MoS2 was prepared by a hydrothermal method for peroxymonosulfate (PMS) activation towards formaldehyde wastewater treatment and synchronous hydrogen evolution. Interestingly, CoS2@MoS2 exhibited high performance on formaldehyde-degrading and hydrogen evolution (k = 12.65 μmol/min), outperforming CoS2 (k = 4.13 μmol/min) and MoS2 (k = 3.28 μmol/min) by 3 and 4 times, respectively. Besides, the impacts of catalyst dosage, PMS dosage, NaOH dosage, FA concentration, and reaction temperature on the system's hydrogen generation performance were thoroughly examined. Moreover, anions (Cl−, NO3− and HCO3−) in aqueous solution were also examined for their impact on hydrogen evolution. Through radical quenching experiments, the superoxide radical (O2−) was identified to be the main reactive oxygen species (ROS), while sulfate radical (SO4−) played a minor role and hydroxyl radical (OH) effect can be ignored in the CoS2@MoS2/PMS system. The heterostructure of CoS2@MoS2 enhanced the conductivity, promoted the activated decomposition of PMS as tested by linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and Tafel slope analysis. Additionally, after four cycles, the composite still presented good hydrogen evolution rate. This study furnishes a new method for constructing catalysts with highly efficient towards in-situ FA wastewater purification and clean energy development.

Improving mechanical properties of hemihydrate phosphogypsum via alkali-activated mineral admixtures

The low strength of hemihydrate phosphogypsum (HPG) limits its wider applications in construction, and the use of alkali-activated mineral admixtures to improve HPG's mechanical properties has enormous environmental benefits. In this paper, slag and fly ash were added to HPG, which was then activated by NaOH. The effects of alkali activation on the mechanical properties of HPG were investigated, and the hydration mechanism of modified and enhanced HPG was investigated by X-ray diffractometer (XRD), Thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR), and Low-field nuclear magnetic resonance (LNMR). The results showed that alkali-activated mineral admixtures can improve the compressive strength of HPG up to 40 MPa with the optimal mix ratio: HPG:(GGBS + FA) = 60:40 by weight, where the ratio of GGBS to FA is 4:1 by weight, and NaOH accounts for 1% by mass of the binder. When NaOH was added at 1 wt% of binder, it could effectively activate slag and fly ash to enhance the mechanical properties of HPG. With the increase of the dosage of NaOH, settings of HPG were prolonged and its strength was reduced. The hydration products such as ettringite (AFt) and C–S–H gel generated by NaOH-activated slag and fly ash can effectively fill the pores of HPG paste and thus improve its mechanical properties. When hydrated for 28d, the decrease in strength due to the increase in NaOH dosage can be attributed to the decrease in AFt generated from hydration. The findings of this study pave the theoretical and technical foundations for greater and wider utilization of phosphogypsum for a sustainable future.

Preparation and alkali excitation mechanism of coal gangue-iron ore tailings non-sintering ceramsite

Non-sintering ceramsite is known for its simplicity in preparation technology and low production costs. The efficient utilization of industrial solid waste for non-sintering ceramsite production has garnered significant attention in green building materials within the framework of low carbon and environmental protection principles. This study focuses on preparing non-sintering ceramsites using non-active solid waste materials, specifically coal gangue and iron ore tailings. Firstly, a single-factor test was conducted to determine the optimal dosage of coal gangue and iron ore tailings. Subsequently, orthogonal tests were performed to investigate the influence of fly ash, NaOH, and aluminum powder on the mechanical properties of non-sintering ceramsite. Finally, the alkali excitation mechanism was elucidated through X-ray diffraction and SEM electron microscope scanning. The results reveal that the optimal proportions for coal gangue and iron ore tailings are 10 % and 35 %, respectively. Among the factors examined, NaOH dosage exerts the most significant impact on the compression strength and bulk density of non-sintering ceramsite, while aluminum powder dosage has the greatest effect on the 1-hour water absorption of the material. The optimal mixing ratio was determined with a total solid waste dosage of 73 %, meeting the national 600-grade standard for non-sintering ceramsite across all performance criteria. Furthermore, the alkali excitation process effectively activates the reactivity of fly ash and coal gangue. This activation leads to the generation of calcium alumina and C-S-H gel, along with other hydration products, which intertwine to form a dense gel structure. This structural enhancement further contributes to the improved performance of non-sintering ceramsite.

Mechanical Properties of Aeolian Sand Concrete Made from Alkali-Treated Aeolian Sand and Zeolite Powder.

The aim of this study is to promote the application of the excited zeolite powder (ZP)with aeolian sand powder (ASP) in the field of aeolian-sand concrete (ASC) production. This study utilises NaOH to treat composite cementitious materials containing aeolian sand and zeolite powders, which were used to replace 50% of the cement in aeolian-sand concrete (ASC). Production of alkali-inspired cement-based windswept concrete(AAZC).The mechanical properties of treated ASC considerably improved, especially when the NaOH dosage was 4% by mass. After curing this sample (denoted as AAZC-4) for 28 d, its compressive strength improved by 17.2%, and its split tensile increased by 16.3%. Potassium feldspar and montmorillonite in zeolite powder and SiO2 in the sand were decomposed by OH- and combined with other elements to generate various silicate gels and A-type potassium zeolite crystals inside the concrete. Microscopic examination showed that the gels and crystals intertwined to fill the pores, decreasing (increasing) the percentage of large (small) pores, thus optimising the pore structure. This substantially improved the mechanical properties of ASC. Freeze-thaw salt-intrusion tests showed that the extent of mass loss, degree of damage and loss of compressive strength of AAZC-4 were similar to those of ordinary concrete but were reduced by 36.8%, 19% and 52.1%, respectively, compared with those of ASC. Therefore, AAZC-4 has a sustainable working performance in chloride-ion permeable environments in cold and arid areas.

Study on the effect of alkali on the production of volatile fatty acids from rhamnolipid‐alkali‐thermal pretreated waste activated sludge

AbstractThis article systematically explores the strengthening effect of NaOH dosage on the fermentation acid production of Waste Activated Sludge (WAS) by the rhamnolipids‐alkali‐thermal combined pretreatment. Analyzed the dissolution characteristics of organic matter in sludge, changes in total volatile fatty acids (VFAs) content and components, and microbial community structure. Research has shown that increasing the amount of NaOH can promote the dissolution of sludge extracellular polymeric substances (EPS) and cell lysis. When NaOH dose was 60 mg/g VS, the dissolution of SCOD was the largest, reaching 5427.78 mg/L. It provides high‐quality substrate for anaerobic flora through the decomposition of refractory humus‐like substances and macromolecular substances, thus improving the production of VFAs. When NaOH dose was 80 mg/g VS, the maximum VFAs yield was 1663.76 mg C/L, and the fermentation type was butyric acid. The increase of NaOH dose promotes the effective enrichment of bacteria, and the dominant bacteria are Proteobacteria, Firmicutes, and Bacteroides at the gate level, with different abundance. The fermentation time plays a decisive role in the evolution of microbial population, and the increase of NaOH dose promotes the enrichment of acid‐producing bacteria, thus improving the production of VFAs.

One-part geopolymer binder based on boron wastes: Effects of calcination temperature and NaOH dosage on strength and microstructure

One-part geopolymer binder based on boron wastes: Effects of calcination temperature and NaOH dosage on strength and microstructure

Electrochemical Oxidation Treatment of Organic Matter in Wastewater from Wet Fermentation of Yunnan Arabica Coffee

Electrochemical oxidation combined with reagents of O3, H2O2 and FeCl2 was conducted in this study to treat the wastewater from wet fermentation of Yunnan arabica coffee. In addition, the effect of oxidants on the efficiency of wastewater treatment, the binding capacities of the oxidants to proteins, the degradation of organic pollutants in the wastewater, and the formation of oxidized organic components were systematically investigated. The results reveal better performance of O3-combined electrochemical oxidation (63.60% COD removal efficiency) for treatment of organic species in coffee wastewater than that of the electrochemical processes with H2O2 (47.70% COD removal efficiency) and FeCl2 (34.48% COD removal efficiency). The synergy of the electrooxidation/O3 process (0.0133 A/cm2, 20 mg/L–2 L/min) could not only raise the pH value (3.70~4.20, 5.14~5.44) of the wastewater and reduce the NaOH dosage of 2.80~3.7 g/L, but also effectively degrade the proteins, lipids, unsaturated hydrocarbons, and carbohydrates, with a total chemical oxygen demand (COD) value above 20,000 mg/L. After the oxidation treatment, some organic components remained in the wastewater, including 31.94% of S-containing organics, lignin, condensed aromatic compounds, and aromatic structural compounds, which are difficult to be utilized by microorganisms. In addition, it was found that OH− could bind to proteins and affect the required amount of NaOH addition, whereas the protein binding energy of O3 is higher than that of H2O2, indicating a stronger ability of O3 to oxidize proteins. Therefore, the combination of O3 and electrochemical oxidation can be considered as an effective method to treat organic pollutants in the wastewater from wet fermentation of Yunnan arabica coffee.

The Impact of NaOH on the Micro-Mechanical Properties of the Interface Transition Zone in Low-Carbon Concrete.

To tackle carbon emissions from cement production and address the decline in concrete's mechanical properties due to the substitution of cement with solid waste (glass powder) and natural mineral admixture (zeolite powder) materials, we employed glass powder and zeolite powder to create composite cementitious materials. These materials underwent alkali activation treatment with a 4% NaOH dosage, replacing 50% of cement to produce low-carbon concrete. Nanoindentation tests and mercury intrusion porosimetry (MIP) were employed to uncover the micro-mechanical properties and influencing mechanisms of alkali-activated low-carbon concrete. The results indicate a notable enhancement in the indentation modulus (19.9%) and hardness (25.9%) of alkali-activated low-carbon concrete compared to non-activated concrete. Simultaneously, the interfacial transition zone thickness decreased by 10 µm. The addition of NaOH led to a reduced volume fraction of pores (diameter >100 nm) and an increased fraction of pores (diameter < 100 nm), thereby reducing porosity by 2.6%, optimizing the pore structure of low-carbon concrete. The indentation modulus, hardness and volume fraction of the hydrated phase derived from Gaussian fitting analysis of the nanoindentation statistics showed that NaOH significantly improved the modulus and hardness of the hydration products of low-carbon concrete. This activation resulted in decreased LDC-S-H gel (low-density hydrated calcium silicate Ca5Si6O16(OH)·4H2O) and pore content, while the HD C-S-H gel (high-density hydrated calcium silicate Ca5Si6O16(OH)·4H2O) and CH (calcium hydroxide crystals Ca(OH)2) content increased by 13.91% and 23.46%, respectively. Consequently, NaOH influenced the micro-mechanical properties of low-carbon concrete by generating more high-density hydration products, reducing pore content, enhancing the pore indentation modulus and hardness, and shortening the interfacial transition zone. This study offers novel insights into reducing carbon emissions and promoting the use of solid waste (glass powder) and natural mineral admixture (zeolite powder) materials in concrete, contributing to the advancement of sustainable construction practices.

REGENERASI KATION DAN ANION UNTUK PENURUNAN MINERAL AIR UMPAN BOILER DI UNIT PENGOLAHAN AIR PT BAKRIE SUMATERA PLANTATIONS, Tbk PALM OIL MILL KISARAN

Water is a crucial factor in ensuring smooth and high-quality production in palm oil mills. Minerals present in water can lead to scale formation, sedimentation, and equipment corrosion. Therefore, the demineralization process with cation and anion regeneration is beneficial to maintain water quality in accordance with op- erational standards. Water plays a vital role in the industrial sector; boilers, as primary steam generators, transform water into vapor through heating. However, operating without good water quality can result in issues like scale formation and corrosion. In water treatment processes, chemical substances are required for purification, such as Nalco 3276 for flocculation and Nalco 8173 for flocculant retention. The mineral content in water also affects chemical reactions, such as causing scale formation in boilers and influencing reaction processes. Demineral- ization is frequently employed across various industrial sectors, including palm oil mills, to treat boiler feedwater and other raw materials. Maintaining stable boiler feedwater usage by controlling pH and total hardness prevents problems in pipelines. This research focuses on cation and anion regeneration to reduce min- eral content in boiler feedwater at PT. Bakrie Sumatera Plantations, Tbk Palm Oil Mill Kisaran, with the aim to analyze the regeneration process using H2SO4 and NaOH dosages and identify factors causing issues during regeneration.

Alkali thermal fusion: A prospective route to enhance the reactivity of low-grade clay and utilize as supplementary cementitious material (SCM)

Common clay deposits contain a variety of minerals that provide low and unpredictable reactivity even after calcination. This study aims to enhance the reactivity of such low-grade clay via alkali thermal fusion, where clay was co-calcined with different dosages of NaOH to achieve superior reactivity. The effects of such co-calcination on the formation of reactive aluminosilicates were monitored using high-temperature in-situ X-ray Diffraction (XRD). Additionally, the role of different alkali dosages on the characteristics of the calcined clays was studied using ex-situ XRD, FTIR, ICP-OES, and 29Si NMR. The co-calcination process significantly enhanced the Al and Si dissolution from the calcined clays, which subsequently improved their pozzolanic properties. All of the alkali-fused SCMs satisfied the modified strength activity index (SAI) requirement and the lower dosages of alkali-containing samples (5 % NaOH) showed 50 % reduction in expansion due to alkali silica reaction.