Ratio Of NaOH Research Articles

Influence of alkaline activators on mechanical properties of environmentally friendly geopolymer concrete under different curing regimes.

Previous studies highlighted the significance of tailoring alkaline activators (AA) to specific fly ash (FA) sources for optimal properties of geopolymer concrete (GPC). This study examines the influence of various AA's properties on mechanical properties and microstructures of local low-calcium FA-based GPC under varying curing conditions. A comprehensive investigation consists of several factors such as NaOH molarities (10M, 12M, 14M, 16M), ratios (1.5, 2.0, 2.5) and ratios (0.5, 0.6). The results reveal a complex relationship, demonstrating that NaOH molarity positively influences compressive strength up to a threshold of 14M, beyond which an adverse effect was observed while, the flexural strength was increased up to 16M. Moreover, the study highlights the complex relationship between ratios and mechanical strengths. Notably, these properties exhibited an increase as the ratio rose up to 2.0, but a subsequent decrease was observed when the ratio reached 2.5. Moreover, proposed regression equations predict the compressive and flexural strengths of both ambient-cured GPC and heat-cured GPC with marginal statistical errors. The optimal GPC mix exhibited 49% lower embodied emissions than the corresponding OPC concrete. GPC has higher cost, but it exhibited lower cost-to-strength ratio compared to OPC concrete.

The effect of artificial metakaolin coarse aggregate on the mechanical and durability properties of lightweight geopolymer concrete

<p style="text-align:justify; margin-bottom:11px"><span style="font-size:11pt"><span style="line-height:150%"><span style="font-family:Calibri,"sans-serif""><span lang="PT-BR" style="font-size:12.0pt"><span style="line-height:150%"><span style="font-family:"Times New Roman","serif""><span style="color:#131413">This study presents a unique methodology for investigating the properties of  Metakaolin Coarse Aggregates (MCA). The NaOH ratios were varied as 8M, 10M, 12M, and 14M, while the NaOH to Na<sub>2</sub>SiO<sub>3</sub> ratio was maintained at 0.5 entire study. The liquid-to-binder (L/B) ratios set at 0.3, 0.35, and 0.4. Testing was conducted on the MCA to determine its physical and mechanical properties, comparing them with those of Natural Coarse Aggregate (NCA). Notably, the 8M mix with a 0.4 L/B ratio was found to be economical for producing MCA and was selected for further research. This chosen mix was then employed to prepare geopolymer concrete with 50% MK and 50% PA, with L/B ratios set at 0.4, 0.45, and 0.5. The NaOH ratio and Na<sub>2</sub>SiO<sub>3</sub> to NaOH ratio were maintained at a constant 8M and 2, respectively. Mechanical and durability properties were compared between Geopolymer concrete with NCA and Geopolymer concrete with MCA. The test results demonstrate that MCA in geopolymer concrete can effectively replace NCA in geopolymer concrete, making it a viable option for structural members. Additionally, microstructural characterization was performed on Geopolymer concrete with MCA mixes with varying L/B ratios of 0.4, 0.45, and 0.5, at 28 days. The study specifically focuses on the Interfacial Transition Zone (ITZ) between MCA and geopolymer paste, revealing an improvement in ITZ and microstructure in the GMCA sample with a 0.4 L/B ratio compared to other mixes.</span></span></span></span></span></span></span></p>

Effectiveness of activated carbon from rubber seed shell as adsorbent of liquid waste of heavy metal

Iron or Fe is classified as a metal that has low toxicity, but if the concentration exceeds the quality standard, it can potentially cause pollution to the environment. This study aims to make activated carbon from rubber seed coat shells as an adsorbent for artificial Fe liquid waste using Fe2(SO4)3. 05 grams of activated carbon was activated using a ratio of 2:1, 3:1, 4:1 (NaOH: charcoal), and then an FTIR test was carried out to see the characteristics of the activated carbon. Measurement of Fe concentration using UV-VIS spectrophotometry, with various concentrations of 1, 1.5, 2, 2.5, 3, 4, 6, and 10 mg/L. After that, an analysis of the effect of contact time with the addition of activated carbon as an adsorbent for heavy metal Fe liquid waste was carried out, using variations of 05, 10, 15, 20, 30, 45, 90, and 120 minutes. An analysis of the effect of Fe concentration, with various concentrations of 10, 20, 30, 40, and 50 mg/L. Obtained from the linear equation of the calibration curve y = 0.0679x - 0.0013 with a correlation coefficient of 0.9996. The results of the third FTIR test showed that the ratio of NaOH and carbon activators did not change significantly. The functional groups that appeared were O-H, C=O carboxylate, C-C-C, aromatic C-H, aromatic C=C, C-O, and Si-O. Activated carbon 2:1, 3:1, and 4:1 have an absorption percentage of 86.72%, 89.45% and 96.37%. The greatest absorption efficiency is at a ratio of 4:1, optimum at 90 minutes. Sample 2:1 has an adsorption capacity of 0.163 mg/g, sample 3:1 of 0.259 mg/g, and 4:1 of 1.340 mg/g. The greatest adsorption capacity of activated carbon is at a ratio of 4:1, adsorption occurs physically (Freundlich) with a multilayer layer.

Ensemble machine learning models for predicting the CO2 footprint of GGBFS-based geopolymer concrete

While geopolymer concrete (GPC) has gained popularity for its environmentally friendly attributes compared to ordinary Portland cement, the absence of a prediction model for the carbon footprint of its constituents presents challenges for optimization within the evolving concrete industry. This study offers a thorough CO2 footprint prediction for ground granulated blast-furnace slag (GGBFS)-based GPC, utilizing advanced AI techniques, including a combination of machine learning models and stacking ensembles. This research statistically examines crucial parameters responsible for CO2 emissions in GGBFS-based GPC production, identifying factors like superplasticizer content, initial curing temperature, and NaOH (dry) content as significant contributors. Emphasizing sustainability, the study advocates optimizing concrete mixtures by considering factors like the NaOH ratio to other activator materials. After rigorously evaluating 12 machine learning models, including ensemble techniques, this study identified M4—a stacking model of Support Vector Regression (SVR) and Neural Network (NN)—as weak models, and Decision Tree (DT) as a meta-model, as the most effective ensemble model for predicting CO2 footprints. The choice of M4 is supported by various performance metrics such as the lowest Mean Squared Error of 88.8 and Root Mean Squared Error of 9.42, alongside the highest R2, Adjusted R2, and Explained Variance scores, all approximately 0.95. Additional analyses, such as Euclidean distance and Taylor diagrams, further substantiate the selection of M4. The findings have practical implications for sustainable and cleaner concrete production, enabling businesses to optimize the CO2 footprint of GGBFS-based GPC.

Surface Engineered Ni-Fe Foam As a Bi-Functional Electrode for Water Electrolysis in Alkaline Media

Using fossil fuels as a main source of energy has resulted in various environmentally hazardous effects, including global warming, climate change, and environmental pollution. Consequently, the development of a sustainable and clean source of energy became of urgent need. Water electrolysis has captured considerable attention as the main technology of hydrogen fuel production. It is particularly enticing due to its eco-friendliness and sustainability. Self-supported electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) have prominent roles in water electrolysis. Growing self-supported metal oxides, hydroxides1, phosphates2, sulfides3, etc. that possess high electrical conductivity, electrocatalytic activity, and structural stability have attracted attention lately. FeNi-based catalysts are considered one of the most promising electrocatalysts for water electrolysis in alkaline solutions. However, improving their catalytic activity and stability is one of the research targets before further practical applications. Nickel foam is widely used as a self-supported electrocatalyst due to its high surface area, low cost, and exceptional catalytic activity, with several studies focused on the deposition of nickel-iron materials on nickel foam for the development of a bifunctional catalyst for water electrolysis4. However, very few studies used NiFe mesh or foam to grow a self-supported catalyst material5.In this study, surface-engineered NiFe foam electrodes were developed by facile control of the Ni/Fe surface ratio via chemical leaching and oxidation with NaOH and NaClO4 followed by electrochemical activation, aiming to design a bifunctional electrocatalyst for both OER and HER. Results revealed that varying the ratios of NaOH and NaClO4 induced significant alterations to the surface composition (different Ni/Fe), and hence the active sites for OER and HER. The physicochemical and structural properties of the NiFe foam were characterized using glancing angle X-ray diffraction (GAXRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). Further, the catalytic activity of the modified electrode was assessed utilizing cyclic voltammetry, linear sweep voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy. References F. Dionigi and P. Strasser, Advanced Energy Materials, 6, 1600621 (2016).Y. Yu et al., Journal of Colloid and Interface Science, 607, 1091–1102 (2022).A. Shankar, R. Elakkiya, and G. Maduraiveeran, New J. Chem., 44, 5071–5078 (2020).H.-S. Hu, S. Si, R.-J. Liu, C.-B. Wang, and Y.-Y. Feng, International Journal of Energy Research, 44, 9222–9232 (2020).C. Sun et al., ACS Appl. Energy Mater., 4, 8791–8800 (2021).

The mathematical model for the optimization of compressive strength of sawdust ash geopolymer concrete

Geopolymer concrete offers an eco-friendlier option compared to traditional cement, as it lowers greenhouse gas emissions during production. It consists of an alkaline solution with sodium or potassium silicate and sodium or potassium hydroxide, as well as a source material abundant in silica and alumina. For this study, thirty geopolymer concrete samples were produced in the lab using a mix design approach from Scheffe’s (5,2) model. The focus of the research was on maximizing the compressive strength of the concrete, especially when incorporating sawdust ash as the source material. The findings indicated that subjecting sawdust ash to pyrolysis in the absence of oxygen significantly impacts its pozzolanic properties and, consequently, the characteristics of the concrete. The research determined the optimal compressive strength of geopolymer concrete incorporating sawdust ash to be 21.673 MPa, along with specific concentration ratios of NaOH, Na2SiO4 to NaOH, sawdust ash in the binder, water to binder, and activator to sawdust ash at 10.5415, 2.0446, 38.6307, 0.0363, and 2.5882 respectively. Furthermore, MATLAB-based computer programs were utilized to optimize and forecast the ideal mixture proportions for sawdust ash-based geopolymer concrete.

Effect of Synthesis Condition on Degree of Deacetylation of Chitosan from Shrimp Waste for Smart Film Applications

Shrimp is an Indonesian’s export commodity with high economic value increasing every year. Usually, shrimps are exported in the form of frozen shrimp without shells, heads, tails, and entrails. It resulted in the accumulation of shrimp waste leading to the increasing environmental pollution. Shrimp waste contains high contents of chitin which can be processed to a chitosan owing several benefits. The purpose of this study is to determine the optimum condition of the synthesis of chitosan from chitin isolated by the autolysis method. The deproteination was carried out by soaking the shrimp waste in an acidic solution (pH 2 – 3) for 10 d. The demineralization process was done by reacting the deproteinated solids in a hydrochloric acid solution at pH 0 – 1 for 24 h. Parameters varied in this study time (1 – 3 h), chitin to NaOH ratio (1:10 – 1:30 (w/v)), and temperature (60 – 120℃). The higher all parameters used, the higher the obtained degree of deacetylation (DD) which is in the range of 18.35±1.13 to 48.6±0.51%. On the other hand, the obtained yield decreased from 50.66±1.98% to 47.78±0.81%. The optimum condition was obtained at a synthesis temperature of 120℃, chitin to NaOH ratio of 1:20 g/mL, and time of 3 h producing chitosan with DD of 54.25 ± 2.27%, and yield of 47.7 ± 0.65%. Chitosan synthesized using optimum conditions produced a relatively homogeneous thin film. Polyaniline was then introduced to the film to obtain a smart film prototype. This smart film was able to detect the pH changes proven by the change in its color. The smart film also could be potentially used as a “smart pack” for detecting product decay which releases ammonia gas.

The potential of catalyst based on palm leaves in biodiesel production as part of palm oil life cycle assesment

The advantages offered by biomass-based heterogeneous catalysts, such as being easily separated from reaction products, being used many times, having low production costs, and being widely available in nature. One of the heterogeneous catalysts that can be used is a sodium silicate catalyst, especially one obtained by impregnating Na metal on a SiO2 matrix derived from biomass ash. In this study, palm leaves have the potential to be used as raw material for the SiO2 matrix because their utilization has yet to be optimal. This research aims to synthesize, characterize, and apply a sodium silicate catalyst based on palm leaves ash in the production of biodiesel from Refined, Bleached, Deodorized, Palm Oil (RBDPO). SiO2 was obtained by calcining palm leaves at a temperature of 700 °C for 3 hours, followed by washing using 1 N HCl solution. In this research, variations in the mole ratio of NaOH: SiO2 were carried out in the synthesis of sodium silicate, namely 1:1, 1.5:1, 2:1, and 2.5:1. This research also evaluates the reusability of the sodium silicate catalyst and the effect of washing using methanol on the biodiesel yield produced. The best sodium silicate catalyst was obtained at a NaOH: SiO2 molar ratio of 1.5:1, with a biodiesel yield of 74.485 % and an ester content of 97.293 %. SEM analysis shows the presence of a porous structure on the catalyst. The existence of the Si-O-Na group has been confirmed using FTIR. BET-BJH analysis has confirmed the presence of a mesoporous structure in the catalyst, with a surface area of 6.4343 m2/g and a pore size of 5.3127 nm. The resulting sodium silicate catalyst can be used up to three times, with a yield of 62.388 %. Catalyst regeneration using methanol is capable of producing biodiesel with a yield of 45.198 %

Estimation of some physical and chemical properties of some types of laundry detergent powder in (Libyan market)

Commercial powdered laundry detergents are very in develop countries and there is a great demand for their different branded types, they are complex chemical compounds whose effectiveness and on several factors and chemical and physical properties. Therefore, some of these properties were studied for ten samples of laundry soaps (powder) circulating in Libyan market, locally made and imported, according to reliable analysis methods. PH and electrical conductivity EC of all samples was measured, and proportions of chloride and caustic soda in the components of the samples were determined. The results were as follows: PH values ranged from 10.08 – 11.28, EC values from (19, 64 – 31.1) ms, CL¯ ratios of samples ranged from (0.02 – 0.07) %, and NaOH ratios from (0.008 – 0.5) %. Through the obtained results, the quality of the Libyan washing powder was studied and compared with some imported soap powders. The PH values of two samples were 10.23, 10.08, EC values 31.1 ms and 24.3 ms, CL¯ ratio of the two samples 0.03%. And NaOH ratio of the two samples 0.02% and 0.03 %. The results indicate that local soap samples have good chemical and physical properties. We recommend studying the environmental pollution resulting from these detergents and their impact on human health. Keywords: powdered laundry detergents, physical and chemical properties, PH, caustic soda, conductivity.

Facile synthesis of a novel, efficient, reusable inorganic adsorbent from volcanic rock powder wastes and its application for the removal of dyes and metals from water

A new, efficient, and reusable inorganic adsorbent (NP.F) was easily synthesized using volcanic rock powder wastes (NP) as a precursor, with the synthesis of NP.F carried out at 550 ºC and with a ratio of NaOH (alkalinizing) and sample NP equal to 1. The samples were used in batch adsorption to uptake Ag+(aq.), Cu2+(aq.), acid green 16 (AG 16), and acid red 97 (AR 97) from aqueous solutions at pH 6.53, 5.98, and 2.3, respectively. NP and NP.F were characterized by different analytical techniques, such as XRD, FTIR, BET, TGA/DTG, etc. The adsorption kinetic carried out at 298 K for dye solutions with concentrations ranging from 50 to 200 mg L−1 and metals from 10 to 100 mg L−1 showed that data fit the pseudo-second-order mathematical model with rapid sorption and process equilibrium was reached after 30 min for dyes and 40 min for metal ions. The Sips model proved adequate to represent the adsorption isotherms of metallic ions and the dye AR 97, while the BET model represented the isotherms of the dye AG 16. The NP.F sample showed notable adsorption capacity for all the contaminants studied; for example, the adsorption capacity of the dye AR 97 was 295 mg g−1, while that of the Ag+ ion was 93 mg g−1. Besides, the adsorption of Cu2+(aq.) ion, dyes AG 16, and AR 97 were endothermic, while the adsorption of Ag+(aq.) was exothermic. Furthermore, even after numerous subsequent adsorption cycles, the NP.F sample maintained a high reusability, suggesting that the sample is qualified to be an adsorbent for removing contaminants from liquid effluents. In conclusion, NP.F could be easily converted into an efficient inorganic adsorbent for colorants and metals.

Effect of Curing Time and Variations in Na2SiO3: NaOH Ratio on the Mechanical Properties of Fly Ash-based Geopolymer Artificial Aggregates using the Crushing Method

Burning coal to produce electrical energy in PLTU produces waste in the form of fly ash. This waste must be managed properly so that it does not cause detrimental environmental effects. Fly ash has potential as a building material because it contains silica, aluminum, and other oxides that can react with alkaline solutions to form geopolymer compounds. Geopolymer has good mechanical properties and is resistant to acidic and alkaline environments. The development of the crushing method for aggregate materials, artificial geopolymers, and fly ash is an interesting work direction because it can utilize fly ash waste and reduce the dependence on aggregates. Moreover, this material can be used to help reduce the effects of development construction on the environment. The crushing method is utilized to obtain geopolymer artificial aggregate with the desired size. Aggregates can be destroyed to become small particles by using destruction techniques and mechanical crushing tools, such as hammer mills, jaw crushers, and ball mills. The aggregate impact value (AIV) percentage reaches 13.20% at a Na2SiO3/NaOH ratio of 2, but it decreases to 12.64% at a Na2SiO3/NaOH ratio of 3.5. The AIV percentage reaches 12.82% without the addition of sand, but it decreases to 12.64% when the added amount of sand is 20%. The AIV percentage increases to 12.76% when the added sand is 40%. Moreover, the AIV percentage reaches 12.64% after curing for 24 hours, decreases to 12.46% after 48 hours of curing, and increases to 12.94% after 72 hours of curing.

A Thermal Study on Foam-Based Eco-friendly Cinder Tiles

This study focusses on usage of fly ash and metakaolin as industrial waste to aerate lightweight foam concrete (LFGC) using hydrogen peroxide. By designing and optimising the components of metakaolin, hydrogen peroxide, and fly ash, physical properties such as mechanical strength, thermal characteristics, and heat resistance are assessed. Lightweight foam concrete has a dry density between 1400 and 1800 kg/m3, a bending strength between 0.7 and 1 MPa, and thermal conductivity between 0.1 and 0.7 W/mK, all of which indicate that it is more lightweight than normal concrete. By dumping solid waste on land, the environment suffers, and it leads to the release of toxic gases into the atmosphere and get polluted. As a byproduct, swapping out the cement with concrete would be a practical and cost-effective way to use the refuse. Alkaline solutions such as NaOH and Na2Sio3 are used to prepare geopolymer concrete. Samples of geopolymer concrete made with fly ash and metakaolin are cured in the oven for 24 hours. Geopolymer concrete is a form of material-based construction in which industrial raw materials supplied by businesses are incorporated into it. This lowers carbon emissions and makes the concrete more environmentally friendly. Using MATLAB, we predict which is the best value of bending strength, thermal conductivity, heat resistance, and dry density of various ash concrete. Effective input variables for geopolymer concrete include the amounts of fly ash, metakaolin, NaOH, and Na2SiO3, Fine aggregate, and the ratio of NaOH and Na2SiO3 and the output variables are bending strength, dry density, thermal conductivity, heat resistance.

Development of a functional catalytic membrane by alkalization of PVA and green synthesis of fuel additive glycerin carbonate with high oxygen content

ABSTRACT Glycerin carbonate with high oxygen content has the potential to be an oxygenated fuel additive that improves fuel properties and reduces harmful gas emissions. Glycerin carbonate was produced from the green solvent dimethyl carbonate and glycerin through a heterogeneous catalytic membrane under environmentally friendly and mild conditions. The PVA/NaOH catalytic membrane was prepared in film form from polyvinyl alcohol (PVA) polymer with good film-forming properties and sodium hydroxide, a strong base. The heterogeneous catalytic membrane obtained by adding sodium hydroxide to the polymer is environmentally friendly with easy recovery. The chemical structure and thermal resistance of the produced catalytic membranes were examined by Fourier-transform infrared spectroscopy and Thermogravimetric analysis. Reaction experiments were carried out in a batch reactor, and the influences of reaction parameters such as time, catalyst amount, DMC/glycerin initial molar ratio, and temperature on the reaction yield were investigated. The maximum glycerin carbonate yield of 93.03% was obtained after 2 h of reaction time, with a NaOH ratio of 7.5% a DMC/Glycerin molar ratio of 3/1, and a reaction temperature of 75°C. Additionally, the influences of reaction variables on glycerin carbonate yield were analyzed and the obtained yield data are supported by the Response surface method (RSM).

Separation of silicon and germanium from the chlorination distillation residue based on co-precipitation of sodium-aluminum–silicon

Germanium (Ge) is known as a critical metal, and dust from coal burning is an important raw material for the extraction of Ge by the chlorination distillation process. Nevertheless, the residue produced by the chlorination distillation process (RCDP) also contains a considerable amount of Ge. The extraction of Ge from RCDP requires the conversion of Si and Ge into soluble compounds, and the efficient separation of large amounts of Si and Al from small amounts of Ge. In this study, Al, Si and Ge in RCDP were converted to soluble sodium slat by sodium roasting. Under the conditions of roasting temperature of 600 ℃, time of 120 min and the mass ratio of NaOH to RDCP of 3:1, 56.92 % of Al, 87.75 % of Si and 91.20 % of Ge are dissolved into solution. According to the formation mechanism of sodium aluminosilicate, the co–precipitation of Na–Al–Si can be promoted by adjusting the composition of the leaching solution to separate Si and Ge. Noteworthy, 73.97 % of Si have been removed by precipitation, while the precipitation ratio of Ge is only 8.77 %. Moreover, the Ge-containing solution is obtained with low Al–Si concentration (Al 0.37 g/L, Si 0.85 g/L and Ge 0.025 g/L). Overall, the obtained nano-microspherical non-dense cluster zeolite products have great potential for the removal of heavy metal ions from wastewater.

Performance modulation and optimization of PE fiber reinforced 3D-printed geopolymer

This paper aims to develop an environmentally friendly and low-carbon geopolymer for 3D printing, which has excellent mechanical and rheological performance. The effect of ground granulated blast furnace slag (GGBS), NaOH and sand on mechanical strengths, 3D printing performance and rheological behavior was investigated to determine the optimum mix proportion for 3D-printed geopolymer. Moreover, polyethylene (PE) fibers were introduced to reinforce the performance of 3D-printed geopolymer. Results show that when the ratio of GGBS, NaOH and sand is 1:0.13:2.67, geopolymer exhibits superior mechanical, 3D printing and rheological properties. Increasing the dosage of GGBS and sand leads to an overall increase in the yield stress but a decrease in the consistency coefficient, indicating that it benefits the stacking and fluidity performance of 3D-printed geopolymer. However, with an increase of NaOH content, the stacking performance increases while the fluidity decreases. Although increasing NaOH and sand content benefits the viscosity recovery performance, an increase in GGBS content has an opposite effect. Incorporating PE fibers significantly increases the flexural strength with an increase of up to 27.8 % and 21.3 % in 7-d and 28-d flexural strength, respectively, given a PE fiber volume of 0.6 %. Increasing the volume of PE fibers leads to a significant rise in the stacking performance but a reduction in the fluidity. Furthermore, adding PE fibers negatively affects the geopolymerization but benefits the hydration process given an increase of Si/Al and Si/Ca ratio identified in PE fiber reinforced 3D-printed geopolymer.

Physical and mechanical properties of meta-halloysite-based geopolymer mortars

Geopolymers are amorphous materials produced by the polymerisation reaction between an aluminosilicate precursor and an alkaline reagent or by activation with phosphoric acid. The aluminosilicate raw material used in the manufacture of geopolymers an be industrial waste, such as fly ash or volcanic ash, blastfurnace slag, or it can be obtained from natural raw materials, such as metakaolin and meta-halloysite. The work aimed to select the composition of an activator for the production of meta-halloysite geopolymers with optimum physico-mechanical properties such as specific and bulk density, porosity, weight, and bulk absorption, as well as flexural and compressive strength. A two-factor experimental design was employed to determine the composition of the alkaline activator for geopolymer mortars, with sodium hydroxide solution molar concentration and sodium silicate to NaOH ratio as variables. Research has shown that increasing the amount of sodium silicate relative to the mass of a 12M NaOH solution in the activator solution improves the compressive strength of geopolymers by 36.8%, while an increase in flexural strength of 14.2% was achieved. As the molar concentration of caustic soda in the activator solution increases from 19.0 to 24.5%, the porosity of geopolymer mortars decreases. The reduction in the ratio of water glass to sodium hydroxide and the reduction in the molar concentration of NaOH increases the mass and volume water absorption of the mortar. Further studies is necessary to determine the optimal mixture of metahalloysite geopolymer, taking into account its functional properties and durability.

Influence of recycled coarse aggregate on properties of fly ash and slag-based geopolymer concrete cured under oven and ambient temperature

Purpose The purpose of this paper is to investigate the effect of the replacement of natural coarse aggregate (NCA) with different percentages of recycled coarse aggregate (RCA) on properties of low calcium fly ash (FA)-based geopolymer concrete (GPC) cured at oven temperature. Further, this paper aims to study the effect of partial replacement of FA by ground granulated blast slag (GGBS) in GPC made with both NCA and RCA cured under ambient temperature curing. Design/methodology/approach M25 grade of ordinary Portland cement (OPC) concrete was designed according to IS: 10262-2019 with 100% NCA as control concrete. Since no standard guidelines are available in the literature for GPC, the same mix proportion was adopted for the GPC by replacing the OPC with 100% FA and W/C ratio by alkalinity/binder ratio. All FA-based GPC mixes were prepared with 12 M of sodium hydroxide (NaOH) and an alkalinity ratio, i.e. sodium hydroxide to sodium silicate (NaOH:Na2SiO3) of 1:1.5, subjected to 90°C temperature for 48 h of curing. The NCA were replaced with 50% and 100% RCA in both OPC and GPC mixes. Further, FA was partially replaced with 15% GGBS in GPC made with the above percentages of NCA and RCA, and they were given ambient temperature curing with the same molarity of NaOH and alkalinity ratio. Findings The workability, compressive strength, split tensile strength, flexural strength, water absorption, density, volume of voids and rebound hammer value of all the mixes were studied. Further, the relationship between compressive strength and other mechanical properties of GPC mixes were established and compared with the well-established relationships available for conventional concrete. From the experimental results, it is found that the compressive strength of GPC under ambient curing condition at 28 days with 100% NCA, 50% RCA and 100% RCA were, respectively, 14.8%, 12.85% and 17.76% higher than those of OPC concrete. Further, it is found that 85% FA and 15% GGBS-based GPC with RCA under ambient curing shown superior performance than OPC concrete and FA-based GPC cured under oven curing. Research limitations/implications The scope of the present paper is limited to replace the FA by 15% GGBS. Further, only 50% and 100% RCA are used in place of natural aggregate. However, in future study, the replacement of FA by different amounts of GGBS (20%, 25%, 30% and 35%) may be tried to decide the optimum utilisation of GGBS so that the applications of GPC can be widely used in cast in situ applications, i.e. under ambient curing condition. Further, in the present study, the natural aggregate is replaced with only 50% and 100% RCA in GPC. However, further investigations may be carried out by considering different percentages between 50 and 100 with the optimum compositions of FA and GGBS to enhance the use of RCA in GPC applications. The present study is further limited to only the mechanical properties and a few other properties of GPC. For wider use of GPC under ambient curing conditions, the structural performance of GPC needs to be understood. Therefore, the structural performance of GPC subjected to different loadings under ambient curing with RCA to be investigated in future study. Originality/value The replacement percentage of natural aggregate by RCA may be further enhanced to 50% in GPC under ambient curing condition without compromising on the mechanical properties of concrete. This may be a good alternative for OPC and natural aggregate to reduce pollution and leads sustainability in the construction.

Classical curing of epoxy modified lignin with polyamine for new Epoxy-Polyimine composite

Lignin, which is the most abundant aromatic polymer in nature was used as a green substitute for the toxic bisphenol A. Here we synthesized the epoxy agent from lignin by reacting lignin with epichlorohydrin. Further this product was reacted with the lignin-amine to give the new epoxy-polyimine composites. This study evaluated the curing of bio-based epoxy resins derived from lignin with aromatic and an aliphatic amine. The thermal stability of the cured lignin-based epoxy samples was evaluated. Epoxidation is an interesting way to develop new uses and applications of lignin. Lignin-based epoxy resins were obtained by the epoxidation reaction using the lignin recovered directly from pulping liquor. For the epoxidation reaction it was optimized the influence of the lignin:NaOH (w/w) ratio, temperature and time of the reaction on the properties of the prepared epoxidized lignin. The structures of lignin-based epoxy resins were evaluated by epoxy index test and FTIR spectroscopy. Optimal conditions were obtained for lignin-based epoxy resin produced at lignin/NaOH = 1/3 at 80 °C for 3 h. Thermogravimetry analysis (TGA) revealed that epoxidation enhances the thermal stability of lignin and may allow a wider temperature range for various applications.

Sawdust Ash as a Sustainable Binder in Geopolymer Concrete: A Study on Split Tensile Strength

Geopolymer concrete can serve as a more environmentally friendly alternative to traditional cement by reducing the release of greenhouse gases during production. It is composed of an alkaline liquid containing sodium or potassium silicate and sodium or potassium hydroxide, along with a source material rich in silica and alumina. In a recent investigation, thirty geopolymer concrete samples were created in the laboratory using a mix design approach. The study focused on optimizing the split tensile strength of the concrete, particularly when using sawdust ash as the source material. The research revealed that subjecting sawdust ash to pyrolysis in the absence of oxygen significantly affects its pozzolanic characteristics and, consequently, the properties of the concrete. The study determined the optimum split tensile strength of sawdust ash-blended geopolymer concrete to be 2.9899 MPa. The specific concentration ratios of NaOH, Na₂SiO₄ to NaOH, sawdust ash in the binder, water to binder, and activator to sawdust ash were found to be 9.75, 1.8750, 37.5, 0.025, and 2.5, respectively. Additionally, computer programs developed using MATLAB were employed to optimize and predict the ideal mix proportion of sawdust ash-based geopolymer concrete.

Alkaline Chemical Neutralization to Treat Acid Mine Drainage with High Concentrations of Iron and Manganese

Due to its high acidity and toxic metal content, acid mine drainage (AMD) needs to be properly treated before being discharged into the environment. This study took the AMD collected from one specific mine in China as a sample and investigated the treatment methodology for AMD. The water quality of the AMD was measured, and the sample was treated with caustic soda (NaOH) and shell powder (one kind of conventional neutralizer, mainly composed of CaCO3) by the neutralization method. The results show that the AMD has a relatively low pH (2.16) and contains high concentrations of Fe (77.54 g/L), Mn (621.29 mg/L), Cu (6.54 mg/L), Ca (12.39 mg/L), and Mg (55.04 mg/L). NaOH was an effective neutralizer to treat the AMD and performed much better than shell powder. Various metals were precipitated, in the order of Fe(III), Cu, Fe(II), Mn, Ca, and Mg. The metal removal mechanisms included precipitation, adsorption, and co-precipitation. The optimal reaction conditions were the reaction duration was selected as 5 min and the mass ratio of NaOH to AMD was 0.16:1 (w:v). By this stage, the pH rapidly increased from 2.16 to 8.53 during AMD-NaOH interactions and various metals were efficiently removed (from 86.71% to 99.99%) by NaOH. The residual mass concentrations of Fe, Mn, Cu, Ca, and Mg after the treatment were 1.52, 1.77, 0.10, 1.65, and 2.17 mg/L, respectively. These data revealed that NaOH was a good treatment regent for this kind of AMD, based on the discharge criteria of China (GB28661 2012). Also, the shell powder was a helpful neutralizer for pH adjustment and copper removal. This neutralization method has the advantages of convenient operation, high speed, good effect, simple equipment, and low infrastructure cost. In addition, the resulting neutralized residue is a valuable and high-quality raw material, which can be used in metal smelting and separation.