Sodium Hydroxide Concentration Research Articles

Ultrasonic-assisted alkali hydrolysis of polyethylene terephthalate fabric and its effect on the microstructure and dyeing properties of fibers

Abstract In this study, ultrasound energy was applied to assist the alkali hydrolysis of polyethylene terephthalate (PET) fabric, and then, the results were compared with those of the mechanical oscillating method, which was used as the control. The effects of various factors such as the sodium hydroxide concentration, the dosage of dodecyl dimethyl benzyl ammonium chloride (DDBAC), and the frequency on the weight loss of the PET fabrics were systematically investigated. The surface appearance and microstructures of the treated fibers with different methods were analyzed using a scanning electron microscope and X-ray diffraction, respectively. The results showed that DDBAC played a prominent accelerating role in the hydrolysis of the PET polymer, and the frequency had a great influence on the weight loss of the PET fabric. Ultrasound with a frequency of 60 kHz showed a similar decomposition rate as the control, resulting in similar weight loss, which was the highest value among the three frequencies (20, 60, and 80 kHz). In addition, the application of ultrasonic energy led to more pits on the fiber surface, a smaller average grain size, and decreased crystallinity of the treated fibers, while the mechanical oscillating method resulted in slightly increased crystallinity. By comparing the K/S value of the dyed fabrics with two commercial disperse dyes, we found that the treatment method had no obvious correlation with the color depth of the treated fabric.

Effect of sodium hydroxide treatment on the fracture toughness of luffa natural fiber reinforced epoxy epikote 828

AbstractMicro‐sized luffa natural fibers (MLNFs) were derived from raw luffa natural fibers from Vietnam by undergoing treatment with sodium hydroxide. This study examined the impact of sodium hydroxide concentration, temperature, and treatment duration on the fracture toughness of epoxy resin 828 reinforced with MLNFs. The results showed that the fracture toughness of the composite, as measured by the critical‐stress‐intensity factor (KIC) and Izod impact strength, was improved after the treatment of the MLNFs with sodium hydroxide. Specifically, with the optimal sodium hydroxide treatment parameters of 6% NaOH at 70 °C for 6 h, the critical‐stress‐intensity factor increased by 93% (from 2.0 to 3.86 MPa m1/2) and the Izod impact strength rose by 44.6% (from 3.81 to 5.51 kJ/m2). The thermal properties and surface structure of MLNFs treated with NaOH were analyzed using thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) images.

Evolutionary Algorithms for Strength Prediction of Geopolymer Concrete

Geopolymer concrete (GPC) serves as a sustainable substitute for conventional concrete by employing alternative cementitious materials such as fly ash (FA) instead of ordinary Portland cement (OPC), contributing to environmental and durability benefits. To increase the rate of utilization of FA in the construction industry, distinctive characteristics of two machine learning (ML) methods, namely, gene expression programming (GEP) and multi-expression programming (MEP), were utilized in this study to propose precise prediction models for the compressive strength and split tensile strength of GPC comprising FA as a binder. A comprehensive database was collated, which comprised 301 compressive strength and 96 split tensile strength results. Seven distinct input variables were employed for the modeling purpose, i.e., FA, sodium hydroxide, sodium silicate, water, superplasticizer, and fine and coarse aggregates contents. The performance of the developed models was assessed via numerous statistical metrics and absolute error plots. In addition, a parametric analysis of the finalized models was performed to validate the prediction ability and accuracy of the finalized models. The GEP-based prediction models exhibited better performance, accuracy, and generalization capability compared with the MEP-based models in this study. The GEP-based models demonstrated higher correlation coefficients (R) for predicting the compressive and split tensile strengths, with the values of 0.89 and 0.87, respectively, compared with the MEP-based models, which yielded the R values of 0.76 and 0.73, respectively. The mean absolute errors for the GEP- and MEP-based models for predicting the compressive strength were 5.09 MPa and 6.78 MPa, respectively, while those for the split tensile strengths were 0.42 MPa and 0.51 MPa, respectively. The finalized models offered simple mathematical formulations using the GEP and Python code-based formulations from MEP for predicting the compressive and tensile strengths of GPC. The developed models indicated practical application potential in optimizing geopolymer mix designs. This research work contributes to the ongoing efforts in advancing ML applications in the construction industry, highlighting the importance of sustainable materials for the future.

Multi-scale modelling of an electrodialysis with bipolar membranes pilot plant and economic evaluation of its potential

Sodium hydroxide and hydrochloric acid are widely used chemicals in different industrial sectors. To minimize costs and risks associated with transportation, handling and storage, these hazardous chemicals can be produced in situ employing electrodialysis with bipolar membranes (EDBM). This work presents a multi-scale model capable of simulating large scale EDBM units with complex stack configuration (i.e., internal staging) that can be used to design and optimize the process. The model was validated in two different process configurations using experimental results obtained from an EDBM pilot plant. Discrepancies between model and experimental results in the range of 2–11 % were obtained. The validated model was used to conduct a techno-economic evaluation adopting the feed and bleed configuration. Results show that current efficiency increases as the current density rises. At 600 A m−2, values of current efficiency between 72 % and 96 % were found for sodium hydroxide concentration in the range of 0.5–1 mol L−1. The levelized cost of sodium hydroxide (LCoNaOH) was evaluated, in the same range of concentrations, demonstrating that values between 280 and 370 € ton−1 can be obtained, fixing the electricity prince (0.1 kWh kg−1) and the triplet specific cost (600 US$ m−2). Moreover, assuming a reduced cost of electricity and triplet to 0.05 kWh kg−1 and 300 US$ m−2, respectively, an absolute minimum of 140 € ton−1 was found for the target 0.5 mol L−1. A double stage EDBM configuration was simulated to show the scale-up potentials of the multi-scale model. A reduction in the LcoNaOH of 10 % was obtained for a target concentration of 1 mol L−1. These results prove the attractiveness of the EDBM technology for producing in situ chemicals.

Production of lignin monomeric alcohols and lipids from oil palm empty fruit bunch by a combination of alkaline nitrobenzene depolymerization and Lipomyces starkeyi bioconversion

The efficient valorization of lignocellulosic biomass into valuable chemicals represents a cornerstone for advancing sustainable bioeconomy practices. This study focuses on the innovative conversion of oil palm empty fruit bunch (OPEFB) into lignin monomeric alcohols and lipids through a novel two-step process combining alkaline nitrobenzene depolymerization and bioconversion by Lipomyces starkeyi. Initially, OPEFB undergoes alkaline nitrobenzene depolymerization to break down complex lignin structures into monomeric aldehydes. The resulting derivates serve as substrates for the bioconversion by L. starkeyi, which is competent at metabolizing lignin-derived compounds into higher-value lignin monomeric alcohols (syringyl, vanillyl, and 4-hydroxybenzyl alcohol) and lipids, simultaneously. The strategy delineates the optimization of depolymerization conditions, sodium hydroxide concentration, nitrobenzene effect, and reaction time to maximize the yield of depolymerized lignin suitable for bioconversion. Subsequently, the bioconversion process toward cell growth, lipid production, and fatty acid profiles in various fermentations by L. starkeyi was explored. The highest syringaldehyde and vanillin obtained reached up to 4.81 mM and 0.64 mM, respectively. Then, it successfully produced 3.57 mM and 0.40 mM of syringyl alcohol and vanillyl alcohol, respectively, with 5.86 g L−1 of the lipid titer. The study demonstrates the potential of this integrated approach to convert OPEFB into valuable lignin-derived biochemicals and lipids, thereby contributing to the development of alternative strategies for biomass utilization efficiently.

Effect of Data Augmentation Using Deep Learning on Predictive Models for Geopolymer Compressive Strength

In recent years, machine learning models have become a potential approach in accurately predicting the concrete compressive strength, which is essential for the real-world application of geopolymer concrete. However, the precursor system of geopolymer concrete is known to be more heterogeneous compared to Ordinary Portland Cement (OPC) concrete, adversely affecting the data generated and the performance of the models. To its advantage, data enrichment through deep learning can effectively enhance the performance of prediction models. Therefore, this study investigates the capability of tabular generative adversarial networks (TGANs) to generate data on mixtures and compressive strength of geopolymer concrete. It assesses the impact of using synthetic data with various models, including tree-based, support vector machines, and neural networks. For this purpose, 930 instances with 11 variables were collected from the open literature. In particular, 10 variables including content of fly ash, slag, sodium silicate, sodium hydroxide, superplasticizer, fine aggregate, coarse aggregate, added water, curing temperature, and specimen age are considered as inputs, while compressive strength is the output of the models. A TGAN was employed to generate an additional 1000 data points based on the original dataset for training new predictive models. These models were evaluated on real data test sets and compared with models trained on the original data. The results indicate that the developed models significantly improve performance, particularly neural networks, followed by tree-based models and support vector machines. Moreover, data characteristics greatly influence model performance, both before and after data augmentation.

Optimizing operational parameters for highly-concentrated sodium hydroxide production via electrodialysis with bipolar membranes from concentrated brines

Sodium hydroxide necessitates the implementation of cleaner production methods that deviate from the conventional practices in the chlor-alkali industry. New sustainable sources such as concentrated brines, which are typically regarded as waste, are currently being investigated for the production of sodium hydroxide using Electrodialysis with Bipolar Membranes (EDBM). This process has the advantages of not producing gas by-products, reducing operational risks, and providing value to waste brines after converting them into acids or alkali solutions. However, the production of sodium hydroxide via EDBM using brines is limited by the low concentration of the final base (e.g. typically below 2 M), which increases the cost of transport. This study aims to overcome this limitation by optimizing parameters such as salt-to-base volume ratio, initial salt concentration, and current density values. Notably, this research is one of the few to employ Response Surface Methodology with a Central Composite Design to maximize the final sodium hydroxide concentration; two models using second-order polynomial equations were proposed. Results showed the possibility to achieve 5.3 M NaOH under a volume ratio range of 9.8:1–10:1, a current density range of 490 A/m−2 to 500 A/m−2, and an initial salt concentration in the range of 6 M NaCl. Moreover, the energetic analysis showed values of specific energy consumption in a range of 2.5 kWh kgNaOH-1-3.5 kWh kgNaOH-1 and specific productivity of the process up to 3.08 tonNaOH year−1 m−2, which are moderate in comparison with values previously presented in literature. Finally, an economic analysis showed that energy was the most significant cost component, making up 89 % of the total process cost, which was estimated to be 0.69 € kgNaOH-1 (concentration 21.2 % w/w). Overall, these high concentration values open a real chance to shift towards sustainable production of NaOH by means of EDBM from brines, highlighting the novelty of this study.

Recycling electric arc furnace slag through tailoring of ambient-cured alkali-activated mortar mix using hybrid AHP-GRA and TOPSIS

Utilizing Electric arc furnace slag (EAFS) as a precursor for alkali-activated mortar production reduces waste and supports alternative cement binders. Since the mix design includes multiple factors, the Taguchi DoE was employed by varying the modifier (fly ash) to precursor (EAFS) ratio (0–75% by mass), activator to precursor ratio (A/P) (0.52–0.66), sodium hydroxide (SH) concentration (8–14 M), and sodium silicate to sodium hydroxide ratio (SS/SH) (1.5–3.0). Analytic hierarchy process (AHP) weighted Grey relational analysis (GRA), and technique for order preference by similarity to ideal solution (TOPSIS), were utilized to achieve a high performing mix. Performance characteristics encompass flowability (flow%), final setting time (FST), compressive strength (f'cu), and flexural strength (f'cr). The optimized mix possessed 75% flowability, 575 min FST, 38 MPa f'cu, 16 MPa f'cr, and 3.75% water absorption. Precursor-to-modifier ratio dominates the mix design. The three mixes—optimized (M17), top-ranked (M8), and least-ranked (M1) were micro-structurally examined using powdered X-ray diffraction, X-ray fluorescence, scanning electron microscopy, energy dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy.

Optimization of banana fibers degumming by high temperature alkaline method and spinning

Banana fibers are a promising textile resource. However, due to their high gum and lignin content, the development of an efficient degumming method is crucial for their successful utilization. This article researches an improved traditional fiber degumming method using the high temperature alkali method, and the effects of sodium hydroxide concentration, time and temperature on the physical properties of banana fibers were investigated through a single factor experiment. The banana fibers were characterized with FTIR, XRD, SEM and chemical composition. The optimized process parameters of degumming can be achieved. The processing temperature was 140 °C and sodium hydroxide concentration was 10% for 1h. The weight loss and residual gum ratio of the fibers reached 51.84 and 4.13% respectively, the breaking strength was 5.57 cN/dtex, and the crystallinity was increased to 61.33%. These results demonstrate the effectiveness of this new degumming method. Additionally, the optimized banana fibers employed a softening process and were subsequently blended with cotton fibers at a 60/40 ratio for 60tex blended yarn. The breaking strength of the blended yarn was 6.22cN/tex, and the bacterial inhibition ratio was above 70%. This improved method is more suitable for mass production with a high degumming efficiency, and has great potential in the industry. Meanwhile, the excellent antimicrobial properties of banana fibers provide new ideas for development in bedding and clothing applications.

A Study on the Treatment and Recovery of Sodium Sulfate (Na<sub>2</sub>SO<sub>4</sub>) Generated When Recovering Valuable Metals (Ni, Co, Mn, Li) from Waste Lithium Ion Batteries(LIBs)

Concerns have arisen regarding the high concentrations of sodium sulfate in wastewater resulting from the waste Li-ion battery wet recycling process. In addressing this issue, Bipolar electrodialysis was employed to desalinate high-concentration sodium sulfate and recover it as sulfuric acid and sodium hydroxide. The investigation encompassed various experimental variables, such as applied voltage (maintained at a constant level), feed solution concentration, the initial concentrations of sulfuric acid and sodium hydroxide, and volume ratio (F/A/B). Optimal conditions were determined by assessing water migration (%), the recovery rates (%) of sulfuric acid and sodium hydroxide, concentration of the recovered substances, process time, and energy consumption. A higher applied voltage was found to reduce process time while increasing energy consumption, with the 25 V condition considered preferable. When utilizing a high-concentration feed solution, energy consumption rises; however, it decreases per unit of processed solution, rendering a 1.30 M Na<sub>2</sub>SO<sub>4</sub> feed solution preferable. Increasing initial concentrations of sulfuric acid and sodium hydroxide substantially prolonged process time and increased energy consumption, emphasizing the advantage of commencing with low initial concentrations. Adjusting the volume ratio facilitated the concentration and recovery of sulfuric acid and sodium hydroxide with minimal impact on process time or energy consumption. Under the identified optimal conditions, the recovery of 1.70 M sulfuric acid and 2.44 M sodium hydroxide was achieved.

A multi-criterial optimization of low-carbon binders for a sustainable high-strength concrete using TOPSIS

The objective of this study is to focus on "low carbon binders," given the adverse environmental impacts resulting from the extensive emission of greenhouse gases. In the current context, the term "geopolymer concrete," often referred to as "low carbon binders," is gaining prominence as a means to develop an eco-friendly binding material. Furthermore, this study focuses on creating high-strength geopolymer binders using ambient curing conditions. Numerous factors are involved in determining the mix ratios for geopolymer concrete. Nonetheless, the reluctance to apply it in practical scenarios arises from an insufficient understanding of how to select the appropriate mix proportions based on these parameters. Therefore, utilizing Multi-Criteria Decision-Making presents the best choice for evaluating the geopolymer parameters. Among several MCDM methods, TOPSIS has been selected for this research. Geopolymer binders are produced using Ground Granulated Blast furnace Slag (GGBS), a by-product from the steel industry and metakaolin (MK), a product from the calcination of clay. A total of thirty-two combinations of geopolymer mortar mixes were created by varying the percentage of metakaolin, the ratio of alkaline activators (sodium silicate to sodium hydroxide, SS/SH), and the concentration of sodium hydroxide (NaOH). The assessment of these mixtures involves nine response factors, encompassing flow characteristics, initial and final setting time, compressive strength (7 and 28 days), initial drying shrinkage, energy consumption, CO2 emission, and financial expenses. A study of the microstructure is carried out to explore the impact of MK presence on geopolymers using GGBS as a base precursor. Hence, techniques for optimizing multiple responses were employed to attain the desired attributes while maintaining all measurable factors within an acceptable range. This approach to optimization holds significant importance, particularly when dealing with geopolymer concrete, as it can enhance its utilization compared to traditional cement-based concrete.

The optimization of sodium hydroxide (NaOH) pre-treatment for reducing sugar production from rice husk using response surface methodology (RSM)

Lignocellulosic biomass is an abundant renewable resource which amounts to 1.3 billion tonnes per year and can be used in a variety of sustainable applications. It is primarily made up of tightly bound cellulose, hemicellulose, and lignin. However, hemicellulose dissolution and delignification pose significant challenges to the utilisation of reducing sugar. To solve this issue, alkaline pretreatment was utilised. The aim of lignocellulosic biomass pretreatment is to break down the complex structure of the biomass and provide better access to the components that can be converted into useful reducing sugar. Response Surface Methodology (RSM) was used to identify the optimal values for the factors influencing the pretreatment. The optimisation parameters were sodium hydroxide concentration (1 – 4 % w/v), pretreatment time (15 – 60 minutes), and solid loading (6 – 16% w/v). Rice husk, which was used as biomass, was hydrolysed enzymatically to produce reduced sugar. The optimum conditions for producing the highest reducing sugar of 15.18 mg/mL from rice husk were 1.67% w/v sodium hydroxide pretreatment, 59.44 minutes of pretreatment time, and 7.67% w/v solid loading. As a result, less alkaline reagents can be used with a longer pretreatment time, thus lowering the cost of pretreatment. Therefore, this shows that RSM was one of the best methods to replace the conventional technique for optimising the parameters of rice husk alkaline pretreatment for reducing sugar production.

Influence of activator ratios and concentration on the physio-mechanical and microstructural characteristics of the geopolymers derived from sandstone processing waste.

Natural stones have been utilized to meet various needs of human civilization since ancient times. The exploitation of any resource is associated with the production of redundant materials called wastes. Sandstone waste (SW) is one such waste obtained during the industrial processing of sandstones. Due to its siliceous composition, extensive yield, and disorganized dumping, noxious conditions related to land and human health are promoted. However, the lack of comprehensive engineering studies, mineralogical analysis, and design methodologies associated with the utilization of sandstone processing wastes restricted their applicability only to fillers or partial substitutes with pozzolans and traditional cement in meager volumes. In the past, limited efforts have been made to utilize SW as a construction entity, particularly for binding purposes. Thus, to enhance the scope of its utilization, a comprehensive investigation has been performed in this research to transform sandstone waste into a novel construction material by geopolymerization. Mix design tailoring and laboratory tests were implemented to understand the effects of sodium hydroxide concentration and sodium silicate to sodium hydroxide ratio on the dissolution and physio-mechanical characteristics of SW-based geopolymers. The activator-to-binder ratio was restricted to 0.4 to obtain pastes with sufficient workability without hindering the properties of the matrix. Besides, a high temperature-curing regime was selected based on SW's crystallographic and reactivity analysis. Subsequently, a total of 48 samples were prepared and tested at the curing age of 28 days. Detailed characterization of SW and SW-based geopolymer samples was performed using optical, X-ray, and infrared spectroscopies aided by electron imaging and thermogravimetric techniques. SW-based geopolymer samples showed compressive strengths in the range of 6-12 MPa, ~2 to 3 times higher than those obtained in previous experimentations. Phase analysis and microstructural examinations confirmed SW's participation in geopolymerization. Overall, it could be advocated that geopolymerization is an innovative approach for solving issues related to the disposal and re-utilization of SW, extending its possible application to the fields of cement mixes, wall tiles, mortars, and masonry as per the commendations of ASTM and ACI committee.

Aplikasi Edible Coating dari Limbah Kulit Udang dengan Aditif Asap Cair untuk Kemasan Sosis Sapi Antibakteri Ramah Lingkungan

Edible coating is a food preservation technique by coating using antimicrobial substances which can inhibit the growth of bacteria. This research aims to develop an edible coating from shrimp shell waste with liquid smoke additives as antibacterial packaging for processing beef sausages. Chitosan is made in three stages, namely demineralization, deproteination and deacetylation. Beef sausages coated with edible coating were tested using organoleptic and antibacterial tests. The results of this research showed that the highest degree of deacetylation of chitosan was found in the variable concentration of sodium hydroxide (NaOH) 55% with a degree of deacetylation value of 93.59%. The water and protein content in beef sausages coated with edible coating with liquid smoke showed values of 52.45% and 12.65% on the 7th day. This is in accordance with the Indonesian National Standards (SNI). Coating beef sausages using edible coating from 2% chitosan with 8% liquid smoke solvent has antimicrobial properties because in the antibacterial test a clear zone appeared on the beef sausages coated with edible coating.

Experimental Study on Geopolymerization of Lunar Soil Simulant under Dry Curing and Sealed Curing.

The construction of lunar surface roads is conducive to improving the efficiency of lunar space transportation. The use of lunar in situ resources is the key to the construction of lunar bases. In order to explore the strength development of a simulated lunar soil geopolymer at lunar temperature, geopolymers with different sodium hydroxide (NaOH) contents were prepared by using simulated lunar regolith materials. The temperature of the high-temperature section of the moon was simulated as the curing condition, and the difference in compressive strength between dry curing and sealed curing was studied. The results show that the high-temperature range of lunar temperature from 52.7 °C to 76.3 °C was the suitable curing period for the geopolymers, and the maximum strength of 72 h was 6.31 MPa when the NaOH content was 8% in the sealed-curing mode. The 72 h strength had a maximum value of 6.87 MPa when the NaOH content was 12% under dry curing. Choosing a suitable solution can reduce the consumption of activators required for geopolymers to obtain unit strength, effectively reduce the quality of materials transported from the Earth for lunar infrastructure construction, and save transportation costs. The microscopic results show that the simulated lunar soil generated gel substances and needle-like crystals under the alkali excitation of NaOH, forming a cluster and network structure to improve the compressive strength of the geopolymer.

Mass transfer phenomena of partially miscible liquids under liquid-liquid slug flow in a circular microchannel

Microreactors have been demonstrated to become an effective tool for increasing mass and heat transfer in heterogeneous chemical processes that are unachievable in batch or continuous stirred tank reactors. The key to superior performance is the availability of a large specific surface area (A/V) in the microsystem for mass and heat transfer between phases. Among the flow patterns generated in the two-phase liquid-liquid flow, slug is an ideal flow with a high stability characteristic, regular velocity, and uniform dimension throughout a microchannel system. The flow behavior gives slugs great potential to increase mass and heat transfer between phases, so optimizing the utilization of microreactors in many chemical process applications needs an in-depth understanding of the liquid-liquid hydrodynamic. Therefore, the current work aims to determine the mass transfer coefficient under liquid-liquid slug flow and the influence of slug dimensions, channel material, volumetric flow rate, and the flow rate ratio of the organic-aqueous phase on the mass transfer coefficient. The experiments were performed in 1 mm (ID) circular PTFE and silicone tubes, with a 30–40 ml/hour flow rate, and sodium hydroxide concentrations of 0.1, 0.13, and 0.15 M were used. The results exhibit that the most prominent overall mass transfer coefficient was 0.121/s, attained at 0.15 M sodium hydroxide concentration, with 40 ml/hour total discharge within the silicone channel. Microchannels generated smaller slug sizes at a higher aqueous phase flow rate than the organic phase. The smaller size provided a large specific surface area (A/V) for enhancing the mass transfer coefficient.

Production of Biocalcium from Fermented Fish Bone Residue for Fish Emulsion Sausage Fortification.

Fermented fish bone residue (FFBR) is an underused by-product of the industrial-scale production of fermented fish sauce. Subjecting FFBR to proper alkaline treatment can transform FFBR into biocalcium, which can be added to fish emulsion sausage (FES) to increase its calcium content. This study comprised two experiments. First, we aimed to find the most suitable alkaline treatment conditions for preparing biocalcium from FFBR. Alkaline treatments combining three sodium hydroxide (NaOH) concentrations (0%, 3%, and 6%) and three soaking times (0, 1, and 2 h) were tested. Quality parameters of alkaline-treated biocalcium (crude protein, crude fat, ash content, calcium, phosphorus, crude fiber, salt content, CIE color values, morphology of biocalcium particles, and the intensity of the fermented fish smell) were assessed. Second, we fortified FES with the properly treated biocalcium (0, 12, 24, or 36 g) and evaluated the sausage's calcium, phosphorus, crude fiber, salt content, pH, CIE color values, texture profile analysis (TPA), emulsion stability, and sensory criteria. It was found that treatment with 3% or 6% NaOH produced better crude protein, ash content, calcium, and CIE color value results than no alkaline treatment. These two NaOH concentrations effectively lowered the salt content and the intensity of the fermented fish smell. However, 3% and 6% NaOH produced similar results. A soaking time of 1 h or 2 h produced better results than no soaking in terms of crude protein, crude fat, ash content, calcium, phosphorus, CIE color values, and the intensity of fermented fish smell. However, 1 h and 2 h produced similar results. It is concluded that 3% NaOH and soaking for 1 h would be the most suitable alkaline treatment to prepare biocalcium from FFBR. Fortifying FES with biocalcium from FFBR increased the calcium and phosphorus contents but slightly reduced TPA. The other FES quality parameters were unaffected by biocalcium fortification.

Sustainable Production of Carboxymethyl Cellulose: A Biopolymer Alternative from Sugarcane (Saccharum officinarum L.) Leaves

This study explores the potential of sugarcane (Saccharum officinarum L.) leaves (SCLs), a significant agricultural waste, for the sustainable production of carboxymethyl cellulose (CMC) utilizing an innovative approach of carboxymethylation with monochloroacetic acid and varying sodium hydroxide (NaOH) concentrations (ranging from 20 to 60 g/100 mL). The optimal carboxymethylation condition was identified as 40 g/100 mL NaOH, which yielded the highest degree of substitution (DS = 0.86). Furthermore, a higher ash content in the obtained CMC indicated significant carboxymethyl substitution within the structure. The chemical structure of cellulose and the resulting polymers were characterized using Fourier transform infrared spectroscopy (FTIR). The FTIR spectrum exhibited characteristic peaks of carboxymethyl groups and their salts at wavenumbers of 1588–1591 cm−1 and 1413–1415 cm−1, respectively. The analyses from X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) revealed detailed insights into the crystallinity and morphology of carboxymethyl cellulose (CMC). The levels of heavy metals, including arsenic, lead, cadmium, and mercury, in the purified CMC were assessed using inductively coupled plasma mass spectrometry (ICP-MS) and were found to be within the recommended WHO/FAO limits, except for lead, which exceeded permissible levels. The prepared CMC demonstrated high purity at 99.34%, surpassing the 98.00% purity requirement for commercial-grade CMC. This product exhibits strong potential for diverse industrial applications, including paper coating, textile sizing and printing, ceramic glazing, and various uses in the oil industry.

Optimization of local modified metakaolin-based geopolymer concrete by Taguchi method

Abstract Geopolymer in recent concrete (GP) has gained significant attention due to its sustainability and environmental friendliness. Local metakaolin-based geopolymer is weaker than geopolymers made from other materials due to its low Si/Al ratio. A consistent mixture design is also lacking because geopolymers are affected by many variables. This study presents a method to find the optimal geopolymer mixture based on locally modified metakaolin as a source of aluminates and silicates using the Taguchi method. Metakaolin was modified using different contents of materials rich in silica, such as silica fume (SF), or materials rich in calcium, such as calcium oxide (CaO) of 5, 10, and 15%. The inclusion of 5% SF, 10% CaO, and a combination of 5% SF and 5% CaO as substitutes for metakaolin increases the compressive strength by 16.8, 6.9, and 22.8%, respectively, compared to the reference mixture without any modifications. In other words, adding 5% SF and CaO increased the molar ratio of SiO2/Al2O3 (R) from 1.782 to 1.914, resulting in the highest compressive strength of 53.3 MPa after 7 days of sun curing. To obtain the optimal mixture that achieves the highest compressive strength, the impact of three main variables, including the concentration of sodium hydroxide (SH), alkali solution-to-binder (Al/B) ratio, and sodium silicate-to-sodium hydroxide (SS/SH) ratio, must be considered using Taguchi method. A total of nine mixtures were investigated. It was found that 13 M of SH, 0.65 Al/B, and 2.5 SS/SH give a high compressive strength of 58.6 MPa at 7 days. Also, it was found that the concentration of SH plays a more important role in increasing the compressive strength than the alkali-to-binder ratio and SS/SH ratio. The scanning electron microscopy images show that the 5% weight replacement of metakaolin by silica and CaO could source fewer and smaller pores and reduce the microcracks’ width.

Development of a Low-Density Waste-Based Geopolymer Construction Material

The construction industry, integral to national infrastructure development, faces environmental challenges attributed to Portland cement’s high energy consumption and carbon dioxide emissions during production. To address this challenge, this study integrated waste fly ash and polystyrene into geopolymers to enhance environmental sustainability and economic feasibility. The objectives included developing low-density geopolymers using polystyrene inclusion, optimizing component mixing ratios, assessing activator concentration effects, determining the optimal curing conditions, and characterizing the resulting geopolymers. Through experimental investigation, low-density geopolymers were developed with optimized component ratios and curing conditions. The experimental procedure began with the classification of fly ash to determine its suitability for various applications, revealing it to be type F. Geopolymers were fabricated using a mixture of fly ash, water, sodium hydroxide activator, and polystyrene. Varied concentrations of sodium hydroxide and polystyrene were employed. Two curing temperatures, 60 °C and 100 °C, were explored. The results showed that greater sodium hydroxide concentrations improved the structure and compressive strength of the geopolymers. The results also demonstrated a significant correlation between the curing conditions and the mechanical properties of the produced geopolymers. The goal of reducing the density of the geopolymers for lightweight thermal-resistant applications was achieved through polystyrene incorporation. However, polystyrene incorporation negatively impacted the compressive strength. The optimum production conditions for the sodium hydroxide-varied samples were 8 g sodium hydroxide/g sample cured at 100 °C, while the optimum production conditions for polystyrene-varied samples were 1 g polystyrene/g sample cured at 60 °C. The findings confirmed the viability of utilizing fly ash and polystyrene wastes to produce sustainable, low-density, thermal-resistant construction materials. Overall, increasing activator concentration enhances the strength and durability of geopolymers, while polystyrene contributes to the development of lightweight geopolymers, provided the appropriate amount is utilized. To ensure replicability, the formulation procedure and input quantities must be tailored according to the intended geopolymer application. These insights offer practical guidance for optimizing geopolymer manufacturing processes towards enhanced sustainability and performance.