1M NaOH Research Articles

Performance evaluation of innovative self-healing corrosion protection coatings for prestressing strands

This study presents the design and experimental evaluation of advanced corrosion protection coatings for application on prestressing strands which are the core constituents of prestressed concrete structures such as bridges. Variety of self-heal coatings embodying corrective and protective phenomena in response to the degrading effects of corrosion have been designed and tested in simulated aggressive weathering conditions. Standard 7-wire prestressing strands coated with self-heal epoxy, self-heal toughened epoxy and hybrid epoxy coating systems were subjected to salt fog spray up to a duration of 2500 h, and 3M CalCl2, 3M NaOH, saturated Ca(OH)2 solutions and distilled water up to 45 days duration. Furthermore, rust creepage of the coated prestressing strands was measured after extended exposure to aggressive corrosive environment. Bond strength of the self-heal epoxy coated prestressing strands was evaluated through pullout test using high-strength concrete.Significant improvement in corrosion resistance, hydrolytic stability, marked reduction in rust creepage, and improved bond strength, brought about by the innovative self-heal epoxy coatings were recorded in laboratory tests. Furthermore, electrochemical impedance spectroscopy (EIS) data proved excellent corrosion protection qualities of self-healing coatings. The ATR-FTIR spectra of various self-heal epoxy coating systems and optic microscopic images of the coatings further verified these findings.

Fractional recovery of proteins and carbohydrates from secondary sludge from urban wastewater treatment plants

The secondary sludge of wastewater treatment plants is an abundant and problematic bacterial biomass that accumulates nutrients from wastewater, mainly as proteins and carbohydrates. Recent studies have focused on energy recovery of this biomass by anaerobic digestion to produce biogas. However, fractional recovery of the sludge components could increase its value and provide the basis for a biorefinery based on this waste. Since ≈ 40-60% of the bacterial dry weight is protein, this biomass could be an important source of functional peptides or amino acids, and the carbohydrates could be used to produce bioplastics or biofuels. This study compares chemical, physical and biological hydrolysis methods and their sequential and assisted combinations to recover proteins and carbohydrates from sludge. Ultrasound-assisted alkaline treatment provided the highest protein solubilization yield (97.2%) with low degradation, resulting in peptide recovery yields of 75.1% with sizes from 70-215 kDa, 40% of essential amino acids and purity of 35.3% with NaOH 1M. The hydrothermal-alkaline combination almost completely solubilized the proteins but not the carbohydrates (77.4%) with high degradation (52.6%). The hydrothermal-acidic combination achieved high carbohydrate solubilization (94%) and recoveries of glucose (63.6%) and xylose (12.6%) but low protein recovery (43.7%) as small size peptides.

3D printable earth-based alkali activated “ink”: Effect of alkali concentration and binder-to-aggregate ratio

This research attempts to investigate the effect of activator concentration (4 mol/L (M) and 8M) and binder-to-aggregate (B:A) ratio (ranging from 1:1 to 1:3 by weight) on extrudability and buildability of 3D printable natural earth-based alkali-activated materials (EAAM). It is found that natural clay in soil, used to replace 25 % of M-sand, imparts higher thixotropy, evident from 90 to 100 % recovery in viscosity compared to 65–80 % for corresponding control (containing only M-sand and no soil). Presence of clay increases the dynamic yield stress than control but reduces the plastic viscosity by 80 – 90 % in EAAM compared to corresponding control where interlocking between sand particles resists smooth extrusion of the material. EAAMs made with 8M NaOH have higher flow retention and maintain 95–100 % recovery in viscosity for longer duration than 4M EAAM. This contributes to superior extrusion quality of 8M EAAM than 4M EAAM. The findings suggest that binder content can be reduced as concentration of NaOH is increased from 4M to 8M. This is evident from lower layer deformation (0.09 % of original height) under self-weight and higher 3D printed buildable height of at least 457 mm in 8M EAAM with B:A of 1:2 compared to a maximum of 375 mm for 4M EAAM at higher B:A of 1:1. Ratios of wet compressive strength to dry compressive strength vary between 0.92 and 1.09 in 8M EAAM compared to 0.79 – 0.85 for 4M EAAM at 28-day age, suggesting lower sensitivity to moisture due to improved clay stabilization. Based on the strength and moisture sensitivity, the developed material can serve as a low-carbon and durable alternative to Portland cement in the construction of masonry elements in buildings, including cavity walls, panels, flooring tiles and façade members.

Penurunan Kadar COD Air Limbah Domestik Menggunakan Fly Ash dengan Metode Adsorpsi

Domestic wastewater was collected from a drainage system on Soekarno Hatta Street, Kalibalau Kencana, Kecepatan District, Bandar Lampung City, with a high Chemical Oxygen Demand (COD) content of 4,867 mg/L. If the wastewater is discharged directly into water bodies, it can reduce the availability of dissolved oxygen, potentially disrupting the survival of aquatic organisms. This research aims to determine the effect of contact time on the reduction of COD levels in domestic wastewater, the effect of fly ash adsorbent both activated and non-activated on the reduction of COD values, and its impact on other parameters according to domestic wastewater quality standards. Fly ash was activated using 6M NaOH and heated at 160°C for 1 hour. The adsorption process was carried out with varying contact times of 30, 60, 90, 120, and 150 minutes, using both activated and non-activated adsorbents with masses of 1.5 and 3 grams. The results of this study showed that the adsorption test with the activated adsorbent with masses of 1.5 and 3 grams reached optimum times of 90 and 60 minutes, respectively, with percentage reductions of 98.78% and 99.03%. In contrast, for the non-activated adsorbent with masses of 1.5 and 3 grams, optimum times occurred at 150 minutes, with percentage reductions of 95.64% and 90.79%, respectively.

Trace Ru Incorporation Boosted Co2P Nanorods for Superior Water Electrolysis and Substrate-Paired Electrolysis Toward Value-Added Chemicals in Alkaline Medium.

Electro-valorization of biomass-derived chemicals has ensured sustainable production of value-added products, an effective approach for reducing carbon footprint, through renewable energy. Electrochemical oxidation and reduction reactions in aqueous media using H2O as a potential source for active hydrogenated and oxygenated species fulfill the purpose. In this study, Ru─Co2P nanorods are explored as a bifunctional electrocatalyst toward valorization of Organics at basic media. The in-situ electrogenerated Co3+ and Co4+ species act as active oxidants toward product selectivity. An overpotential of 68mV is found for hydrogen evolution reaction (1m NaOH) with Ru─Co2P. Further, used as cathode, Ru─Co2P effectively reduces furfuraldehyde to furfuryl alcohol and p-nitrophenol to p-aminophenol. Ru doping enables ease of formation of active species both for reduction and oxidation, faster charge transfer between catalyst to absorbates. Density Functional Theory calculation establishes Ru incorporation in Co2P surface results in enhanced adsorption of substrates. Ru doping modulates the electronic structure of Co2P which changes the density of states resulting in faster water dissociation and water splitting. To reach 10mAcm-2 current density only 1.6V is required for water electrolysis, whereas 1.4V is enough for substrate-paired electrolysis with simultaneous oxidation of benzyl alcohol and reduction of p-nitro phenol.

Synthesis of Ag/Cu decorated 3D self-assembled nanowire TiO2 photocatalyst for hydrogen production: a promising pathway towards sustainable energy generation.

Here, synthesis and characterization of TiO2 with different morphologies along with the cost-effective bimetallic decoration on optimized 3D self-assembled nanowire TiO2 (NWT) photocatalyst (Ag/Cu-NWT) with overwhelming hydrogen production rate is reported. All the photocatalysts were well characterized by different characterization techniques. Initially, the effect of morphology change obtained by changing the NaOH concentration has been studied for TiO2. Morphology obtained at 10M NaOH solution, i.e., NWT (678μmol/g), showed better hydrogen production than morphology obtained at 5M (410μmol/g), 15M (210μmol/g), and 20M (160μmol/g) NaOH solutions. Further, with the aim to achieve comparable or better activity low-cost photocatalyst as compared to Pt-TiO2 system, NWT was decorated with various Cu percentages and then with a minimal percentage of Ag on an optimized Cu-NWT photocatalyst. The observed trend for photocatalytic hydrogen production has been found to be P25 TiO2 < NWT < 1.0Cu-NWT < 0.5Pt-NWT ≤ 0.1Ag/1.0Cu-NWT. The marked increase by a factor of 103 in hydrogen production for the optimized bimetallic 0.1Ag/1.0Cu-NWT (10,184μmol/g) photocatalyst compared to P25 TiO2 (99μmol/g), nearly threefold increment in hydrogen production than an optimized 1.0 Cu-NWT (3907μmol/g) photocatalyst and comparable hydrogen production as compared to 0.5Pt-NWT (10,050μmol/g) may be attributed to the successful synthesis of a highly porous NWT morphology, which offers large surface area, increased light absorption combined with the synergistic effects of surface plasmon resonance (SPR), and the Schottky barrier for H+ reduction to H2 gas. The optimization of TiO2 morphology and an inexpensive bimetallic decoration strategy opens up promising opportunities for the development of cost-effective photocatalysts in the realm of energy and environment.

Cellulose extraction from Cladophora rupestris for extraction of nanomaterials

Abstract Cellulose from macroalgae is potential for the extraction of nanomaterials due to its availability and its great fraction in the biomass. Cladophora rupestris is a macroalgae and is a good material to which a cellulose may be extracted. The said macroalgae has no value-added products or uses yet. It has a lignocellulosic profile of: alpha-cellulose, 33.43 %; hemicellulose, 15.48%; holocellulose, 48.93; acid soluble lignin, 2.22%; acid insoluble lignin, 22.33%, extractives, 5.67% and total ash, 39.65%. Identifying the best method and conditions for the extraction of cellulose from the said material is a challenge that needs to be addressed. The process for the cellulose extraction considered variations on drying (oven, air, and sun drying), defatting (using solvents: methanol and hexane; and extraction time: 8 hrs and 4 days), solvent drying (oven and air drying), alkaline pre-treatment (0.1, 0.5, and 1M NaOH), fixed conditions on bleaching, bleached biomass oven drying. The biomass weight losses were monitored for some steps, attributing this on the removal of the lignin and extractives. The lignocellulosic profile of the crude cellulose extracted from the macroalgae using the best conditions was determined indicating an increased fraction of the cellulose components in the biomass and a transformation of the rigid biomass into a soft and paper-like texture. The functional groups present on the cellulose was determined. The extracted cellulose was used to produced cellulose nanofibril (CNF) with fiber diameter of the CNF ranges on 14.29 – 37.50 nm and crystallinity index of 92.48%. Attempts were done on extraction of cellulose nanocrystal (CNC) utilizing microwave-assisted acid hydrolysis (MAAH) and semi-batch acid hydrolysis (SBAH); and variation on the acid used (sulfuric acid, and oxalic acid), concentration of the acid, and the temperature conditions.

Using a cellulose-complementary oligosaccharide as a tool to probe exposed cellulosic surfaces in cotton fibres and growing plant cell walls.

Cellulosic microfibrils in plant cell walls are largely ensheathed and probably tethered by hydrogen-bonded hemicelluloses. Ensheathing may vary developmentally as hemicelluloses are peeled to enable cell expansion. We characterised a simple method to quantify ensheathed versus naked cellulosic surfaces based on the ability to adsorb a radiolabelled 'cellulose-complementary oligosaccharide', [3H]cellopentaitol. Filter-paper (cellulose) adsorbed 40% and >80% of aqueous 5 nM [3H]cellopentaitol within ∼1 and ∼20 h respectively. When [3H]cellopentaitol was rapidly dried onto filter-paper, ∼50% of it was desorbable by water, whereas after ∼1 day annealing in aqueous medium the adsorption became too strong to be reversible in water. 'Strongly' adsorbed [3H]cellopentaitol was, however, ∼98% desorbed by 6 M NaOH, ∼50% by 0.2 M cellobiose, and ∼30% by 8 M urea, indicating a role for hydrogen-bonding reinforced by complementarity of shape. Gradual adsorption was promoted by kosmotropes (1.4 M Na2SO4 or 30% methanol), and inhibited by chaotropes (8 M urea), supporting a role for hydrogen-bonding. [3H]Cellopentaitol adsorption was strongly competed by non-radioactive cello-oligosaccharides (Cell2-6), the IC50 (half-inhibitory concentration) being highly size-dependent: Cell2, ∼70 mM; Cell3, ∼7 mM; and Cell4-6, ∼0.05 mM. Malto-oligosaccharides (400 mM) had no effect, confirming the role of complementarity. The quantity of adsorbed [3H]cellopentaitol was proportional to mass of cellulose. Of seven cottons tested, wild-type Gossypium arboreum fibres were least capable of adsorbing [3H]cellopentaitol, indicating ensheathment of their microfibrillar surfaces, confirmed by their resistance to cellulase digestion, and potentially attributable to a high glucuronoarabinoxylan content. In conclusion, [3H]cellopentaitol adsorption is a simple, sensitive and quantitative way of titrating 'naked' cellulose surfaces.

Sustainable construction materials from alkali-activated waste fiberglass and waste refractory

In this work, waste fiberglass was up-cycled, alone, or mixed with used alumina-zirconia-silica (AZS) refractory from dismantled glass melting furnaces. Alkali activation was performed by suspending fiberglass and fiberglass/AZS powders in NaOH aqueous solution of various concentrations (8M, 6M, and 3M). The activation of waste fiberglass with 8M NaOH yields a gel with calcium and sodium-containing aluminosilicate hydrates. The addition of AZS refractory enabled the release of aluminates into the solution, which had beneficial effects on the mechanical properties. Low molarity activation yielded weaker materials which could be used as precursors for firing at moderate temperatures (800 °C and 1000 °C) to create cellular glass-ceramics, with a total porosity of up to 92 %. The firing of 8M activated samples resulted in glass ceramics with a 66–75 % porosity range and compressive strength of 10–23Mpa. The compressive strength-to-density ratio before and after firing was comparable to that of established commercial construction materials.

Multifunctional applications of novel copper magnesium vanadate nanoparticles: Photocatalytic dye degradation and electrochemical properties

The multifunctional applications of nanomaterials in energy saving, electrochemical energy storage, and sensing devices are a current research trend. Novel Copper Magnesium Vanadate (CMV-CuMg2V2O8) nanoparticles have been synthesized by solution combustion method. The crystallite size calculated from XRD and TEM results was found to be 21 nm. The band gap estimated from UV–Vis DRS of CMV nanoparticles was found to be 3.82 eV. Its multifunctional applications were explored through for energy conversion, storage and sensing applications. Photocatalytic degradation of Acid Red-88 (AR-88) dye was conducted using CMV nanoparticles as photocatalyst under UV light. CMV nanoparticles modified carbon paste electrodes were prepared and its cyclic voltammetry (CV), Electrochemical impedence spectroscopy (EIS) and Galvanostatic charge–discharge (GCD) analysis were carried out using 1M KCl and NaOH electrolyte. With excellent specific capacitance of 266 Fg−1 in KCl electrolyte and 242 Fg−1 in NaOH electrolyte at 5 mV/s scan rate, CMV NPs was demonstrated to be a promising electrode material for supercapacitors. Electrochemical sensing analysis was carried out using the same electrode for the detection of paracetamol and ibuprofen within the range of 1–5 mM. The resulting copper magnesium vanadate nanoparticles have been verified as a possible electrode material for next-generation energy storage devices.

Ultrastable Carboxyl-Functionalized Pore-Space-Partitioned Metal-Organic Frameworks for Gas Separation.

Isoreticular chemistry, which enables property optimization by changing compositions without changing topology, is a powerful synthetic strategy. One of the biggest challenges facing isoreticular chemistry is to extend it to ligands with strongly coordinating substituent groups such as unbound -COOH, because competitive interactions between such groups and metal ions can derail isoreticular chemistry. It is even more challenging to have an isoreticular series of carboxyl-functionalized MOFs capable of encompassing chemically disparate metal ions. Here, with the simultaneous introduction of carboxyl functionalization and pore space partition, a family of carboxyl-functionalized materials is developed in diverse compositions from homometallic Cr3+ and Ni2+ to heterometallic Co2+/V3+, Ni2+/V3+, Co2+/In3+, Co2+/Ni2+. Cr-MOFs remain highly crystalline in boiling water. Unprecedentedly, one Cr-MOF can withstand the treatment cycle with 10m NaOH and 12m HCl, allowing reversible inter-conversion between unbound -COOH acid form and -COO- base form. These materials exhibit excellent sorption properties such as high uptake capacity for CO2 (100.2 cm3g-1) and hydrocarbon gases (e.g., 142.1 cm3g-1 for C2H2, 110.5 cm3g-1 for C2H4) at 1 bar and 298K, high benzene/cyclohexane selectivity (up to ≈40), and promising separation performance for gas mixtures such as C2H2/CO2 and C2H2/C2H4.

Dual-capable spinel cobalt oxide nanoparticles for electrocatalytic oxygen evolution and water contaminant removal.

This study investigates the synthesis and electrocatalytic performance of cobalt oxide (Co3O4) nanoparticles for the oxygen evolution reaction (OER) and their role in water treatment as contaminant removal agents. Cobalt oxide nanoparticles are recognized as promising materials in electrocatalysis due to their tunable properties and nanoscale engineering potential. Here, fine cobalt oxide nanoparticles are synthesized using the sol-gel method followed by various sintering temperatures to achieve precise control over surface morphology, size, and shape. Characterization via high-resolution scanning electron microscopy (HRSEM) and high-resolution transmission electron microscopy (HRTEM) elucidates the impact of sintering temperature on nanoparticle properties. Thin film electrodes of cobalt oxide are fabricated using the doctor blade method and evaluated using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Among the tested sintering temperatures, cobalt oxide electrodes sintered at 600°C exhibit superior catalytic activity, demonstrating an overpotential of 258mV (vs RHE) at 10mAcm-2 current density and a Tafel slope of 17.33mV dec-1. Furthermore, these electrodes demonstrate excellent stability, maintaining OER performance for 10h in 1M NaOH electrolyte. Additionally, the role of cobalt oxide nanoparticles in water treatment is explored using inductively coupled plasma atomic emission spectrometry (ICP-AES). Experimental results reveal that lower sintering temperatures enhance the electrocatalytic properties of cobalt oxide nanoparticles, highlighting their potential contribution to sustainable energy and water treatment technologies. This work underscores the significance of cobalt oxide nanoparticles as dual-functional materials for advancing electrocatalysis and water purification applications, thus paving the way for the development of efficient and environmentally friendly technologies.

Experimental metasomatic alteration of titanite in a series of metamorphic fluids at 700 °C and 200 MPa

Seven experiments exploring the reaction of titanite with various hydrothermal solutions have been carried out at 700 °C and 200 MPa for a run duration of 16 days. In experiments involving fluids consisting of NaCl+H2O, KCl+H2O, CaCl2+H2O, 2M NaOH, or 2M KOH, no reaction of the titanite with the fluid was observed other than a slight dissolution of the titanite. Experiments involving NaF+H2O and Ca(OH)2+H2O resulted in visible alteration of the titanite in texture and composition, coupled with the formation of perovskite. In the NaF+H2O experiment, perovskite, enriched with rare earth elements (REE), formed as euhedral to subhedral crystals on the surface of the recrystallized titanite. In the Ca(OH)2+H2O experiment perovskite took in minor amounts of REE, and formed as a reaction rim partially replacing the titanite via a coupled dissolution-reprecipitation reaction. Wollastonite, along with minor calcite, and grossular garnet, formed as an outer rim on the perovskite. In the NaF+H2O experiment major and trace elements were leached from the titanite, whereas in the Ca(OH)2+H2O experiment no leaching of major or trace elements was observed. Nb/Ta, Th/U, and Y/Ho were investigated as potential indicators of hydrothermal processes. While the Nb/Ta ratio was altered in the experimentally metasomatised titanite, the degree of alteration was the same for both fluids. In contrast, only small changes in the Th/U and Y/Ho ratios between the altered and original titanite were seen for either experiment. The formation of perovskite at the expense of titanite in NaF+H2O or Ca(OH)2+H2O fluids demonstrates how titanite reacts with these fluids in simple, low silica activity systems under mid to upper crustal P-T conditions.

Mesoporous carbon particles by biomass waste based on sulfonation and copper oxide functionalization as efficient and stable electrode material for supercapacitor.

Here, the hierarchical mesoporous-activated carbon particles obtained by KOH activation from pistachio shell wastes are modified by both the sulfonation process and CuO doping by hydrothermal heating (CuO@S-doped PSAC) for use as a supercapacitor. It is predicted that the electrochemical performance of the porous carbon electrode material obtained by such CuO doping and sulfonation process will be significantly increased with increased Faradaic capacitance. The electrochemical performance of CuO@S doped PSAC composite is systematically investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge/discharge (GCD) in the presence of 1M H2SO4, 1M Na2SO4, and 1M NaOH as electrolytes. The CuO@S doped PSAC-based electrode shows excellent stability with high specific capacitance up to 397.16 F/g at 0.1 A/g and 92.64% retention. Furthermore, FTIR, SEM, XRD, EDS, and nitrogen adsorption/desorption analyses are used for the characterisation of the obtained composites. Based on a significant supercapacitor performance, the synthesis strategy of carbon-based electrode material containing sulfonation and CuO modifications derived from agricultural biomass waste material is predicted to be a valuable example.

Strong yet Tough Catalyst-Free Transesterification Vitrimer with Excellent Fire-Retardancy, Durability, and Closed-Loop Recyclability.

Despite great advances in vitrimer, it remains highly challenging to achieve a property portfolio of excellent mechanical properties, desired durability, and high fire safety. Thus, a catalyst-free, closed-loop recyclable transesterification vitrimer (TPN1.50) with superior mechanical properties, durability, and fire retardancy is developed by introducing a rationally designed tertiary amine/phosphorus-containing reactive oligomer (TPN) into epoxy resin (EP). Because of strong covalent interactions between TPN and EP and its linear oligomer structure, as-prepared TPN1.50 achieves a tensile strength of 86.2MPa and a toughness of 6.8MJm-3, superior to previous vitrimer counterparts. TPN1.50 containing 1.50 wt% phosphorus shows desirable fire retardancy, including a limiting oxygen index of 35.2% and a vertical burning (UL-94) V-0 classification. TPN1.50 features great durability and can maintain its structure integrity in 1M HCl or NaOH solution for 100 days. This is because the tertiary amines are anchored within the cross-linked network and blocked by rigid P-containing groups, thus effectively suppressing the transesterification. Owing to its good chemical recovery, TPN1.50 can be used as a promising resin for creating recyclable carbon fiber-reinforced polymer composites. This work offers a promising integrated method for creating robust durable fire-safe vitrimers which facilitate the sustainable development of high-performance polymer composites.

Fatigue analysis of ambient-cured geopolymer concrete for high-traffic pavements.

The building sector is growing at a rapid rate, leading to an increased demand for construction materials. Concrete made with Ordinary Portland Cement (OPC) has long been the preferred choice due to its excellent bonding properties and versatility as demanded by construction process. However, the manufacturing of Ordinary Portland Cement (OPC) leads to negative impacts on the environment, with the cement sector responsible for around 5-8% of global CO2 emissions. In addition, the manufacture of OPC necessitates significant amounts of natural raw materials and energy. Contrastingly, using geopolymers promises to save substantial amounts of energy and reduce CO2 emissions. This potential has sparked growing interest in the application of geopolymers within transportation infrastructure. For pavements, the workability requirement is less, and hence, geopolymer concrete (GPC) is a viable option, but fatigue-resistance of GPC is not seen reported in literatures. This article evaluates the properties of geopolymer concrete with low-calcium fly ash partially replaced with ground granular blast furnace slag (GGBS) with 8M NaOH alkaline solution and cured under ambient atmospheric conditions to evaluate its usage in pavements and develop an environmentally sustainable and durable GPC capable of withstanding heavy traffic. The study involves adjusting the pavement quality concrete (PQC) mix design; evaluating the mechanical characteristics, abrasion resistance, and shrinkage strain of the GPC; and analyzing its microstructure. Additionally, the study compares the fatigue life of GPC to that of PQC using various Weibull distribution approaches. The results showed that GPC4 (70% Fly ash and 30% GGBS) mix achieved best results at 28days, with a compressive strength of 45.68MPa, split tensile strength of 3.76MPa, and flexural strength of 4.62MPa. Also, shrinkage strains were nearly 31% lesser than PQC at 90days. In addition, developing GPC needs 27% lesser embodied energy than PQC. Fatigue analysis prove that ambient cured fly ash-GGBS based geopolymer concrete with 8M NaOH exhibits less stress development than PQC at medium loads, even though it is brittle. Thus, the study proves that it is suitable as a material for pavements to resist medium-loaded traffic-resisting pavements.

Strength and Acid Resistance of Mortar with Different Binders from Palm Oil Fuel Ash, Slag, and Calcium Carbide Residue

This study deals with the use of ground palm oil fuel ash (GPOFA) in combination with ground granulated blast furnace slag (GGBFS) and ground calcium carbide residue (GCR) to produce the binary and ternary binders-based alkali activated mortar. The appropriate content of materials in each binder type was determined as a function of compressive strength. The results revealed that both GPOFA:GGBFS and GPOFA:GCR binders had an optimum blending ratio of 70:30 wt%, while the GPOFA:GGBFS:GCR binder was 55:30:15 wt%. An alkaline catalyst of NaOH was admixed to the best mixture in each binder type to stimulate the mortar's compressive strength. The sulfuric acid (H2SO4) resistance of the mortar in terms of weight change was also examined. The addition of 1M NaOH in both binary and ternary binders could enhance the compressive strength and H2SO4 resistance of the mortar. The highest compressive strength and lowest weight change due to soaking in H2SO4 solution were found in the ternary binder mortar with a 1 M NaOH. The mortar with GCR immersed in H2SO4 solution resulted in an increased weight, which was different from that of the mortar without GCR. The microstructural analysis of the alkali-activated pastes indicated more reaction products than in the case of the pastes without alkali activator. However, a higher concentration of 2 M NaOH resulted in a poor microstructure, which had a negative effect on the compressive strength and H2SO4resistance. Doi: 10.28991/CEJ-2024-010-07-08 Full Text: PDF

Batch Adsorption of Tannins from Stevia Leaf Extract using Activated Carbon: An Investigation into Adsorption Isotherms and Adsorption Energy

Stevia leaf extract (Stevia rebaudiana Bertoni) could have been utilized as an alternative natural sweetener because it possessed a sweetness level 300 times that of sucrose sugar. However, stevia leaf extract still contained a bitter taste attributed to the presence of tannins. The method that can be used to reduce tannin content is batch adsorption using activated carbon. This study aimed to investigate the batch adsorption process for the tannin content of stevia leaf extract using activated carbon with variable adsorption times ranging from 5 to 180 minutes, which included the appropriate adsorption isotherm model and adsorption energy. Stevia leaves were extracted through maceration with 70% ethanol. The results of the stevia leaf extract were adsorbed in batches using activated carbon treated with 1M NaOH. The analysis was carried out by testing the tannin content (mg/g TAE) using a UV-Vis spectrophotometer at a wavelength of 735 nm and calculating the adsorption isotherm and adsorption energy. The results showed that the tannin content before adsorption was 0.910 mg/g TAE, and the lowest tannin content was 0.040 mg/g TAE at 100 minutes. The tannin content decreased between 5–90 minutes, remained constant, reached equilibrium at 95–120 minutes, and increased again at 125–180 minutes. The suitable adsorption isotherm model was the Freundlich isotherm with a value of R2 = 0.9998; KF = 25.293 [(mg/g)(L/mg)1/nf], and adsorption energy = -8.03 kJ/mol. The adsorption that occurred was classified as physical adsorption.

MANFAAT AKTIVASI FLY ASH BATU BARA DENGAN VARIASI KONSENTRASI NAOH SEBAGAI ADSORBEN

Water is one of the most important natural resources for human life. However, there are some problems that cause water to get polluted and not be used properly, one of which is the liquid waste of the hydrocarbon industry. Fly ash is a residue from coal combustion. Fly ash can be used as an adsorbent to reduce the content of hazardous fluid waste that could threaten human life. The study aims to find out the best NaOH concentration ratio between 1 M and 3 M added to activate fly ash against COD decrease, BOD, TSS, pH, and color change in Kutawaru Cilacap battery waste. The study passes through several stages, namely the first phase of activation of fly ash with NaOH at concentration ratios of 1M and 3M with a ratio of 1:5 for 3 hours. Then, in the adsorption process, the activated fly ash is mixed with battery liquid waste. The final phase is the testing of batik waste at the DLH Cilacap. The results obtained are at the concentration of 1M NaOH because it can reduce COD, BOD, and TSS up to 76%. With the result of COD of 3286 mg/L, BOD of 4921 mg/L, and TSS of 115 mg/L, whereas the results of concentration 3M, with COD of 3615 mg/L, COD 5397 mg/L, and TSS of 36 mg/L, PH for both these concentrations of 8 and the change in color of waste batik that remains black concentrated.

Nutrient Removal Efficiencies in a Bioretention Cell Using Pre-Treated Coconut By-Product as Carbon Source

Abstract In this research, the appropriateness of alkali pre-treatment on coconut by-products was managed by exposing coconut husk and shell to 2M NaOH. The powdered samples were analysed for morphology observation, Fourier Transform Infrared (FTIR), Particle Size Analyzer (PSA), and water quality tests. Weakening the hemicellulose structure resulted from subjecting the coconut shell to alkali pre-treatment shown in the morphology observation. Furthermore, the FTIR analysis exhibited the presence of O-H stretch in all pre-treated samples representing an indication for occurring the lignin breakdown, while an absence of the C=O functional group was shown in both additive samples after their subjection to alkali pre-treatment. In PSA analysis, the particles of all samples were found finer than the particle size distribution standards, in which the smallest D50 was obtained for the treated coconut shell (TCS), followed by untreated coconut shell (UCS), untreated coconut husk (UCH), and treated coconut husk (TCH). Among all the powdered samples (TCS, UCS, UCH, and TCH) analysed in this study, only TCH values met the ranges provided and recommended by the Urban Stormwater Management Manual for Malaysia (MSMA) and the Australian Department of Sustainability, Environment, Water, Population, and Communities (DSEWPC). Meanwhile, a poor removal rate for total suspended solids (TSS) was attained due to the contribution of TSS by the filter media which caused the TSS rates to surpass the inlet values. Additionally, the presence of a high concentration of total phosphorous (TP) in all the tested samples indicated their capabilities to provide PO43 in the bioretention cell, which is a vital nutrient for the plant’s growth. In contrast, Ammoniacal Nitrogen (AN) with a concentration rate as low as 4 mg/L was observed throughout the test periods which showed a significant reduction compared to the rate of AN at the inlet samples ranged between 5.2 and 11.4 mg/L. The findings indicated that coconut by-products, when subjected to an alkali pre-treatment process, are appropriate for incorporation as additives in bioretention filter media.