Optimum NaOH Concentration Research Articles

Development and Characterization of Alkali-Activated Lithium Slag-Fly Ash Composite Cement

As the demand for environmental sustainability grows in the global construction industry, traditional cement production faces significant challenges due to high energy consumption and substantial CO2 emissions. Therefore, developing low-carbon, high-performance alternative cementitious materials has become a research focus. This paper proposes a new low-carbon cement (alkali-activated lithium slag-fly ash composite cement, ALFC) as a substitute for traditional cement. First, the alkali activation reactivity of lithium slag (LS) is enhanced through calcination and grinding, revealing the reasons behind its improved reactivity. Then, alkali-activated LS and fly ash were partially used to replace cement to prepare ALFC, and the effects of the water-to-binder ratio (W/B), LS content, and NaOH addition on the flowability and mechanical properties of ALFC were investigated. XRD, SEM/EDS, and TG/DTG analyses were conducted to examine its hydration products and microstructure, revealing the hydration mechanism. The results show that the flowability of ALFC increases with W/B but decreases with a higher LS content. When W/B is 0.325 and the LS content is 25 wt.%, flowability reaches 200 mm, meeting construction requirements. LS calcined at 700 °C for 1 h significantly enhanced ALFC’s 90-day flexural and compressive strengths by 39.73% and 58.47%, respectively. The primary hydration products of ALFC are C-S-H, N-A-S-H, and C-A-S-H gels, with their content increasing as the NaOH concentration rises. The optimal NaOH concentration and LS content for ALFC are 2 mol/L and 25 wt.%, respectively.

Preparation of Zeolite A from Ion-Adsorbing Rare Earth Tailings for Selective Adsorption of Pb2+: An Innovative Approach to Waste Valorization.

Ion-adsorbing rare earth tailings (IRETs) contain a large amount of clay minerals, which are a potential source of silicon and aluminum for the preparation of zeolite materials. The complexity of the tailings' composition and the impurity composition are the main difficulties in the controllable preparation of zeolite. Herein, IRETs were treated by classification activation technology for the preparation of IRET-ZEO, which was used for the removal of heavy metal Pb2+ in water. A new method of resource utilization of ion-type rare earth tailings is realized by "treating waste with waste". The results showed that the IRETs were classified and then thermally activated, and the optimal activation parameter was calcination at 850 °C for 1 h. The optimal NaOH concentration used in the crystallization process was 5 mol/L, with a crystallization time of 3 h and a crystallization temperature of 85 °C, and the crystallization product was zeolite A. The removal rate of the Pb2+ solution with an initial concentration of 100 mg/L was as high as 96.7% in an acidic solution with a pH value from 2 to 5.5. In particular, when the solution pH was higher than 4.2, the adsorption rate of Pb2+ was close to 100%. The IRET-ZEO showed a fast adsorption rate (5 min to reach adsorption equilibrium), a large adsorption capacity (378.35 mg/g), excellent acid resistance, and selectivity and regenerability for Pb2+. This work provides a new strategy for the green resource utilization of IRETs and the treatment of lead-containing wastewater.

Assessing the impact of alkali pretreatment of rice husk on its composition and product portfolio: Tradeoff between biogas and valuable materials recovery for sustainability

The burning of agricultural crop residues has evolved into a significant global issue with far-reaching implications for public health and environmental integrity. Utilizing biochemical methodologies to valorize these residues presents a dual advantage, mitigating disposal challenges while concurrently fostering wealth generation through bioenergy production and the creation of value-added materials. Nevertheless, the biodegradation of residues faces impediments due to the presence of recalcitrant silica and lignin. To assess the efficacy and elucidate the performance of biochemical approaches, this study investigates the impact of NaOH treatment (2%, 4%, 6%, 8%, and 10% w/v) on rice husk (RH) at 90 °C for 2 h initially followed by anaerobic digestion (AD) for biogas generation. This recovers silica, yielding residual pulp devoid of lignin, a raw material for biogas generation. Analytical investigation through FE-SEM reveals mild fissures and surface ruptures in 4% NaOH-treated RH, while XRD shows a crystallinity index increase from 43.3% (untreated RH) to 69.4% (NaOH-treated RH). The optimal NaOH concentration, yielding 0.16 g/g of silica and 0.206 L/g VSadded of biogas is 4%. These results highlight tailored NaOH's potential for enhancing silica recovery and biogas production from RH. Spearman's correlation analysis reveals a strong correlation (0.9–1.0) among the reduction in volatile solids (VS %), total solids (TS %), methane yield (mL/g VSadded), and biogas yield (mL/g VSadded). P values for artificial neural network (ANN) and fuzzy models consistently range from 10−4 to 10−19. Achieving sustainability necessitates balancing the trade-off between maximizing biogas production and optimizing silica recovery for an environmentally sound and efficient system.

Electroless brassing of historical artefacts

Abstract The topic of this work was the investigation of an alternative brassing technique consisting of electroless zinc plating of a copper object in a strongly alkaline solution and subsequent annealing to achieve a characteristic brass appearance. Within the scope of the work was the determination of the mechanism of zinc deposition on the copper surface, the optimisation of the NaOH concentration (30 and 40 wt. %), time of deposition (5-120 min), as well as temperature (150 and 200 °C) and annealing time (15 – 60 min). Electrochemical methods (potentiodynamic curves and open-circuit potential), metallography, X-ray diffraction (XRD), and glow-discharge optical emission spectroscopy (GD-OES) were used to study the brassing mechanism. Electrochemical measurements have shown that zinc powder significantly decreases the surface potential of copper to the value of zinc itself and also acts as a reducing agent. The diffusion of zinc in copper was found to occur during the primary deposition of zinc with the formation of the γ phase (Cu5Zn8). The optimal NaOH concentration is 40 wt.% and the deposition time is 60 min. The optimal conditions of annealing are 200 °C and 60 min. The primary γ phase is transformed during the annealing process into β and α phases.

Investigation into the alkali-activation of lithium slag: A sustainable alternative to conventional cement with optimized mechanical properties

Utilizing lithium slag as a precursor for alkali-activated cementitious materials offers a sustainable alternative to conventional cement, addressing both environmental pollution and land-use challenges posed by lithium slag waste. Additionally, this practice reduces energy consumption and CO2 emissions associated with cement production. This study presents a novel methodology involving high-temperature calcination and mechanical grinding to enhance the reactivity of lithium slag. Analytical techniques, such as X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), were employed to elucidate the mechanisms behind lithium slag's increased reactivity. Subsequently, these activated materials were used to formulate alkali-activated lithium slag cement composites (ALC). Various factors, including the calcination temperature, water-to-cement ratio, NaOH concentration, and lithium slag content, were investigated for their effects on the fluidity and mechanical properties of the mortar. Analytical techniques including XRD, scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), FTIR, and thermogravimetric analysis (TGA)/derivative thermogravimetry (DTG), were used to explore the hydration mechanisms. Results indicate that the optimal calcination temperature for lithium slag was 700 °C, while the optimal NaOH concentration was 1 mol/L. ALC exhibited robust mechanical properties, with compressive, flexural, and fluidity measures reaching 37.66 MPa, 10.13 MPa, and 200 mm, respectively. Predominant hydration products were found to be N-A-S-H and C-A-S-H. The production cost of 1 ton of ALC is $49.8, which is roughly 70% of the cost of producing 1 ton of OPC. Additionally, the total CO2 emissions and energy consumption of producing ALC amount to 60.56% and 64.95% respectively, compared to the total CO2 emissions and energy consumption of producing 1 ton of OPC.

Pembuatan dan Karakterisasi Kertas Kemasan Berbasis Ampas Kunyit dan Jahe Merah dengan Variasi Konsentrasi Natrium Hidroksida

The production of herbal beverages such as ginger, turmeric, and other spices generates waste that is commonly discarded. The cellulose content in red ginger is about 60-80%, and in turmeric, it is 50%. The high cellulose content makes red ginger and turmeric waste suitable for use as raw materials for paper production. The objective of this research is to determine the optimum conditions for making paper based on red ginger and turmeric waste. The pulp formation process was carried out using the Semi-Mechanical Method, which involves the addition of chemical solutions and grinding, on a mixture of turmeric and red ginger waste (60:40) with variations of NaOH concentration at 8%, 10%, and 13% (w/v). The papermaking process began with refining and drying the waste, cooking the pulp, adding water and kaolin filler, and then printing. Characterization included antibacterial testing, tensile strength, and grammage. Based on the pulp characterization results at the optimum NaOH concentration of 8%, the moisture content was 8.89%, cellulose content was 49.28%, and lignin content was 9.28%. These parameters comply with the national standard (SNI) for packaging paper. The paper characterization results showed a tensile index of 2.12 Nm/gram, an antibacterial inhibition zone of 5 mm, and a grammage of 13 g/m2. This research indicates that the NaOH concentration influences the moisture, cellulose, and lignin content. Furthermore, based on the characterization results, paper made from turmeric and ginger waste has the potential to be used as antimicrobial packaging paper.

NaOH-Activated Natural Glauconite for Low-Cost Adsorption of Congo Red Dye

To explore the adsorption of Congo red (CR) dye from textile effluent, natural clay glauconite was employed as a sustainable and inexpensive adsorbent. The effects of varying concentrations of sodium hydroxide (NaOH) on glauconite alteration were examined. Furthermore, this research focuses on the optimal NaOH concentration that improves removal efficiency and adsorption capacity. Thus, four NaOH solutions of concentrations ranging from 1 M to 4 M were used to activate glauconite raw (GL), indicated as GLACT1M, GLACT2M, GLACT3M, and GLACT4M. These samples were characterized using different analysis tools. The effects of starting concentration, adsorption time, adsorbent dosage, pH, temperature, and reusability on removal efficacy were all investigated. The data show that the CR removal efficiency increases with modification up to a 2 M NaOH activation, beyond which it begins to decrease. At 25 °C and pH 7, the CR removal efficiencies were ~77%, 72%, 80%, 34.5%, and 30.5% by GL, GLACT1M, GLACT2M, GLACT3M, and GLACT4M, respectively. Batch experiments were performed to explore both the kinetics and isotherms of CR adsorption to determine the impact of different experimental conditions accurately. Moreover, isotherm interpretations demonstrated that the Freundlich isotherm closely matches the experimental results. The pseudo-second-order model clearly explains the obtained results (R2 = 0.998) from 5 to 25 ppm for GL, GLACT1M, GLACT2M, and GLACT3M, but GLACT4 is expressed by the Elovich model from 20 to 25 ppm. The reusability investigation revealed that the reusability of adsorbents could be achieved efficiently. The findings suggest that glauconite and its NaOH-activated forms can be employed as natural and affordable adsorbents for removing CR from textile effluent.

Influence of Alkali Treatment on Mechanical Properties of Short Cocos nucifera Fiber Reinforced Epoxy Based Sustainable Green Composite

ABSTRACT The present study deals with finding the optimum fiber content and effect of alkali treatment on the mechanical properties of the proposed Cocos-nucifera-reinforced polymer matrix composite. The present work is carried out in two different phases. First, the optimum fiber weight fractions for untreated Cocos nucifera composite are found out and later the effect of alkali treatment on the mechanical behavior of composite with optimum weight fraction of fibers selected in the first phase is determined. Proposed composites are mechanically characterized to determine the optimum fiber percentage to be used in composite and the effect of NaOH treatment on the mechanical properties of the composite with optimum fiber percentage is studied along with the determination of optimal NaOH concentration to be used. The results were analyzed by comparing the mechanical properties of the various composites and the effect of alkali treatment on the fibers of the composites was also studied. The obtained results showed that proposed composite with 40 wt% untreated fiber exhibits better mechanical properties compared to its counterparts and treating the fibers of the composite with 10% NaOH concentration further enhances the mechanical properties of the composite. The proposed composite can be a potential candidate for automobile interior application.

Study on Mechanical Properties of Banana Fiber-Reinforced Materials Poly (Lactic Acid) Composites

Synthetic materials reinforced with natural fibers are attracting great attention of scientists and researchers. Sustainability and eco-friendly nature along with easy availability and low cost are the key reasons. In this work, a natural fiber such as a banana fiber was investigated to create bioavailable materials while enhancing mechanical properties. The banana fiber was extracted from banana sheath by the mechanical method combined with chemical treatment with NaOH 1, 2, 3, 4, and 5%. Treatment of the banana fiber with NaOH effectively removes other impurities from the fiber surface and the fiber surface becomes rough, increasing the compatibility and bonding between banana fiber and PLA. The reported optimum NaOH concentration was 5% banana fiber used for the material polylactic acid (PLA) composite/banana fiber. The composites (BF) were prepared by the hot melt mixing method. The results showed that 20% by weight of banana fiber gave good results and the mechanical strength values kept at the specified level (tensile strength: 52.57 MPa, flexural strength: 70.35 MPa, impact strength: 155.45 J/m and hardness: 23.8 Hv). SEM observations showed visual evidence that surface impurities were removed from the fiber by NaOH treatment.

Optimization of Typha Fibre Extraction and Properties for Bio-Composite Applications Using Desirability Function Analysis.

The effect of extraction time, temperature, and alkali concentration on the physical and mechanical properties of cattail (Typha latifolia L.) fibres were investigated using five levels of time (4, 6, 8, 10, and 12 h), four levels of temperature (70, 80, 90, and 95 °C), and three levels of NaOH concentration (4, 7, 10%, w/v) in a 3 × 4 × 5 factorial experimental design. The extraction parameters were optimized for bio-composite application using a desirability function analysis (DFA), which determined that the optimum extraction time, temperature and NaOH concentration were 10 h, 90 °C, and 7%, respectively. A sensitivity analysis for optimal treatment conditions confirmed that the higher overall desirability does not necessarily mean a better solution. However, the analysis showed that the majority of optimum settings for time, temperature, and concentration of NaOH found in the sensitivity analysis matched with the optimum conditions determined by DFA, which confirmed the validity of the optimum treatment conditions.

Recycling of Precast Concrete Waste Sludge With Paper Mill and Biomass Ashes for Lightweight Granulated Aggregate Production

The construction and demolition waste generation is increasingly evolving with the rapid urbanization, with more than a quarter of the produced waste being landfilled without further treatment or recycling strategy. Hence, sustainable management and valorization methods such as recycling in construction materials is becoming increasingly essential to tackle the economic and environmental burdens of landfilling waste. Construction and demolition waste recycling has been intensively studied. However, the present study proposes a promising solution for recycling construction and demolition wastes (CDWs) from the precast concrete waste sludge and ashes from paper mill sludge and biomass. Artificial lightweight aggregates were designed and produced by alkali activating a mixture of 50–90 wt% of dried and milled CDW with 3–25 wt% of ash and 5–35 wt% of blast furnace slag. The properties of the produced aggregates were assessed via density, water absorption, porosity, and crushing tests, in addition to microstructural characterizations using XRD and scanning electron microscopy SEM analysis. The optimum NaOH concentration was 8M with the highest mechanical properties and lowest efflorescence. The produced aggregates revealed a high crushing force of 82 N at 28 days with 50 wt% CDW, 15 wt% biomass ash, and 25 wt% blast furnace slag presenting a possible recycling pathway for such side-stream materials.

The Comparison of the Environmental Impact of Waste Mineral Wool and Mineral in Wool-Based Geopolymer.

Waste generated in fine wool production is homogeneous and without contamination, which increases its chances of reuse. Waste mineral wool from demolition sites belongs to the specific group of waste. However, the storage and collection require implementing restrictive conditions, such as improper storage of mineral wool, which is highly hazardous for the environment. The study focuses on the leachability of selected pollutants (pH, Cl−, SO42−) and heavy metals (Ba, Co, Cr, Cu, Ni, Pb, Zn) from the waste mineral wool. As a solution to the problem of storing mineral wool waste, it was proposed to process it into wool-based geopolymer. The geopolymer, based on mineral wool, was also assessed regarding the leaching of selected impurities. Rock mineral wool is very good for geopolymerisation, but the glass wool needs to be completed with additional components rich in Al2O3. The research involved geopolymer prepared from mineral glass wool with bauxite and Al2O3. So far, glass wool with the mentioned additives has not been tested. An essential aspect of the article is checking the influence of wool-based geopolymer on the environment. To investigate the environmental effects of the wool-based monolith and crushed wool geopolymers were compared. Such research has not been conducted so far. For this purpose, water extracts from fragmented geopolymers were made, and tests were carried out following EN 12457-4. There is no information in the literature on the influence of geopolymer on the environment, which is an essential aspect of its possible use. The research results proved that the geopolymer made on the base of mineral wool meets the environmental requirements, except for the pH value. As mentioned in the article, the geopolymerisation process requires the dissolution of the starting material in a high pH (alkaline) solution. On the other hand, the pH minimum 11.2 value of fresh geopolymer binder is required to start geopolymerisation. Moreover, research results analysed in the literature showed that the optimum NaOH concentration is 8 M. for the highest compressive strength of geopolymer. Therefore, the geopolymer strength decreases with NaO concentration in the NaOH solution. Geopolymers glass wool-based mortars with Al2O3 obtained an average compressive strength of 59, the geopolymer with bauxite achieved about 51 MPa. Thus, Al2O3 is a better additional glass wool-based geopolymer than bauxite. The average compressive strength of rock wool-based geopolymer mortar was about 62 MPa. The average compressive strength of wool-based geopolymer binder was about 20–25 MPa. It was observed that samples of geopolymers grout without aggregate participation are characterised by cracking and deformation.

PNP Hydrogel Prevents Formation of Symblephara in Mice After Ocular Alkali Injury.

PurposeTo create an alkali injury symblephara mouse model to study conjunctival fibrosis pathophysiology and test polymer nanoparticle (PNP) hydrogel as a preventative therapeutic.MethodsMice were injured using NaOH-soaked filter paper to determine the optimal NaOH concentration to induce the formation of symblephara. Injured mice were observed for 7 days to detect the formation of symblephara. Forniceal shortening observed on hematoxylin and eosin (H&E)-stained tissue sections was used as a symblephara marker. Alpha-smooth muscle actin (α-SMA) expression, Masson's trichrome assay, and periodic acid–Schiff (PAS) staining were used to determine myofibroblast expression, collagen deposition, and goblet cell integrity. PNP hydrogel, with multivalent, noncovalent interactions between modified biopolymers and nanoparticles, was applied immediately after alkali injury to determine its ability to prevent the formation of symblephara.ResultsForniceal shortening was observed in H&E images with 1N NaOH for 2 minutes after 7 days without globe destruction. PNP hydrogel prevented forniceal shortening after alkali injury as observed by H&E histology. α-SMA expression and collagen deposition in eye tissue sections were increased in the fornix after injury with 1N NaOH compared with uninjured controls. PNP hydrogel treatment immediately after injury reduced α-SMA expression and collagen deposition in the forniceal region. Mucin-secreting goblet cells stained with PAS were significantly lower in alkali-injured and PNP hydrogel–treated conjunctivas than in uninjured control conjunctivas.ConclusionsWe observed that 1N NaOH for 2 minutes induced maximal forniceal shortening and symblephara in mice. PNP hydrogel prevented forniceal shortening and conjunctival fibrosis after injury. This first murine model for symblephara will be useful to study fibrosis pathophysiology after conjunctival injury and to determine therapeutic targets for cicatrizing diseases.Translational RelevanceThis mouse model of symblephara can be useful for studying conjunctival scarring disease pathophysiology and preventative therapeutics. We tested PNP hydrogel, which prevented the formation of symblephara after injury.

Effects of hydrothermal parameters on the physicochemical property and photocatalytic degradation of bisphenol A of Ti-based TiO2 nanomaterials

Effects of hydrothermal parameters on morphology, crystal structure, light absorption, separation efficiency of photo-generated charge carriers, and photocatalytic removal of Bisphenol A (BPA) of Ti-based TiO2 nanomaterials were systematically investigated. Through changing hydrothermal parameters, TiO2 nanobelts, TiO2 nanosheets and TiO2 nanowires were prepared. With increasing NaOH concentration, hydrothermal temperature, and hydrothermal time, more TiO2 with (101) crystal plane grew on Ti substrate, resulting in higher crystallinity. The UV-light absorption enhanced with increasing NaOH concentration, but decreased with improving hydrothermal temperature, hydrothermal time, and HCl concentration. Variation of UV-light absorption was mainly affected by morphology, and UV-light absorption of TiO2 nanomaterials with different morphologies was arranged in order of nanobelts > nanosheets > nanowires. The hydrothermal growth of TiO2 nanomaterials on Ti plate conformed to Ostwald ripening mechanism. Variation trend of photo-generated current was consistent with that of BPA degradation, they both first increased and then decreased within investigated range. The optimal NaOH concentration, hydrothermal temperature, hydrothermal time, and HCl washing concentration were 1 M, 170℃, 28 h, and 0.1 M, respectively. Under this condition, Ti-based TiO2 nanosheets exhibited the highest BPA removal efficiency (92.7%), which was due to highly ordered nanosheet structure, good crystallinity, appropriate UV-light absorption and high separation efficiency of electron-hole pairs.

Fibrous packaging paper made of oil palm fiber with beeswax-chitosan solution to improve water resistance

Many fibrous residual wastes have been considered as potential substitutes of wood pulp, especially oil palm fiber. However, a disadvantage of fibrous residual wastes for packaging production is the poor water resistance properties. To improve these aspects, a beeswax-chitosan solution was applied as coating on packaging paper, and the drying was done by hot pressing. The paper samples were made with different concentrations of NaOH (15%, 17.5% and 20% w/v) in alkali pulping process and with different doses of pulp by moist weight (200–300 g) to a paper frame (400 × 400 mm2) before testing their physical properties (average thickness; grammage; density; and water absorbency time) and mechanical properties (tensile strength; and tensile index). The biodegradation time was also tested. The optimal NaOH concentration found was 20.0%w/v. The average thickness of paper produced with 200, 250, and 300 g pulp per frame ranged from 0.92 mm to 2.20 mm, while the basis weight or grammage increased from 499 g/cm2 to 1461 g/cm2. The average grammage and smoothness of paper were increased by coating in comparison to non-coated paper, but presented bulk reduction from that of non-coated paper partly due to drying by hot pressing. The maximum 21.74 kN/m tensile strength and 96 min water absorbency time were observed for paper coated with beeswax–chitosan solution, while 0.75 kN/m tensile strength and 15 min water absorbency time were found for uncoated paper. About 70% weight losses were seen for all papers over decomposition for up to 60 days when buried in soil. The results obtained from this study opens the door for further work on oil palm fiber in paper making. The oil palm fiber has potential as a resource for fibrous paper production when coated with beeswax-chitosan solution for a long water absorbency time, and its use could contribute against deforestation.

Effect of NaOH on plasma electrolytic oxidation of A356 aluminium alloy in moderately concentrated aluminate electrolyte

Plasma electrolytic oxidation(PEO) of cast A356 aluminum alloy was carried out in 32 g/L NaAlO2 with the addition of different concentrations of NaOH. The stability of the aluminate solution is greatly enhanced by increasing the concentration of NaOH. However, corresponding changes in the PEO behaviour occur due to the increment of NaOH concentration. Thicker precursor coatings are required for the PEO treatment in a more concentrated NaOH electrolyte. The results show that the optimal NaOH concentration is 5 g/L, which improves the stability of storage electrolyte to about 35 days, and leads to dense coatings with high wear performance (wear rate: 4.1×10−7 mm3·N−1·m−1).

The Optimazion of Bioethanol Production from Rice Husk using Simultanous Saccharification and Fermentation Methods

The optimum condition of bioethanol production was studied by determining NaOH concentration, leaving time, and bioethanol content. The research started with delignification reaction using NaOH (alkaline pre-treatment), continued by saccharification process with Aspergillus niger and fermentation process with Saccharomyces cerevisiae. The resulted bioethanol was purified using destilation process and characterized with Gas Chromatography (GC). The result showed that optimum NaOH concentration was 3%, the leaving time optimum at 105 minutes, and the bioethanol content was 10.9966%.

Optimization of hydrolysis of polyacrylonitrile-kapok fiber composite for the adsorption of lead ions in aqueous solution

The adsorptive uptake of polyacrylonitrile-kapok fiber composite (PAN-KpF) for Pb(II) ions was improved by employing hydrolysis using sodium hydroxide (NaOH). The hydrolysis conditions, namely, reaction temperature, NaOH concentration, and reaction time, were optimized by response surface methodology (RSM) combined with three-level three-factorial Box-Behnken design (BBD) based on the adsorption capacity for Pb(II) uptake. Statistical analysis results suggest that the optimum reaction temperature, NaOH concentration, and reaction time for the hydrolysis of PAN-KpF are 55.28 °C, 3.96 w/w%, and 52.04 min, respectively. In addition, the predicted adsorption capacities calculated from the second-order polynomial regression were in relatively good agreement with the experimental results. The data points fit closely into a linear correlation with an R2 value of 0.9317. The effects of initial solution pH, adsorbent dosage, initial solution concentration, and contact time for the adsorption of Pb(II) onto the hydrolyzed PAN-KpF were investigated. Isotherm studies indicate that the adsorption was described well by the Langmuir isotherm model, wherein the maximum monolayer adsorption capacity for Pb(II) is 74.07 mg/g. This is 80 % higher than the adsorption capacity for unhydrolyzed PAN-KpF. Lastly, kinetic studies reveal that Pb(II) uptake is predicted by the pseudo-second-order kinetic model.

Improved glucose recovery from durian peel by alkaline-catalyzed steam pretreatment.

Durian (Durio zibethinus Murr.) peel, as agricultural waste, is a potential under-utilized lignocellulosic biomass that is sufficiently available in Thailand. In this study, durian peel from monthong (D. zibethinus Murr. cv. Monthong) and chanee (D.zibethinus Murr. cv. Chanee) were subjected to pretreatment with sodium hydroxide (NaOH) under autoclaving conditions to improve glucose recovery. The effect of NaOH concentration (1%, 2%, 3%, and 4%) and autoclave temperature (110 °C, 120 °C, and 130 °C) was investigated based on the amount of glucose recovered. The optimal NaOH concentration and autoclave temperature were determined to be 2% and 110 °C, respectively, under which maximum glucose (36% and 35% in monthong and chanee peels, respectively) was recovered. Glucose recovery was improved by about 6-fold at the optimal pretreatment condition for both pretreated monthong and chanee when compared to the untreated durian peels. Scanning electron microscopy (SEM) showed great changes to the surface morphology of pretreated durian peel from the two cultivars. X-ray diffraction (XRD) analysis also revealed a rise in cellulose crystallinity index (CrIs) after pretreatment. A combination of mild NaOH concentration and autoclaving is a very effective pretreatment technique for maximum glucose recovery from durian peel.

Effect of synthesis parameters on the development of unconfined compressive strength of recycled waste concrete powder-based geopolymers

The main object of this study is to investigate the geopolymerization potential of recycled waste concrete powder (RWCP) as well as the effects of synthesis parameters, including the molarity of NaOH solution, the mass ratio of water glass to NaOH solution (WG/NH), the mass ratio of liquid alkali activator to solid powder (L/S), and the curing conditions (curing temperature, curing time and curing method), on the development of unconfined compressive strength (UCS) of recycled waste concrete powder-based geopolymers. The recycled waste concrete powder (RWCP) (size < 0.075 mm) was utilized as source material, and water glass and sodium hydroxide (NaOH) were used as alkaline activators to synthesize geopolymer specimens. The dissolution of alumino-silicate from the RWCP under different concentrations of alkaline solutions was studied. The UCS of the resulting geopolymers synthesized under different conditions was tested. Further, the microstructure and mineral composition of the final products were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) technology. The results indicate that the dissolution of Si4+ and Al3+ in raw materials (RWCP) was highly affected by the alkali content and dissolution time. Increasing the alkali content, water glass content and L/S ratio was all conducive to enhancing the UCS of geopolymers. The optimum NaOH concentration corresponpded to 14 mol/L, WG/NH ratio of 1.5 and L/S mass ratio of 0.4. A maximum 7-day UCS of 14.32 MPa was achieved by wet curing at 70 ℃ for 24 hours. Microscopic analysis showed that the final products were mainly composed of amorphous hydrated calcium silicate and hydrated sodium aluminosilicate gels. However, due to the low activity and high calcium content of RWCP, most of crystalline phases and some unreacted substances still existed in the end products as inactive fillers, resulting in a relatively low UCS of the synthesized geopolymers. Baded on the research, it can be concluded that RWCP can be recycled as the precursor to synthesize geopolymer binder.