Higher NaOH Concentrations Research Articles

Dimensional Stability Properties of Medium Density Fibreboard (MDF) from Treated Oil Palm (<i>Elaeis guineensis</i>) Empty Fruit Bunches (EFB) Fibres

The aim of the study was to investigate the effect of pre-treatments by using sodium hydroxide (NaOH) and acetic acid on oil palm Empty Fruit Bunch (EFB) fibres for the production of Medium Density Fibreboard (MDF). The EFB fibres were treated with chemicals in the concentration range of 0.2%, 0.4%, 0.6% and 0.8% prior to refining. Single-homogenous layer MDF with 12 mm thickness and density of 720 kg/m3 was produced. Urea-Formaldehyde (UF) was applied at 10% loading (based on dry weight of dry fibres) as a binder. The physical properties (Water Absorption (WA) and Thickness Swelling (TS)) of the produced panels were tested according to European Standard, EN 622-5:2006. The results show that types of chemical used had greater effects than concentration on the dimensional stability of the MDF. EFB fibres treated with acetic acid produced MDF with better dimensional stability compared to the MDF NaOH treated fibres. High concentration of NaOH produced poor dimensional stability in the panels.

The synthesis, characterization and catalytic activity of the hierarchical TS-1 with the intracrystalline voids and grooves

Hierarchical TS-1 with grooves and intracrystalline voids was prepared by TPAOH/NaOH treatment. With increasing NaOH concentration, the dissolution–recrystallization process was intensified, the relative crystallinity and microporous properties decreased, the secondary pore volume increased. Although the dissolved species could be recrystallized, Na+ prevented the titanium incorporation, which increased the extra-framework titanium content. In phenol hydroxylation, improved activity and H2O2 efficiency were achieved when NaOH was no more than 0.1mol/L, which may be a result of the positive influences of the secondary pores. At higher NaOH concentration (>0.1mol/L), the activity and H2O2 efficiency decreased due to the negative influences of the non-framework titanium.

Parametric study of hydrothermal soft chemical synthesis and application of Na0.44MnO2 nanorods for Li-ion battery cathode materials: Synthesis conditions and electrochemical performance

In this paper, synthesis parameters were thoroughly investigated to understand and optimize the hydrothermal soft chemical synthesis of Na0.44MnO2 nanorods. Structural characterization reveals that a layered Na-birnessite precursor, a high NaOH concentration (15.0 mol/L) and a high hydrothermal reaction temperature (180 °C) are required for rapid formation of the tunnel Na0.44MnO2 phase. Additionally, the hydrothermal reaction time is greatly reduced to 8 h. More significantly, from electrochemical testing it is observed that the cycling stability and rate capability of Na0.44MnO2 electrode materials are enhanced after the addition of carbon nanotubes. The capacity retention increases from 70% to 82% at 0.1 A/g after 50 cycles, and the Li storage capacity at a high rate of 2.0 A/g increases from 45 mAh/g to 99 mAh/g. The parameters are optimized for fast, high-yield and large-scale production of high performance Na0.44MnO2 nanorod cathode materials used in lithium-ion batteries.

Removal of Oxidation Fragments from Multi-walled Carbon Nanotubes Oxide Using High and Low Concentrations of Sodium Hydroxide

Modification of multi-walled carbon nanotubes surface (MWCNT) using the mixture of $${{{\rm HNO}}_{3}/{{\rm H}}_{2}{{\rm SO}}_{4}}$$ is widely employed for MWCNT surface oxidation, but it also leads to shortening and thinning of the CNT layers causing fragmentation. The carbonaceous fragments had adsorbed on the surface is not removed from the sample in conventional treatments; however, the addition of NaOH successfully cleans the oxidized material. In this article, MWCNT was functionalized using $${{{\rm HNO}}_{3}/{{\rm H}}_{2}{{\rm SO}}_{4}}$$ as oxidizing agent and evaluate the impact of using high and low concentrations of NaOH to purify CNT oxide. The presence of oxidized groups as hydroxyl and carboxyl has been demonstrated by FTIR. The thermal stability of MWCNT and MWCNT-O after and before purification was studied by TGA, and the degree of its crystallinity was examined by XRD. The defect degree occurs during the oxidation process was confirmed by Raman spectroscopy. TEM images showed the presence and the absence of wrinkles and the adsorbed carbonaceous fragments.

Compressive strength, Bending and Fracture Characteristics of High Calcium Fly Ash Geopolymer Mortar Containing Portland Cement Cured at Ambient Temperature

This article presented the compressive strength, modulus of rupture and fracture characteristics of high calcium fly ash (FA) geopolymer mortars containing Portland cement type I (PC) with different sodium hydroxide (NaOH) concentrations (6, 10 and 14 molars). PC was added at the dosages of 0, 5, 10 and 15 % by weight of solid powder binder. Sodium silicate (Na2SiO3) and NaOH solutions were used as the alkali activators. Na2SiO3 to NaOH ratio of 2.0, alkaline liquid to binder ratio of 0.60, sand to binder ratio of 1.00 and curing at ambient temperature were used for all mixtures. Test results indicated that the use of PC as additive enhanced compressive strength, modulus of rupture and fracture characteristics of high calcium fly ash geopolymer mortar and NaOH concentrations also had significant affect on these properties. The use of 10 % PC with 14M NaOH resulted in high calcium FA geopolymer mortar with improved modulus of rupture and fracture characteristics.

Optimization of hydrolysis and volatile fatty acids production from sugarcane filter cake: Effects of urea supplementation and sodium hydroxide pretreatment

Different methods for optimization the anaerobic digestion (AD) of sugarcane filter cake (FC) with a special focus on volatile fatty acids (VFA) production were studied. Sodium hydroxide (NaOH) pretreatment at different concentrations was investigated in batch experiments and the cumulative methane yields fitted to a dual-pool two-step model to provide an initial assessment on AD. The effects of nitrogen supplementation in form of urea and NaOH pretreatment for improved VFA production were evaluated in a semi-continuously operated reactor as well. The results indicated that higher NaOH concentrations during pretreatment accelerated the AD process and increased methane production in batch experiments. Nitrogen supplementation resulted in a VFA loss due to methane formation by buffering the pH value at nearly neutral conditions (∼6.7). However, the alkaline pretreatment with 6g NaOH/100g FCFM improved both the COD solubilization and the VFA yield by 37%, mainly consisted by n-butyric and acetic acids.

Optimization of Sodium Hydrosulfide Synthesis for Metal Recovery from Wastewater Using Flue Gas Containing H2S

AbstractSodium hydrosulfide (NaSH), which is utilized for recovering rare metals, was synthesized in a laboratory-scale batch reactor by absorbing a simulated flue gas containing H2S into NaOH solution. The effects of H2S flow rate, NaOH concentration, and reaction time on the synthesis of NaSH were examined. With an increase in the H2S flow rate, the absorption ratio, conversion ratio, and total NaSH productivity showed a decreasing tendency. On the other hand, a higher concentration of NaSH could be synthesized with a higher concentration of NaOH. Most of the Na2S (the intermediate product) were produced at a pH>12, and the NaSH synthesis reaction was feasible at a pH 11.5. Contrary to the increased H2S flow rate, increased NaOH concentration resulted in an enhanced Na2S/NaSH ratio. With a maximum equivalent ratio of NaOH/H2S at 0.88, the chemical composition of the product could maintain equilibrium with the highest NaSH concentration and less than 1% weight-to-weight ratio (w/w) Na2S concentration.

Ultrasonic cleaning of 3D printed objects and Cleaning Challenge Devices

We report our experiences in the evaluation of ultrasonic cleaning processes of objects made with additive manufacturing techniques, specifically three-dimensional (3D) printers. These objects need to be cleaned of support material added during the printing process. The support material can be removed by dissolution in liquids with or without ultrasonic cavitation.Distinctive stages in the cleaning processes were found for two different liquids (water and NaOH solutions). The combination of ultrasound and high concentration of NaOH has the best results for support material dissolution in the particular conditions studied.The sonication of cleaning processes in ultrasonic baths is typically a slow process. Here we show the advantages of using an ultrasonic horn to clean the surface of small parts and holes more effectively.We introduce a Cleaning Challenge Device design to be used for the universal evaluation of cleaning performance of different equipment or processes, and specifically for ultrasonic baths. The results and conclusions can be of use for different cleaning situations besides 3D printed parts, such as when deciding which protocol has a better performance or comparing different equipment.

Factors influencing formation of highly dispersed BaTiO3 nanospheres with uniform sizes in static hydrothermal synthesis

Highly dispersed BaTiO3 nanospheres with uniform sizes have important applications in micro/nanoscale functional devices. To achieve well-dispersed spherical BaTiO3 nanocrystals, we carried out as reported in this paper the systematic investigation on the factors that influence the formation of BaTiO3 nanospheres by the static hydrothermal process, including the NaOH concentrations [NaOH], molar Ba/Ti ratios (RBa/Ti), hydrothermal temperatures, and durations, with an emphasis on understanding the related mechanisms. Barium nitrate and TiO2 sols derived from tetrabutyl titanate were used as the starting materials. The as-synthesized BaTiO3 samples were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, thermogravimetry, differential thermal analysis, and FT-IR spectra. The highly dispersed BaTiO3 nanospheres (76 ± 13 nm) were achieved under the optimum hydrothermal conditions at 200 °C for 10 h: [NaOH] = 2.0 mol L−1 and RBa/Ti = 1.5. Higher NaOH concentrations, higher Ba/Ti ratios, higher hydrothermal temperatures, and longer hydrothermal durations are favorable in forming BaTiO3 nanospheres with larger fractions of tetragonal phase and higher yields; but too long hydrothermal durations resulted in abnormal growth and reduced the uniformity in particle sizes. The possible formation mechanisms for BaTiO3 nanocrystals under the static hydrothermal conditions were investigated.

Changes in Vanadium Acid Radical Ions During Leaching From Petroleum Coke

The infrared spectrogram of vanadium leachate from petroleum coke was studied under different conditions. The change in vanadium acid radical ions in leachate was analyzed, and the three kinds of vanadate ions can be transformed while leaching condition was changed. When the leaching time was prolonged, the ion of vanadium dimer acid radical ions was formed to V-O chemical bond by depolymerization; when the leaching temperature increased, the ion of vanadium dimer V-O-V was exploded to V-O and V-OH chemical bond; when the leaching environment was under medium and low NaOH concentration, the V-OH was partly turned to vanadium dimer acid radical ions and V-O; and when the leaching environment was under high NaOH concentration, the leaching rate did not change essentially, and the ions remained unchanged. At last, the ions changing rules were further verified through the Raman spectrum of leachate under different NaOH concentrations.

Renewable cellulose source: isolation and characterisation of cellulose from rice stubble residues

SummaryThe substantial amount of agricultural waste associated with rice stubble is a critical issue in Thailand as it still contains a high amount of cellulose. Thus, the conditions for cellulose isolation from Thai rice stubble were developed. It was found that cellulose at a higher NaOH concentration (10%) or higher isolation temperature provided a higher whiteness index (WI) value and α‐cellulose content after 3 h of isolation process. Extraction using 10% NaOH at 55 °C for 3 h was determined as optimum conditions for the isolation of cellulose from rice stubble. The removal of most hemicelluloses and lignin was confirmed by Fourier transform infrared spectroscopy. The yield, WI value and α‐cellulose content of rice stubble cellulose were 30.67%, 75.69% and 90.05%, respectively. Cellulose from rice stubble is suitable for use as fibre or for the synthesis of cellulose derivatives that are widely used in food and pharmaceutical products.

Effect of spodumene leaching with sodium hydroxide on its flotation

Effects of NaOH on flotation of spodumene, quartz and feldspar using oleic acid as a collector were investigated through microflotation tests and bench scale flotation tests. It was determined that NaOH acted more than a pH regulator in the tests. The X-ray photoelectron spectroscopy revealed that spodumene was preferentially leached by conditioning with high concentration of NaOH in the solution and exposed more Li positive sites on the mineral surface leading to an improved flotation.

Structural and dynamic changes of lignin in Eucalyptus cell walls during successive alkaline ethanol treatments

A sequential treatment of Eucalyptus with 70% ethanol containing 0.4, 1.0, 2.0, 3.0, and 5.0% NaOH at 80°C for 2h, was used to isolate the lignins in the present study. The lignin fractions obtained were subjected to comprehensive composition analysis and structural characterization. Additionally, the lignin distribution and topochemical changes within morphologically distinct cell wall regions were investigated by confocal Raman microscopy. The most noteworthy features of the lignin fractions were the almost absence of bound polysaccharides, and the degradation of lignin resulted from a comparatively high concentration of NaOH. The lignin fractions turned out to be mainly composed of β-O-4′ linkages combined with low amounts of β–β′ and β-5′ linkages. Confocal Raman microscopy was combined to assist monitor the course of delignification during the successive alkaline treatment processes visually, and the Raman spectra analysis revealed that the dissolution rate of lignin in the secondary wall was higher than that in cell corner middle lamella regions during this process. Data from this study potentially enhances the understanding of the mechanisms of alkaline treatment acting on Eucalyptus and facilitate the value-added utilization of the lignin fractions in future biorefineries.

Microstructure, morphology and magnetic properties of Ni nanoparticles synthesized by hydrothermal method

Powder samples containing high purity nickel nanoparticles (NPs) were prepared by hydrothermal method from Ni(II) chloride hexahydrate (NiCl2·6H2O) under the presence of sodium hydroxide (NaOH) with different concentrations between 5 and 25 mol/L. The synthesis of the NPs occurs through chemical reduction at relatively low temperature (140 °C). The Ni NPs have a face-centred cubic (fcc) crystal structure with a lattice parameter value close to that of pure Ni (a = 3.52 Å). The average crystallite size determined from x-ray diffraction is around 20 nm, except for the sample synthesized under the highest NaOH concentration (25 mol/L), which has the largest average size (>30 nm). The powder morphology at the sub-micrometre length scale looks like agglomerates of Ni-NPs that drastically changes their shape depending on the NaOH concentration, from flower (5 mol/L) to a dendritic-like (25 mol/L). All the samples are ferromagnetic at room temperature with saturation magnetization values between 50 and 52emu/g, and a coercive field that increases with the NaOH concentration from around 135 (5 mol/L) up to 180Oe (25 mol/L).

Ageing of polyethersulfone ultrafiltration membranes under long-term exposures to alkaline and acidic cleaning solutions

Six commercial ultrafiltration membranes made of polyethersulfone from Microdyn Nadir, Koch Membrane Systems and GE Osmonics were exposed to 0.01, 0.1 and 1.0M nitric acid (HNO3) and sodium hydroxide (NaOH) solutions at 50°C for 150 days. Water permeability, molecular weight cut-off curves, ATR-FTIR, SEM-EDS, AFM and contact angle measurements were employed to evaluate membrane ageing.All membranes showed a high resistance to acidic solutions keeping their chemical and morphological properties almost invariant. The alkaline ageing did not induce any substantial change in the Nadir membranes but, the stability of Koch and GE Osmonics support layers was compromised at high NaOH concentrations, leading to even the complete degradation of these supports in some cases. This was confirmed by ATR-FTIR, SEM and GC–MS analysis. The Nadir membrane resistance to alkaline conditions was found to be in the support layer material composition (mixture of polyethylene and polypropylene). Koch and GE Osmonics membranes support material (polyethylene terephthalate) broke down into its monomers under strong alkaline conditions via hydrolysis reaction.Almost all membranes showed changes in membrane performance which were attributed to their conditioning or their degradation. Regardless of the cause, those changes took place mainly in the first 10 days of exposure.The influence of temperature on the ageing was also studied under the strongest alkaline condition. Its effect on chemically stable membranes were negligible whereas for the others, higher temperatures led to faster support layer degradation.

Mercerization Effect on Morphology and Tensile Properties of Roselle Fibre

Natural fibres are preferred compared to synthetic fibres because of several advantages such as biodegradable, lightweight, low cost and good mechanical properties. Roselle is one of the plants found to be suitable to be used to produce natural fibres. Although natural fiber reinforced composites are becoming widely used, several weaknesses such as lack of good interfacial adhesion, low melting point and poor resistance to moisture absorption are harmful to its further acceptance. Chemical treatment is a method that can improve the interfacial bonding, stop water absorption, clean the fibre and increase surface roughness. In this study, roselle fibres were immersed in Sodium hydroxide (NaOH) with 3 different concentration (3, 6, and 9%). The results before and after treatment were compared. Scanning electron microscope was used to examine the surface morphology. Tensile properties of roselle fibre were performed to study the tensile properties. Results shows that the higher concentration of NaOH will increase the surface roughness and have higher ability to clean the fibre. For tensile properties, 6% of NaOH give the highest tensile strength. It can be concluded that, 6% of NaOH is the most suitable concentration to clean roselle fibre and while maintaining good tensile properties.

Fast preparation of Na0.44MnO2 nanorods via a high NaOH concentration hydrothermal soft chemical reaction and their lithium storage properties

This paper describes a high NaOH concentration hydrothermal soft chemical reaction to prepare Na0.44MnO2 nanorods. In this process, Na-birnessite precursors and concentrated NaOH solution are introduced into the hydrothermal reaction. As a result, the hydrothermal time can be significantly shortened from 96 to 24 h, the hydrothermal temperature can be reduced from 205 to 180 °C and the yield of Na0.44MnO2 can be increased from about 0.6 to about 2.4 g/(mL.day), respectively. Furthermore, the obtained Na0.44MnO2 nanorods with one-dimensional tunnel structures exhibit favorable electrochemical lithium storage properties, which make them promising for the cathode materials of lithium-ion batteries.

Selective release of phosphorus and nitrogen from waste activated sludge with combined thermal and alkali treatment

Selective release characteristics of phosphorus and nitrogen from waste activated sludge (WAS) were investigated during combined thermal and alkali treatment. Alkali (0.001–1.0N NaOH) treatment and combined thermal-alkali treatment were applied to WAS for releasing total P(T-P) and total nitrogen(T-N). Combined thermal-alkali treatment released 94%, 76%, and 49% of T-P, T-N, and COD, respectively. Release rate was positively associated with NaOH concentration, while temperature gave insignificant effect. The ratio of T-N and COD to T-P that released with alkali treatment ranged 0.74–0.80 and 0.39–0.50, respectively, while combined thermal-alkali treatment gave 0.60–0.90 and 0.20–0.60, respectively. Selective release of T-P and T-N was negatively associated with NaOH. High NaOH concentration created cavities on the surface of WAS, and these cavities accelerated the release rate, but reduced selectivity. Selective release of P and N from sludge has a beneficial effect on nutrient recovery with crystallization processes and it can also enhance methane production.

Optimized Process for Separating NaOH from Sodium Aluminate Solution: Coupling of Electrodialysis and Electro-Electrodialysis

Most bauxite-produced alumina is obtained by the Bayer process, but the production efficiency is limited by the slow gibbsite crystal growth due to the high concentration of NaOH in sodium aluminate solution. Here electrodialysis (ED) and electro-electrodialysis (EED) are coupled to separate NaOH from the sodium aluminate solution so as to enhance the gibbsite crystal growth rate and achieve high alumina production efficiency. The ED or EED process is also investigated before the coupling process to find the optimal operating conditions. The ED process indicates that the optimized current density is in the range of 45–60 mA cm–2 and the optimal membranes are CMV/AMV. The current density of 60 mA cm–2 can achieve a high recovery ratio (ηOH– 92.6%), low energy consumption (2.38 kW h kg–1), but a relatively high Al(OH)4– leakage ratio (ηAl(OH)4– 15.1%). The EED process indicates that with the optimized current density of 30 mA cm–2 and membrane CMV, the ηAl(OH)4– can be “zero” and the energy consumption can be as low as 2.07 kW h kg–1, but the treatment capability is low since OH– ions cannot be recovered directly and a single cation exchange membrane is used. The coupling process can combine the advantages of ED and EED, so that the ηOH– can keep a high value of 90.9%, the ηAl(OH)4– decreases to a low value of ∼5%, and the energy consumption remains low at 2.25 kW h kg–1. Overall, the coupling process of ED and EED is an excellent method to separate NaOH from the sodium aluminate solution.

Polypropylene composites reinforced with untreated and chemically treated coir: Effect of the presence of compatibilizer

The effect of coir surface modification on the compatibility of polypropylene (PP)/coir fiber (CF) composites, in the presence and absence of compatibilizer (maleic anhydride grafted polypropylene, PP-g-MA) was assessed. Chemical pulping of the fibers was performed with 2, 4, 8, and 12% NaOH solutions for a period of 2 h at (100 ± 4)°C. Pressed composite samples were subjected to tensile testing, scanning electron (SEM) and atomic force microscopy (AFM). Lignin and holocellulose concentrations of untreated and treated coir were determined. Pulping resulted in increased tensile strength of the composites containing coir treated with up to 2% NaOH, due to increased fiber roughness as evidenced by AFM. This property decreased when higher NaOH concentrations were used, likely due to increased deterioration of coir. The presence of compatibilizer in the PP composites containing treated coir altered adhesion due to chemical changes of the fiber surface. At high NaOH concentrations increased delignification and therefore increased exposure of hydroxyls favors reaction between the fiber hydroxyls and the carboxyl acids of the hydrolyzed maleic anhydride, present in the composites. POLYM. ENG. SCI., 55:2050–2057, 2015. © 2014 Society of Plastics Engineers