Addition Of NaOH Research Articles

Combined effects of NaOH, NaCl, and heat on the gel characteristics of duck egg white

In this paper, the effects of NaOH, NaCl, and heat on the appearance, physical characteristics, and gel structure of duck egg white (EW) jointly induced by NaOH, NaCl, and heat were investigated. Results showed that the absolute value of zeta potential (TAV-ZP) of gel samples increased, hunter whiteness decreased, gel opacity decreased, and the microstructure of gel appeared as a loose network structure with increased NaOH addition. With the increase of NaCl addition, TAV-ZP of gel samples decreased, hunter whiteness increased, gel opacity increased, the microstructure of gel became dense. With the increase of heating temperature, TAV-ZP of gel samples decreased, hunter whiteness decreased, gel opacity increased, the microstructure of gel became dense first and then loosened. The results of SDS-PAGE, surface hydrophobicity, T2, hardness, cohesiveness indicated that protein molecules underwent cross-linking, aggregation, and unfolding during duck EW gelation jointly induced by NaOH, NaCl, and heat. The results of strain-stress curve showed that all gel samples had a good anti-compressed ability. The results of central composite design showed that the best treatment of gel was heating temperature 91 °C, NaOH 0.48%, and NaCl 0.3%.

Effect of sucrose on CO2 storage, vaterite content, and CaCO3 particle size in indirect carbonation using seawater

Indirect carbonation is a technology for carbon capture, utilization, and storage that is used to reduce the concentration of CO2, and it may be also used to produce vaterite for drug delivery materials. However, vaterite is difficult to produce at the sizes and production volumes required for these applications. In this study, we investigated the effects of sucrose additions to seawater in an indirect carbonation process to increase CO2 storage, generate vaterite, and reduce CaCO3 particle size. In addition, sucrose was added before and after Ca elution and the CO2 storage, vaterite content, and CaCO3 particle size results were compared. By adding sucrose to seawater, the CO2 storage capability was doubled, the vaterite content increased by 34%, and the CaCO3 particle size decreased by 41% compared to results using seawater alone. When the molar ratio of sucrose to Ca in the Ca eluate was 1:2, the vaterite content was at its highest and the particle size was the smallest. At this ratio, the supersaturation of the Ca eluate was maximized due to the high Ca concentration and pH. Adding sucrose before Ca elution had many advantages compared to adding sucrose after Ca elution: the vaterite content increased, the particle size decreased, and most significantly, CO2 storage and CaCO3 production doubled and the addition of NaOH for carbonation was unnecessary. Because seawater and sucrose used in this study are non-toxic and inexpensive, the economical mass production of small-sized pure vaterite using this technology is feasible.

Phase dissolution and improving properties of completely decomposed granite through alkali fusion method

Low-reactive completely decomposed granite (CDG) was successfully synthesized by thermal activation with the addition of NaOH at low alkali/CDG mass ratio of 0.1/1. During alkali fusion, the degree of amorphicity of CDG rich in kaolinite (Al2Si2O5(OH)4) increased and a significant reduction of the peak intensities occurring between 20 and 45 (o2 theta) was observed. Reactivity analysis indicated that, initial CDG requires high molar NaOH to provide a proper dissolution, whereas fused CDG exhibits high reactivity (29Si = 555.57 ppm; 27Al = 223.73 ppm) at low NaOH concentration. Moreover, results from the setting time, varied between 15 and 45 min, indicating that alkali fusion is very effective for improving the dissolution of the fused CDG under Na2SiO3 solution. However, the setting time decreases as the reaction degree accelerates. FTIR analysis of the fused CDG presented lower wavenumber band of around 975 cm−1, confirming a decline of crystalline phases. In addition, SEM-EDS characterization and alkalinity analysis showed a compactness of the structure due to the liberation of enough sodium aluminosilicate gel. Finally, results from the mechanical test (4.75–39.55 MPa) and water solubility inferred that, by enhancing the reactivity of CDG by alkali fusion and by addition of up to 15% GGBS, CDG can be optimally recycled as an alternative source material to produce geopolymers.

Effect of salinity on the characteristics, pH-triggered demulsification and rheology of crude oil/water nanoemulsions

The interest in utilizing nanoemulsions in a number of industrial applications is growing rapidly because of their superiority over conventional emulsions. Therefore, the formulation of highly stable crude oil-in-water nanoemulsions with different salinity (i.e., NaCl) levels is preseented in this study. Despite the observed extreme emulsion stability, zeta potential of the nanoemulsions decreased with increasing the salt concentration as a result of the charge screening effect induced by NaCl addition. Charge screening effect and, accordingly, the weakening of the electrostatic repulsion range and strength resulted in an increase in the average droplet size and also in a wider size distribution as the salinity level in the nanoemulsions increased. Additionally, the nanoemulsion viscosity also increased with increasing the salt concentration, however, the increase was marginal (except at 20 g/L NaCl). One interesting and unprecedented observation reported herein is the change in the nanoemulsion flow behavior from shear-thinning to Newtonian and then to shear-thickening as the applied shear rate increased. Nonetheless, at a salt concentration of 20 g/L NaCl, the shear-thickening behavior disappeared. Another important finding is that the presence of NaCl made the on-purpose destabilization of these stable nanoemulsions through the addition of NaOH or HCl (i.e., pH-alteration induced demulsification) more effective.

Low-temperature thermal conversion of Al-substituted goethite in gibbsitic bauxite for maximum alumina extraction.

The conversion of Al-substituted goethite (Al-goethite) to hematite in gibbsitic bauxite is conducive to alumina extraction during the Bayer process and the enrichment of iron minerals in red mud. In this work, mineralogical characteristics of gibbsitic bauxite were identified by AMICS analysis, and the low-temperature thermal conversion behavior of both synthetic Al-goethite and natural Al-goethite in gibbsitic bauxite were investigated through thermal gravity analysis, phase transformation, and microstructure studies. Results show that the proportion of aluminum in Al-goethite reached 12.68% of the total aluminum content in gibbsitic bauxite. The conversion of synthetic Al-goethite to hematite starts at ∼280 °C, while that of natural Al-goethite starts at ∼320 °C, and the addition of NaOH can accelerate the conversion. The formed hematite inherits the needle-like appearance of the original Al-goethite, has many holes on the surface due to dehydroxylation, and no migration of aluminum elements occurs during the roasting process, indicating that Al-goethite transformed into porous Al-substituted hematite (Al-hematite), which is beneficial to the extraction of the aluminum retained in the hematite structure during Bayer digestion. To confirm the above results, digestion experiments (without or with roasting for typical Bayer digestion or low-temperature roasting-Bayer digestion) were carried out with gibbsitic bauxite and the one roasted at 400 °C for 30 min as raw materials, respectively. Compared to the typical Bayer digestion, the relative alumina recovery of low-temperature roasting-Bayer digestion increased from 90.06% to 95.65%, the red mud yield decreased from 36.32% to 34.08%, and the grade of Fe in red mud increased from 48.45% to 52.88% at 270 °C for 60 min. Enhanced transformation of Al-goethite significantly improves alumina recovery and the resultant iron-rich red mud can be easily co-processed in the steel industry, thus significant emission reduction of red mud from the Bayer system might be achieved.

Biogas production from corn stalk as agricultural waste containing high cellulose material by anaerobic process

Many developing countries like Indonesia are experiencing serious problems associated with fossil energy reserves that has declined in line with population growth. To overcome these problems is necessary to renewable energy sources. Biomass-based renewable energy sources are a major contributor to renewable energy. Agricultural waste is biomass containing lignocellulose and can be converted into biogas. This study aims to determine the effect of pretreatment of corn stalks on the yield of raw biogas. The raw materials used were corn stalks. The corn stalks are treated by physical pretreatment with particle size reduction, biological pretreatment with the addition of EM-4 as much as 3% v/v, 5% v/v, 7% v/v total, and the addition of NaOH as chemical pretreatment as much as 0.25 N, 0.50 N, and 0.75 N. After that, the substrate of corn stalks and cow manure are mixed in the biodigester with ratio 1:1, each substrate 18 g of total solid mass. Micronutrients (urea) were added as much as 0.3 g, then neutral pH was adjusted using HCl. Fermentation is carried out at ambient temperature. The volume of biogas was measured every two days by water displacement method. The fermentation process is observed for 62 days. Best results are obtained from corn stalks 20 mesh with the addition of EM-4 7% v/v and, where a maximum daily biogas yield 19.86 L/kg on day 28 and the total biogas production reached 215.77 L/kg. In conclusion, combination of physical, biological and chemical pretreatment of corn stalks are proven to increase the yield of biogas.

Thorium ion exchange separation from rare earth elements ore samples following a combined attrition and dissolution procedure

Autogenous grinding (without grinding media) may provide some advantages if satisfactory lixiviation efficiency can be achieved on larger grain sizes. This grinding strategy requires less energy and offers important cost savings and reduction of GHG emissions in the mining industry compared to other commonly used approaches. Two attrition cells (1.2 L, 12 L) were designed to conduct a wet autogenous grinding. The combined grinding and leaching experiments were performed using six Canadian rare earth elements (REEs) ore samples to solubilize the REEs while grinding the ore in a modified attrition mill. Sulfuric, hydrochloric and nitric acids were compared under various operating conditions on three different types of ore samples (carbonatite, sedimentary, peralkaline). The addition of an alkaline step was also investigated. Metals dissolution in the 1.2 L attrition mill with or without NaOH addition (T = 20 °C, solid/liquid ratio = 20%, acid concentration [HNO3] = 7.5 M, time = 1 h) was found effective for the carbonatite ore (solubilization efficiencies of 91–99% Th, 29–32% U, 85–91% LREEs, 84–94% HREEs) and the sedimentary ore (solubilization efficiencies of 89–99% Th, 98–99% U, 22–83% LREEs, 48–99% HREEs). Actinide elements often comprise a significant component in REEs ore samples and are considered impurities. Their presence in primary REE mineral resources is problematic from a regulatory and health physics perspective. To overcome these issues, anionic, cationic and chelating resins were tested to remove Th from the nitric leaching liquor. Best separation results were obtained with the impregnated resin Lewatit VPOC 1026. To the best of our knowledge, this is the first time that Lewatit VPOC 1026 was reported in the literature for Th separation from REEs.

Hydrogen reduction of bauxite residue and selective metal recovery

Bauxite residue (BR) is an industrial by-product generated during the production of alumina from bauxite ores in the Bayer process. BR is environmentally hostile due to it is high alkalinity and fine particle size distribution. In this work, BR is blended with NaOH and subsequently reduced with hydrogen, in order to develop an intermediate material rich in magnetite and sodium aluminate, and by doing so, enable the recovery of iron, aluminium as well as sodium. Several process parameters, such as sodium dosage, reduction temperature and soaking time, on the qualities of the final material, were assessed. The highest conversion degree from hematite to magnetite was 96 % and it occurred for 20 wt% NaOH addition to BR, and reduction with 5 vol% H2, for 120 min at 500 °C. The aluminum oxides were transformed into water-soluble sodium aluminate phases, with a range of other interesting metals enriched in the resulting residue. The work herein demonstrates the potential of the suggested process as a near zero-waste process for BR.

Detection of Microorganisms in Body Fluids via MTT-PMS Assay.

Early detection of microorganisms is essential for the management of infectious diseases. However, this is challenging, as traditional culture methods are labor-intensive and time-consuming. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide-phenazine methosulfate (MTT-PMS) assay has been used to evaluate the metabolic activity in live cells and can thus be used for detecting living microorganisms. With the addition of NaOH and Tris-EDTA, the same approach can be accelerated (within 15 min) and used for the quick detection of common bacterial pathogens. The assay results can be evaluated colorimetrically or semi-quantitatively. Here, the quick detection by MTT-PMS assay was further investigated. The assay had a detection limit of approximately 104 CFU/mL. In clinical evaluations, we used the MTT-PMS assay to detect clinical samples and bacteriuria (>105 CFU/mL). The negative predictive value of the MTT-PMS assay for determining bacteriuria was 79.59% but was 100% when the interference of abnormal blood was excluded. Thus, the MTT-PMS assay might be a potential “rule-out” tool for bacterial detection in clinical samples, at a cost of approximately USD 1 per test. Owing to its low cost, rapid results, and easy-to-use characteristics, the MTT-PMS assay may be a potential tool for microorganism detection.

PHYSICOCHEMICAL AND FATTY ACID PROFILE OF FISH OIL FROM RED SNAPPER HEADS (LUTJANUS MALABARICUS) REFINED FROM VARIOUS NAOH CONCENTRATIONS

The red snapper fillet industry only uses 40–50% of its fish meat; the rest becomes waste. Red snapper fillet waste can be used as raw material for fish oil rich in Polyunsaturated Fatty Acid through the extraction process. Extracted fish oil quality can be improved through a neutralization process. This research aims to determine the degree of Baume NaOH that can produce fish oil with the best physicochemical properties. This study used a simple completely randomized design with three replications. The results showed that the difference in the degree of Baume NaOH significantly affected all characteristics of fish oil except yield and density. The neutralization process with the addition of NaOH 16°Be effectively improves the quality of fish oil and can maintain the unsaturated fatty acid content of fish oil. Neutralized fish oil has the characteristics of an acid number of 2.67 mg KOH/g, a peroxide value of 0.79 meq/kg, a p-anisidin number of 1.34 meq/kg, and a total oxidation number of 2.90 meq/kg. Identification of fatty acids and heavy metal contamination in fish oil before and after neutralization showed that the dominant fatty acid in fish oil was in the form of saturated fatty acids (50.58-67.51%) and heavy metal contamination in the form of arsenic 3.61-4.07 ppm.

Preparation of ZnO/Brucite Functional Composite Powder by the Mechanochemical Method

In this experiment, ZnO/brucite composite powder was prepared through the mechanochemical method; further, the properties, particle morphology, and structure of the composite powder were characterized. The results show that mechanical grinding action can promote the production of a large number of surface ions with unsaturated coordination number on the surface of brucite and ZnO particles, thereby promoting hydroxylation of the particle surfaces. The addition of NaOH to the composite system can also aid the further activation of the surface of the brucite and ZnO particles and the formation of more associated hydroxyl groups. Finally, a core–shell composite powder is formed with weak forces such as hydrogen bonds and van der Waals forces as the connecting bonds.

Controlled moderative sulfidation-fabricated hierarchical heterogeneous nickel sulfides-based electrocatalyst with tripartite Mo doping for efficient oxygen evolution

An electrocatalyst with heterogeneous nanostructure, especially the hierarchical one, generally shows a more competitive activity than that of its single-component counterparts for oxygen evolution reaction (OER), due to the synergistically enhanced kinetics on enriched active sites and reconfigured electronic band structure. Here this work introduces hierarchical heterostructures into a NiMo@NiS/MoS2@Ni3S2/MoOx (NiMoS) composite by one-pot controlled moderative sulfidation. The optimal solvent composition and addition of NaOH enable NiMoS to own loose and porous structures, smaller nanoparticle sizes, optimal phase composition and chemical states of elements, improving the OER activity of NiMoS. To achieve current densities of 50 and 100 mA cm−2, small overpotentials of 275 and 306 mV are required respectively, together with a minor Tafel slope of 58 mV dec−1, which outperforms most reported sulfide catalysts and IrO2. The synergistic effects in the hierarchical heterostructures expose more active sites, adjust the electronic band structure, and enable the fast charge transfer kinetics, which construct an optimized local coordination environment for high OER electrocatalytic activity. Furthermore, the hierarchical heterostructures suppress the distinct lowering of electrical conductivity and collapse of pristine structures resulted from the metal oxidation and synchronous S leaching during OER, yielding competitive catalytic stability.

Controlled Hydrolysis of a Nickel–Ammonia Complex on Pt Nanoparticles for the Preparation of Highly Active and Stable PtNi/C Catalysts

Thermal annealing at high temperatures is usually employed to alloy Pt with transitional metals to produce Pt-based electrocatalysts in an oxygen reduction reaction for polymer exchange membrane fuel cells. How to curb thermal annealing induced aggregation and sintering has been a major concern in post-treatment. Here we developed an optimized impregnation method by controlled hydrolysis of a nickel–ammonia complex on Pt/C via dropwise addition of NaOH to form homogeneously dispersed catalyst precursors. These precursor powders are then subjected to thermal annealing and subsequent acidic leaching to produce alloyed A-PtNi/C catalysts. A-PtNi/C displayed a high mass activity (MA) and specific activity (SA) of 0.903 A mgPt–1@0.9 V and 2.36 mA cm–2, respectively. In addition, the electrochemical surface area (ECSA) and MA only suffered losses of 3 and 33%, respectively, after an accelerated durability test. Both activity and stability of A-PtNi/C far exceed the 2020 Department of Energy target set for ORR catalysts.

A comparative study on the effects of NaOH and CaCl2 additives on dewatering properties and product characteristics of oily scum via hydrothermal treatment

Hydrothermal treatment (HT) is used to upgrade oily scum for its disposal and utilization. The effects of sodium hydroxide (NaOH) and calcium chloride (CaCl2) on the dewatering properties and product characteristics of oily scum via HT were investigated in this study. Results showed that NaOH and CaCl2 proved effective in terms of increasing the liquid product and decreasing the moisture content in hydrochars. Compared with NaOH, CaCl2 resulted in a higher liquid product and a greater moisture removal capacity after HT of oily scum. The addition and adding concentrations of NaOH or CaCl2 had significant influences on combustion behaviors of hydrochars. The combustion kinetic parameters of hydrochars derived from HT of oily scum with NaOH or CaCl2 were obtained. The results can provide valuable reference for enhancing the dewaterability and resource utilization of oily scum.

An optimum process for anaerobic digestion of wild tree wastes under alkaline pretreatments in biogas plants

In the present study, a new strategy was developed by integrating mathematical modeling, restrictive goals, and desirability analysis to improve anaerobic digestion of wild tree wastes and clean biogas production. For this purpose, different mixtures (inoculum : terebinth waste : cow manure) and pretreatments (NaOH and urea) were tested based on a combined D-optimal experimental design. The results indicated that biogas production of mixtures with higher cow manure amounts was more purified, with higher terebinth waste had more CO and CO2, and with higher inoculum had more H2S. Further, the addition of NaOH and urea below 1.5% improved the quality of biogas. By overlaying the biogas parameters according to the restriction goals, the best ranges of the inoculum : terebinth waste : cow manure were equaled to 0−10% : 4−22% : 71−97%, and the best concentration ranges of NaOH and urea were 0.19−1.83% and 0−1.2%, respectively. Using these optimum ranges of the input factors, CH4, H2S, CO2, CO, corrected CH4, T90, cumulative biogas production and cumulative methane production were >50.3%, <0.0003%, <9.85%, =0%, >66.21%, >4.89 day, >799.02 mL and >8.49 mL/gVS, respectively. It can be concluded that to improve the biogas plant efficiency in the areas with high tree wastes, a lot of cow manure is needed (> 3 times of tree wastes), and the substrates should be chemically pretreated with NaOH amount less than 1.83% and urea amount less than 1.2%.

Hydrothermal Pretreatment of Rice Straw with Alkaline Addition for Enhancing Biogas Production in Semicontinuous Anaerobic Digester

This study presents the results of hydrothermal pretreatment of rice straw on its ability to improve the biogas production process in anaerobic digesters. Hydrothermal treatment on rice straw biomass was carried out with the addition of 0%, 3% and 5% NaOH (w/w rice straw) for one hour at a temperature of 140 °C. This study showed that hydrothermal and alkaline hydrothermal pretreatments were able to increase organic degradation of rice straw as indicated by an increase in the dissolution of lignin and hemicellulose from rice straw. Temperature and NaOH worked synergistically to dissolve lignocellulose in the hydrothermal pretreatment process. In the semicontinuous digester fed with pretreated rice straw, NaOH content in the pretreatment stage was found to give significant effect in enhancing biogas production. Average daily biogas production by the untreated rice straw, hydrothermal pretreated without NaOH addition, hydrothermally treated rice straw with 3% NaOH and 5% NaOH was 23.9, 57.1, 95.8 and 108.8 L/kg rice straw, respectively.

Boron extraction using selective ion exchange resins enables effective magnesium recovery from lithium rich brines with minimal lithium loss

• Li + loss decreases from 13.7 to 1.4% during Mg(OH) 2 precipitation in the absence of boron. • Chemical-grade Mg(OH) 2 precipitation was possible from brines free of B. • Amberlite IRA743 resin selectivity extract boron from raw Li reach brines. • Resin saturated with boron can be regenerated and reused with the same efficiency. • The high water intake in the presence of B is associated with hydroboracite formation. Magnesium hydroxide is a commodity chemical, produced in almost pure form from seawater through precipitation. Even though Li brines contain high concentrations of Mg 2+ cations, the precipitation of Mg(OH) 2 from them is not common. Rather it is typically coprecipitated with other salts and becomes a waste. The crystallization of chemical-grade Mg(OH) 2 from a Li + rich brine that contained 3.1 g/L Mg 2+ and 1.3 g/L Li + , was investigated by means of NaOH and CaO addition. Direct precipitation of Mg(OH) 2 leads to considerable Li loss and impure crystals due to the brine uptake into the crystal cake. In order to increase the sedimentation rate and decrease the brine loss, a boron extraction step was introduced, which consisted of initial polishing using Amberlite IRA743. It was possible to extract B to below the ICP detection limit from native salt lake brines selectively and regenerate the ion exchangers for repetitive cycles. Upon the extraction of boron, the Mg(OH) 2 sedimentation rate, increased while the loss of Li + from the brine decreased from 13.7 ± 1.2 to 1.5 ± 0.4%. Precipitation with CaO as an alkalizing agent generated a mixture of crystals and a Li + loss between 6.7 ± 0.8 and 3.8 ± 0.7%. When the boron-free brine was alkalized by NaOH, an increase in the degree of crystallinity of Mg(OH) 2 crystal structure was verified by XRD and a purity of 95 ± 2% for the solid was obtained. The high water intake in the presence of B was associated with the presence of hydroboracite in intercalation within the brucite. It was expected that, if the hydroboracite was present as an intercalation, this structure would be disrupted more easily by the ultrasound, potentially resulting in a loss of the hydroboracite d-spacings. Concluding, subsequent B and Mg removal steps from Li + rich brines result in the production of 95% pure Mg(OH) 2 leaving a brine for high purity lithium salt precipitation, thereby bringing a second attractive product from brine processing.

The effect of NaOH addition on the characteristics of tilapia skin collagen

Research on fish collagen is now growing rapidly as the use of collagen in industry increases. Collagen extraction begins with the removal of non-collagen proteins using bases to maximize the extraction process. This research aims to determine the effect of differences in NaOH concentrations on the characteristics of tilapia skin collagen. NaOH in collagen extraction serves to remove alkaline soluble proteins to optimize the collagen extraction process. The bases used were NaOH with the concentration of 0.5, 1.0, and 1.5%. The extraction was carried out using the acid method. Using SEM, observation parameters for crude collagen from the tilapia skin include collagen yield, functional group analysis, lightness, and surface morphology. The results of functional groups analysis showed that the collagen obtained in all treatments had typical collagen characteristics, i.e., amide A, amide B, amide I, amide II, and amide III. The non-collagen deproteination treatment with 0.5% NaOH could produce better collagen than the 1.0 and 1.5% concentrations, as indicated by the highest yield (20.42%) and lightness (93.22). Morphological analysis showed that the collagen extracted has an irregular branched fiber structure.

Biological and physico-chemical mechanisms accelerating the acclimation of Mn-removing biofilters

This study investigated treatment strategies which accelerated the acclimation of new Mn-removing biofilters to help utilities respond to changing Mn regulations, such as the recent introduction of a health-based maximum acceptable concentration and a reduction in the aesthetic objective for Mn in drinking water by Health Canada. Bench-scale filters of either GAC or anthracite media were fed with applied water containing Mn (17–61 μg/L) from a full-scale plant over 294 days. Treatment strategies included the addition of H2O2 (1 mg/L) and/or an increase in pH from 6.8 to 7.5 through the addition of NaOH. The potential physico-chemical and biological mechanisms responsible for accelerated biofilter acclimation under the various redox conditions were investigated through thermodynamic modelling, to predict homogeneous Mn oxide formation, and 16S rRNA gene amplicon sequencing, to characterize the microbial community within the filters. GAC filters treated with NaOH, and both H2O2 and NaOH, were the first to acclimate (< 20 μg/L Mn in filter effluent) after 59 and 63 days respectively, while the ambient GAC filter took almost 3 times as long to acclimate (168 days), and the anthracite filters which received the same chemically adjusted water took almost 4 times as long (226 and 251 days, respectively). The accelerated acclimation in the treated GAC filters was likely due to physico-chemical oxidation via three potential mechanisms: (1) homogeneous oxidation of dissolved Mn(II) to Mn(III)/Mn(IV) oxides and the subsequent removal of oxides from solution through adherence to the GAC surface, (2) adsorption of dissolved Mn(II) to GAC and subsequent homogeneous or biological oxidation, or (3) formation of colloidal Mn(III)/Mn(IV) oxides and subsequent adsorption of dissolved Mn(II) to the Mn colloids. In the untreated GAC filter and all anthracite filters, which did not benefit from improved redox conditions or an active surface, physico-chemical mechanisms alone were insufficient for consistent Mn removal to less than 20 μg/L. Acclimation in these filters was delayed until a microbiome enriched with bacteria capable of biological nitrification and Mn oxidation evolved within the filters. The acclimated microbiome was consistent between GAC and anthracite filters and was significantly different from the non-acclimated microbiome (p < 0.001) initially formed during the early operation of the filters. Interestingly, treatment with NaOH, and NaOH and H2O2, which accelerated physico-chemical oxidation in GAC filters, was observed to delay the development of biological oxidation in anthracite filters, and thus deferred acclimation. Although some filters took longer to acclimate than others, once acclimation was reached all filters had a similar microbiome and were able to consistently remove Mn to below 20 µg/L.

Stability of gamma-valerolactone under pulping conditions as a basis for process optimization and chemical recovery

This study focuses on the investigation of the extent of the γ-valerolactone (GVL) hydrolysis forming an equilibrium with 4-hydroxyvaleric acid (4-HVA) in aqueous solutions over a wide pH range. The hydrolysis of a 50 wt% GVL solution to 4-HVA (3.5 mol%) was observed only at elevated temperatures. The addition of sulfuric acid (0.2 × 10–5 wt% to 6 wt%) at elevated temperatures (150–180 °C) and reaction times between 30 and 180 min caused the formation of 4 mol% 4-HVA. However, with decreasing acidity, the 4-HVA remained constant at about 3 mol%. The hydrolysis reactions in alkaline conditions were conducted at a constant time (30 min) and temperature (180 °C) with the variation of the NaOH concentration (0.2 × 10–6 wt% to 7 wt%). The addition of less than 0.2 wt% of NaOH resulted in the formation of less than 4 mol% of sodium 4-hydroxyvalerate. A maximum amount of 21 mol% of 4-HVA was observed in a 7 wt% NaOH solution. The degree of decomposition after treatment was determined by NMR analysis. To verify the GVL stability under practical conditions, Betula pendula sawdust was fractionated in 50 wt% GVL with and without the addition of H2SO4 or NaOH at 180 °C and a treatment time of 120 min. The spent liquor was analyzed and a 4-HVA content of 5.6 mol% in a high acidic (20 kg H2SO4/t wood) and 6.0 mol% in an alkaline (192 kg NaOH/t wood) environment have been determined.