Alkaline Reagents Research Articles

Characteristic modification of alkalized corn stalk and contribution to the bonding mechanism of fuel briquette

In this paper, corn stalk was alkalized by gradient concentrations of sodium hydroxide and briquetted with anthracite coal. The bonding mechanism was explored by a combined analysis of physicochemical, microstructure and mechanical properties. Alkaline treatment had a large effect on decomposing most of lignin and dissolving the carbohydrates in corn stalk even at a low concentration of 1%. With the increase in alkaline concentration (for 1%–2%), the degree of decomposition of hemicellulose and amorphous cellulose increased gradually. When the concentration of alkaline reagent was higher than 3%, more than 40% of hemicellulose was degraded. A complete surface structure of a spatial network was achieved when corn stalk was treated by 2% alkaline, which mainly contributed to the bonding performance of compound briquette. Under this condition, the ratio of cellulose to hemicellulose to lignin was approximately 7.0:2.5:0.5, and it also exhibited a good pyrolysis performance for energy conversion.

φ–pH diagram of As–N–Na–H2O system for arsenic removal during alkaline pressure oxidation leaching of lead anode slime

In order to illustrate the thermodynamic characteristics of arsenic during alkaline pressure oxidation leaching process of lead anode slime (NaNO3 as oxidant; NaOH as alkaline reagent), the φ–pH diagrams of As–Na–H2O, N–H2O, As–N–Na–H2O systems at ionic mass concentration of 0.1 mol/kg and temperatures of 298, 373, 423 and 473 K were established according to thermodynamic calculation. The results show that the existence forms of arsenic are associated with pH value, which mainly exists in the forms of H3AsO4, H2AsO4−, HAsO42−, and As2O3 in lower pH region, while it mainly exists in the form of when pH>11.14. High alkali concentration and high temperature are advantageous to the arsenic leaching. The alkaline pressure oxidation leaching experiments display that the tendency of arsenic leaching rate confirms the thermodynamic analysis results obtained from the φ–pH diagrams of As–N–Na–H2O system, and the highest leaching rate of arsenic reaches 95.85% at 453 K.

Ликвидация последствий аварийных разливов нефтепродуктов в Арктической зоне России с использованием технологии реагентного капсулирования

Arctic zone of the Russian Federation occupies a large area of the country and it differs from other regions with special climatic conditions. In winter air temperature can be lowered to 70°C below zero in the Arctic, and almost all the territory is located in the permafrost zone. The main potential sources of emergency conditions resulted in oil products used as finished raw materials, fuel and lubricants which will inevitably fall into the soil, are operated machinery and equipment for the hydrocarbons extraction and transportation. Weak self-recovery potential of soils in a short growing season and low temperatures involves the development and use of adapted to arctic conditions technologies for rapid overcoming of accidental oil spills consequences. We propose adapted to arctic conditions technology for rapid consequences elimination of accidents involving oil spills. Decontamination technology of soils polluted with oil products is based on the encapsulation of the pollutant (reagent encapsulation technology) with an alkaline reagent based on calcium. We used as a reagent powdered building quick lime; it is carbonate rock calcine or a mixture of this product with mineral additives (calcium oxide). The main advantage of the reagent encapsulation technology is decontamination efficiency of contaminated soils compared to traditional technologies of decontamination. One more important factor is low market value of lime as compared to other reagents, biological substances and solvents for the oil products extraction. We describe the basic steps of the reagent encapsulation technology in decontamination of soils contaminated with oil products. If we use exotherm process energy of chemical decontamination of soils contaminated with oil products, in combination with a forced feed of carbon dioxide to decontamination zone; then at the stage of coat formation from calcium carbonate on the surface of the pollutant it allows to complete decontamination of soils contaminated with oil products using the reagent encapsulation technology in extreme Arctic natural climatic conditions. We describe the principle of equipment operation allowing to carry out decontamination of soils contaminated with oil products using reagent encapsulation technology in Arctic climatic conditions. Encapsulated material obtained as a result of decontamination of soils contaminated with oil products, is resistant to natural and anthropogenic factors, such as moisture, temperature changes, acid rain and high pressure. We present the results of experimental studies for determining the optimal amount of the reagent required for the efficient completion of the decontamination of snow contaminated with motor oil, and soils contaminated with oil products depending on the degree of contamination and the type of pollutant. Our studies confirm that the reagent encapsulation technology showed good performance in severe climatic conditions and they are suitable for decontamination of soils and snow contaminated with gasoline, diesel fuel and engine oil.

Identification, characterization and in silico ADMET prediction of Roflumilast degradation products

The present study reports the degradation behavior of roflumilast (RFL), a new drug developed for the treatment of chronic obstructive pulmonary disease. The degradation of RFL was tested under various stress conditions as per the guidelines of the International Conference on Harmonization. The degradation products (DPs) of RFL were identified, characterized and in silico predictions were made of their pharmacokinetic properties, absorption, distribution, metabolism, excretion and toxicity (ADMET). RFL was subjected to various stress conditions including photodegradation, alkaline and acidic hydrolysis, oxidative and metallic degradation. After analysis by HPLC-DAD, the DPs were isolated by preparative TLC and characterized by high resolution mass spectrometry (HRMS), 1H NMR, 13C NMR and infrared (IR) spectroscopy. RFL tablets were prepared by the addition of solid stressing substances such as excipients and storage in an accelerated stability chamber (40°C; 75% r.h.) for sixteen months. Resulting DPs from the tablets were analyzed by UFLC-QTOF. The most drastic degradation conditions for RFL were 5M NaOH(aq), 6M HCl(aq), 7.5% v/v peracetic acid, which resulted in the isolation of four DPs. However, milder degradation conditions (1M NaOH(aq) and photolysis) generated six DPs (DP-1, 2, 3, 5, 7 and 8), and are more similar to the actual conditions the drug will be exposed. For tablets containing RFL exposed to an alkaline reagent, two DPs were formed: DP-1 and DP-11. Whereas RFL-containing tablets exposed to acid and oxidizing agents, formed one product DP-11. Forced degradation of RFL led to the formation of eleven DPs, seven of which have never been previously reported. RFL is stable under metallic stress and it is relatively stable during photodegradation testing. The UFLC-QTOF methodology detected a greater number of DPs that formed during the stress conditions tested when compared to the HPLC-DAD methodology. In silico prediction of the ADMET properties of the RFL degradation products and metabolites produced in this study are potentially hepatotoxic.

Facile Fabrication of Large-Aspect-Ratio g-C3N4 Nanosheets for Enhanced Photocatalytic Hydrogen Evolution

Exfoliation of bulk graphitic carbon nitride (BCN) into two-dimensional (2D) nanosheets is one of the effective strategies to improve its photocatalytic performance. Compared with BCN, the 2D g-C3N4 nanosheets (CNNS) have larger specific surface areas and more reaction sites. With the etching assistance of anhydrous ethylenediamine, BCN can be successfully peeled off into 2D CNNS with a large lateral size of more than 15 μm which is much larger than that of other works. After appropriate etch by anhydrous ethylenediamine, the specific surface area of g-C3N4 expands from 4.7 to 31.1 m2 g–1 and the photocatalytic hydrogen evolution rate increases 7.4 times, from 4.8 to 35.3 μmol h–1. In contrast to other reported methods, the strategy to fabricate 2D CNNS in this work is convenient and it is the first time to report the fabrication of 2D CNNS with the assistance of alkaline reagent.

Homogeneous alkalization of cellulose in N-methylmorpholine-N-oxide/water solution

Alkali cellulose is an important intermediate in the production of cellulose derivatives. N-methylmorpholine-N-oxide (NMMO)/H2O was used as a homogeneous reaction medium for the cellulose alkalization process to intensify the alkalization degree and improve the substitution uniformity. The morphology, specific surface area and crystalline structure of pristine cellulose, the as-synthesized alkali cellulose and dissolved-regenerated cellulose were characterized by SEM, BET, XRD and FT-IR, respectively. The results showed that the homogeneous reaction medium not only offered a low mass transfer resistance, but also facilitated a disruption of the hydrogen bond in cellulose, thus resulting in the transformation of the cellulose structure from complicated stacking chains to simple glucose chains. The interior hydroxyl groups in the cellulose became accessible to the alkaline reagent NaOH to enhance the alkalization process for the increase in bonding alkali content and the improvement in substitution uniformity. The bonding alkali content was calculated by the difference between total added alkali and free alkali and was achieved as 0.61 g/g cellulose at the optimized operation conditions: reaction temperature of 95 °C, reaction time of 90 min, NMMO dosage of 90.00 g, cellulose 1.0 g and NaOH concentration of 1.40 wt%. Meanwhile, in the conventional alkalization process, the bonding alkali content was just 0.41 g/g cellulose. The alkali cellulose prepared in NMMO/H2O medium has a large specific surface area of 125 m2 g−1 and an extremely low crystallinity degree. The NMMO/H2O system represents a potential homogeneous solvent for the cellulose alkalization process.

A New Methodology for the Characterisation of Natural Dyes on Museum Objects Using Gas Chromatography–Mass Spectrometry

ABSTRACTThe derivatising agent m-(trifluoromethyl)phenyltrimethylammonium hydroxide (TMTFTH) has been employed for more than a decade at the Canadian Conservation Institute (CCI) to extract natural dyes from historical textiles and other dyed substrates. The alkaline reagent breaks the bonds between the colourants and the mordant ions or functional groups of the substrate, releasing the dye compounds into the extraction solution, and derivatises polar functionalities to produce compounds that are amenable to subsequent analysis by gas chromatography–mass spectrometry (GC–MS). This approach allows for the identification of the colourants, and is also useful in determining the presence of degradation products from the dyes and substrates, non-dye marker compounds, auxiliary compounds added to the dye bath, and substances present on the object through anthropogenic use, conservation treatments, or possible pesticide contamination. This paper discusses compounds formed through the reactions of TMTFTH with flavonoid dyes (dyer’s buckthorn, old fustic, weld, red sandalwood, and brazilwood), quinone dyes (madder, Relbunium, Galium, cochineal, lac, and walnut), indigoid dyes (indigo, Tyrian purple, and indigo carmine), turmeric, marigold, lupin and several lichen species. Results from a selection of historical dyed textiles and other decorative objects analysed at the CCI are provided to illustrate applications of the methodology.

Ni(II) removal from aqueous solution by biosorption and flocculation using microbial flocculant GA1

Generally, most biomaterials present high biosorption capacity for heavy-metal ions. In this study, alkaline reagents and microbial flocculant GA1 (MBFGA1) were combined to remove Ni(II) from aqueous solution. Response surface methodology was employed to optimize the flocculation and biosorption conditions with the Ni(II) removal rate as the response, as well as to analyze the biosorption capacity. At initial Ni(II) concentration of 100 mg L−1, the optimal conditions were predicted to be 1.3 × 10−2% (w/w) CaO, 6.59 × 10−3% (w/w) MBFGA1, and stirring time of 61.97 min, at which the Ni(II) removal rate and biosorption capacity of MBFGA1 could reach 99.35% and 225.16 mg g−1, respectively. The biosorption behavior, Fourier-transform infrared spectra, and environmental scanning electron microscopy analysis demonstrated that adsorption bridging with precipitation enmeshment was the most likely mechanism. Analysis of the mechanism and procedure indicated that synergistic flocculation and biosorption by MBFGA1 resulted in the significant Ni(II) removal.

Electrospinning of silk fibroin from all aqueous solution at low concentration

Non-woven mats of Bombyx mori silk fibroin were fabricated using electrospinning with an all aqueous solution at <10wt% without any co-existing water soluble polymer such as PEO. The fibroin aqueous solution electrospinnability was affected by the fibroin molecular weight and the spinning solution pH. Hot-water treatment without any alkaline reagent or soap produced higher molecular weight fibroin than the typical degumming process did. The higher molecular weight fibroin provided good electrospinnability. Results show that the basic solution (pH10–11) is important for electrospinning at low concentrations of 5wt%. Evaluation of structural and mechanical properties of the non-woven mat fabricated with water solvent revealed that it is safe for use in the human body. It is anticipated for wider use in medical materials such as cellular scaffolds for tissue engineering.

A practical method for extending the biuret assay to protein determination of corn-based products

A modified biuret method suitable for protein determination of corn-based products was developed by introducing a combination of an alkaline reagent with sodium dodecyl sulfate (reagent A) and heat treatments. The method was tested on seven corn-based samples. The results showed mostly good agreement (P>0.05) as compared to the Kjeldahl values. The proposed method was found to enhance the accuracy of prediction on zein content using bovine serum albumin as standard. Reagent A and sample treatment were proved to effectively improve protein solubilization for the thermally-dried corn-based products, e.g. corn gluten meal. The absorbance was stable for at least 1-h. Moreover, the whole measurement of protein content only needs 15-20min more than the traditional biuret assay, and can be performed in batches. The findings suggest that the proposed method could be a timesaving alternative for routine protein analyses in corn processing factories.

A case study for a cost-benefit-based, stepwise optimization of thermo-chemical WAS pre-treatment for anaerobic digestion

Waste-activated sludge (WAS) may be considered a resource generated by wastewater treatment plants and used for biogas-generation but it requires pre-treatment (PT) for enhanced biogas-yields and reduced WAS disposal costs. To date, a number of studies on the optimization of such PT focused on improved biogas yields but neglected inferred energy and resource consumption. Here, we aimed to identify the most promising thermo-chemical PT-strategy in terms of net energy output and cost-efficiency by optimizing PT temperature and the amount and sort of the alkaline reagent used. We compared methane-potentials and disposal costs of untreated and treated WAS and conducted an annual cost-benefit calculation. We defined 70 °C and 0.04 M NaOH as ideal PT-conditions being both, low-energy demanding and efficient. Applying these conditions, enhanced biogas-yields and improved dewaterability led to reduced electricity and disposal costs of 22 and 27%, respectively, resulting in savings of approx. 28% of the yearly WAS-related expenditures of a wastewater treatment plant. Despite multiple benefits in running costs, the implementation of WAS-PT was not recommendable in the presented case study due to high investment costs.

Designing micro- and mesoporous carbon networks by chemical activation of organic resins

Carbon xerogels with ultrahigh micro- and mesopore volumes were synthesized from the activation of polymeric resins prepared by sol–gel polycondensation of resorcinol/formaldehyde mixtures in basic medium and subcritical drying. Various activating conditions (e.g., agent, temperature, impregnation conditions) were used and it was found that the textural features of the resulting carbon xerogels are linked to the experimental procedure of the activation reaction to promote the porosity development. The shrinkage and structural collapse of the fragile resins typically obtained upon annealing at high temperatures (during carbonization and/or physical activation) is suppressed when the impregnation of the chemical activating agent is performed under controlled conditions. If the alkaline reagent (either KOH or K2CO3) is put in contact with the resin by wet impregnation (liquid/solid); under such conditions, the intimate contact between both compounds allows the formation of microporosity during the activation along with the enlargement and/or preservation of the mesoporosity of the pristine resin. Furthermore, the chemical activation via wet impregnation allows the combination of high surface areas and the preservation (even higher development) of the mesoporosity created during the synthesis of the resin. The effect of the impregnation method was found highly dependent of the reagent and activation temperature, highlighting the possibility to design micro-mesoporous carbon xerogels at low temperatures with a subtle control of the activation conditions.

PREPARATION AND PROPERTIES OF CHITOSAN FROM CRAB SHELL CONTAINING RAW MATERIAL BY ELECTROPHYSICAL PROCESSING

Traditional technologies of chitosan producing involve the use of hard alkali-acidtreatment of crab shell raw materials, which negatively affects the main qualityparameters of chitosan (molecular weight, the degree of deacetylation). Wepropose an alternative technical approach. It involves the useofelectrohydraulicshocks,whichuseextra-long bits.Theproposed approach has thefollowing advantages:the stages of grinding and deproteinizationof the rawmaterialsare combined,the additional use ofalkaliis excluded at the stage ofdeproteinization.For comparative characteristics of the structure of the polymer theIR-spectra of the samplesof chitosanwere removed. Chitosan, obtained usingelectrohydraulic treatment is not inferior in its physico-chemical parameters ofchitosan, obtained by using alkaline reagents. It is possible to organize the processof chitosan production on the base of the enterprises for shrimp processing.Specific requirements for physico-chemical and functional properties of chitosancontainingsubstances make the actual means and methods of control of the targetparameters, the key of which are qualitative identification and comprehensivedetermination of chitosan in the composition of film-forming compositions andfilms coatings. As the chromophore to measure the surface potential of the chitosansubstances, we used 1-aniline-8-naphthalenesulfonate (ANS). The maximumfluorescence of the dye in chitosan films is shifted to longer wavelengths comparedto chitosan gels, because of the increased polarity of the medium of films on theattitude to gel-like chitosan substances. The data obtained by thefluorimetricstudies can be used in the development of methods for the detection of chitosan.

Self-assembly behaviors of molecular designer functional RADA16-I peptides: influence of motifs, pH, and assembly time

In the current study, we present three designer self-assembling peptides (SAPs) by appending RADA 16-I with epitopes IKVAV, RGD, and YIGSR, which have different net charges and amphiphilic properties at neutral pH. The self-assembly of the designer SAPs is intensively investigated as a function of pH, canion type, and assembly time. The morphologies of the designer SAPs were studied by atomic force microscope. The secondary structure was investigated by circular dichroism. The dynamic viscoelasticity of designer SAP solutions was examined during titration with different alkaline reagents. Our study indicated that both electrostatic and hydrophilic/hydrophobic interactions of the motifs exhibited influences on the self-assembly, consequentially affecting the fiber morphologies and rheological properties. Moreover, NaOH induced a quicker assembly/reassembly of the designer SAPs than Tris because of its strong ionic strength. Therefore, our study gained comprehensive insight into the self-assembling mechanism as references for developing RADA 16-I–based functional SAPs.

ИССЛЕДОВАНИЕ ВЛИЯНИЯ ЩЕЛОЧНОЙ ОБРАБОТКИ НА СОСТАВ И СВОЙСТВА ЭЛЕМЕНТАРИЗОВАННОГО ЛЬНЯНОГО ВОЛОКНА

The possibility of modification of linen fibers according to the essentially new technological scheme which includes purposeful destruction of connective tissues by the action of cyclic de-forming loads (elementarization) with the subsequent chemical processing is proved. The analysis of properties of the obtained elementary fibers of natural origin has shown that geometrical indicators of flax elementary fibers are close to the ones of cotton and wool fibers, and their du-rability is considerably higher, that gives the prospects to create innovative products for technical, textile and medical purposes on their basis. The influence of chemical processings, modeling the processes of modification and upgrading of flax materials, on the composition of basic admixtures and properties of elementarized fibers is investigated. It is shown that the high extent of purification of elementarized fibers raises the possibility of cellulose destruction. The selection of chemical reagents and concentration and time parameters of the process, which provide the optimum extent of purification of elementarized fibers without the destruction of its cellulose component, is carried out. It is determined that chemical processings of elementarized flax fibers in comparison with the cottonized ones have to be carried out in softer conditions: the concen-tration of alkali – to 2 g/l, the processing duration – up to 60 min. As the alkaline reagent the bases weaker than sodium hydroxide can be applied, in particular, sodium carbonate. The insig-nificant destruction of cellulose noted during the subsequent influence of an oxidizer is confirmed by small contents of carboxyl and aldehyde groups in it and also by the durability indexes of new type of fibers: the durability of fibers before and after the chemical processings has no significant differences and is within the limits 40,4–42,0 sn/tex.

One-step synthesis of magnetic nanocomposite Fe3O4/C based on the waste chicken feathers by a green solvothermal method

The magnetic Fe3O4/C nanocomposite was one-step synthesized via a facile green solvothermal method from Fe(NO3)3·9H2O and waste chicken feathers (CF), without adding any reductive and alkaline reagents. The results demonstrate that Fe3+ ions are adsorbed and enriched on the surface of CF and partially reduced to Fe2+ by CF, which facilitate the in-situ conversion of Fe3+ and Fe2+ to Fe3O4. Simultaneously, Fe3+ ions can enhance/catalyze the carbonization of CF, and thereafter inducing the successful preparation of Fe3O4/C nanocomposites. In addition, the as-prepared Fe3O4/C nanocomposites exhibit increasing magnetic properties with increasing the amount of CF from 0.000 to 2.600g. The enhanced magnetic property was also discussed.

Understanding the Abnormal Capacity of Metal Hydroxide Anode Material for Next Generation Lithium Rechargeable Batteries

Graphitic carbon is extensively used as anode material in most of the commercial lithium-ion batteries (LIBs) due to its low cost and high coulombic efficiency. However, capacity of carbon anode (372mAh/g and 830mAh/mL) is limited by the reversible electrochemical intercalation of lithium ions in its structure. So, alternative research directions and different anode materials are currently being investigated with an aim to achieve high capacity and cycling stability. Recently nano-material research has shed light on many high performing materials. Among these, cobalt hydroxide has been recognized as one of the potential candidates for anode materials because of its novel electric and electrochemical properties[1]. Co(OH)2 with a sheet-like structure tends to form a layered assembly, thus it has the benefit of improved ion transport and better contact of electro-active materials with electrolyte. Several methods have been used to synthesize the hexagonal β-Co(OH)2 nano sheets including facile hydrothermal and homogeneous precipitation with sodium hydroxide as the alkaline reagent. Co(OH)2-Graphene Nano Sheet (GNS) composite was reported in 2010[2] as anode material for LIBs with superior electrochemical performance and its reaction mechanism was suggested as: Co(OH)2 + 2Li+ +2e- → Co + 2LiOH (577mAh/g). GNS acted as synergistic effect to synthesized material for achieving higher capacity (1120mAh/g) because GNS could relieve the volume expansion during cycling and also, give excellent electronic conductivity. Co(OH)2-nanosheets/ Co3O4-nanoparticle hierarchical structure has also been reported[3] as anode material for LIB’s with enhanced capacity and performance. However, unlike the composite materials, bare Co(OH)2 anode material still has trouble with showing good electrochemical performance for lithium ion batteries, which may be due to insufficient electrolyte soaking between layers and severe volume expansion during the cycling. Herein, we successfully synthesized colloidal silica assisted sheet-like nano-structured Co(OH)2 using cobalt (Ⅱ) nitrate hexahydrate (Co(NO3)2∙6H2O, 97%, m.p. 55 ̊C, Aldrich) as precursor through simple synthetic strategy. Even though synthesized nano-structured Co(OH)2 is not a composite material, shows excellent reversible capacity (~1000 mAh/g) during the electrochemical cycling beyond the theoretical capacity after the first irreversible discharge process, and exhibits excellent rate capability with a good cycle performance. This research also included its novel reaction mechanism during electrochemical cycling with lithium. Structural and electrochemical properties of synthesized material were studied by electrochemical tests and combination of the synchrotron radiation based X-ray diffraction (XRD)/ X-ray absorption spectroscopy (XAS) techniques. Changes in the bulk structure were studied by XRD whereas local structure changes around Co during cycling were systematically investigated by recorded XAS data. Based on these results, novel reaction mechanism about the nano-structured Co(OH)2 anode material during electrochemical cycling was suggested specifically. This finding will not only be helpful in a more complete understanding of the reaction mechanism of metal oxide based anode materials but also will offer valuable guidance for developing new anode materials with abnormal high capacity for next generation rechargeable batteries. More detailed discussion will be presented at the time of meeting. [1]. Huang, X.-l et al., Journal of Materials Chemistry, 2012. 22(9): p. 3764. [2]. He, Y.-S et al., Electronbbn chemistry Communications, 2010. 12(4): p. 570-573. [3]. Dong, Q et al., Materials Research Bulletin, 2011. 46(8): p. 1156-1162.

Removal of heavy metal ions from water by an combined sorption–crystallization process using activated clays

The degree of comminution of materials in an ultrasonic field has been theoretically estimated by calculating the maximum and minimum energy inputs necessary for this process (upper and lower estimates have been obtained). The degree of comminution of kaolin in an ultrasonic bath determined by light and electron microscopy is in satisfactory agreement with the theoretical estimates. The efficiencies of heavy metal ion (Cu2+, Ni2+) removal from aqueous solutions in the following processes have been compared: adsorption on natural materials (kaolin and bentonite), chemical precipitation in homogeneous crystallization, and integrated sorption–crystallization process using activated clays. The highest purification efficiency has been attained in the integrated process preceded by ultrasonication of the clay slurry and alkaline reagent. Use of these sonochemically activated additives has shortened the duration of the integrated process and has increased the degree of removal of toxic metals to 102–103. Clays have been demonstrated to act as a sorbent, a heterogeneous crystallization stimulator, and a coagulant accelerating the sedimentation of the solid phase.

Sequential biological process for molybdenum extraction from hydrodesulphurization spent catalyst

Spent catalyst bioleaching with Acidithiobacillus ferrooxidans has been widely studied and low Mo leaching has often been reported. This work describes an enhanced extraction of Mo via a two stage sequential process for the bioleaching of hydrodesulphurization spent catalyst containing Molybdenum, Nickel and, Aluminium. In the first stage, two-step bioleaching was performed using Acidithiobacillus ferrooxidans, and achieved 89.4% Ni, 20.9% Mo and 12.7% Al extraction in 15 days. To increase Mo extraction, the bioleached catalyst was subjected to a second stage bioleaching using Escherichia coli, during which 99% of the remaining Mo was extracted in 25 days. This sequential bioleaching strategy selectively extracted Ni in the first stage and Mo in the second stage, and is a more environmentally friendly alternative to sequential chemical leaching with alkaline reagents for improved Mo extraction. Kinetic modelling to establish the rate determining step in both stages of bioleaching showed that in the first stage, Mo extraction was chemical reaction controlled whereas in the subsequent stage, product layer diffusion model provided the best fit.

Subcritical Water Hydrolysis Treatment of Waste Biomass for Nutrient Extraction

Nutrients were extracted from corn stalks, peanut shells, de-oiled peanut meal, chicken manure, and sewage sludge by a subcritical water (SCW) hydrolysis reaction. Compared with the other feedstock, the aqueous phases extracted from de-oiled peanut meal showed the highest water-soluble organic carbon, amino acid, total nitrogen, and phosphorus contents. The effects of solution pH, final hydrothermal temperature, and reaction time on nutrient extraction from de-oiled peanut meal were investigated. The analysis showed that alkaline reagents promoted liquefaction. The highest yield of the total primary nutrients (82.6%) was obtained with extraction reaction at 180 °C for 1.5 h using 0.1 mol/L KOH. The liquid fraction from this reaction was investigated for its potential use as a fertilizer with germination experiments. A higher germination index and root activity were obtained using the liquid extract with the appropriate dilution. These results indicated that subcritical water hydrothermal treatment is a viable way to recover nutrients from biomass wastes. In addition, de-oiled peanut meal is a suitable feedstock for the production of nutrient-rich liquid extract.