Aqueous Ammonia Treatment Research Articles

Effects of soaking aqueous ammonia pretreatment on chemical composition and enzymatic hydrolysis of corn stover

Effects of soaking aqueous ammonia pretreatment on chemical composition and enzymatic hydrolysis of corn stover. The aim of this research was to investigate the effect of applying two different temperatures of the soaking aqueous ammonia treatment on the chemical composition and enzymatic hydrolysis yield of the corn stover. Native corn stover as well as solid fractions after 20 h of alkali pretreatment performed at 15% ammonia solution and at 50 °C or 90 °C were analysed in terms of cellulose, holocellulose, lignin and extractives content. Both untreated and treated samples were subjected to the enzymatic hydrolysis and hydrolysates were examined with a high performance liquid chromatography (HPLC). Results indicated a significant development of enzymatic digestibility of the SAA treated biomass. Furthermore, a 38.7% and a 68.9% delignification levels in the biomass treated with ammonia at respectively 50 °C and 90 °C process comparing to the raw material were achieved.

Enhanced toluene adsorption/desorption dynamic performances over modified USY zeolites after an aqueous ammonia treatment.

The dynamic adsorption/desorption performances of modified hierarchical USY zeolites treated with an ammonia solution (NH4OH) at different concentrations were investigated using gas-phase toluene as an indicator. The characterization results indicated that the ammonia treatment could result in the expansion of microporous channels and the formation of a mesoporous structure without evident decrease in crystallinity. The experiment results regarding dynamic adsorption/desorption performances revealed that the mass transfer resistance of modified USY adsorbents were greatly reduced treating with NH4OH. Among the modified samples, the 0.1 mol L−1 NH4OH treated USY adsorbent exhibited large adsorptive capacity and highest desorption rate, which show good cyclic performance that could preserve its adsorbent capacity after 20 cycles. In contrast, pristine USY samples had lost around 28% of the initial adsorption capacity after 20 cycles. Moreover, the NaOH-treated sample showed great crystallinity decline compared to the NH4OH-treated samples due to excessive silicon atom leaching from the USY framework, and had lower adsorption capacity under humid conditions. Therefore, NH4OH-modified USY zeolites could be promising adsorbents for the adsorption/desorption process of volatile organic compounds (VOCs).

A novel safety treatment strategy of DEHP-rich flexible polyvinyl chloride waste through low-temperature critical aqueous ammonia treatment

Flexible polyvinyl chloride (f-PVC) contains high content of plasticizers and chlorine. Improper treatment of waste f-PVC can easily lead to resource wasting and bring environmental risks. In this work, a novel strategy for resource recycling and dechlorination of waste f-PVC containing high content of di-(2-ethylhexyl) phthalate (DEHP) was developed by using low-temperature critical aqueous ammonia (LCA) process. The LCA treatment of waste DEHP-rich f-PVC (WDP) was performed at the temperature range of 200–400 °C with the ammonia concentration of 1%–5%. The results indicated that the LCA temperature had a significant effect on the chemical composition of decomposition products. High concentration of 2-ethyl-1-hexanol (86.12%), which is an important chemical feedstock and is derived from the decomposition of DEHP, could be obtained from WDP by the LCA process at 250 °C, and the concentration of 2-ethyl-1-hexanol decreased markedly with increasing the temperature. Benzaldehyde and acetophenone were generated when the temperature increased to 300 °C, and their concentrations increased with the rise of temperature. The increase of the ammonia concentration and the temperature could enhance the dechlorination efficiency of WDP. The dechlorination could reach 98.7% at 300 °C. This result showed that the LCA process was a promising and high-efficiency strategy for the sustainable management of WDP.

Lignin extraction from oil palm empty fruit bunch fiber (OPEFBF) via different alkaline treatments

This study was conducted to investigate the efficiency of lignin extraction from oil palm empty fruit bunch fiber (OPEFBF) by using aqueous sodium hydroxide and aqueous ammonia solutions. In this study, the aqueous ammonia treatment was conducted via three different modes, namely low temperature-long time soaked treatment (LTLt-NH3), high temperature-short time soaked treatment (HTSt-NH3), and low temperature-long time replenished treatment (LTLt-Rep-NH3). Low- and high-temperature treatments were conducted at 50 and 100 °C, respectively. The efficiency of lignin extraction upon aq. NaOH treatment at 120 °C and solid content of 1:17 (OPEFBF-to-liquid) for 180 min was not significantly different with the LTLt-Rep-NH3 treatment at 50 °C and solid content of 1:7 (OPEFBF-to-ammonia) for 4 days. Among the tested methods, LTLt-Rep-NH3 treatment was proved to be the best lignin extraction method. Under the optimum conditions, approximately 64% of Klason lignin had been removed from the OPEFBF and about 33.0 ± 2.2% of lignin was successfully recovered, with minimal lignin structural deconstruction.

Hybrid dilute sulfuric acid and aqueous ammonia pretreatment for improving butanol production from corn stover with reduced wastewater generation

An efficient hybrid pretreatment method was developed for butanol production from corn stover using dilute sulfuric acid (DA) and aqueous ammonia (AA). With the optimized AA concentration, treatment temperature and time of 10% AA, 80 °C and 24 h, the hybrid pretreatment could effectively dissolve hemicellulose and lignin with solid recovery rate of 37.45% and lignin reduction rate of 86.77% compared to those of 57.75% and 45.84% from single DA pretreatment. By washing 1 time after each step treatment, sugar yield and butanol production were increased to 401.76 mg/g-CS and 10.89 g/L from 346.04 mg/g-CS and 9.33 g/L obtained without washing. Compared with conventional single DA and AA pretreatment methods, wastewater generation was reduced to 0.83 L/g-butanol from 2.11 and 3.46 L/g-butanol, indicating this hybrid pretreatment could be an effective approach for improving butanol production from lignocellulosic feedstocks.

Structural features and enzymatic digestibility of Napier grass fibre treated with aqueous ammonia

We characterised the structural changes of Napier grass after treatment with aqueous ammonia (27%, w/w) at a solid:liquid ratio of 1:12 for 14 days at ambient temperature and evaluated its enzymatic digestibility. This treatment protected carbohydrates in the fibre and greatly reduced lignin content (58.7% lignin removal), resulting in the deconstruction of the fibrous matrix. Although the relative cellulose content increased, the degree of crystallinity of the treated fibre increased only marginally from 42.9 to 50.0%, which can be attributed to the partial disruption of the cellulose crystal structure. Aqueous ammonia treatment markedly promoted the enzymatic cellulose digestibility, increasing from 18 to 53% with an enzyme loading of 30FPU/g biomass. Supplementation of cellulase with xylanase (30FPU cellulase+100XU xylanase/g biomass) improved the final extent of hydrolysis and greatly enhanced the final glucose yield, approaching to 80% glucan conversion.

Photocatalytic oxidation of aqueous ammonia using atomic single layer graphitic-C3N4.

Direct utilization of solar energy for photocatalytic removal of ammonia from water is a topic of strong interest. However, most of the photocatalysts with effective performance are solely metal-based semiconductors. Here, we report for the first time that a new type of atomic single layer graphitic-C(3)N(4) (SL g-C(3)N(4)), a metal-free photocatalyst, has an excellent photocatalytic activity for total ammonia nitrogen (TAN) removal from water. The results demonstrated that over 80% of TAN (initial concentration 1.50 mg · L(-1)) could be removed in 6 h under Xe lamp irradiation (195 mW · cm(-2)). Furthermore, the SL g-C(3)N(4) exhibited a higher photocatalytic activity in alkaline solution than that in neutral or acidic solutions. The investigation suggested that both photogenerated holes and hydroxyl radicals were involved the TAN photocatalytic oxidation process and that the major oxidation product was NO3(-)-N. In addition, SL g-C(3)N(4) exhibited good photocatalytic stability in aqueous solution. This work highlights the appealing application of an inexpensive metal-free photocatalyst in aqueous ammonia treatment.

Behavior of cellulose and xylan in aqueous ammonia pretreatment.

The effect of aqueous ammonia on the solubilization of cellulose and xylans was investigated by detecting the amounts of reducing sugars and monosaccharides in the treatment liquors. The degree of cellulose and xylan solubilization increased with the increase of treatment temperature. When the treatment temperature increased from 20 to 90 °C, the amounts of reducing sugars released from Avicel and cellulose fiber by 21 % ammonia at a solid to liquid ratio of 1:10 for 24 h increased from 1.0 and 0.9 to 4.4 and 2.7 mg/g dry matter (DM), respectively. The amounts of reducing sugars released from wheat straw, beechwood, and oat spelt xylans increased from 1.2-7.0 to 3.3-13.5 mg/g DM. Xylans appeared to be more susceptible than cellulose in aqueous ammonia treatment. Structure analysis of untreated and treated Avicel and cellulose fiber showed that aqueous ammonia increased the specific surface area and crystallinity index of cellulose. Most of the cellulose and xylan that were solubilized existed in the form of oligomers such as cello-oligosaccharides and xylo-oligosaccharides. Xylobiose and xylotriose were the main oligosaccharides released from oat spelt xylan by aqueous ammonia treatment as confirmed by electrospray ionization-mass spectrometry. The results here indicated that a slight amount of cellulose and xylans was solubilized and low amounts of cellulase inhibitors, oligomers, were found during mild aqueous ammonia pretreatment process. Therefore, from the economical perspectives, mild ammonia pretreatment would be favorable for aqueous ammonia pretreatment of lignocelluloses.

Hierarchization of USY Zeolite by NH4OH. A Postsynthetic Process Investigated by NMR and XRD

Ammonia treatment of USY zeolite has led to a new hierarchical material. The local and global structural changes during the transformation have been monitored by XRD and by 1H, 29Si, and 27Al solid-state NMR. A wealth of 1D and 2D NMR protocols were applied, including 1H DQ–SQ (double-quantum–single-quantum), 27Al MQMAS (multiple-quantum magic angle spinning), 29Si MAS (magic angle spinning) and CPMAS (cross-polarization magic angle spinning), and 1H–29Si HETCOR (heteronuclear correlation). The effects of aqueous ammonia treatment, different thermal post-treatments, and rehydration were studied. An increasing loss of crystallinity was observed upon increasing duration of ammonia treatment. Under the experimental conditions, a few percent of silica was lost into solution and no loss of aluminum was observed. However, increasing numbers of silanol groups were detected. The progressive transformation induces formation of mesopores, reduction of the fraction of the sample exhibiting Bragg crystallinity, and apparition of a dense, amorphous aluminosilicate phase. The latter contains ammonium ions and strongly bound water, both of which are resistant to thermal decomposition up to 350 °C. After about 24 h of treatment, the zeolite fraction is completely transformed into the amorphous phase. At intermediate stages, a complex hierarchical material is obtained with mesopores and zeolitic micropores next to a dense amorphous aluminosilicate, containing ammonium ions, highly structured water, and silanol nests.

Bioconversion of novel substrate Saccharum spontaneum, a weedy material, into ethanol by Pichia stipitis NCIM3498

Rising fuel prices and environmental issues have paved the way for the exploration of cellulosic ethanol. However, challenges involving substrate hydrolysis and cost-effectiveness still limit the efficient bioconversion and utilization of cellulosic ethanol. We aimed to evaluate a cheaper and abundantly available wild sugarcane variety, Saccharum spontaneum, as the raw substrate for bioconversion of ethanol by Pichia stipitis NCIM3498. Three different strategies for substrate hydrolysis using acid (dilute sulfuric acid) and alkali (dilute sodium hydroxide) and aqueous ammonia (AA) treatment followed by enzymatic hydrolysis were studied. A maximum of 631.5±3.25 mg/g sugars with 89.38% hydrolytic efficiency (HE) could be achieved after enzymatic hydrolysis of AA-pretreated S. spontaneum. All the substrate hydrolysates were evaluated for ethanol conversion in batches by P. stipitis. The microbial fermentation of released sugars into ethanol showed (g/g) 0.36±0.011, 0.384±0.022, 0.391±0.02, and 0.40±0.01 yield from detoxified acid hydrolysate and acid-, NaOH- and AA-pretreated substrate S. spontaneum enzymatic hydrolysates, respectively.

Oriented Thin Films of Polyaniline by Friction Transfer Method

Oriented thin films of polyaniline (emeraldine base) were prepared by the friction transfer method by rubbing solid polyaniline against a glass substrate to form a thin coating film on the substrate. Characterization by polarized ultraviolet-visible-near infrared spectra showed the dichroic property of the films, suggesting that the polyaniline was oriented on the glass substrate. Hydrochloric acid treatment transformed the film into emeraldine salt without loss of orientation. Moreover, the oriented film of emeraldine base could be recovered by aqueous ammonia treatment of the emeraldine salt. The oriented film could also be doped with camphorsulfonic acid.

Morphology and dispersivity modulation of hollow microporous spheres synthesized by a hard template route

Uniform hollow microporous silica spheres (HMS) have been synthesized in an easy route using polystyrene spheres (PS) and cetyltrimethylammonium bromide (CTAB) as co-templates at room temperature in concentrated aqueous ammonia. The hexagonally ordered pore channels are formed on the shell of the HMS. Effects of various processing parameters such as the tetraethyl orthosilicate (TEOS) adding rate, the amount of aqueous ammonia and ultrasonic treatment, on the dispersivity and morphology, were investigated. The slow syringing addition of TEOS favors the formation of highly dispersed hollow spheres with a certain and uniform shell thickness. More aqueous ammonia and proper time of ultrasonic are helpful to the synthesis of uniform hollow silica spheres with good dispersivity. The morphology, dispersivity and micropore structure of as-synthesized HMS were characterized using X-ray diffraction, N 2 sorption isotherms, scanning electron microscope and transmission electron microscope.

Synthesis of Some Novel 2,4-Disubstituted Thiazoles as Possible Antimicrobial Agents

A series of 4-aryl-2-(3-methyl-7-substituted quinoxaline-2-one-1-yl)-1,3-thiazoles ( 6a–l ) and 4-substituted alkyl-2-(3-methyl-7-substituted quinoxaline-2-one-1-yl)-1,3-thiazoles ( 8a–i ) were synthesized in good yield by condensing 2-(3-methyl-7-substituted l,2-oxoquinoxalin-1(2H)-yl)ethanethioamides ( 5a–c ) with substituted phenacyl bromide and dichloroacetone followed by treatment with secondary amines, respectively. The intermediates, 5a–c were conveniently obtained by reacting phosphorus pentasulphide with 2-(3-methyl-7-substituted-2-oxoquinoxalin-1(2H)-yl) acetamides ( 4a–c ) which in turn were synthesized from ethyl (3-methyl-7-substituted-2-oxoquinoxalin-1(2H)-yl) acetates ( 3a–c ) by aqueous ammonia treatment. The newly synthesized compounds were characterized by IR, 1 H NMR, 13 C NMR, and Mass spectral and elemental analyses. These compounds were screened for in vitro antibacterial activity against five pathogenic strains and antifungal activity against four fungi. Preliminary results revealed that some of the synthesized compounds showed promising antimicrobial activity.

Fractionation of Flax Shives by Water and Aqueous Ammonia Treatment in a Pressurized Low-Polarity Water Extractor

Fractionation of flax shives into cellulose, hemicellulose, and lignin with a two-stage extraction process using water and aqueous ammonia was carried out in a pressurized low-polarity water extractor operated at different temperatures, flow rates, and ammonia concentrations. During the first stage with water, 84% of hemicellulose and 32% of lignin were removed at 190 degrees C at a flow rate of 1.5 mL/min for 30 min. During the second stage with aqueous ammonia, more than 77% of the lignin was removed, and hemicellulose removal reached 95% at 200 degrees C at a flow rate of 0.5 mL/min and with a solvent/feed ratio of 40 mL/g. The temperature and flow rate had a significant effect on lignin removal. The impact of additives (anthraquinone and hydrogen peroxide) and modifications (overnight soaking, reduced particle size, and elevated temperature) on lignin extraction was also studied. The combination of higher temperatures and reduced particle sizes resulted in enhanced lignin extraction. The extraction profiles of free phenolics (vanillin, acetovanillone, and vanillic acid) during the two-stage processing were monitored and compared with those of lignin.

Effects of urea and aqueous ammonia treatment on the composition and nutritive value of maize residues

Two trials were conducted to investigate changes in chemical composition and nutritive value of maize residues treated with urea and aqueous ammonia. In Experiment I, maize stalks, husks and cobs were chopped into pieces of approximately 1 cm length. Aqueous NH 3 (3%) and feed grade urea equivalent to 3% NH 3 were sprayed into 100 g duplicate samples on DM basis, thoroughly mixed, stored in plastic containers and kept for 3 week at ambient temperature (25–27 °C). Proximate composition and in vitro dry matter digestibility of test materials were determined. In Experiment II, 100 kg batches of the maize residues were chopped and treated as in Experiment I but stored in 205 l drums lined with black polythene sheet. Feed intake and nutrient digestibility of treated materials were evaluated with 18 mature WAD sheep averaging 19.8 kg BW. Treatment improved ( P < 0.05) intake and digestion coefficients for N, DM, NDF, ADF and OM but there were no differences ( P > 0.05) between aqueous NH 3 and urea treatments. Feed grade urea or the equivalent weight of fertilizer grade urea can be used to improve the nutritional value of maize residues for small ruminant feeding during off season periods.

Fractionation of corn stover by hot-water and aqueous ammonia treatment

The efficiency of biomass utilization can be significantly improved by fractionation of biomass. A two-stage percolation process was investigated for pretreatment and fractionation of corn stover. The two-stage process is composed of hot water treatment followed by treatment with aqueous ammonia, both applied in a flow-through (percolation) reactor. The first stage processing is intended for hemicellulose removal whereas the second stage is intended for delignification. The pretreated material was nearly pure cellulose and both reagents are cheap and environmentally friendly. The conditions that achieve satisfactory level of biomass fractionation and acceptable enzymatic hydrolysis were identified in terms of reaction temperature, flow rate (retention time) and reaction time for each stage. With proper operation of two-stage treatment, fractionation of biomass was achieved to the extent that the xylan fraction is hydrolyzed with 92–95% conversion, and recovered with 83–86% yields; and the lignin removal is 75–81%. The remaining solid after two-stage treatment contained 78–85% cellulose. The two-stage treatments enhanced the enzymatic digestibility to 90–96% with 60 FPU/g of glucan, and 87–89% with 15 FPU/g of glucan. In two-stage treatment, the composition and digestibility data indicate that the lignin content in the biomass is one of the major factors controlling the enzymatic digestibility.

Quenching of Porous Silicon Photoluminescence by Ammonia Hydrogen Peroxide Mixture

Low resistivity p‐type porous silicon (PS) samples are subjected to oxidation treatment in an ammonia hydrogen peroxide mixture (APM) and to etching in 0.00035% and 0.0014% ammonia solutions at room temperature for 10 to 2700 s. Photoluminescence (PL) properties of the treated PS are correlated with chemical states and microstructures analyzed by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The intensity of the red PL from PS is increased by 0.00035% ammonia solution, decreased by 0.0014% ammonia solution, and almost completely quenched by an APM. FTIR analysis shows that the ammonia solutions do not affect the chemical states of the PS surface, which is terminated primarily by hydrogen. Immersion in an APM replaces the hydrogen‐terminated surface with an oxygen‐terminated surface. SEM observations indicate that the thickness of the PS layer is reduced with aqueous ammonia treatment for 2700 s, but not with APM treatment. These results suggest that the PL quenching by an APM may relate to the dehydrogenated surface. © 2000 The Electrochemical Society. All rights reserved.

α-Chloroacetyl capping of peptides: an N-terminal capping strategy suitable for Edman sequencing

Use of an α-chloroacetyl group allows for the conditional N -terminal capping of peptides. This capping group is easily introduced and stable over a broad pH range, but can be converted to glycine by aqueous ammonia treatment in order to perform N -terminal Edman peptide sequencing.

Effects of pH on Nucleation and Crystal Growth Processes of Hydrous-Zirconia Fine Particles.

The formation retes of monoclinic hydrous-zirconia particles produced by the hydrolysis of ZrOCl2 solutions with and without an addition of aqueous ammonia or anion-exchange treatment were measured to clarify the effects of pH on the nucleation and crystal growth processes of hydrous zirconia. At pH ranges below 1.2, the crystal growth rate of primary particles of hydrous-zirconia increased monotonously with increasing pH, but the nucleation rate was independent of pH. When the pH was kept at around neutrality, amorphous hydroxide formed. The tendency of crystal growth rate of primary particles to increase at low pH can be explained by the blocking action for crystal growth of Cl- ions attracted on the particle surface, through the formation of an electric double layer.

Synthesis of Quaternary 1-[2-(Phosphonomethoxy)ethyl] Derivatives of 2,4-Diaminopyrimidine and Related Acyclic Nucleotide Analogs

Quaternization of 2,4-diaminopyrimidine (2) by diisopropyl 2-chloroethoxymethanephosphonate (3) followed by bromotrimethylsilane treatment and subsequent hydrolysis gave zwitterionic N1-[2-(phosphonomethoxy)ethyl] derivative, hydrogen {[2-(2,4-diaminopyrimidin-1-io)ethoxy]methyl}phosphonate (5). Its structure was confirmed by X-ray crystallography. The same product was obtained from 2-amino-4-[(dimethylaminomethylene)amino]pyrimidine (6) by an analogous reaction sequence followed by an aqueous ammonia treatment after the transsilylation reaction. Also the quaternizations of 4,6-diaminopyrimidine (7) and 2,4,6-triaminopyrimidine (8) with the halo derivative 3 afforded the zwitterionic N1-substituted compounds 9 and 10, respectively. In contrast to this regiospecific reaction, 2-aminopyrimidine (11) gave on treatment with compound 3 and following deprotection the exo-N2-isomer 13. This compound was also obtained by the reaction starting from 2-[(dimethylaminomethylene)amino]pyrimidine (12) which was prepared by treatment of compound 11 with dimethylformamide dineopentyl acetal. Also 2,3-diaminopyridine (14) gave by the above reaction a mixture of 2-amino-3-{[2-(phosphonomethoxy)ethyl]amino}pyridine (15) and quaternary N1-[2-(phosphonomethoxy)ethyl] derivative (16). None of these analogs of the antiviral PMEDAP exhibited any antiviral activity against DNA viruses or retroviruses, nor any cytostatic activity.