Addition Of KOH Research Articles

Characterization of the C-terminal Domain of a Potassium Channel from Streptomyces lividans (KcsA)

KcsA, a potassium channel from Streptomyces lividans, is a good model for probing the general working mechanism of potassium channels. To date, the physiological activator of KcsA is still unknown, but in vitro studies showed that it could be opened by lowering the pH of the cytoplasmic compartment to 4. The C-terminal domain (CTD, residues 112-160) was proposed to be the modulator for this pH-responsive event. Here, we support this proposal by examining the pH profiles of: (a) thermal stability of KcsA with and without its CTD and (b) aggregation properties of a recombinant fragment of CTD. We found that the presence of the CTD weakened and enhanced the stability of KcsA at acidic and basic pH values, respectively. In addition, the CTD fragment oligomerized at basic pH values with a transition profile close to that of channel opening. Our results are consistent with the CTD being a pH modulator. We propose herein a mechanism on how this domain may contribute to the pH-dependent opening of KcsA.

Modulation of Optical Properties of Gold Nanorods on Addition of KOH

Gold nanorods are known to exhibit two distinct surface plasmon oscillations namely, transverse and longitudinal bands corresponding to oscillations of conduction electrons along width and length of gold nanorods. Considerable changes in these surface plasmon resonance peak positions occurred when KOH was added to the nanorod solution. Nanorods with initial longitudinal plasmon band at 739, 796, and 895 nm are studied with variation in KOH concentration. While the longitudinal plasmon resonance peak showed blue shift, transverse plasmon resonance peak exhibited only intensity variations. Changes could be attributed to the shape transition of gold nanorods on variation of pH in the solution. Shape transition of gold nanorods is confirmed by transmission electron microscopy images.

Nature of the Aqueous Hydroxide Ion Probed by X-ray Absorption Spectroscopy

X-ray absorption spectra of aqueous 4 and 6 M potassium hydroxide solutions have been measured near the oxygen K edge. Upon addition of KOH to water, a new spectral feature (532.5 eV) emerges at energies well below the liquid water pre-edge feature (535 eV) and is attributed to OH- ions. In addition to spectral changes explicitly due to absorption by solvated OH- ions, calculated XA spectra indicate that first-solvation-shell water molecules exhibit an absorption spectrum that is unique from that of bulk liquid water. It is suggested that this spectral change results primarily from direct electronic perturbation of the unoccupied molecular orbitals of first-shell water molecules and only secondarily from geometric distortion of the local hydrogen bond network within the first hydration shell. Both the experimental and the calculated XA spectra indicate that the nature of the interaction between the OH- ion and the solvating water molecules is fundamentally different than the corresponding interactions of aqueous halide anions with respect to this direct orbital distortion. Analysis of the Mulliken charge populations suggests that the origin of this difference is a disparity in the charge asymmetry between the hydrogen atoms of the solvating water molecules. The charge asymmetry is induced both by electric field effects due to the presence of the anion and by charge transfer from the respective ions. The computational results also indicate that the OH- ion exists with a predominately "hyper-coordinated" solvation shell and that the OH- ion does not readily donate hydrogen bonds to the surrounding water molecules.

A new environmental friendly clay catalyst for one-pot coiodination and epoxidation of alkenes

The commercial Brazilian clay Bentonit Brasgel™ was characterized by chemical and textural analyses, XRD, and 27Al and 29Si MAS-NMR, that indicated the presence of alpha-quartz and smectite as clay-minerals. This natural clay proved to be an efficient catalyst for the conversion of alkenes into epoxides by the reaction with iodine/water followed by in situ addition of KOH in hexane (80-91 % yield). Similar results were obtained with Bentonit Brasgel™ intercalated with Ag(I).

The preferential oxidation of CO in excess hydrogen: A study of the influence of KOH/K 2CO 3 on CuO–CeO 2− x catalysts

The preferential oxidation of CO in rich hydrogen has been studied for CuO–CeO 2− x catalysts. The catalysts were prepared by co-precipitation with K 2CO 3 + KOH as precipitators and characterized using N 2 physisorption isotherms, high resolution transmission electron microscopy (TEM), and X-ray diffraction (XRD). The results indicate that nano-structured CuO–CeO 2− x catalysts are obtained, and that the ratio of KOH/K 2CO 3 has a beneficial influence on the properties of CuO–CeO 2− x catalysts, i.e., with the addition of KOH, the particle sizes grow smaller, CuO–CeO 2− x catalysts have larger surface areas, CuO species in CuO–CeO 2− x are more easily reduced and achieve higher catalytic performance in the preferential oxidation of CO in rich hydrogen. CO conversion higher than 99% with O 2 selectivity of 100% is obtained for CuO–CeO 2− x catalysts with KOH/K 2CO 3 equal to 4:0 at a temperature of 90–110 °C and a space velocity of 30,000–120,000 ml g −1 h −1.

A Method for Estimating the Relative Degree of Saponification of Xanthophyll Sources and Feedstuffs

Saponification of xanthophyll esters in various feed sources has been shown to improve pigmentation efficiency in broiler skin and egg yolks. Three trials were conducted to evaluate a rapid liquid chromatography procedure for estimating the relative degree of xanthophyll saponification using samples of yellow corn, corn gluten meal, alfalfa, and 6 commercially available marigold meal concentrates. In each trial, samples were extracted using a modification of the 1984 Association of Official Analytical Chemists hot saponification procedure with and without the addition of KOH. A comparison of the chromatography results was used to estimate percent saponification of the original sample by dividing the nonsaponified extraction values by the saponified extraction values. A comparison of the percent saponified xanthophylls for each product (mg/kg) was: yellow corn, 101; corn gluten meal, 78; alfalfa, 97.9; and marigold concentrates A through F, 99.8, 4.6, 99.0, 95.6, 96.8, and 6.6, respectively. These results indicate that a modification of the 1984 Association of Official Analytical Chemists procedure and liquid column chromatography can be used to quickly verify saponification and can be used to estimate the relative degree of saponification of an unknown xanthophyll source.

Physicochemical Properties of Alkaline Aqueous Sodium Metaborate Solutions

Background: The transition to a hydrogen fuel economy is hindered by the lack of a practical storage method and concerns associated with its safe handling. Chemical hydrides have the potential to address these concerns. Sodium borohydride (sodium tetrahydroborate, NaBH4), is the most attractive chemical hydride for H2 generation and storage in automotive fuel cell applications, but recycling from sodium metaborate (NaBO2), is difficult and costly. An electrochemical regeneration process could represent an economically feasible and environmentally friendly solution. Method of Approach: We report a study of the properties of concentrated NaBO2 alkaline aqueous solutions that are necessary to the development of electrochemical recycling methods. The solubility, pH, density, conductivity, and viscosity of aqueous NaBO2 solutions containing varying weight percentages (1, 2, 3, 5, 7.5, and 10wt.%) of alkali hydroxides (NaOH, KOH, and LiOH) were evaluated at 25°C. The precipitates formed in supersaturated solutions were characterized by x-ray diffraction and scanning electron microscopy. Results: All NaBO2 physicochemical properties investigated, except solubility, increased with increased hydroxide ion concentration. The solubility of NaBO2 was enhanced by the addition of KOH to the saturated solution, but decreased when LiOH and NaOH were used. The highest ionic conductivity (198.27S∕m) was obtained from the filtrate of saturated aqueous solutions containing more than 30wt.%NaBO2 and 10wt.% NaOH prior to filtration. At 10wt.% hydroxide, the viscosity of the NaBO2 solution was the highest in the case of LiOH (11.38 cP) and lowest for those containing NaOH (6.37 cP). The precipitate was hydrated, NaBO2 for all hydroxides, but its hydration level was unclear. Conclusions: The use of KOH as the electrolyte was found to be more advantageous for the H2 storage and generation system based on NaBO2 solubility and solution half-life. However, the addition of NaOH led to the highest ionic conductivity, and its use seems more suitable for the electroreduction of NaBO2. Further investigations on the impact of KOH and NaOH on the electroreduction of NaBO2 in aqueous media have the potential to enhance the commercial viability of NaBH4.

Synthesis and crystal structures of supramolecular compounds of polynuclear aluminum(III) aqua hydroxo complexes with cucurbit[6]uril

Supramolecular compounds of the di-, trideca-, and triacontanuclear aluminum aqua hydroxo complexes, viz., [Al2(OH)2(H2O)8]4+, [Al12(AlO4)(OH)24(H2O)12]7+, and [Al30O8(OH)56(H2O)26]18+, respectively, with the organic macrocyclic cavitand cucurbit[6]uril (C36H36N24O12) were prepared by evaporation of aqueous solutions of aluminum nitrate and cucurbit[6]uril after the addition of pyridine, ammonia, KOH, or NaOH at pH 3.1–3.8. X-ray diffraction study demonstrated that the aqua hydroxo complexes are linked to the macrocycle through hydrogen bonds between the hydroxo and aqua ligands of the polycations and the portal oxygen atoms of cucurbit[6]uril.

Semi-Continuous Gas-Liquid Phase-Transfer Catalyzed Reaction of o-Phenylene Diamine and Carbon Disulfide by Tertiary Amines and in the Presence of Potassium Hydroxide

The phase-transfer catalyzed reaction of o-phenylene diamine and carbon disulfide to synthesize 2-mercaptobenzimidazole (MBI) in a gas/alkaline solution of KOH two-phase medium was carried out in a semi-continuous reactor. Tributylamine of competitive price was employed as the catalyst to promote the reaction rate. The reaction is also enhanced by the addition of KOH to the reaction mixture. Gas-phase carbon disulfide of higher temperature is continuously introduced to the reactor for the reaction. The main advantage of the present system is that the reaction is carried out at relatively high temperature in the semi-continuous reactor. Carbon disulfide first dissolves in the organic phase and reacts with tertiary amine in the organic-phase solution to produce an active intermediate (R3N–CS2). Then, this active intermediate further reacts with o-phenylene diamine to produce the desired product MBI. Based on the experimental observation, a reaction mechanism is proposed. A kinetic model which considered the two-step reaction was developed. A pseudo first order rate law is sufficient to describe the reaction. The effect of the reaction conditions, such as: the amount of tributylamine (TBA), agitation speed, initial concentration of carbon disulfide, flow rate of gas phase, amount of o-phenylene diamine and temperature, on the conversion and the apparent rate constant are investigated in detail.

High-performance electric double-layer capacitors using mass-produced multi-walled carbon nanotubes

Mass-produced multi-walled carbon nanotubes (MWNTs, which have the trademark VGNF®) have been investigated for their potential for use in electric double-layer capacitors (EDLCs). The variation aspects of these MWNTs by KOH activation showed quite interesting features. The gravimetric capacitance enhancement and specific surface area on KOH activation increased linearly. However, the capacitance per unit surface area has a maximum at 200 wt. % of KOH addition. The VGNF-KOH 500 sample exhibits a capacitance enhancement as much as 13 times greater (28.3 F/g) than that of the as-grown materials (2.2 F/g), under the conditions of charging up to 3.5 V and discharging at a current density of 10 mA/cm2. Interestingly, for this MWNT (VGNF®), selective attack on its amorphous carbon impurity has also been observed, as demonstrated from both scanning electron microscopy observations and Raman spectra. Consequently, the results of this study will provide insight into the potentiality of using MWNTs for EDLC electrodes, which would enable the cheapest production cost among the various types of carbon nanotubes.

Synthesis, Chiroptical Properties, and pH Responsibility of Aspartic Acid- and Glutamic Acid-Based Helical Polyacetylenes

l-Aspartic and l-glutamic acid-based novel N-propargylamides, (S)-HC⋮CCH2NHCOCH(CH2COOcyclohexyl)NHCOOt-Bu (1) and (S)-HC⋮CCH2NHCOCH(CH2CH2COOcyclohexyl)NHCOOt-Bu, were synthesized and polymerized using a rhodium catalyst. The corresponding polymers [poly(1) and poly(2)] with moderate molecular weights were obtained in good yields. CD and UV−vis spectroscopic analyses revealed that poly(1) and poly(2) took helical structures, whose tightness was different. The presence of intramolecular hydrogen bonding was confirmed by liquid-state IR spectroscopy. Poly(1a) and poly(2a) carrying free carboxyl groups were obtained by alkaline hydrolysis of poly(1) and poly(2). Poly(1a) did not form a helix, while poly(2a) formed a helix undergoing inversion of helical sense and change of tightness upon addition of KOH.

Variation in microbiologic profiles among pregnant women with bacterial vaginosis

The purpose of this study was to determine if clinical findings and sociodemographic variables among bacterial vaginosis (BV)-positive pregnant women are associated with different microbiologic profiles. Pregnant women were assessed for BV by Nugent criteria. BV+ women were separated into 6 mutually exclusive microbiologic groups. In unadjusted analyses, we compared (1) sociodemographic and behavioral characteristics, and (2) 3 clinical characteristics among BV+ women with and without Mobiluncus (M+ vs M-). Unadjusted data were analyzed using the chi-square test. Multiple logistic regression was used to assess the likelihood of having clinical signs of BV in women with and without Mobiluncus spp while controlling for confounders. A total of 1756 BV+ pregnant women were followed. The M+ group (n=702) was significantly more likely than the M- group (n=1054) to be non-Hispanic black (80.9% vs 66.2%; P < .0001), older than 21 years (61.7% vs 48.7%; P < .0001), and to have had more than 3 lifetime sexual partners (66.4% vs 54.9%; P < .0001). The M+ group was also more likely to have clue cells on wet mount (63.9% vs 47.2%; P < .0001) and a positive amine odor after addition of KOH (57.2% vs 45.0%; P=.001). There was no difference in other demographic variables or physician diagnosis of abnormal vaginal discharge. In the adjusted analyses for each clinical outcome, all findings were consistent with the unadjusted analyses. BV+ pregnant women with Mobiluncus spp are more likely to have clue cells present on wet mount, a positive amine odor after KOH preparation, and to be older, non-Hispanic black, and have had more lifetime sexual partners compared to BV+ women without any Mobiluncus species.

Influence of steam sterilisation on soil chemical characteristics, trace metals and clay mineralogy

Soil sterilisation with steam under pressure and additives, such as CaO or KOH that react exothermically in water, is an alternative technology to fumigants. The influence of soil sterilisation (system ‘Bioflash’, Ecoflash SC 600) on the chemical behaviour of organic matter, heavy metals (Cd, Cu, Zn and Pb) and clay mineralogy was investigated on three typical soil materials (Ap horizons) with different carbonate contents. These materials were treated in the laboratory in wooden containers. Soil heating produced temperatures ranging between 60–80 °C for at least 20 min. The treatment generally seemed to increase the pH values and may lead in the long-term to a certain alkalisation with high dosages of CaO or KOH. The effects of the CaO treatment on the K and Ca speciation in the soil were rather small, whereas those of the KOH treatment were more pronounced for K. The addition of KOH favoured the fixation of K in the interlayers of smectite. The XRD measurements were in agreement with the chemical speciation of K. The K chemistry was affected by the treatment by higher contents of the fixed fraction. Organic matter partially decreased after the soil heating treatment. The behaviour of the heavy metals was also affected. In some cases, the EDTA-extractable fractions of Cu, Zn or Pb as well as the soluble fractions of Cu and Zn were distinctly changed after the treatment. The soil-heating treatment probably affected the type and amount of organic ligands and also the adsorbing surfaces that control the solubility of the heavy metals. The heavy metal solubility, however, still remained low after the treatment. The effects of the soil sterilisation on the chemical and mineralogical properties did not seem to be dramatic. It is, however, difficult to predict possible changes if the treatment is repeated over years to decades. We presume that there might be quite substantial effects (especially on the behaviour of organic matter under certain circumstances) in the long term if, as seen at some sites, changes (i.e. decrease) are already measurable after one treatment. Mulching or the addition of organic manure would be possible measures to counter a destabilisation of the soil (i.e. increase in soil erosion susceptibility) and a continuous disintegration of the organic matter pool.

Low-dose secnidazole in the treatment of bacterial vaginosis

Objective To determine whether bacterial vaginosis could be cured with a single 1-g oral dose of secnidazole. Material and methods A total of 80 women were recruited at the outpatient gynecologic clinic of Manuel Noriega Hospital, Maracaibo, Venezuela. Diagnosis and patient enrollment were based on the Amsel criteria. The participants were randomized to 2 groups. In group 1 ( n=44) participants received a single 1-g oral dose and in group 2 ( n=32) participants received a single 2-g oral dose of secnidazole. Clinical cure was defined as the absence of the characteristic symptoms (a bad odor and a grossly abnormal discharge) and at least 2 of the following: vaginal pH less than 4.5, no fish odor on addition of KOH, and no Gardnerella vaginalis or clue cells on wet-mount examination. Cytologic cure was defined as an absence of G. vaginalis on a Papanicolaou (Pap) smear. Results Clinical cure was experienced by 95.5% of the women who received the 1-g oral dose and by 97.4% of the women who received the 2-g oral dose of secnidazole. There was no significant difference between the groups in the clinical resolution of bacterial vaginosis. Following treatment, results were negative for G. vaginalis in 94.7% of the women. In group 1, 41 women (93.2%), and in group 2, 31 women (96.9%) had cytologic cure. The Pap smear revealed G. vaginalis in 3 of the women in group 1 and 1 of the women in group 2 ( P=0.47). Twenty-seven women (35.5%) reported mild side effects. More women had adverse effects in group 1 ( n=16) than in group 2 ( n=11) but this difference was not statistically significant. Conclusion This clinical study showed that a single 1-g oral dose of secnidazole is effective to cure bacterial vaginosis associated with G. vaginalis.

The Nature of Co in Synthetic Co-substituted Goethites

AbstractThe crystallochemical features of Co in Co-substituted goethite solid-solutions prepared by two different procedures have been studied using infrared, X-ray photoelectron and electron energy loss spectroscopies. It was found that the path followed for the synthesis of Co-substituted goethite determines the oxidation state of Co in the goethite structure. Thus, in the solid-solution prepared by precipitation with Na2CO3 of an Fe(II) aqueous solution containing Co(II) cations, followed by the aerial oxidation of the precipitate, the Co cations were found to be divalent, whereas trivalent Co was incorporated into the goethite obtained by ageing a solution containing Fe(III) and Co(II) cations precipitated by the addition of KOH. This different behavior is explained by the higher pH of goethite formation in the latter case, which favors the oxidation of the Co(II) cations.

Synthese und Reaktionsverhalten von {[Hf](μ-σ,π-C≡CR)2 }Ni(CO); die Röntgenstrukturanalyse von [(η5-C5H4SiMe3)2Hf(C≡CtBu)]2O / Synthesis and Reaction Behaviour of {[Hf](μ −σ ,π -C≡CR)2}Ni(CO); the Solid-State Structure of [(η5–C5H4SiMe3)2Hf(C≡CtBu)]2O

Abstract The synthesis of the heterobimetallic hafnium(IV)-nickel(0) complexes {[Hf](μ-σ ,π- C≡CR)2}Ni(CO) (3a, [Hf] = (η5-C5H5)2Hf, R = Ph; 3b, [Hf] = (η5-C5H4SiMe3)2Hf, R = tBu) in which an early (Hf) and a late (Ni) transition metal atom are bridged by σ - and π-bound alkynyl groups succeeds by treatment of [Hf](C≡CR)2 (1a, [Hf] = (η5-C5H5)2Hf, R = Ph; 1b, [Hf] = (η5-C5H4SiMe3)2Hf, R = tBu) with equimolar amounts of Ni(CO)4 (2). The reaction chemistry of 1and 3towards different substrates is discussed. Treatment of 3bwith P(OMe)3 (4a) affords the mononuclear nickel monocarbonyl complex Ni(CO)[P(OMe)3]3 (5), while the reaction of 1aor 1bwith MCl2 (6a, M = Fe; 6b, M = Ni; 6c, M = Co) produces by an cyclopentadienyl transfer from hafnium to M the sandwich compounds (η5-C5H4R’)2M (M = Fe: 7a, R’ = H; 7b, R’ = SiMe3; M = Ni: 7c, R’ = H; 7d, R’ = SiMe3; M = Co: 7e, R’ = H). Addition of KOH to 1b or 3b, respectively, affords the homobimetallic hafnium complex {[Hf](C≡CR)}2O (8) in which two [Hf](C≡CR) fragments are bridged by an oxygen atom. Possible reaction mechanisms for the formation of 5, 7and 8by starting from 1or 3will be given. The result of the X-ray structure analysis of 8is reported. Complex 8crystallises in the monoclinic space group C2/c with the cell parameters a = 24.437(8), b = 14.655(5), c = 14.123(4) Å, β = 101.67(2)◦, V = 4953(3) Å3, Z = 4 and D = 1.454 g cm−3. Complex 8contains a linear Hf-O-Hf unit with pseudo-tetrahedral coordinated hafnium atoms.

Force measurements between Teflon AF and colloidal silica particles in electrolyte solutions

The interaction force between a very hydrophobic polymer surface and colloidal silica particles with a roughness of 10–15 nm has been measured in aqueous solutions of KOH and KCl using an atomic force microscope. The interaction can be described according to the DLVO theory by an electrical double-layer force that is repulsive at long distances and attractive at short distances and an attractive van der Waals force. The electrical double-layer potentials are compared to the zeta potentials of Teflon AF and the silica spheres. The roughness of the silica particles leads to an underestimation of the short-range attraction and the surface potential. Both KCl and KOH solutions affect the potential of the interacting surfaces. OH − ions that adsorb preferentially to the Teflon AF surface create higher potentials than Cl − ions. Range and strength of the attractive interaction are not affected by KCl solutions but reduced by addition of KOH. This can be explained by decreasing potential differences between the silica sphere and Teflon AF with increasing KOH concentration. In addition, the preferential adsorption of OH − ions may lead to a reduction of the van der Waals interaction. The presence of nanobubbles, too, might play a role.

Role of base addition in the liquid-phase hydrodechlorination of 2,4-dichlorophenol over Pd/Al 2O 3 and Pd/C

The aqueous-phase batch hydrodechlorination (HDC) of 2,4-dichlorophenol (2,4-DCP), over 1 wt/wt% Pd/Al 2O 3 and Pd/C has been investigated with/without the addition of NaOH, NH 4OH, LiOH, KOH, RbOH, and CsOH; bulk solution pH spanned the range 1.5–13. The reaction was operated in the kinetic-controlled regime with 2-chlorophenol (2-CP) as the only intermediate partially dechlorinated product which reacts further to yield phenol; cyclohexanone was formed over Pd/Al 2O 3, but not Pd/C, prior to the completion of dechlorination. An increase in fractional dechlorination with the addition of base was observed and can be attributed to a suppression of HDC inhibition due to the HCl that is generated. The initial HDC activity and selectivity delivered by both catalysts were pH dependent and differences in response to bulk solution pH variations are discussed in terms of the nature of the reactive species in solution and the amphoteric behavior of the Pd supports. The Pd/Al 2O 3 catalyst is characterized by a high surface charge density while Pd/C bore a low basic functionality density on a high surface area carrier. A maximum initial HDC rate over Pd/Al 2O 3 was attained at pH 7–9 while a higher pH (⩾9) results in more effective HDC for Pd/C, effects that are linked to chloroarene dissociation and surface charge effects. In the case of Pd/C, the initial HDC rate with the addition of alkali metal hydroxide ( 0.074 mol dm −3 ) increased in the order Li +≈Na +<K +≈Rb +<Cs +, a sequence that matches the adsorption affinity on a negatively charged carbon surface; HDC over Pd/Al 2O 3 was insensitive to the nature of the alkali metal cation. The action of NH 4OH, as a weak base, is also considered.

Structural features necessary to obtain a high specific capacitance in electric double layer capacitors

Two classes of carbon materials with different microstructures were chosen for electric double layer capacitors (EDLCs). One is a mesophase pitch-based carbon fiber (MPCF). The other is an isotropic pitch-based carbon fiber (IPCF). Both series of samples were activated by KOH with varying the KOH addition fraction. The MF-series prepared from MPCFs by several KOH fractions exhibited a good capacitance in comparison with the IF-series prepared from IPCFs, although the former had smaller specific surface areas than those of the latter. The specific capacitance per weight (F/g) of both samples increased with an increase in KOH fraction. Further evaluation of the capacitance using the specific capacitance per unit area elucidates the efficiency of the surface area. The MF-series prepared by the addition of 200–250 wt.% KOH showed a larger capacitance per unit volume and surface area under the same charge/discharge conditions, despite their smaller specific surface areas.

Reduction of no by low-volatile coal chars with or without catalyst addition

NO reduction by lean coal chars with emphasis on the effect of adding the catalyst KOH to the chars on the NO reduction efficiency was studied. The experiments were conducted in a drop-tube furnace at temperatures of 1173-1323 K under fuel-rich conditions. Experimental data for the NO reduction efficiency obtained by using the lean coal chars containing different KOH contents are compared and, thus, the effort of KOH addition on the NO reduction can be revealed. Experimental results show that the NO reduction ability of the original lean coal char is very poor, but the NO reduction efficiency can be enhanced appreciably when KOH is added into the char. This can be explained by the fact that KOH can strongly catalyze the NO reduction by the lead coal char under fuel-rich conditions. Gas temperature and oxygen concentration in the reaction area are also shown to be important parameters influencing the NO reduction.