Adsorption Characteristics of Microporous Carbons from Apricot Stones Activated by Phosphoric Acid

Crushed apricot stone shells were impregnated with varying H₃PO₄ acid concentrations (20–50 wt%), followed by carbonisation at 573–773 K. The products were characterised by nitrogen gas adsorption. Analysis of the nitrogen isotherms by the DR and α_s methods proved that most of the obtained carbons are highly microporous, with high surface areas (⩾1000 m² g^-1) and very low mesoporosity. Increasing acid concentration, at 573 and 673 K, increases surface area and pore volume, whereas at 733 K a small decrease in both parameters appears at higher H₃PO₄ concentrations. Whole apricot stones produce activated carbon of inferior porous characteristics. Development of the extensive pore structure was described in light of the effect of H₃PO₄ on the lignocellulosic mataerial during carbonisation.     

Activated carbon from sugar cane bagasse by carbonization in the presence of inorganic acids

Dried ground bagasse, impregnated with 50% inorganic acids and carbonized at 500°C, showed the sequence H₃PO₄ > H₂SO₄ > HCl > HNO₃, with respect to the efficiency of activation. Treatment with phosphoric acid of various concentrations (30–50 wt%) was followed by carbonization at 300–500°C for 3 h. Pore structure parameters were determined from the low-temperature adsorption of nitrogen, by applying the BET and α_s methods. Activated carbons obtained at low temperatures are essentially microporous with a low degree of mesoporosity. At higher temperatures products of higher surface area and total pore volume with developed mesoporosity and low microporosity are formed. An increase in the period of carbonization leads to a small decrease in both surface area and pore volume. Activated carbons with surface areas > 1000 m² g^?1 and mean pore dimensions around 2·0 nm, suitable for various purposes, are thus obtained.     

Resin modification on interlaminar shear property of carbon fiber/epoxy/nano‐CaCO3 hybrid composites

Epoxy resin was modified by adding a silane coupling agent/nano‐calcium carbonate master batch. Then, samples of binary carbon fiber/epoxy composites and ternary fiber/nano‐CaCO₃/epoxy were prepared by hot press process. The interlaminar shear strength (ILSS) of the carbon fiber/epoxy composites was investigated and the results indicate that introduction of the treated nano‐CaCO₃ enhances ILSS obviously. In particular, the addition of 4 wt% nano‐CaCO₃ leads to 36.6% increase in the ILSS for the composite. The fracture surfaces of the carbon fiber/epoxy composites and the mechanical properties of epoxy resin cast are examined and both of them are employed to explain the change of ILSS. The results show that the change of ILSS is primarily due to an increase of the epoxy matrix strength and an increase of the fiber/epoxy interface. The bifurcation of propagating cracks, stress transfer, and cavitation are deduced for the reasons of strengthening and toughening effect of nano‐CaCO₃ particles. POLYM. COMPOS., 38:2035–2042, 2017. © 2015 Society of Plastics Engineers     

Barium titanate‐based nanodielectrics of two chemically recyclable thermosets

In this work was investigated the effect of the addition of barium titanate (BaTiO₃) on electrical properties of two chemically recyclable thermosets, polyhemiaminal (PHA) and polyhexahydro‐s‐triazine (PHT), both fabricated from 4,4′‐oxydianiline (ODA), an ether derivative of aniline and paraformaldehyde. Thermal and mechanical properties as well as chemical recyclability of the two polymers and their nanocomposites/nanodielectrics were also investigated. In addition, a quantitative analysis was conducted of the nanoparticle dispersion in the PHA‐/PHT‐based BaTiO₃‐containing nanocomposites using transmission electron microscopy imaging and the nearest‐neighbor distance index and this index was used to analyze the investigated properties in connection with the proper mechanisms. Regarding the electrical properties for both neat polymers, conductivity values of the order of 10^?8 S m^?1 at 100 Hz were observed and dielectric constant values close to 2.80 for both polymers at 1 kHz. The addition of 0.5 wt% of BaTiO₃ ferroelectric nanoparticles increased by about 44% the dielectric constant (1 kHz) and conductivity (10² Hz) of the PHA‐based nanocomposite. PHA and PHT exhibited glass transition temperature (T_g) values in the range 125–180 °C. An increase of 7 °C in T_g was observed after the incorporation of 0.5 wt% of BaTiO₃ into PHA. Concerning the mechanical properties, values in the range 4.00–4.45 GPa for reduced modulus and 0.30–0.43 GPa for nanohardness for PHA and PHT polymers were observed. Independently of filler content or polymer matrix, both mechanical properties were enhanced after the addition of BaTiO₃. The chemical recycling of PHA/PHT and all nanocomposites in the initial ODA reagent after sulfuric acid treatment was successfully characterized using the NMR and Fourier transform infrared spectroscopic techniques. © 2018 Society of Chemical Industry     

The effect of graphene nanoplatelet thickness on the fracture toughness of Si3N4 composites

Si₃N₄ composites with 3 and 5?wt% of graphene nanoplatelet (GNP) additions were prepared by spark plasma sintering. We used both commercially available GNPs and thinner few-layer graphene nanoplatelets (FL-GNPs) prepared by further exfoliation through ball milling with melamine addition. We found that by employing thinner FL-GNPs as filler material a 100% increase in the fracture toughness of Si₃N₄/3?wt% FL-GNP composites (10.5?±?0.2?MPa?m^1/2) can be achieved as compared to the monolithic Si₃N₄ samples (5.1?±?0.3?MPa?m^1/2), and 60% increase compared to conventional Si₃N₄/3?wt% GNP composites (6.6?±?0.4?MPa?m^1/2). For 5?wt% filler content the increase of the fracture toughness was near 50% for both GNP and FL-GNP fillers. The hardness of the composites decreased with increasing GNP content. However, composites reinforced with 5?wt% of FL-GNPs displayed 30% higher Vickers hardness (12.8?±?0.2?GPa) than their counterparts comprising conventional GNP fillers (9.8?±?0.2?GPa). We attribute the enhanced mechanical properties obtained with thinner FL-GNPs to their higher aspect ratio leading to a more homogeneous dispersion, higher interface area, as well as smaller pores in the ceramic matrix.     

Mechanical properties of carbon fiber composites modified with nano-SiO2 in the interphase

The performance of carbon fibers-reinforced composites is dependent to a great extent on the properties of fiber–matrix interface. To improve the interfacial properties in carbon fibers/epoxy composites, nano-SiO₂ particles were introduced to the surface of carbon fibers by sizing treatment. Atomic force microscope (AFM) results showed that nano-SiO₂ particles had been introduced on the surface of carbon fibers and increase the surface roughness of carbon fibers. X-ray photoelectron spectroscopy (XPS) showed that nano-SiO₂ particles increased the content of oxygen-containing groups on carbon fibers surface. Single fiber pull-out test (IFSS) and short-beam bending test (ILSS) results showed that the IFSS and ILSS of carbon fibers/epoxy composites could obtain 30.8 and 10.6% improvement compared with the composites without nano-SiO₂, respectively, when the nano-SiO₂ content was 1 wt % in sizing agents. Impact test of carbon fibers/epoxy composites treated by nano-SiO₂ containing sizing showed higher absorption energy than that of carbon fibers/epoxy composites treated by sizing agent without nano-SiO₂. Scanning electron microscopy (SEM) of impact fracture surface showed that the interfacial adhesion between fibers and matrix was improved after nano-SiO₂-modified sizing treatment. Dynamic mechanical thermal analysis (DMTA) showed that the introduction of nano-SiO₂ to carbon fibers surface effectively improved the storage modulus of carbon fibers/epoxy.     

Prediction of microbial growth rate in biofilters by using the nutrient diffusion coefficient

In this study, an optimal process for preparing a synthetic filter material with nitrogen nutrient (PVA/peat/KNO₃ composite beads) was developed for biofiltration and the optimal initial nitrogen concentration of the boric acid and phosphate aqueous solutions was found to be 3.94 and 1.52 g nitrogen L^?1, respectively. The water‐soluble nitrogen content in the prepared composite beads was higher than that of the compost. The mass transport process for the water‐soluble nitrogen dissolving out of the composite beads occurred in two stages: external mass transport occurred in the early stage and an intraparticle diffusion process occurred in the long‐term stage. The rate of water‐soluble nitrogen dissolving out during the external mass transport process increased with increasing the concentration of KNO₃ aqueous solution and that during the intraparticle diffusion process had a maximum value for the composite beads that had been immersed in 0.384 M KNO₃. The path of water‐soluble nitrogen dissolving out from the composite beads was that the water‐soluble nitrogen dispersed in the peat phase firstly diffused into the outer poly(vinyl alcohol) (PVA) phase and then it diffused out of the bead surface. The percentage of volatile organic compounds (VOCs) removed by the biofilter from an air stream remained above 99% for 230 days for the composite beads that had been immersed in KNO₃ before packing. The microbial growth rate had a maximum value for the composite beads that had been immersed in 0.384 M KNO₃ and was higher than that of the compost by a factor of 1.49. The rate of nitrogen dissolving out during the intraparticle diffusion process could be used as an index to predict the microbial growth rate in the biofilter. Copyright © 2005 Society of Chemical Industry     

Thermal conversion of PR Spring bitumen-derived heavy oil in the presence of Na/alumina

The thermal cracking of PR Spring bitumen-derived heavy oils in the presence of hydrogen was studied in a fixed-bed reactor as a function of process operating variables. The reactor was filled with a catalytically inert sodium exchanged alumina. The packing consisted of an alumina hydrodenitrogenation catalyst support which had been impregnated with 2 wt.% sodium to reduce the acidity of the alumina. Thermal reactions were investigated with regard to denitrogenation, desulfurization, demetallation, Conradson carbon residue (CCR) reduction and residuum conversion. The process operating variables investigated were temperature (642–683 K), and WHSV (0.25–0.74 h⁻¹). The reactor pressure and hydrogen-to-oil ratio were fixed at 13.7 MPa and 890 m³/m³ (5000 scf H₂/bbl); respectively, in all experiments. The product distributions and yields were also determined as a function of process operating variables. Residuum conversion over the sodium-impregnated catalyst support was greater in all cases relative to nitrogen and sulfur removal due to thermal cracking of the residuum. Only low levels of heteroatom conversion were possible via thermal reactions. The extent of nitrogen removal over the sodium-impregnated catalyst support was lower than that of all other classes of component-types. Significant levels of CCR conversion were obtained despite the absence of metal sulfides on the alumina and were attributed to hydrothermal conversion.     

Heterogeneous Reactions of Chlorine Nitrate and Dinitrogen Pentoxide on Sulfuric Acid Surfaces Representative of Global Stratospheric Aerosol Particles

Increasing evidence from field measurements, modeling studies, and laboratory experiments suggests that heterogeneous reactions on stratospheric sulfate aerosol particles can change the partitioning in the nitrogen and chlorine families and thereby affect global ozone levels. In this study, a Knudsen cell flow reactor was used to measure the uptake of ClONO₂ and N₂O₅ by sulfuric acid solutions representative of background and volcanic stratospheric aerosol particles. The uptake coefficient (γ) of chlorine nitrate on 50–75 wt% H₂SO₄ at 223 K was found to be markedly dependent on the acid concentration, with γ ranging from about 1 × 10⁻² to 1 × 10⁻⁴. These results are in good agreement with literature reports and the data fit the expression log γ= 1.87 – 0.074 × (wt% H₂SO₄). This reaction will thus have its largest impact when stratospheric temperatures are low and sulfuric acid aerosols are most dilute. Uptake of N₂O₅ was studied on solutions with compositions in the range 58–96 wt% H₂SO₄ at temperatures from 193 to 303 K. N₂O₅ reacted readily on sulfuric acid surfaces with uptake coefficients of about 0.06. The uptake coefficient was found to be independent of the sulfuric acid concentration and the solution temperature over the ranges studied. These results suggest that the reaction of N₂O₅ with H₂O will occur readily on sulfuric acid aerosol particles for most stratospheric conditions.     

Spherical microporous/mesoporous activated carbon from pulping black liquor

BACKGROUND: A simple and effective method with environmental and economic benefits has been developed to produce spherical lignin and spheroidal microporous/mesoporous activated carbon from pulping black liquor. RESULTS: Spherical lignin with regular size of about 100 nm was obtained at 90 °C after 8 h treatment at pH 2. Pyrolysis of spherical lignin was impregnated with H₃PO₄ producing spheroidal microporous/mesoporous activated carbon with high apparent Brunauer–Emmett–Teller (BET) surface area of 1972 m² g^?1 and high carbon content of 68.0 wt% at 700 °C with impregnation ratio of 1:7. CONCLUSION: The process was inexpensive, sustainable, environment‐friendly and suitable for large‐scale production. Copyright © 2011 Society of Chemical Industry     

Investigation on the Reaction of Powdered Tin as a Metallic Fuel with Some Pyrotechnic Oxidizers

Thermogravimetry (TG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC) have been used to examine the thermal behavior of Sn+KClO₃, Sn+KNO₃, and Sn+KClO₄ pyrotechnic systems and the results were compared with thermal characteristics of individual constituents. TG curves for tin powder, heated alone in air, showed a relatively slow oxidation above 570 °C. From thermal results the decomposition temperatures of KClO₃, KClO₄, and KNO₃, in nitrogen atmosphere, were measured at 472, 592 and 700 °C, respectively. For the Sn+KNO₃ pyrotechnic system, the tin oxidation was completed within the range of 480 to 500 °C. Replacing KNO₃ with KClO₄ led to an increase of thermal stability of the pyrotechnic mixture. Among above‐mentioned pyrotechnic mixtures, Sn+KClO₃ has the lowest ignition temperature at about 390 °C. The apparent activation energy (E), ΔG^#, ΔH^# and ΔS^# of the combustion processes were obtained from the DSC experiments. Based on these kinetic data and ignition temperatures, the relative reactivity of these mixtures was found to obey in the following order: Sn+KClO₃>Sn+KNO₃>Sn+KClO₄.     

A new type of poly(vinyl alcohol)/nitrocellulose/granular activated carbon/KNO3 composite bead used as a biofilter material

A new type of poly(vinyl alcohol)/nitrocellulose/granular activated carbon/KNO₃ composite bead was prepared and shown to be suitable for use as a filter material in the biofiltration process. This composite bead was a porous spherical particle with a diameter of 2.4–6.0 mm and a density of 1.125 g/cm³. The amount of water-soluble nitrogen dissolved out of this composite bead was 145.5 mg N/g dry composite bead. The biochemical kinetic behaviors of n-butyl acetate in a spherical poly(vinyl alcohol) (PVA)/nitrocellulose (NC)/granular activated carbon (GAC)/KNO₃ composite bead biofilter (NC biofilter) and a spherical PVA/peat/GAC/KNO₃ composite bead biofilter (peat biofilter) were investigated. The values of the half-saturation constant K _s for the NC biofilter and the peat biofilter were 33.55 and 35.54 ppm, respectively. The values of the maximum reaction rate V _m for the NC biofilter and the peat biofilter were 23.83 and 22.46 ppm/s, respectively. Diffusion-limited zero-order kinetics were regarded as the most adequate biochemical reaction model for the two biofilters. The microbial growth rates and biochemical reaction rates for the two biofilters were inhibited at higher inlet concentrations. The biochemical kinetic behaviors of the two biofilters were similar. The maximum elimination capacities of the NC biofilter and the peat biofilter were 170.72 and 174.51 g C/h m³ bed volume, respectively. The PVA/nitrocellulose/GAC/KNO₃ composite bead made it easier for the microbes to adjust to their new environment and secrete exocellular enzymes to break down the substrate.     

Effect of Li+ on the acidity of metaphosphate—alkali nitrate melts

The effect of additions of LiNO₃ on the titration behaviour of sodium trimetaphosphate (TMP) in fused KNO₃ is examined. The presence of as low as 2 wt% LiNO₃ in KNO₃ melt at 350°C causes neutralization to occur in a single step consuming one oxide equivalent/equivalent NaPO₃. That the reaction continues step-wise through the formation of P₂O^4?₇ is proved from experiments involving this last acid. LiNO₃ shifts the O₂-electrode potentials in pyrophosphate containing melts to the same values measured in TMP containing melts. Li⁺ ions also affect the stability of TMP in KNO₃ melt. Decomposition occurs at a rate increasing with the rise of both LiNO₃ content and temperature of the melt. These peculiar effects are explained in terms of ion-pair formation and the relative high acidity of Li⁺ ion.     

Rape oil transesterification over heterogeneous catalysts

This work studies the application of KNO₃/CaO catalyst in the transesterification reaction of triglycerides with methanol. The objective of the work was characterizing the methyl esters for its use as biodiesel in compression ignition motors. The variables affecting the methyl ester yield during the transesterification reaction, such as, amount of KNO₃ impregnated in CaO, the total catalyst content, reaction temperature, agitation rate, and the methanol/oil molar ratio, were investigated to optimize the reaction conditions.The evolution of the process was followed by gas chromatography, determining the concentration of the methyl esters at different reaction times. The biodiesel was characterized by its density, viscosity, cetane index, saponification value, iodine value, acidity index, CFPP (cold filter plugging point), flash point and combustion point, according to ISO norms. The results showed that calcium oxide, impregnated with KNO₃, have a strong basicity and high catalytic activity as a heterogeneous solid base catalyst.The biodiesel with the best properties was obtained using an amount of KNO₃ of 10% impregnated in CaO, a methanol/oil molar ratio of 6:1, a reaction temperature of 65 °C, a reaction time of 3.0 h, and a catalyst total content of 1.0%. In these conditions, the oil conversion was 98% and the final product obtained had very similar characteristics to a no. 2 diesel, and therefore, these methyl esters might be used as an alternative to fossil fuels.     

Sintering of porous alumina obtained by biotemplate fibers for low thermal conductivity applications

In this research report, a sintering process of porous ceramic materials based on Al₂O₃ was employed using a method where a cation precursor solution is embedded in an organic fibrous cotton matrix. For porous green bodies, the precursor solution and cotton were annealed at temperatures in the range of 100–1600 °C using scanning electron microscopy (SEM) and thermogravimetric (TG) analysis to obtain a porous body formation and disposal process containing organic fibers and precursor solution. In a structure consisting of open pores and interconnected nanometric grains, despite the low porosity of around 40% (calculated geometrically), nitrogen physisorption determined a specific surface area of 14 m²/g, which shows much sintering of porous bodies. Energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analytical methods revealed a predominant amount of α-Al₂O₃ in the sintered samples. Thermal properties of the sintered Al₂O₃ fibers were obtained by using the Laser Flash which resulted in the lower thermal conductivity obtained by α-Al₂O₃ and therefore improved its potential use as an insulating material.     

Synthesis of a new type poly(vinyl alcohol)/peat/bamboo charcoal/KNO3 composite bead used as biofilter material

A new type poly(vinyl alcohol) (PVA)/peat/bamboo charcoal (BC)/KNO₃ composite bead was prepared, which has a diameter of 2.4–6.0 mm and a density of 1.133 g/cm³ and is a porous spherical particle. The biochemical kinetic behaviors of n‐butyl acetate in PVA/peat/BC/KNO₃ spherical composite bead biofilter (BC biofilter) and PVA/peat/granular activated carbon (GAC)/KNO₃ spherical composite bead biofilter (GAC biofilter) were investigated. The values of half‐saturation constant K_s for BC biofilter and GAC biofilter were 27.89 and 27.95 ppm, respectively. The values of maximum reaction rate V_m for BC biofilter and GAC biofilter were 13.49 and 13.65 ppm/s, respectively. Zero‐order kinetic with the diffusion limitation was regarded as the most adequate biochemical reaction model for the two biofilters. The microbial growth rate and biochemical reaction rate for two biofilters were inhibited at higher inlet concentration, and the degree of inhibitive effect was more pronounced in the inlet concentration range of 100–800 ppm. The biochemical kinetic behaviors of the two biofilters were similar. The maximum elimination capacity of BC biofilter and GAC biofilter were 111.65 and 122.67 g C/h m³ bed volume, respectively. The PVA/peat/BC/KNO₃ composite bead was suitable as a biofilter material. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of damping structural integration materials via the formation of nanostructure in triblock copolymer modified epoxy resins

Amphiphilic triblock copolymer Poly(ε-caprolactone)-block-polydimethylsiloxane-block-poly(ε-caprolactone) (PCL-b-PDMS-b-PCL, LDL) was synthesized via the ring-opening polymerization of ε-caprolactone in the presence of hydroxyl-terminated polydimethylsiloxane (HTPDMS) and was utilized to modify epoxy. The tensile strength and elongation at break were simultaneously enhanced when the triblock copolymer was incorporated. With increasing the concentration of the triblock copolymer, the damping temperature range (tanδ >0.25) was broadened from 21 °C to 34.5 °C. Meanwhile, the storage modulus of the composites and the values of tanδ had no significant decrease. When the concentration of the triblock copolymer was 20 wt%, the value of K_IC attained 1.68 MN/m^3/2, which was 1.56 times that of the neat epoxy (1.08 MN/m^3/2). Besides, the characterization of hydrophobic and hydrophilic performance indicated that the incorporation of the triblock copolymer made epoxy resins transformed from hydrophilic to hydrophobic. It is expected that damping composites obtained by this method may be used as damping structural integration materials in future.     

Influence of silane coupling agents on the surface energetics of glass fibers and mechanical interfacial properties of glass fiber-reinforced composites

The effect of various silane coupling agents on glass fiber surfaces has been studied in terms of the surface energetics of fibers and the mechanical interfacial properties of composites. γ-Methacryloxypropyltrimethoxysilane (MPS), γ-aminopropyltriethoxysilane (APS), and γ-glycidoxypropyltrimethoxysilane (GPS) were used for the surface treatment of glass fibers. From contact angle measurements based on the wicking rate of a test liquid, it was observed that silane treatment of glass fiber led to an increase in the surface free energy, mainly due to the increase of its specific (or polar) component. Also, for the glass fiber-reinforced unsaturated polyester matrix system, a constant linear relationship was observed in both the interlaminar shear strength (ILSS) and the critical stress intensity factor (K_IC) with the specific component, γ_S ^SP, of the surface free energy. This shows that the hydrogen bonding, which is one of the specific components of the surface free energy, between the glass fibers and coupling agents plays an important role in improving the degree of adhesion at the interfaces of composites.     

Thermal,electrical, and mechanical properties of addition-type liquid silicone rubber co-filled with Al2O3 particles and BN sheets

The addition-type liquid silicone rubber (ALSR) co-filled with spheroidal Al₂O₃ and flaky BN was prepared by the mechanical blending and hot press methods to enhance the thermal, electrical, and mechanical properties for industrial applications. Morphologies of ALSR composites were observed by scanning electron microscopy (SEM). It was found that the interaction and dispersion state of fillers in the ALSR matrix were improved by the introduction of BN sheets. Thermal, electrical, and mechanical performances of the ALSR composites were also investigated in this work. The result indicated that the thermal conductivity of ALSR can reach 0.64 W m⁻¹ K⁻¹ at the loading of 20 wt% Al₂O₃/20 wt% BN, which is 3.76 times higher than that of pure ALSR. The addition of Al₂O₃ particles and BN sheets also improve the thermal stability of ALSR composites. Moreover, pure ALSR and ALSR composites showed relatively lower dielectric permittivity (1.9–3.1) and dielectric loss factor (<0.001) at the frequency of 10³ Hz. The insulation properties including volume resistivity and breakdown strength were improved by the introduction of flaky BN in the ALSR matrix. The volume resistivity and characteristic breakdown strength E₀ are 6.68 × 10¹⁵ Ω m and 93 kV/mm, respectively, at the loading of 20 wt% Al₂O₃/20 wt% BN. In addition, the mechanical characteristics including elongation at break and tensile strength of ALSR composites were also enhanced by co-filled fillers. The combination of these improved performances makes the co-filled ALSR composites attractive in the field of electrical and electronic applications.     

Effect of nitrogen,phosphorus and molybdenum application on growth and symbiotic N2-fixation of groundnut in an acid sandy soil in Niger

Two field experiments were conducted in 1988 and 1989 on an acid sandy soil in Niger, West Africa, to assess the effect of phosphorus (P), nitrogen (N) and micronutrient (MN) application on growth and symbiotic N₂-fixation of groundnut (Arachis hypogaea L.). Phosphorus fertilizer (16 kg P ha^–1) did not affect pod yields. Addition of MN fertilizer (100 kg Fetrilon Combi 1 ha^–1; P + MN) containing 0.1% molybdenum (Mo) increased pod yield by 37–86%. Nitrogen concentration in shoots at mid pod filling (72 days after planting) were higher in P + MN than in P – MN fertilizer treatment. Total N uptake increased from 53 (only P) to 108 kg N ha^–1 by additional MN application. Seed pelleting (P + MoSP) with 100 g Mo ha^–1 (MoO₃) increased nitrogenase activity (NA) by a factor of 2–4 compared to P treatment only. The increase in NA was mainly due to increase in nodule dry weight and to a lesser extent to increase in specific nitrogenase activity (SNA) per unit nodule dry weight. The higher NA of the P + MoSP treatment was associated with a higher total N uptake (55%) and pod yield (24%). Compared to P + MoSP or P + MN treatments application of N by mineral fertilizer (60 kg N ha^–1) or farmyard manure (130 kg N ha^–1) increased only yield of shoot dry matter but not pod dry matter. Plants supplied with N decreased soil water content more and were less drought tolerant than plants supplied with Mo. The data suggest that on the acid sandy soils in Niger N deficiency was a major constraint for groundnut production, and Mo availability in soils was insufficient to meet the Mo requirement for symbiotic N₂-fixation of groundnut.